Charles Sirois explains three trends that are altering traditional distinctions between services and technologies:

Agribusinesses buy hypercommunication services from hypercommunication suppliers. However, if Sirois is right, in spite of convergence, "fragmented" services and prices (which vary by network technologies and content) will confuse agribusinesses. Furthermore, carriers use many different hypercommunication technologies to reach the locations agribusinesses need for communication. These technologies include transmission technologies, infrastructure technologies, interconnection facilitating technologies, or voice-data consolidation technologies. Each technology, in turn, may be composed of hardware, software, conduit, and protocols.

Specific technologies may seem unimportant to agribusiness managers when they need no technical knowledge of the underlying network in order to communicate. However, the strengths and weaknesses of particular technologies become important if there are frequent interruptions (downtime), if costs skyrocket, or if rural areas will not be served. Additionally, agribusinesses can choose technologies tailor made to specific strategies. Finally, agribusinesses also rely on capital purchases of hypercommunication CPE (Customer Premise Equipment). CPE technologies include computers, faxes, telephone systems, and other devices. CPE must be compatible with the existing equipment and software of both the agribusiness and its hypercommunication vendors. Additionally, an agribusiness may need hypercommunication services such as programming, web design, Internet promotion, repair, technical support, or network planning.

Basic knowledge of what hypercommunication services and technologies are could help an agribusiness manager simultaneously save money, improve communications with existing customers, plan future needs, and reach new customers. This Chapter provides descriptions of the major hypercommunication services and technologies that are available (or shortly will be) to Florida agribusinesses.

Organization of Chapter 4 is straightforward. Section 4.1 covers ways that hypercommunication services and technologies are converging into a single market. Section 4.2 discusses QOS (Quality of Service) and the many popular definitions of bandwidth. Bandwidth, data rate, throughput, and delay are often lumped together under a popular definition of bandwidth even though they are examples of individual QOS metrics that objectively appraise separate parts of hypercommunications quality and quantity. The next sections differentiate hypercommunication transmission technologies between wireline (4.3) and wireless (4.4). Section (4.5) touches on hypercommunication support services, facilitation, and consolidation (convergence-enabling) technologies. Then, hypercommunication services and technologies related to specific services are divided into four sub-markets: traditional telephony (4.6), enhanced telecommunications (4.7), private data networking (4.8), and Internet (4.9). The Chapter concludes with a summary comparing the usefulness of transmission technologies and service groups to agribusiness (4.10).

Chapter 4 uses technical sources (articles, texts, white papers, and standards) to provide overviews of the three global technological areas and four specific service sub-markets. Further details came from trade publications and informal discussions with industry sources. Where possible, deployment of services was examined firsthand in businesses around Florida. History provides the basis for constructing the three global technology sections and four specific service sub-markets. Now, each sub-market represents a share of the converging hypercommunications market.

There is a danger to approaching hypercommunications through historically defined sub-markets because that view emphasizes regulated monopolies such as telephone ILECs and cable TV providers. Both federal and state regulatory environments have changed dramatically in the past five years. Thinking about separate services and technologies (using either the interpersonal or mass communication model alone) does not apply now as it did when the 1934 Communications Act (the organic legislation to the 1996 TCA) became law. In the year 2000, the hypercommunications infrastructure consists of the PSTN, the Internet backbone, private data networks, along with "dark fiber" and other landline infrastructure (such as cable television systems). Additionally, terrestrial and satellite wireless networks form part of the hypercommunications infrastructure.

Although the hypercommunication model is replacing the formerly separated interpersonal and mass communication model with a myriad of interconnected choices, convergence is not yet a reality. Hence, while there is some danger in using sub-markets to characterize what hypercommunication services and technologies are, Chapter 4 is best organized around the current structure of hypercommunications. Convergence is the process that will modify today's sub-markets into tomorrow's converged marketplace. It is therefore appropriate to begin by naming dimensions of convergence that are affecting the technologies and sub-markets that form the basis for the rest of Chapter 4.

Virtually every segment of the world’s economy (including agriculture) is affected by the convergence of basic telephony, enhanced telecommunications, the Internet, and private networking into hypercommunications. While the inevitability of convergence is taken for granted, the rate of convergence and the form it will take cannot be. Convergence would happen automatically except for institutional and attitudinal barriers including regulation, competition, speed of diffusion, and competing standards. Converge means "to move, turn, or be directed toward each other or toward the same place." [Webster's New World Dictionary, 1960, p. 323]

In a rapidly expanding marketplace with frequent introductions of new services and technologies, convergence means that further horizontal and vertical integration of the hypercommunication market will occur with profound implications for individual agribusinesses. Convergence has already been described as a process where two separate communications models (interpersonal and mass) and their separate telecommunications networks evolve into a single hypercommunications model that uses a mesh of networks. This view matches Alan Stone's definition of "boundary problems" due to the clash of old and new technologies. According to Stone, the first boundary problem was telephone-radio, followed by telephone-computer, TV-radio, etc [Stone, 1997]. Instead of entirely replacing the old technology such clashes can lead to new uses for the old technology. For example, radio had been expected to die because of television and the demise of movie theatres was expected because of VCRs. In both cases, the market was able to absorb the new technology without eliminating the old.

However, because of the diversity of hypercommunication services and technologies it is difficult to speak of boundaries in the same breath as convergence. Instead of discrete boundaries, convergence has analog dimensions. For agribusiness, hypercommunications convergence has five similar dimensions, each based on a clash between old and new. Each dimension is important to agribusiness because the result of the clash will determine capital costs and variable expenses.

The first dimension of convergence is device-device convergence, the convergence of previously differentiable electronic hardware devices into multi-purpose units. The telephone, fax, television, radio, and computer are beginning to converge together into DTE (Data Terminal Equipment), or multi-functional user devices. As one newspaper article put it:

The main question is whether the computer will completely replace the office telephone, fax machine, and copier. Device-device convergence is becoming increasingly important as agribusinesses equip offices and train employees. While there can be substantial savings to capital budgets from purchasing one device to do the job several previously did, a dangerous dependency on a single technology or connection can occur unless there are redundancies. For example (unlike a computer terminal), individual telephone sets do not become useless every time a computer spreadsheet crashes, nor do telephones suffer downtime during every LAN outage.

A second dimension of convergence is content-carrier convergence. Content-carrier convergence is also called confluence:

The third dimension of convergence, carrier-device convergence occurs when the hypercommunications carrier and the communications device used to communicate become the same. An extreme example of carrier-device convergence was used by pre-breakup AT&T. Telephone customers had to lease telephones from AT&T that were manufactured by AT&T’s Western Electric subsidiary. A recent consumer action against AOL is another example. The plaintiffs charge that once Internet Explorer for AOL was installed, it became impossible for the computer to be used to access a competing OSP or ISP if the consumer switches providers. The inter-relatedness of hypercommunications technologies can mean that a service provider will be unwilling or unable to provide services if an agribusiness already owns a certain make of equipment or is located in a particular area. Substantial switching costs to change providers can occur in this way.

In the fourth dimension, regulatory convergence, as separately regulated industries come together, so will taxes, regulations, and governmental policy. Quoting George Gilder again, Globerman, Janisch, and Stanbury state what is behind regulatory convergence:

The regulatory task becomes more difficult as new services and technologies, (especially the unregulated Internet) create new regulatory territory.

The changes convergence is bringing promise to be truly revolutionary according to Gilder:

An important barrier to convergence is the lack of SLAs (Service Level Agreements) or signed contracts between buyer and seller setting out QOS guarantees. "The realization of a multiservice utopia will not happen until service guarantees become a fundamental part of the convergence landscape." [Morency, 1998, p. 23] The increasing importance of hypercommunication SLAs means agribusinesses need to be intimately familiar with bandwidth and other QOS metrics that establish SLA terms. Bandwidth and QOS metrics are the weights and measures of hypercommunications, but are hardly as standardized as those agribusinesses are used to in other markets.

No hypercommunications term is subject to more confusion or used more frequently than bandwidth. While an understanding of bandwidth is important to agribusinesses hoping to use hypercommunications services and technologies, bandwidth is not a complete description of the speed, overall quality, or value of a particular service or technology. Bandwidth-related measures are most often used to define and price hypercommunications services and technologies. However, excess reliance on one term obscures a more comprehensive set of characteristics called QOS (Quality of Service) metrics that are more important to agribusiness hypercommunication strategies. This section is designed to be a practical guide for agribusinesses hoping to understand bandwidth and other QOS so as to become more informed hypercommunication buyers.

This section and the following three (4.3 through 4.5) apply generally across the specific service and technology sub-markets discussed the last half of the Chapter from 4.6 through 4.9. To provide the right technical foundation, large amounts of supporting technical details are presented here in section 4.2. Readers who are already familiar with signal conversion, how modems work, and the subtleties of bandwidth, throughput, and data rate may go directly to (4.2.3). There, a general QOS model is introduced to provide an analytical framework of agribusiness hypercommunication networks. The reference model integrates QOS metrics and bandwidth with material from Chapter 3 such as the three core engineering problems of communication networks and the four technical objectives of network managers.

Other readers may need to take advantage of all four sub-sections in 4.2, being aware that tables 4-1 through 4-4 and figures 4-1 through 4-22 trace the main points, with the text available for additional support. In the first sub-section (4.2.1), bandwidth and five other QOS characteristics most often confused with bandwidth are discussed. The critical distinction between signals and messages and the difference between operational speed and capacity are explained. Then, a practical example of computer modem communication (4.2.2) underscores bandwidth's separateness from other QOS metrics. The last section (4.2.4) presents agribusinesses with a thumbnail sketch of the QOS dimensions used in buying and selling hypercommunication services and technologies.

4.2.1 The Relationship between Bandwidth and Speed

For several reasons, bandwidth has taken on an imprecise meaning that goes beyond its specific technical definition as a capacity measure (as introduced in Chapter 3). One reason for this is that the technical nature of hypercommunications tends to be confusing. Technical terms such as bandwidth become confused with closely related technical terms. A second reason for the overuse of bandwidth is that bandwidth is the unit most often used to price hypercommunications services and to describe infrastructure, networks, and individual connections. This multiplicity of uses causes instant misunderstanding since bandwidth is variously used as a stock measure, a flow measure, an accounting cost, and a capacity constraint. In short, bandwidth is used popularly to compare the speed, capacity, reliability, and quality of hypercommunication services, carriers, and technologies.

Furthermore, there is a lack of uniformity in "expert" opinion about what bandwidth is. As more sources are consulted, more variations in definition are encountered. For example, a well-received book aimed at business MIS and telecommunications managers defines bandwidth as "the speed with which data travels, measured in bits per second (bps)" [Bezar, 1995, p. 75]. However, in Bezar's glossary bandwidth becomes:

However, the meaning of bandwidth also depends on the relationship among bandwidth, bits, and speed, a complex recipe with three main ingredients. First, a hypercommunications message (voice, data, or video) and the signal that carries it are different entities. Signals can be analog or digital while message content also can be analog or digital. Second, signal transmission may use broadband technology, carrierband technology, or baseband technology. Third, there can be a difference between the upstream and downstream rate and capacity (directional asymmetries) for a variety of scientific and technical reasons. These ingredients need to be examined before QOS can be understood.

The first ingredient is the distinction between signal domain and message content. The signal-message distinction is rooted in Shannon's mathematical theory of communication, shown in Figure 4-1 [Shannon, 1948; Shannon and Weaver, 1949].

Figure 4-1: Shannon's schematic of a communications system.

The information content of a message and the domain of the signal are two distinct entities. Messages may have either analog or digital information content (source domain) depending on the equipment (DTE) at the information source and destination. Information sources "represented by a physical quantity that is considered to be continuously variable and has a magnitude directly proportional to the data" are analog [GSA, FED-STD-1037C, p. 1996, A-14]. Analog message content refers mainly to voice telephone calls, though it can include audio, graphics, video, and readings from scientific sensors (such as pressure, temperature, and position). Digital information sources are "represented by discrete values or conditions (or) are discrete representations of quantized values of variables, e.g., the representation of numbers by digits perhaps with special characters and the 'space' character." [GSA, FED-STD-1037C, 1996, p. D-18] Digital message content includes almost all data communications and Internet traffic. The advent of digital cameras, digital image scanners, CDs, etc. has created digital replacements for previously analog sources.

The signal is an electric current or electromagnetic wave used to carry an encoded representation of the message from the transmitter to the receiver. Signals may be digital or analog depending on the transmitting and the receiving equipment DCE (Data Communications Equipment) on each end as shown in Figure 4-1. According to Hill Associates, "Signaling is analog if the signal transmitted can take on any value in a continuum . . . Signaling is digital if the signal transmitted can take on only discrete states." [Hill Associates, 1998, p. 303.1.3, italics theirs] Switches, routers, and other kinds of intermediate DCE must be in the same domain as the signal or signal conversions must occur. If necessary, signals are decoded into the appropriate source domain before reaching their destination.

Digital signals offer many advantages over analog ones. For example, many separate digital signals may be interleaved and sent together to permit several separate conversations on a single line (multiplexing). Digital messages can be encrypted before their transmission as signals to prevent eavesdropping and to provide security. Often, severely degraded digital signals may be reconstructed, providing perfect copies of the original source. However, excess interference can prevent an entire digital signal from reaching a source, while distorted analog signals would be garbled but received under similar conditions. Digital signals require more bandwidth than analog signals do, but they are still less costly to transmit [FitzGerald and Dennis, 1999].

Table 4-1 shows the four combinations of digital or analog information content and analog or digital signals. Since each combination has different physical characteristics, each kind requires specialized hardware. These combinations also apply to signal-signal conversions and intermediate transformations that can occur in the transport level of a communication network, especially over long distances. Table 4-1 and Figure 4-1 show that Shannon’s (1948) "information source" and "destination" are now known by the more general term, DTE. In a purely discrete system DTE are digital. In a purely continuous system DTE are analog. In a mixed system, DTE can be digital or analog.

Common digital DTE devices include computers and certain digital telephones. These devices send and receive digital messages whether text files, e-mails, voice mail, or graphics and video. Common analog DTE devices include most telephones, microphones, speakers, and certain scientific instruments.

Table 4-1: Mapping from source domain to signal domain.
 

From: source domain (cols.) To: signal domain (rows)	From: Digital Sources (bits) (Digital Message Content)	From: Analog Sources (Hz) (Analog Message Content)
To: Digital Signal (bps)	(Purely discrete system) Digital-Digital transformation DCE example: DSU/CSU Function: map discrete states of information domain onto discretely varying signal domain.	(Mixed system) Analog-Digital conversion (ADC) DCE examples: Codecs (Coder-Decoders) or Digitizers (ADC) Function: map continuous states of information domain onto discretely varying signal domain. Has quantizing error.
To: Analog Signal (Hz)	(Mixed system) Digital-Analog conversion (DAC) DCE examples: Modems (DAC is modulator) or Interpolators (DAC) Function: map discrete states of content domain onto continuously varying signal domain.	(Purely continuous system) Analog-Analog transformation DCE example: POTS (transducer) Function: map continuously varying states of content domain onto continuously varying signal domain.

 

The receivers, transmitters, and switches of Shannon's communications system also are generalized by the term DCE (Data Communications Equipment or Data Circuit-terminating Equipment). DCE are specific to the signal domain (analog or digital) while DTE depend on the message domain as well. The two need not be separate devices from the user’s point-of-view.

DCE transmit and receive each end of a hypercommunication (and often in between) in the appropriate signal domains. A common DCE example is a computer modem. A modem is a transmitter that modulates digital content into an analog signal on one end and a receiver that demodulates analog signals back into digital form to reach the destination. Similar DCE devices exist for other signal domain, source domain combinations. For example, codecs (coder-decoders) are circuits (or software) serving as built-in DCE used to make conversions within digital DTE.

Therefore, in some cases such as telephones (both analog and digital), DTE and DCE are in the same device. For example, an analog telephone contains a microphone to capture the analog voice source that is then converted by a transducer into electronic waves that are sent as analog signals.

Figure 4-2 (direction of communication read from left to right) depicts signal conversion or transformation for the four cases alluded to in Table 4-1. In a purely continuous system (upper right, Figure 4-2), analog messages are modulated onto analog signals (continuously varying representations of the source message) over a carrier wave as in the cases of POTS and traditional broadcast radio and TV. A carrier is signal with known characteristics that is modulated to carry information. Using a carrier, the receiver can extract the message because it knows the characteristics of the carrier wave. However, noise or unintended changes to the carrier will be interpreted as part of the information. The bandwidth (transmission capacity) of channels over which analog signals pass is the difference in Hertz (cycles per second) between the minimum and maximum frequencies.

Figure 4-2: Simplified Signal Conversion and Transformation.

A purely discrete system (shown in the lower right of Figure 4-2) features a digital source carried by a digital signal (coded word representation of the source message) as in the case of Ethernet, ISDN, and DSL. With digital signal transmission, bandwidth is expressed in a bit rate (bits per second, bps). Bandwidth is expressed in Hertz (Hz, cycles per second) for analog-analog transformations.

However, the best unit to express bandwidth in is often confused between bps and Hz for the other two cases (mixed systems) when conversion (rather than transformation) occurs. In DAC (Digital source to Analog signal Conversion), shown on the lower left of Figure 4-2, the digital domain of the message is mapped onto an analog signal domain in order to reach the destination. In ADC (Analog source to Digital signal Conversion), shown in the upper left of Figure 4-2, the analog domain of the message must be mapped onto a digital signal domain. In such mixed systems, both Hz and bps may be used to describe bandwidth, depending on the context.

In ADC, analog messages may be converted into digital signals through codecs (coder-decoders) to become signal pulses. Typically, these pulses are modulated over a carrier pulse as in the case of digital wireless mobile telephone. Computer modems and cable modems perform both ADC and DAC. A modem modulates digital data (messages) into analog signals when it sends and demodulates analog signals to digital data when it receives. There can be several such signal conversions at intermediate DCE between the sender and receiver.

Analog signal modulation refers to alterations made by DCE in the characteristics of analog carrier waves, impressed on the amplitude (signal strength), phase (wave phase) and/or the base frequency of the wave. Analog signals (continuous waves) may be modulated (coded) in several methods including AM (Amplitude Modulation), FM (Frequency Modulation), PM (Phase Modulation), and QAM (Quadrature Amplitude Modulation).

Digital signals (discrete pulses) are modulated (encoded) through various kinds of PCM (Pulse Code Modulation) such as PAM (Pulse Amplitude Modulation), PDM (Pulse Duration Modulation), and Pulse Position Modulation (PPM). Digital signals are aperiodic (non-repeating patterns) so frequency cannot be used to describe them. However, a digital signal can be approximated by an n-th order series of harmonic sine waves. Each harmonic has its own amplitude, phase, and frequency. The minimum significant spectrum is the minimum frequency range (frequency spectrum) needed to represent the original signal and n-th order harmonics. The bandwidth of a signal is the width of the frequency spectrum it occupies.

When expressed in Hertz, the bandwidth of an analog medium for a digital signal provides a range of frequencies that can be transmitted. If this range is smaller than the minimum significant spectrum, more bandwidth is needed to allow the receiver to reproduce the original source signal.

When the end-to-end observed speed of communication between sender and destination DTE is considered, other characteristics beyond the bandwidth (capacity) of a single link or the bit rate of a given DCE are involved. These characteristics (summarized in Table 4-2) include throughput, data rate, delay, and jitter. Importantly, the focus of the first four characteristics in the table (each of which is often misleadingly called bandwidth) is primarily on digital bits.

Table 4-2: Bandwidth and QOS measures with which it is most often confused.
 

Item	Units	Scope	Measures
Bandwidth	Analog (Hz) Digital (bps)	Single Link or Point-to-Point (DCE-DCE, transmission link only)	Signal carrying capacity of a segment(s) of a communications link. Width of communications link.
Bit Rate	bps	DCE operational speeds	Baud rate x log2 n, or the operational speed of DCE with log2n code bits (n-level coding)
Data Rate	bpst	Single Network Link or multiple channel traffic between DCEs	Error-free aggregate speed at a point or through a segment. Includes overhead.
Throughput (pure or effective)	Max(bps) or bpst	End-to-End (sender DTE through receiver DTE)	Pure (maximum) throughput: End-to-end transmission capacity of user information from sender to receiver. Observed (effective) throughput or throughput rate: rate at which system processes and transmits user information (does not include overhead).
Delay	mst	End-to-End (DTE to DTE or DCE to DCE for troubleshooting)	Time it takes a bit to move across transmission time. Length of communications link.
Jitter	mst,t+n	End-to-End (DTE-DTE or DTE-DCE)	Variation in delay. Descriptive statistic.

 

When expressed in Hertz, bandwidth represents the raw capacity of a noiseless, analog channel before digital data are imposed. When expressed in bps, bandwidth represents the maximum attainable bit rate in a single direction of a noiseless link with no other traffic. The bandwidth or more precisely bit rate associated with a given bandwidth in Hz depends on the baud rate and coding rate. A sampling or baud rate is directly proportional to the bandwidth. The coding rate (number of levels in the code) multiplied by the sampling (baud) rate equals the bit rate, the rate at which DCE are designed to operate. Environmental noise can decrease the coding rate so that the difference between bit rate and bandwidth becomes larger. Noise and quantizing error can further in increase errors so that the gap between data rate and bit rate becomes larger.

The bit rate (operational speed of DCE in bits per second) that can be accommodated by any medium is proportional to bandwidth. Therefore, the greater the bit rate, the larger the bandwidth (capacity of a connection) needs to be. Thus, bandwidth typically exceeds the bit rate, which in turn exceeds the data rate.

The third characteristic, data rate (also known as the data signaling speed) measures "the aggregate rate at which data pass a point in the transmission path", typically expressed in bits per second (bps) [GSA, FED-STD-1037C, 1996, p. D-4]. Since the data rate is an error-free rate from DCE to DCE, it may be less than the bit rate and always below the bandwidth.

The next characteristic, throughput, can be expressed in two ways. Throughput is an end-to-end (DTE to DTE) measure that can be expressed as "pure throughput", a theoretical capacity (maximum attainable bps), or as an observed "throughput rate" in bps at time t, where bps_t is an actual observation [Sheldon, 1998, p. 972]. Both pure throughput and the throughput rate (also called effective throughput) differ from bandwidth because they are end-to-end measures of the rate at which user information (not counting retransmission of errors or transmission of overhead) is processed and transmitted. Pure throughput is similar to bandwidth in that it is a capacity, but it is an end-to-end capacity, rather than the capacity of a point-to-point access line or transport link. For example, the compression of voice or data files improves throughput but does not change bandwidth, bit rate, or the next characteristic, data rate.

Throughput, because it is an end-to-end measure that includes compression but excludes error and overhead, cannot be compared directly to bandwidth, data rate, or bit rate. However, due to compression and in spite of overhead, an observed throughput rate (sometimes called information rate) often is greater than the data rate, bit rate, or even the bandwidth of a particular network segment between the sender and destination. Throughput is the speed measure experienced most by users.

Another QOS characteristic often erroneously confused with bandwidth, delay, is included in throughput. Delay (also called latency) is the actual length of time it takes a bit to travel across a transmission line [Sheldon, 1998, p. 256]. There are three kinds of delay: propagation delay, switching delay, and queuing delay. Propagation delay results from transmission media variables. For example, copper wire has a higher propagation delay than fiber optic cable, while satellite transmissions have higher propagation delays than line-of-sight wireless transmissions do. Propagation and switching delay do not depend on usage levels. However, queuing delay is zero at low use and rises due to congestion bottlenecks that result from high network loads (a systemwide ratio of effective throughput to capacity). Taken together, switching and queuing delay are often called throughput delay since they are variable. The number of hops a signal is switched over a network and the overall network load tend to vary from moment to moment.

The variation in delay, jitter is another way to indicate quality. Jitter refers to the variability of delay measures through time. Low jitter and delay are critical to voice conversations and real-time broadcasting. The highest quality connections are those with a tightly distributed average delay of less than 100ms. Poorer quality connections tend to experience longer delays and greater jitter. For example, satellite transmissions often average near 350ms, with a range from 150ms to 600ms. Pure throughput assumes no jitter and only propagation delay. Since effective throughput is an actual measure, it can reflect both switching and queuing delays. A series of effective throughput observations are needed to measure jitter.

Before proceeding to a computer modem example that clarifies the entries in Table 4-2, it is important to understand the second ingredient of the complex mixture of speed and QOS, the transmission (or signal) technology. First, the word broadband has to be defined. Broadband is used to refer to a range of capacity (or speed). Broadband also is used to describe a particular analog signal transmission technology. Egan characterizes the speed and capacity connotation as follows:

Broadband also describes a specific signal technology where signals themselves (rather than bandwidth) are classified as baseband, broadband, and carrierband. This second use of broadband refers to a type of analog signal transmission technology (typically with a digital source domain) using shared lines. Two other signal transmission technologies are baseband and carrierband.

Broadband signal technology sends multiple analog signals over a range of frequencies (in channels, similar to radio frequencies) over shared conduit. Since noise tends to accumulate in such a scheme, amplifiers are used to regenerate attenuated signals. Because multiple channels are available, many messages may travel at once over a broadband transmission link without automatically exhausting available bandwidth (capacity). Broadband signal technologies distribute modulated data, audio, and video signals over coax, twisted pair, or fiber optic cable. Broadband is the easiest way to deliver a common signal to a large group of locations. Without the addition of electronics that limit eavesdropping, it is possible (with the right knowledge and equipment) to intercept broadband transmissions.

Broadband includes networks that multiplex multiple, independent networks onto channels in a single cable. This may be done through FDM (frequency division multiplexing) where two or more simultaneous and continuous channels are derived by assigning separate parts of the available frequency spectrum (bandwidth) to each channel [GSA, FED-STD-1037C, 1996, p. F-17]. Under FDM, signals that are coincident in time are separated in space so that a particular subscriber receives some of the total bandwidth of the connection that serves their location all of the time.

Broadband network technologies allow many networks or channels to coexist on a single cable. Broadband traffic from one network does not interfere with traffic from others because each network uses different radio frequencies to isolate signals by vibrating each signal at a different frequency as it moves over the conduit. Used in this sense, broadband is the opposite of baseband, which separates digital signals by sending them at timed intervals. A broadband subscriber receives analog signals over his own channel on a shared link while a group of baseband subscribers receives common digital signals over a link that is not shared.

Baseband signals are digital (always having digital source domains as well), requiring all of the available bandwidth in a single, shared connection. Broadband signals are analog (having either analog or digital sources) and move over unshared channels on a shared connection [Hill and Associates, p. 303.1.5, 303.1.7]. Carrierband signals are a hybrid of the two.

Baseband signals are used to connect stations on Ethernet LANs and in localized point-to-point or dedicated circuit communication (such as ISDN and HDSL). Baseband signals are transmitted without modulation on a carrier wave, having been digitally imposed on a single base frequency [FitzGerald and Dennis, 1999]. Baseband transmissions use repeaters to regenerate bi-directional attenuated signals. However, even when using repeaters, baseband transmissions are limited in distance compared to broadband. For this reason, baseband signal transmission is frequently used by CPE networks such as LANs.

Any guided medium can be used for baseband signal transmission. The baseband of a broadband signal is the original frequency range before modulation into a more efficient, higher frequency range. Baseband network technologies use a single carrier frequency range (channel) and require all stations attached to the network to participate in every transmission. However, only one digital baseband signal (using the entire capacity of the channel) at a time is permitted. Time Division Multiplexing (TDM) is used to allow users to share connections by taking turns so that all of the bandwidth is used some of the time. Under TDM, a digital signal that is coincident in space is separate in time.

Carrierband is a type of baseband technology where the signal is modulated before transmission over a baseband connection. Standard baseband transmission is un-modulated but is multiplexed to allow multiple transmissions to occupy the path at once. Carrierband technology uses signals that are modulated but not multiplexed so that the entire bandwidth of the channel is available in separate channels (for separate uses) for a single subscriber such as an agribusiness. Individual subscribers send and receive a mix of digital and analog signals over a dedicated (un-shared) link that can carry more than one kind of traffic at once. For this reason, carrierband is sometimes called single-channel broadband and is used in HSLN (High-Speed Local Networks) to link "mission critical" processors to each other or processors to peripherals [Maguire, 1997]. Carrierband technology is also used as a digital access level connection, such as in certain DSL services.

At the access level, cable TV broadband users share capacity for Internet access with dozens to hundreds of other subscribers over a broadband network. Telephone company digital lines such as DSL and ISDN serve individual subscribers only. Of the three signal technologies, agribusinesses are affected differently by each one. Baseband technologies are commonly part of Ethernet LANs at agribusiness offices. Broadband technologies support services that are offered by Cable TV and wireless firms, typically to small offices and farm residences. Carrierband technologies are sold to agribusinesses by ILECs, ALECs, ISPs, and others but are subject to distance limitations that will be covered in 4.3.

The third and final ingredient in the complex mixture of capacity, speed, and bandwidth is directionality or symmetry. For example, the upload and download bandwidth to bps relationship for a digital source to analog signal conversion depends on both the Nyquist Theorem [1924, 1928] and Shannon's Law [Shannon, 1948]. Furthermore, various sampling, symbolization, and encoding schemes are used by DCE to modulate the signal in order to impose or pack the message content into an electromagnetic pulse or onto a carrier wave. These concepts can introduce directional asymmetries that get specific attention in the next example regarding computer modem communications.

4.2.2 Computer Modems: Bandwidth and QOS

An example concerning the ubiquitous computer modem will further differentiate bandwidth from other QOS metrics. Modems are a particular kind of DCE designed only to work with analog signals and digital sources. Indeed, some say that the modem is a DCE that has reached maturity and is not part of the converged future. However, since modems are broadly representative of DCE (while computers represent DTE) the following example gives a simple lesson in bandwidth, speed, and analog-digital conversion that has broader applicability.

The modem is still a dominant form of connection to the Internet and data networking for households and for many agribusinesses as Figure 4-3 reveals. In 1999, Neilsen NetRatings found that fewer than six percent of U.S. households had Internet access faster than that offered by 56k modems [CyberAtlas, 2000].

Figure 4-3: Internet Access by Speed, 1999.

Indeed, a majority of households (53%) own modems that are slower than 56 kbps. Additionally, modems that perform at relatively high data rates in urban settings may perform poorly or not at all in rural areas. Thus, the expected obsolescence of the modem will not occur for three to five years for many Florida agribusinesses because of infrastructure problems [FPSC, 1999]. Chapter 5 will provide more details.

The bandwidth of the analog voice channel (telephone line) as shown in Figure 4-4 is 3200Hz wide (3500Hz - 300Hz). This bandwidth was engineered decades ago by AT&T's Bell Labs (when bandwidth was considered to be an extremely scare resource) as the absolute minimum needed to adequately represent the human voice.

Figure 4-4: Bandwidth of analog telephone line is 3200Hz.

Natural speech is concentrated between 75Hz and 8000Hz, though the human ear has a range of recognition from 75Hz up to 20kHz [EAGLES, 1997]. When the nationwide Bell System was built, filters were placed to block frequencies above 3500Hz from being carried on local lines. A modem attempts to transmit at the highest operational speed (bit rate) that it can given this bandwidth limitation, the equipment it connects with, and the amount of noise present in the line and introduced in the conversion process.

Analog-digital conversion (ADC) produces line noise as a byproduct and is, therefore, more sensitive to bandwidth limitations than DAC. It is for this reason that the so-called 56k modems (now generally known as V.90 standard modems) have a higher download than upload speed. Before this asymmetry of speed is covered, it is important to understand the steps in each conversion process.

ADC takes a continuous (in time and amplitude) waveform and converts it to a time-discrete, but amplitude-continuous series of pulses. There are three steps (sampling, quantizing, and coding) in ADC. The first step, sampling, begins the process of converting the waveform into pulses by sampling amplitude values every T microseconds (?s). During sampling, the waveform is scaled into sampling intervals where the sampling frequency, 1/T is also known as the modem’s symbol rate.

According to the Nyquist Theorem, the symbol rate (also called the baud rate) used must be less than twice the bandwidth. So, for example, a 3200Hz (cycles per second) signal could be sampled with a frequency of up to 6400 symbols per second. Thus, T the size of a single sampling interval (symbol) is 156.25 ?s, which is the minimum constant interval at which the modem samples. In reality, 3200 baud is a commonly sampled rate because 6400 baud is unattainable in practice. Each sample becomes a separate PAM (Pulse Amplitude Modulation) pulse.

The Nyquist Theorem further specifies the levels to be used in the next step of ADC, quantization. Given bandwidth W, then the highest signaling rate C in a noiseless channel is given by C = 2W log₂M, where M is number of coding levels [Maguire, 1997, Module 5, p. 13a]. The number of levels equates to the number of bits per quantization level. In quantizing, digits are assigned to the sampled signals by rounding off (quantizing) the PAM pulses using non-linear companding schemes. When 256 discrete amplitude levels are used to compand the original signal into a quantized sample, eight bits (log₂ M) are necessary. The number of bits per level is log₂ M, so that a 512 level representation contains exactly nine bits, etc.

The third step is coding. In coding, the amplitude levels are mapped into bits that can be understood by digital DTE or DCE. The standard coding rate is eight or nine bits. Given the 3200Hz bandwidth and an eight bit coding scheme (based on a 256 level quantization), the highest bps to be expected under the Nyquist Theorem from a noiseless telephone line would be 51.2 kbps.

However, two forms of noise reduce the maximum rate in practice. The first of these, quantizing noise, results from the second step and increases with the number of levels. Hence, it is not possible to add quantizing levels ad infinitum or the resulting line noise would cause data rates to fall. Once quantizing noise has been added to the line, it remains there (slowing the rate down) even after digital conversion has been accomplished. This is a particularly limiting case for sending (but not necessarily for receiving) data over a line. To discourage added noise, only the most robust levels can be used to code with so that in practice 256 levels may translate to 128 [3com Corp., 1999, p. 4]. Other forms of noise on lines (a particular problem in rural areas) affect speed in each direction.

Shannon's work on coding led to the development of Shannon's Law which states that the maximum speed C, equals W log₂ (1+(S/N)) bps, where S/N is the un-standardized signal to noise ratio. The signal to noise ratio (SNR) is commonly measured in dB (decibels) where the SNR equals 10 log₁₀(S/N) dB. The 33.6 kbps upload bit rate (maximum operational speed) advertised for both V.34+ and V.90 modems (over 70 percent of those in use) would require a SNR of 31-32dB for such a speed to be achieved. That SNR is far higher than that typically found, even on lines with a short distance to the serving CO. Thus, noise and the engineered bandwidth in Hz are the chief limitations on the usable capacity of analog line in bps.

To review, the baud rate multiplied by bits/baud (the coding rate) yields the bit rate (operational maximum) of the modem or other DCE. However, high line noise and the presence of noise from quantization itself place limitations on the achievable data rate. When a 28.8 kbps bit rate modem is advertised, it usually is a 3200 baud unit with a signaling (coding) rate of 9bits/baud. Higher speeds are obtained by increasing the baud rate, but bauds above 3429 are rarely obtained in practice due to quantization and/or line noise. Rural telephone lines are notoriously noisy, partially due to the age of the copper lines and also because noise is a function of the distance to the telephone CO.

DAC reverses the steps of ADC. First, the digital bits are modulated at a certain signal speed, governed as before by the Nyquist Theorem. Then, interpolation is used to reconstitute an analog profile of the digital signal pulses. Finally, the digital pulses are decoded into analog waveforms for analog transmission.

Importantly, physical laws preventing speeds greater than 33.6 kbps on upload are less constricting on the download side if certain conditions are met. An important reason is that quantizing noise is not present in DAC. To see this, consider how modems are used to connect with the Internet, a process that is illustrated in Figure 4-5.

Moving from left to right, a modem transmission (upload) follows a path from the customer premises (1) over the access level to the local serving central office (2) of the telephone company. While most calls to modems are local, they commonly are made to ISP numbers in a different telephone exchange with a different telephone CO (3), so the transmission flows over the telephone company's transport level to reach the ISP's CO. Then, the call flows over the ISP's telephone access level to reach a modem bank at the ISP premises (4).

Figure 4-5: Under V.34+ and prior standards, upload and download speeds are restricted to rates under 33.6 kbps.

An upload consists of no fewer than four signal conversions, labeled one through four. A download consists of no fewer than four conversions, labeled negative one through negative four. Of all eight conversions, only three (shown in bold as 2, -2, and -4) are ADC conversions that result in noise that would affect the signal in any direction. The last ADC (-4) occurs once the signals are no longer on the wire, so it does not create quantization noise on any line.

Another example, with a 56 kbps modem, shows the directional limitations of DAC and ADC. When the 56 kbps modem calls over a special digitally equipped telephone line and hooks up with compatible equipment, Shannon's Law and the Nyquist Theorem do not vanish. However, due to the absence of quantizing noise and the removal of ADC on the opposite end, download baud rates of up to 8000 may be negotiated with a seven bit per baud coding rate. The 56 kbps modem process is illustrated in Figure 4-6.

Figure 4-6 differs from the V.34+ (Figure 4-5) case in one obvious way. The ISP has purchased a special digital line (a channelized T-1 or an ISDN-PRI T-1) that allows the V.90 equipment at the ISP's premises to interact directly with the telephone company's transport network. Instead of a telco POP (Point of Presence) on the ISP end, a block arrow is drawn to show that the ISP connection is physically on the transport network. In addition, only one conversion (2) is in bold since that is the only ADC conversion that creates quantizing noise that would follow it to the Internet site at which uploading would occur. The download path is free from quantizing noise on the line. Of course, other kinds of line noise would still be present, creating an important reason that 56 kbps Internet access is spotty or even completely absent in many parts of rural Florida.

Figure 4-6: V.90 (56k) modems have no quantizing line noise on download, increasing speed.

By now, it should be clear that bandwidth is both a practical and a theoretical measure. Shannon's Law and the Nyquist Theorem provide upper theoretical bounds on channel capacity, while modem advertisements claim a lower theoretical number (an operational bit rate), perhaps more realistic, but still abstract from reality. Line noise and the CPE (modem or other device) on the other side are additional variables. For this reason, modems and other DCE are designed to operate at many different bit rates (operational speeds) because of the variability involved. During the course of a session, modems (like other CPE) must synchronize rates with the bit rate and line conditions on the other end. Hence, during each session, a 56 kbps modem will dynamically adjust (negotiate) upload bit rates of from 300bps to 33.4 kbps (and many levels in between) and download bit rates from 56 kbps down to 300 kbps.

However, the data rate of an actual transfer varies from the advertised bit rate even under low noise conditions because of other sources of variability, the manufacturer, and model. Figure 4-7 shows test results for thirty-one modems Data Communications magazine lab tested over a six thousand-foot local loop under controlled conditions ["V.34 Modems: You Get What You Pay For." Data Communications magazine, 1995]. Note that the different brands of V.34-Plus (ITU standard) modems did not perform identically under the three tests, although line conditions were the same throughout. V.34 modems are designed to have upload bit rates of up 28.8 kbps and download bit rates of up to 33.6 kbps.

Figure 4-7: Modem Test Variability among V.34 modem brands.

The top line shows the throughput for a (one-way) text download. Due to compression, throughput exceeds the advertised bit rate, the popularly defined "bandwidth" of the telephone line. The middle line of Figure 4-7 shows the two-way average throughput based on binary compressed files. Again, in every case but one, the observed throughput exceeds 28.8 kbps, but that is comparing an end-to-end throughput to the maximum operational data rate (advertised maximum bit rate). Finally, the bottom line shows the average two-way binary file transfer throughput. Notably, while every brand was advertised as a 28.8 kbps modem (able to transmit and receive), the top two had maximum average binary throughputs of 27.4 kbps. When the tests were repeated over different lines (30,000 foot rural local loops), results were as much as sixty percent below Figure 4-7 (when a transfer could occur at all) [Data Communications, 1995].

Figure 4-8 shows that the results for the most recent 56k modem standard V.90 indicate somewhat less variability among readings than the 1995 tests of Figure 4-7.

Figure 4-8: Variability among tested V.90 modems.

The one-way (download) text throughput rate (shown on the right y-axis) approached 120kbps on two of the modems shown. While no modem had a data rate of 56 kbps for downloads, the striped columns show that all were above 40kbps. On the upload side, most experienced just under or just over 30kbps data rates as shown by the solid columns.

When modems communicate over networks, the observed data rate and throughput also depend on network QOS variables. Figures 4-9 and 4-10 show how variability in telephone line noise, network congestion, and other factors prevent the advertised "bandwidth" of a modem from being observed in data rates in practice.

Instead of showing laboratory test averages, Figures 4-9 and 4-10 compare incoming data rates (experienced by the author) from the same web site (un-cached in memory) using the same modem and connection. Readings were taken minutes apart, using AnalogX NetStat Live version two software. In Figure 4-9, the average data rate was 13.5 kbps. For Figure 4-10, the average data rate was 17.9 kbps. However, in addition to the fact that in one case the same size file loaded many seconds faster, there were different accelerations in data rates as each transfer proceeded.

The results cannot be explained by any one factor. The differences may be due to an interaction among line noise, other simultaneous requests on the remote web site, the different routes taken by the individual packets of each transfer, ISP network load, and overall Internet congestion.

The computer modem examples have demonstrated several points. First, the theoretical bandwidth of a connection (in this case a telephone line), while often equated with the advertised bit rate (operational speed), differs from the throughput experienced by users and also from the measured data rate of the connection. Furthermore, differences due to manufacturer, line quality, and network conditions affect QOS metrics.

Figure 4-9: 285 KB File Download in 21 seconds on 33 kbps modem.

Figure 4-10: Minutes later, the same modem downloads the same file in only 16 seconds.

Until now, the focus has been on QOS metrics that are popularly mistaken for bandwidth. However, QOS metrics must be able to handle the full set of simple point-to-point and inter-networked connections of an agribusiness hypercommunications network (that may handle hundreds of simultaneous requests for voice, video, and data). Before more general QOS metrics (including many that are completely unrelated to bandwidth) can be explained, a reference model that is more general than the simple modem example is needed.

4.2.3 QOS Reference Model

At this stage, it is helpful to recall the three network engineering problems and the four objectives of network management from Chapter 3. Any network has combinatorial, probabilistic, and variational problems of engineering. These are sometimes loosely called possibilities, probabilities, and the positive and negative synergies between the two. The way an agribusiness and its hypercommunication vendors define and approach these three engineering problems determines how effectively communications occurs and how efficiently hypercommunications dollars are spent. Additionally, the way the four network objectives are achieved by the carrier influences the efficacy of the agribusiness's connection and the cost efficiencies of the carrier. While the modem example showed that not everything is under either party’s control, a QOS reference model will help isolate who controls what.

Instead of two modems, consider a more general agribusiness network such as that in Figure 4-11. Assume that the network is a true hypercommunications network that can carry voice, video, data, fax, e-mail, and Internet traffic. Communications occurs not only among and within offices, but also with customers, employees, and suppliers both nationally and internationally. Notice that the largest node (location) in the fictional agribusiness network depicted is at the headquarters in Loxahatchee, Palm Beach County. Another office is in Homestead, Miami-Dade County. Two smaller locations are in Chuluota, Seminole County and in Southern Highlands County. Suppose that six point-to-point links connect the hypercommunications traffic among offices. Each link could use one or more services and one or more technologies to carry traffic.

Figure 4-11: Links (connections) and nodes (locations) in an agribusiness network.

The HQ-Homestead, HQ-Chuluota, and HQ-South Highlands links are bold to indicate that a greater amount of traffic flows on these three main links than through the three others. To link any two locations in Figure 4-11, an end-to-end communications pipeline must be able to handle downstream, upstream, and two-way traffic. Users may communicate through computers, telephones, fax machines, or other DTE.

This is further illustrated by summarizing the elements of a single connection between two points as in Figure 4-12. The figure shows various CPE (Customer Premises Equipment) the agribusiness owns in Loxahatchee and in Homestead. On the Loxahatchee end, workstations, storage, and mainframe devices are shown on the uppermost part of the diagram. On the Homestead end, PCs are shown on the upper end of the local network. This configuration between the two locations suggests that traffic will mainly be downstream (from HQ) data traffic as data base information at HQ is accessed by Homestead users. However, data traffic between the two points could just as easily consist of an upstream flow at another part of the day when, for example, sales numbers or other reports are sent to HQ. Two-way traffic could occur between telephones at each location (as shown in the middle part of the local network on either end) or through a mix of computer and telephone traffic (shown in the lower part of the local network on either end). Figure 4-12 shows how varieties of devices (connected in local networks at both locations) allow a mix of traffic to flow between the locations.

Figure 4-12: Hypercommunications pipeline includes multi-directional traffic and various CPE.

However, Figure 4-12 is both too general and too specific to serve as a general model for use throughout the Chapter. It is too specific because (in addition to the direction of transmission) it mentions numerous user devices such as telephones, faxes, data storage, etc. Figure 4-12 is too general because it appears as though the communications pipeline between Loxahatchee and Homestead can only be a point-to-point link, rather than a more broadly defined network connection.

Figure 4-13 reveals six essential parts of a hypercommunications link between users at HQ and users at any other office without differentiating among services and technologies, or specifying network switching. The six parts are: carrier network (1), carrier POP (2), POP-edge access link (3), edge device (4), inside network (5), and user device or DTE (6).

Figure 4-13: Six essential elements of reference model of a hypercommunications link.

It is easiest to work from the inside out of Figure 4-13 to describe the six essential elements. Assume that two-way, upstream, and downstream traffic may be carried between the two points, though each type may be handled differently depending on the service or technology. By formulating the model this way, it is clear that bandwidth is not the only QOS characteristic an agribusiness will be interested in, because bandwidth describes the separate capacities of parts (1), (3), and (5). Each essential element also represents a possible threat to the security and reliability of communications.

The first essential element of a hypercommunications link is the carrier network (1). The carrier network, often called a backbone, is depicted as a cloud because there are many different paths and switching technologies that may be used to transport traffic through the backbone. Usually, the backbone is national or international in scope, carrying traffic for thousands of carrier customers. Bandwidth of backbone networks can range from T-3 (45 Mbps) and upwards over fiber optic cable, satellite, or microwave pathways. While the bandwidth of the carrier's backbone is likely to be more than adequate for the needs of individual customers, congestion can occur if the backbone is oversold or mismanaged by the carrier. Importantly, this central network is also the path over which communications with the outside world occur, though the reference model now is focused on Homestead to Loxahatchee. Carrier networks are covered in more detail in several parts of Chapter 4 including 4.3.4 (data and voice transport), ATM (4.8.3), SONET (4.8.4), and Internet transport (4.9.1). In many cases, carrier networks are already converged networks that handle both voice and data together, though often through parallel structures.

The second essential part of the reference model is the carrier's local POP (Point of Presence). POPs are locations where connections serving a particular area terminate so that traffic can be placed onto the backbone. For example, the POP that serves Homestead might be located in Miami and the POP for Loxahatchee might be located in West Palm Beach. The wireline (or wireless) distance from an agribusiness location to a POP can determines if a particular service can be offered. While each POP is a potential bottleneck, the DCE at a POP typically can handle far more bandwidth than a single customer needs. However, if a POP is oversold or mismanaged by the carrier an agribusiness may not be able to communicate. Carrier POPs are discussed in the context of 4.3 (wireline transmission) and 4.4 (wireless transmission). They appear again as the discussion turns to specific services such as CO technologies that support enhanced telecommunications (4.7.2) and Internet access (4.9.1).

The third essential element is the POP to edge device pipeline (3) that transmits messages between the each local POP and its corresponding agribusiness location. This element is often called the local loop or "the last mile", even though it may be far longer than a mile. Depending on the technology or service, the last mile may be wireline or wireless and be called a link, local loop, circuit, or path. With broadband signaling, the capacity of the connection from the business' edge device to the POP is shared with other customers (like a telephone party line), while with baseband or carrierband signaling it is dedicated to a single user. Depending on which is the case, there may be a potential for congestion. Access conduit is discussed in 4.3.1 and under infrastructure in Chapter 5. Access loops (the physical connection used to support various services) are given further coverage in discussions of the telephone infrastructure (4.3.2) dedicated circuits (4.7.3), and of circuit-switched digital services (4.7.4).

Fourth, edge devices at each location (4) enable that location to connect to the pipeline. Inside a business' wiring closet, also called the MDF (Main Distribution Frame), an interface is needed to link the carrier's transmission network to the network inside the business. From this point outward, all equipment is CPE (Customer Premises Equipment) because it is physically located at the agribusiness's site and owned or leased by the agribusiness. Edge devices can be interfaces or ports as simple as a telephone jack, or as complex as a T-1 NIU (Network Interface Unit) or CSU (Customer Service Unit). Edge devices must be compatible with the outside carrier equipment and the inside CPE equipment. Edge devices are most important as specific enhanced telecommunications CPE (4.7.1) and circuits (4.7.3 and 4.7.4) are covered. Specialized edge devices are used for private data networking and Internet services as well.

Moving out from the edge device in Figure 4-13, the fifth essential element in the reference model is the inside (local) network at each location. The local network controls how communications travel from the edge device to the user's device as well as how communications between people at that location travel. The local network includes conduit (wiring and cabling), network hardware, and network software. Regardless of the carrying capacity of the external parts of the hypercommunications link, the management, traffic level, and capacity of the local network can prevent an agribusiness from using the bandwidth it pays for or achieving desired data rates. Local network hardware and software must be compatible with the edge devices and with the carrier for reliable service to be expected. A general local hypercommunications network must be distinguished from a local area computer network (LAN) described in 3.5.3 and 3.5.4. However, voice-data consolidation technologies (4.5.4) and call center technologies (4.7.2) can be used along with Internet technologies to create converged networks. Local conduit is discussed in 4.3.1 for the wireline case and in 4.4 and 4.8.5 for wireless cases.

The sixth and last essential element of the QOS reference model is DTE. DTE include telephones, computers, fax machines, and other hardware directly used by people at either end to communicate. DTE must be compatible with local network hardware and software. Each device has its own individual capacity to send and receive communications. User devices on each end must either be compatible or have intermediate CPE to allow interconnection. In some cases, a single malfunctioning user device can slow or completely obstruct communications across the link.

Figure 4-14 ties these six parts together into a general QOS reference model to be used for the rest of Chapter 4. Note the three levels of the reference model: customer premises, access, and transport. The customer premises level is entirely under the control of the agribusiness at each location.

Figure 4-14: General QOS reference model.

The access level is the connection between the agribusiness and the carrier network from the edge device at the agribusiness to the network gateway at the carrier's POP. The transport level (as shown here) is a single carrier’s network, but it may be several interconnecting networks owned and managed by separate carriers depending on the distance from receiver to sender.

4.2.4 Fifteen Dimensions of QOS

Now that the reference model is established, the chief QOS dimensions of interest to agribusinesses can be considered. QOS is one of many acronyms in hypercommunications, but is perhaps the most important being one of the twelve essential hypercommunication terms mentioned in Table 1-1.

At first glance, QOS seems to be a simple concept, having to do with measurable degrees of quality customer satisfaction. However, hypercommunication service quality is affected by many issues such as: system reliability and redundancy, customer service and billing, the usefulness and availability of technical support, as well as a number of engineering parameters, software-hardware bugs and idiosyncratic events. QOS concerns apply to all three levels of the reference model (access, transport, and network), but most SLAs cover the transport or transport and access levels only. This is since the carrier cannot be expected to control situations that are on customer premises.

Often, each area has many specific parameters that may or may not be measurable. Indeed, the method of measurement, software package, level of measurement, periodicity, and who will do the measuring are themselves important issues. However, there is not enough space here to delve into the methodology of measurement by dimension.

Table 4-3 introduces fifteen QOS dimensions of greatest importance to agribusinesses. The first six QOS dimensions (bandwidth, bit rate, data rate, throughput, delay, and jitter) have already been introduced in 4.2.1 and were covered briefly in the modem example in 4.2.2.

Table 4-3: Fifteen QOS dimensions
 

Dimension	Description & Level(s)	Example
1. Bandwidth	Maximum capacity of a link (Access, Transport, & CPE).	3200kHz analog telephone line has up to 56 kbps possible download and a maximum 33.6 kbps upload capacity.
2. Throughput	Transfer speed noticed by users.	Why does it take so long for something to display?
3. Bit Rate	Variable operational speeds of DCE.	Is DCE flexible enough to adapt to many possible speeds?
4. Data Rate	Actual speed.	How fast did a transfer occur?
5. End-to-End Delay	Time it takes for a bit to go from sender to receiver.	1000ms is too long for voice calls, may be fine for e-mail.
6. Jitter	Variation in delay.	Why does the video come and go?
7. Connection Establishment Delay	Time it takes for connection to establish. (Access)	Lengths of time it takes a modem to dial and connect so session can begin.
8. Connection Establishment Failure Probability	Probability that a given connection attempt will not establish. (Access)	Chance that modem cannot obtain connection (busy modem bank, etc.)
9. Network Transit Delay	Time from transport sender to receiver POP. (Transport)	Varies depending on network load, management.
10. Error Rate	Fraction of lost or garbled messages in a sample period.	How often is a sent e-mail not received?
11. Security	Ability of others to intercept or copy messages or gain access to network.	Can messages be intercepted or modified? Can intruders fabricate identities or masquerade as users to gain entrance to system? Is system prone to attack?
12. Priority Classification Availability	Ability of certain kinds of traffic to be sent and received first.	If the company president needs to send an urgent message, can it be bumped ahead of routine traffic?
13. Resilience	Chance that any network level will spontaneously fail.	Can lines be accidentally cut or experience periodic downtime?
14. Environmental Specifications and Safeguards	Likelihood that power failures or weather events will affect communication.	Do carriers have emergency backup generators? Will a thunderstorm or solar flare interrupt quality?
15. Overall Failure Probability	Fraction of time any QOS dimension fails to reach standard.	Probability of at least one QOS metric being violated.

Sources: Maguire, 1997; Sheldon, 1998; FitzGerald and Dennis, 1999.

The seventh QOS issue, connection establishment delay, refers to the length of time it takes to establish a connection. Like many of the other dimensions, it depends heavily on the user's perception, the specific service, technology, and DCE and DTE. The simplest example is the length of time it takes for a modem to dial and establish a satisfactory connection to the Internet. It also is applicable to the length of time it takes a telephone call to complete. Some services (such as DSL, cable modem, and T-1 dedicated circuits) are "always-on" and hence, have no connection delay. The eighth QOS category, connection establishment failure probability, refers to the probability of getting a busy signal when a modem dials AOL, for example. In that case, there has been a failure to reach the Internet. For other services, the definition is similar.

The ninth dimension of QOS, network transit delay, refers to the average delay in ms that it takes for a bit to transverse the carrier's network. Unlike end-to-end delay (which is observed), network transit delay is a statistical average that does not count delay resulting from access loop or customer premises conduit and equipment. The carrier may not have control over those other forms of delay, but will have control over transit delay. Hence, most SLAs or carrier statistics that describe delay refer to transit delay (transport level) only. Similarly, most jitter statistics refer to transit jitter, rather than jitter based on end-to-end delay. It can be important as to whether the transit delay and jitter measurements are averages between two points, weighted averages across an entire network, or measured in some other way.

The tenth dimension, error rate, may be a residual measure (on average equal to zero) for some services and an efficiency measure for others. The specific transmission technology and switching method determine the importance of the error rate. In packet switching, the error rate is a background rate that may slow transfers, but switching redundancies and error checking routines are able to recover or correct errors in most cases. Even if the error rate is high across a network such as the Internet, the communication may appear to have been error-free from the user's perspective. Other errors include lost, misdirected, or duplicate e-mails.

Security, the eleventh QOS dimension, is perhaps the most difficult to measure. Security refers to whether others are able (or may be able) to intercept or copy messages or to gain access to network. A security failure can occur at the message, user, or system level. Security failures on any level can result from actions taken within a business, from inside the carrier's network, or from outside.

A security failure on the message level refers to whether outside parties can intercept, modify, or copy messages routinely or intermittently. User level failures refer to whether an outside party can spoof or fabricate the identity of a user and use the communications system, or masquerade as a valid user and gain access that way. A third kind of security failure is a system level failure. System level failures include hacker-vandal attacks and viruses. Hacker attacks begin when outsiders spy on a system to gather confidential information in order to gain later unauthorized systemwide or administrative access to it. Vandals are hackers who maliciously damage systems. Vandals may attempt to crash the system, destroy stored information, or prevent valid users from using the system. Viruses (which do not need to be placed by hackers or vandals) are malicious or annoying software instructions that can do anything from disable a system to cause inconvenience to a single user.

Measuring security failures or violations can be difficult because they can be hidden easily and may not be discovered until after damage has been done. Hardware and software firewalls, security audits, and other methods are used to try to prevent, deter, or catch violations. It is important that a company and the carrier have a security policy that defines violations and prevents vulnerability even to a single point of failure. Vulnerability to a single point of failure means that one person or station (DCE and DTE) could compromise the entire system.

Another QOS dimension is priority classification ability. Priority may be established on a per message, per connection, per user, or a per service basis. The best price for a particular message or service request depends on capacity limitations on how many messages (or how much total traffic) may be sent at once, where, and in what form, and by whom.

The simplest example is the case of a business telephone network with line reduction. Under line reduction, the number of simultaneous incoming and outgoing calls is limited by the number of telephone line equivalents, rather than the number of employees or telephone sets. Since the purpose of a network is to share resources and lower costs it would defeat the purpose to allow each employee their own telephone line and computer, or to allow every telephone its own exclusive line. However, if all lines are busy, it may be that some users (such as the CEO) need guaranteed placement at the top of the waiting queue or the ability to place a call instantly if the network is full. Voice traffic can be prioritized in several ways.

Prioritization can be more difficult for data traffic or unified data-voice traffic. Certain services and technologies allow the carrier or customer-subscriber to establish priority traffic levels. The highest levels can be carried (for a premium price) at high speeds and superior reliability, leaving other levels to be sent later or get the electronic equivalent of a busy signal. For example, video and voice traffic may require real-time, low delay, and low latency connections that would be a waste of resources for e-mail or routine data transmissions.

Resilience is the thirteenth and possibly most difficult to predict QOS dimension. Resilience refers to the chance that any element of the network will spontaneously fail, causing the complete loss of a particular service(s). Resilience encompasses system reliability. While operational failure probability is concerned with the probability that a particular call or message will fail to achieve certain benchmark standards (such as annoying interference or repeated delay), resilience concerns a total loss of service or outage.

Outages can be complete (network wide) or localized (several connections or customers). Outages can also be random, intermittent, or singular. Singular (one time or episodic), complete outages can result from easily diagnosed causes such as accidental construction cuts of an optical fiber (causing loss of service over an entire carrier network), or they can result from complex equipment failures. As the name suggests, random events occur with no particular frequency and can result in localized or complete interruptions, usually for short periods. Intermittent events occur without apparent regular order, but are often due to complex software-hardware interactions that create hard-to-diagnose sequences of events that trigger partial failure. Intermittent events are more likely to be localized.

Closely related to resilience are environmental specifications and safeguards. Environmental specifications represent the expectations of engineers regarding the operating ranges or time-to-failure of DTE, DCE, and conduit. Environmental specifications include the length of continuous operation, temperature range, humidity range, and the resistance to environmental factors of specific equipment. Environmental standards of electronic equipment also include how well equipment can withstand lightning strikes, electrical spikes or jolts, and other hazards that can cause permanent or temporary failures of components or entire systems. Many wireless transmission technologies require the right atmospheric conditions to operate at peak performance or partial performance losses can occur due to cloud cover or complete interruptions can result from rain, wind, and electrical or solar storms.

Environmental safeguards include systems designed to handle indoor problems such as power outages, emergency hurricane operation, fireproofing, and workplace as well as outdoor environmental concerns. Safeguards may be needed on both the customer premises and carrier network. Some of these include emergency backup generators, surge protection, and redundant connections in case of failure of the main system.

Redundancy refers to how well system backups and contingencies are able to restore benchmark service using secondary or tertiary networks or carriers. The Internet, for example, is a network that was originally designed to remain functional even in case of global thermonuclear war due to built in redundancies. However, it is little consolation to an agribusiness if the Internet is itself still functioning when their ISP's modem bank has broken down, denying them access.

The overall failure probability is the chance that at least one of the fourteen other QOS dimensions will fail to attain the standard set for it. Overall failure may be thought of as the chance that anything will go wrong during a particular period. The probability of overall failure is derived using probability theory to obtain estimates of all independent and dependent events associated with each dimension.

4.2.5 QOS in Practice

Now that the fifteen dimensions have been sketched, it is important to understand more about how they apply in practice. A typical agribusiness may have multiple telephone lines, multiple locations, multiple users of the data network, and other variables that affect how QOS is conceived and measured.

Table 4-4 gives an overview of how QOS dimensions can affect agribusinesses in several ways. In the first column, each dimension is categorized in terms of the three core engineering problems and the four technical objectives of network managers from Chapter 3. The following codes are used into indicate the three core engineering problems: combinatorial (C), probabilistic (P), and variational (V). For the four network optimization objectives, the codes used are: sending rate control (SRC), conduit signal modulation rate (SMR), overall network optimization (ONO), and receiving flow control (RFC). Table 4-4 is a general but subjective guide to the relative importance of QOS dimensions.

While pricing may be based on bandwidth (a capacity constraint), users are directly affected by throughput and data rate instead. Indeed, the data rate or bit rates are constraints on the value of a service, along with reliability in general. Throughput is especially important in the pricing of DTE. For example, computer speeds and memory capacities have a direct relationship to what users actually experience as throughput. The bit rate affects the pricing of DCE such as modems and DSU/CSUs. When modems are advertised at 56 kbps, this only means they are capable only of that as a maximum operational rate. For larger agribusinesses with many locations, the network transit delay of the carrier may be important to price and SLA negotiations.

The kinds of traffic most affected by any QOS dimension also involve many details such as message primitive, traffic mixture, and network load. Generally, interactive services such as voice or video are most sensitive to delay and jitter because they are real-time or conversational in nature. Not surprisingly, connection-establishment delay and establishment failure probabilities influence all kinds of traffic carried by services that require the establishment of a connection. Internet traffic (web pages, FTP, e-mail, Intranet, etc.) and computer network traffic are listed as most affected by security, though most firms have a higher dollar loss from misuse of long distance telephone calls.

Table 4-4: Importance of various QOS dimensions
 

Dimension	Engineering & network area	Role in pricing	Traffic Most Affected	Impact of violation on user or firm
1. Bandwidth	ONO	High	Data	Theoretical
2. Throughput	ALL	High for DTE	Uncompressed Data	Possibly high
3. Bit Rate	V; SRC, RFC	High for DCE	Data	Indirect
4. Data Rate	ALL	High	Data (video and graphic)	Possibly high
5. End-to-End Delay	C,V; ONO	Low	Interactive (voice, video)	Moderate
6. Jitter	V; ONO	Low	Interactive (voice, video)	Moderate
7. Connection Estab. Delay	P; SRC, RFC	Low	Dial-up Internet, connection-oriented services	High
8. Connection Estab. Failure Probability	P; ONO	Low, causes carrier switching	Dial-up Internet, voice, other connection-oriented services	High
9. Network Transit Delay	C,V; ONO	Moderate	Interactive (voice, video)	Moderate
10. Error Rate	ALL	Low	Data	Usually Low
11. Security	ONO	Low	Internet and data	None to Extreme
12. Priority Classification	C; ONO	If available determines pricing	Voice, Interactive, Mission-critical data	None to Serious
13.Resilience	P; ONO	Low	All	Extreme
14.Environmental Specs. And Safeguards	P; ONO	Low	Mainly to preserve data in emergency	Varies by user
15.Overall Failure Probability	ALL	Low	Varies by event	Varies by event

 

The impact of problems in each dimension on individual users and firms are shown in the last column of Table 4-4. Some firms have been destroyed by hacker attacks on un-backed up data, or by revelations of proprietary information and conversations to competitors or the public. Resilience is especially important to the firm, because a violation conveys the complete inability of some or all parts of corporate communications to occur. A business that relies on telephone calls from customers can hardly afford to have calls lost.

Often, when carriers advertise ninety-nine percent or 99.9 percent reliability, they are speaking about resilience. However, with 8.7 thousand hours in a year, a 99.9 percent reliability guarantee allows almost nine hours of total loss in communication to occur before a hypercommunication carrier can be said to have violated that agreement [REA, 1992, p. 1-13]. If those nine hours come during harvest or a heavy season for an agribusiness, (indeed some failures may be most probable at high use levels) they can be devastating. Similarly, if ninety-nine percent reliability is quoted, over 87 hours without service are permitted. Except in rare cases, business losses due to a communications failure are not covered by SLAs, though part of the carrier's bill may be.

There are other QOS dimensions besides those covered. For instance, there are a host of engineering parameters that are set to establish service benchmarks. A carrier has a tradeoff between keeping costs and prices down and ensuring customers a high probability that the system will not be so congested that it is unavailable. The conflict between lowering costs and losing customers is inherent in hypercommunications production. Other engineering benchmarks include intermediate DCE settings that enable interconnection variances below the j.n.d. (just noticeable difference) of consumers or that affect only a proportion of the customer base. Hardware-software bugs and system downtime are frequent possible threats.

Other QOS customer concerns include customer service, custom billing, and technical support. The methods by which customers report problems or get information about system outages (along with how rapidly problems are corrected) are perhaps most important. Billing concerns and the availability, efficacy, and cost of technical support are other QOS concerns. Access by customers to user-friendly technical support is a potential source of carrier revenue either through keeping customers from leaving in frustration or through billing for tech support. However, technical support is a carrier cost as well because twenty-four-hour, seven-day service is expensive to provide, especially when some customers overuse tech support.

Before concluding the section on QOS in operation, five topics merit brief coverage. First, any measure of speed depends on the acceleration allowed by various protocols based on file size and type. For example, streaming media protocols (used for voice calls, audio, and certain compressed video files) use a fraction of available capacity to transmit communication. Where an entire video or audio program is to be transferred (such as over the Internet), the protocol bit rate prevents the data rate from rising to consume all available bandwidth. Files are sent not as a unit, but as a bit limited stream so the download will occur within a fraction of capacity.

Other kinds of transfers experience limitations on acceleration. Limited acceleration can mean that data rates will never rise to meet capacity. Many businesses have short bursts of traffic with relatively small individual data (file) exchanges. Hence, a firm with a high total traffic volume is punished by limited acceleration if it rarely exchanges multi-megabit or gigabit data files. Limited acceleration means that if large binary data files are transferred, only then does the protocol between sending DCE and receiving DCE allow the bit rate to change to accelerate to the available speed within a channel.

Two figures demonstrate how acceleration works in practice. In the first figure, (Figure 4-15), the data rate accelerates quickly and remains at 1.4 Mbps (1400kbps) during most of the file transfer. In Figure 4-16, the bit rate does not limit the acceleration in data rate, so that the larger the file, the faster the speed becomes. Clearly, it may matter if a particular carrier, CPE, DCE, or service supports one or the other type of acceleration. In some cases, the highest speeds are reserved for the transfer of large files only, rather than for other kinds of communication.

Figure 4-15: Bit rate is fixed so that data rate rises to and holds a certain speed.

Figure 4-16: Bit rate does not limit acceleration in data rate.

A second operational topic concerns the profile of total traffic through the business day. Rather than measure the speed of a single transfer as in the last two figures, QOS metrics are used to assess whether too much or too little capacity has been purchased by looking at all traffic combined. Many circuits (such as frame relay) use two ways to price: the channel rate and the CIR (Committed Information Rate). The channel rate is a data rate ceiling, while the CIR is a guaranteed data rate floor. To save money, an agribusiness may choose a low CIR, hoping that other customers of the carrier will not congest the circuit to obtain the higher channel rate without paying full price. However, if other customers of the carrier had needed the difference between the channel rate and CIR, the budget-minded agribusiness would have been denied it.

Figure 4-17 shows a capacity of 1.544 Mbps, a common limit encountered with frame relay, T-1, and ISDN-PRI circuits. The maximum, minimum, and average hourly traffic levels of a representative weekday (data rate of all users over a connection) are shown. In this case, the CIR is 256 kbps. The average maximum hourly traffic from or to the agribusiness exceeds the CIR from just after 8 a.m. until 9 p.m. The profile could be the result of a mix of voice (lumpy increments) and data traffic (bursts), but the hourly averages do not show the differences between the two traffic types very well.

The low average hourly traffic line (bottom bold line) shows that even at low usage levels, the CIR is exceeded around 11:00 a.m. and from 16:30 to about 18:30 in the afternoon. The maximum hourly traffic rate is at the capacity from around 16:00 to 17:30, while the average hourly traffic rate has a morning and an afternoon spike at over 400kbps and over 600 kbps, respectively. These results suggest that a greater CIR should be obtained (unless the firm wants to risk connection failures) or that automated traffic must be spaced more widely throughout the day, or both. Network planners often base the channel rate on the maximum busy hour, but the optimal CIR depends on the carrier’s other customers.

Figure 4-17: Example of hypercommunications traffic in a business.

However, as Figure 4-18 reveals, the average hourly rate masks more dramatic minute-to-minute averages. Figure 4-18 focuses on part of the business' peak time (busy hour) in the late afternoon, from 16:30 to just after 17:00. While the average hourly figures suggest that maximum average needs exceed the 1.544 Mbps capacity for almost two hours per day, the minute-to-minute figures suggest that only about eight minutes does this occur. Indeed, a close examination of the minute data reveals that only eight minute-long periods have ever had averages that reached 1.544 Mbps. Some technologies and services allow extra bandwidth to be purchased above the contractual CIR and channel rates. However, a twenty-four hour advance notice may be required for such BOD (Bandwidth on Demand) offerings.

Figure 4-18: Minute-to-Minute Variability may be greater.

As the regular workday closes, traffic dips to low levels. However, just before 17:00 hours, traffic rises again. This gap represents the time of day when the IT department assumes that "normal" operations have decreased enough that automated, routine "end-of-day" data transfer can begin. The problem may be that rather than "needing" more bandwidth, IT personnel schedules and automation routines may need to be more spread apart, since the connection has plenty of extra capacity in late evening, overnight, and early morning hours. Importantly, there can be connection establishment delays due to being over the CIR that can also be involved.

Finally, Figure 4-19 demonstrates delay and jitter. The X-axis depicts the twenty hops an Internet packet takes to travel from Fort Lauderdale, Florida (Plantation) through Atlanta and Sydney, Australia to reach the Australian Government's Antarctica site at Mawson, Antarctica.

Figure 4-19: Example of Jitter: Variation in Delay, Antarctica from Plantation, FL on 12/16/99.

The bars denote the independent maximum, average (mean), and minimum delays (round-trip between Plantation and each intermediate router) in ms using the Ping Plotter ping-trace program from a sample of 1000 cases taken on 12/16/1999. The total delay statistics to Antarctica and back were 3520ms for the maximum, 554ms for the average, and 437ms for the minimum. Jitter can be measured in relative or absolute terms; for Mawson, 330 was the standard deviation with a standard error of 14.9.

Clearly, most agribusinesses do not require connections to Antarctica, but similar results can occur to places as near as Mexico or the Caribbean. However, the jitter example demonstrates three things. First, delay is sensitive to distance. Hence, the more distant a connection, the longer delay will be. Second, delay is sensitive to the service used. Satellite connections especially (used in the hop from SFX, San Francisco, to Australia, and in the hop from Hobart, Tasmania to Antarctica) introduce delay simply because of the distance from earth to ground and back again. Third, jitter is not inherently sensitive to distance. If the agribusiness had required connection through the first Atlanta hop, jitter would have been greater than if the connection had been in Australia. This is symptomatic of congestion at that hop. Fourth, in many kinds of service (especially Internet-based services), both the carrier and the customer have no control over network routing or the number of hops. Each hop increases the chance that a communication will experience a QOS violation of some kind.

Unlike bandwidth, jitter is a constantly changing measurement that depends on the measurement program used, time of day, general network load, etc. Therefore, different readings would be observed on other days of the week, at various times of day, and with other software measuring programs.

A fourth operational topic concerns the tradeoff between regular file transfers and streaming file transfers as illustrated by Figures 4-20 and 4-21. In Figure 4-20, three kinds of files (text e-mail, web page, and graphic) are shown by their size in KB (KiloBytes) on the left axis, represented by columns. The shaded area shows the fastest length of time in seconds (on the right axis) that a modem (56 kbps) would take to download each file completely.

Simple text e-mails and web (HTML) page content (text and light graphics) take less time since they are smaller files than a graphic file of over 200KB. Each kind of file requires a complete file transfer to become visible at the destination, so the capacity and data rate help determine how soon communication occurs. Both the download time and the data rates vary.

Figure 4-20: Non-streaming file transfers by speed and download length.

Figure 4-21: Data rate and file size of a one-minute download by protocol.

For real-time or mixed traffic such as streaming media and telephone calls, there is another way to view the situation by allowing the data rate and time to remain fixed. Figure 4-21 shows the capacity needed to download a one minute voice call (using two compression schemes), a one minute streaming audio .WAV file, a one minute .RM (streaming) compressed video, and a one minute .MPG (non-streaming) video. Here the tradeoff is among competing conversion protocols, each of which requires a fixed data rate (on the right axis) over an entire minute to transmit the file size (shown in KB on the left axis).

In one minute, a 577 kbps connection could carry one MPG video, twenty-seven RM video files (21.33 kbps each), six WAV voicemails (86.6 kbps each), nine PCM (G.711) telephone conversations (64 kbps each), or thirty-six ADPCM16 telephone conversations (16 kbps each). These different uses of the same bandwidth are at the center of converged network allocation. Obviously, the video quality in frames per second of the MPG are likely to surpass that of the Real Media RM protocol, just as the PCM G.711 telephone quality will typically surpass that of the ADPCM compressed call.

Recall that throughput refers to the ability of CPE and DTE at both ends to transmit and receive compressed files. The rate referred to above would be an end-to-end throughput rate because coding shortcuts compress messages into fewer bits, enabling faster transport. The savings in speed can be dramatic, but they are due to software rather than increasing the data rate of the communications pipeline. The difference is apparent when two video files (MPG and RM) are compared in Figure 4-21. The RM file designation was developed by Real Audio, so it requires a particular software package to be installed on the each end. The RM video will have fewer frames of video per second than the MPG. However, the RM video stream offers equivalent (or superior) sound and will be seen almost immediately by the user who would have to wait for transmission of the entire MPG file to see it.

The last operational point to cover is symmetry. Figure 4-22 reveals how dramatic the differences between wireline and wireless hypercommunication technologies can be both in terms of advertised upload and download speed among technologies.

Figure 4-22: Bandwidth symmetry compared among wireline and wireless technologies.

The dashed horizontal grid lines on the y-axis of Figure 4-22 are units of 1.544 Mbps (T-1 speeds). From left to right, the technologies delivered through copper conduit include: DSL Lite (1.544 Mbps download, 512 kbps upload), ADSL (10 Mbps, 768 kbps), ISDN-PRI and T-1 (1.544 Mbps, symmetric). Hybrid fiber-coax conduit can deliver VDSL (version 1, 13 Mbps, 2 Mbps) and Cable modems (3 Mbps, 400 kbps). The technologies delivered by fiber optic are T-3 (44.736 Mbps, symmetric) and OC-1 (51.840 Mbps, symmetric), though higher OC (SONET) speeds are available. The remaining technologies shown are wireless. Wireless technologies include mobile GSM (symmetric, 270.8 kbps), MMDS/MDS (1,544 Mbps, 768 kbps), 2.4 GHz (1.544 Mbps, symmetric), direcPC satellite (2 Mbps, 33.4 kbps), other satellite (400 kbps, 33.4 kbps), and LMDS upperband (27 Mbps, 3.5 Mbps).

Figure 4-22 reveals several patterns that will be seen again as Chapter 4 unfolds. First, fiber optic conduit surpasses wireless and other wireline conduit in overall speed and symmetry. Second, many of the faster technologies (wireless and wireline) are asymmetric, offering faster download than upload speeds. Third, none of these numbers can be taken as indications of actual data rates that will be achieved by agribusinesses in practice. With the exception of fiber optic conduit, both wireline and wireless technologies exhibit larger asymmetries, especially as speed increases. Finally, within each technology, dramatic variations from the speed estimates shown can occur because of scant real-world data and differences between carrier sales claims and actual experience [FCC 99-5, 1999].

To conclude, some argue that the trend towards uniform digitization means that bandwidth is becoming a commodity, based on the bit as a unit. However, such a view ignores six important points to agribusiness. First, not all bits are equal because information does not equal data. Furthermore, the transmission of bits (whether data or information) does not ensure communication. Third, no business advantage can be obtained if a particular location has insufficient digital infrastructure capacity so that needed hypercommunication services are not available. Fourth, the transmission of a message from a sender to receiver depends on message primitive, message type, and other factors discussed in Chapter 3.

Fifth, a real-time video cattle auction has different capacity and speed requirements from a text e-mail message, a web page, or a telephone conversation even if each is digital. It is often stated that all a business needs to do is to decide on how much "bandwidth" it "needs", and then hypercommunication needs will have been taken care of. Capacity (along with speed, reliability, latency, and how well the hypercommunication carrier manages the network) is important. However, when bandwidth is used (as it so often is) as a synonym for speed or as a commodity a firm buys in the market, other more specific QOS dimensions have to be controlled for. It can be a costly mistake to compare prices, services, technologies, and carriers based only on bandwidth.

Finally, understanding a set of QOS metrics rather than bandwidth alone can save agribusinesses from unexpected problems and extra costs. The kinds of QOS metrics that a particular agribusiness would agree to in an SLA with a carrier for access and transport differ from the QOS dimensions it would use for its own LAN.

The next three sections cover hypercommunication technologies applicable over all kinds of services. Wireline transmission technologies (4.3) carry hypercommunication signals over several kinds of wire conduit in their journey from sender to receiver. Conduit types include copper wires, cables, and fiber optics. A number of specific enabling technologies (such as DSL, ISDN, and cable broadband) support wireline transmissions. Wireless transmission technologies (4.4) carry hypercommunication signals over airwaves. Wireless transmissions use RF (radio frequencies), microwaves, infrared, and other methods as conduit. Specific enabling technologies support a range of services over wireless as well. Then, section 4.5 covers support services, and facilitation and consolidation technologies.

Three technologies are used to transmit hypercommunication signals from sender to receiver. The technologies that enable communication signals to travel over wire, cable, or fiber are known as wireline technologies. Wireless technologies exclusively use unguided media such as radio waves. The third way to transmit signals is over a hybrid system, a combination of wireline and wireless technologies. For example, a long distance telephone call may use microwave transmission over the carrier transport network, but rely on wireline technologies at the access levels at both ends.

The discussion in this section assumes that the communications pipeline is entirely wireline from end to end. During the wireless and facilitating technologies sections (4.4 and 4.5), wireless and hybrid wireline-wireless networks are considered. It is important to realize that most of the hypercommunication services covered in sections 4.6 through 4.9 can be provided through either wireline or wireless technologies.

The discussion in this section covers four topics. Sub-section 4.3.1 discusses guided media or conduit, the wire and cable that carry hypercommunication signals from sender to receiver. The next section (4.3.2) covers the physical plant of the (ILEC) local telco, which already supports an array of services beyond POTS. Then in 4.3.3, the cable TV (cableco) infrastructure and so-called dark fiber plants of electric and other utilities are covered. Large or well-located agribusinesses may be able to connect directly to the backbone and transport networks (4.3.4), bypassing telco and cableco access levels entirely.

The physical plant or infrastructure includes conduit, junction boxes, manholes, MDFs, and various kinds of DCE including routers and switches. In a converging market, wireline distribution technologies can carry services beyond those offered by traditional monopolies associated with each infrastructure. For example, an urban or suburban agribusiness could easily use the telco "plant" to carry its data and Internet traffic, the cableco plant to carry telephone, or even the electric utility's infrastructure to carry data traffic. Convergence means that every infrastructure will be able to carry every kind of traffic. In all cases, the agribusiness needs to buy or lease DCE, DTE, and conduit.

4.3.1 Conduit

The skeleton of any wireline communications network is conduit. There are three chief kinds of conduit in common use: two-wire (and four-wire) twisted pair copper loops, coaxial cable, and fiber optic cable. Within each type, there is considerable variability in the speed, capacity, and distance supported by various sub-categories. While many QOS metrics are constrained by physical properties of conduit, new technologies are constantly being introduced that can squeeze faster speeds from existing conduit. Additionally, compression technologies and new conduit categories can extend distance, throughput, bit rates, and data rates.

Figure 4-23 repeats the QOS reference model, showing again the three parts of the communication path between two points to reveal the need for specialized wireline technologies and conduit.

Figure 4-23: Wireline section coverage by reference model.

Conduit is the only topic here in section 4.3 that bridges all three levels shown in Figure 4-23. First, the customer premises side of the demarcation point has conduit for the inside or local network at the agribusiness. Second, there is conduit in the access level between the agribusiness and the carrier's POP. Third, there is conduit within the transport level (carrier network).

Since specialized conduit exists at each level, it is easy to confused the copper twisted pair cable used in the telephone access network with the copper twisted pair used as customer premise conduit for computer LANs. Furthermore, no level uses a single kind of conduit alone. For example, the transport level may transverse thousands of miles and several carrier networks in the case of long distance telephony. When a carrier other than the ILEC provides a communications path at the transport level, there is a handoff point from the ILEC (which provides the access loop) to the other carrier (such as an ALEC, ISP, or IXC). The handoff point may be at the local POP or inside the ILEC's transport network. Hence, the transport level can consist of more than one carrier's transport network. The Internet backbone, for example, is a network of transport networks.

The first way wireline transmission is accomplished is by insulated copper conduit, either two-wire twisted pair or four-wire twisted pair (Quad). Both are used in the access layer to traverse the last mile between a subscriber's premises and the location where the carrier's network begins, the POP in Figure 4-23. Many wireline services in addition to POTS can use the copper wire plant built by the ILEC to connect to a local wire center, CO, or POP owned by the ILEC.

Competitors of ILECs such as (ALECs) use the ILEC's local loop to transmit communications to their own POP switch or to a POP co-located at the ILEC’s CO. Long-distance carriers (IXCs) also use the ILEC's local loop so customers can access IXC networks. Facilities-based ALECs and IXCs use their own transport network for PSTN traffic. Non-facilities based ALECs and IXCs lease transport networks from other firms. For non-telephony services such as Internet and private data networking, the ILEC’s local copper loop connects to a POP owned by an ISP (or other carrier) or to a server co-located at the ILEC’s CO. Internet and data traffic normally travel over a transport network that is separate from the PSTN.

Twisted pair may carry analog or digital signals. The bandwidth (capacity) of twisted pair depends on length (distance traveled), category, and wire gauge. The gauge of the wire refers to its thickness, with a 24-26 gauge being the typical used for telephone. Ordinary telephone twisted pair can achieve a maximum data rate of four Mbps for a distance of up to ten kilometers (6.2 miles). Category 5 or 6 UTP (Unshielded Twisted Pair) copper used for LANs on customer premises can achieve much higher data rates, but for considerably shorter distances. Wiring standards are defined for the six categories of twisted pair in Table 4-5.

Table 4-5: Copper twisted-pair wire categories.
 

Category	Uses	Bandwidth (data rate)	Distance	Cost
Category 1 (1 pair)	Pre-1983 installed telephony (access)	3.1 Hz (28 kbps)	5 miles	NA
Category 2 UTP (2 pair)	Telephony (access), legacy data (CPE)	2 MHz (to 4 Mbps)	6.2 miles	$0.11/ft. (bulk)
Category 3 UTP (4 pair)	Analog or digital telephony CPE, Ethernet (to 10 Mbps), Token Ring (to 16 Mbps)	To 16 MHz (to 45 Mbps)	1000 ft. run	$0.11/foot (bulk), $0.21/ft. (plenum)
Category 5 UTP	Standard for Ethernet horizontal (to desktop), ATM	To 100 MHz, (to 155 Mbps)	300 ft. run, 800 ft. total	$0.12-$0.17/ft. (bulk), $0.32/ft. (plenum)
Enhanced Category 5 UTP	Higher quality Cat 5, minimizes crosstalk	200-350 MHz (to 200 Mbps)	1000 ft.	$0.17/ft. (bulk), $0.40/ft. (plenum)
Category 6 UTP	Gigabit Ethernet	350 MHz and up (To 1 Gbps)	1000 ft.	$0.15-$0.22 ft. (bulk), $0.35/ft. (plenum)
STP	Token Ring	4-16 Mbps	1000 ft.	$0.27/ft. (bulk)

Sources: Tower, 1999, Sheldon, 1998.

In reading Table 4-5, realize that each row in the table supports the features of the category above it. Over sixty percent of U.S. buildings have Category 5 as their local conduit. Category 2 is typically found on the access level only, while categories 3 and above are strictly for use on customer premises.

Two-wire and four-wire twisted pair (quad) may differ in several additional ways. Quad telephony wiring is often thought of as the extra wire pair that accompanies the regular telephone two wire pair going into homes so that an additional line may be added. Quad twisted wire is also used for long analog loop distances due to its easy use with amplifiers, on customer premises, or in the digital access loops to support high-speed services such as HDSL (High Data rate DSL) [Paradyne, 1999, p. 23; Schlegel, 1999]. Copper wire is used for both baseband and carrierband transmission technologies on customer premises and in the access level.

Coaxial cable is another kind of wireline conduit. A hollow outer cylindrical conductor of solid copper encloses a single inner wire conductor. The cable can be between one and one-half inch in diameter. Coaxial cable (coax, for short) has a bandwidth of up to one GHz that can theoretically support data rates of up to 400-500 Mbps over longer distances than twisted pair.

At one time, coax (able to support from 600 to 10,800 voice circuits per cable) was regularly used in the telephone transport level. Now, while coax is still used in the telephone transport network leading out of rural areas, it is most likely to be found on customer premises. Coax is used intensively at the access level by cable TV carriers to carry video, voice, and data. Coaxial cable is used to transmit data, voice, and video using baseband and broadband transmission technologies. Coax can transmit either digital or analog signals. Coaxial cable is less likely to have cross talk or interference than twisted pair. Coax can be used at higher frequencies and data rates than twisted pair can as well. For example, the L5 CCITT coax specification calls for an analog cable (with operating frequency of 3.12 to 60.6 MHz) capable of carrying 10,800 voice channels. However, the T-4 digital designation can carry 4,032 voice channels with a data rate of 274.176 Mbps [Maguire, 1997, module 5, p. 27].

To transmit digital signals effectively over longer distances with coax, repeaters are needed. A data rate of up to 800 Mbps can be achieved with repeaters spaced every five thousand feet. The three main types of coaxial cable are RG-58 A/U (Thinnet, stranded wire core), RG-58/U (Thinnet, solid wire core), RG-59 (Thicknet, cable TV and broadband), and RG-62 (ArcNet). CATV cable can be further categorized by format: subsplit, midsplit, highsplit, or dual. Each of these four formats is 75 Ohm coax with 75 Ohm terminators. Bandwidth for subsplit ranges from 5-30 MHz (inbound) and 54 to 500 MHz outbound up to more recently deployed dual with a 40 to 400 MHz inbound and 40 to 400 MHz outbound bandwidth [Maguire, 1997, module 6].

Cable types cannot be mixed on a network without intermediate devices. Through the use of "resistance to ground", coaxial cable is often called a balanced transmission line because the conductors have equal resistance per unit length and equal capacitance and inductance between each conductor and ground. Additional advantages of coax are that it is flexible and easy to install and provides better resistance to electronic interference than twisted pair. Disadvantages include the cost (more expensive than UTP), the difficulty in changing configurations, and the requirement for repeaters to cover longer distances. Thinnet is generally not suitable for use between buildings. Both coax and copper twisted pair can be tapped, presenting something of a security risk [Tower, 1999].

Fiber optic cable offers very high bandwidth, measured in THz (trillions of Hertz), so that the entire usable RF spectrum can be carried on a single strand. Fiber optic cable is predominately used at the transport level where efficient, bulk transmission is a necessity, though hybrid fiber-coax (HFC) is now in the access level in some cases. The maximum length of a fiber optic segment can range from around twenty miles to several hundred miles before a repeater is needed.

Fiber optic cable and the necessary transmitters and receivers are costly. Six-fiber cables cost (in materials alone) at least $5,800 for two miles and $29 thousand for ten miles, while 48-fiber cables cost $16,360 for two miles and $81,840 for ten miles. The materials cost of fiber optic cable is small compared to installation, labor, and the price of fiber optic transmitters and receivers needed to establish communications [IEC, 1999, p. 6]. Multimode fiber used for data communications costs $0.70 per foot, while single mode fiber (used more in video) costs from $2.80 per foot and up [Tower, 1999].

Optical fiber is a thin, typically flexible conduit (also called waveguide) that conducts light rays using silicon glass or plastic fibers through its core. These fibers are clad with special glass or plastic coatings (cladding) with a layered plastic jacket designed to prevent moisture, crushing, or other hazards from breaking the internal fibers. Strands pass signals in only one direction so separate strands are needed for sending and receiving. Messages are converted into optical signals (photons), which are transmitted (flashed) down the optical fiber by a laser or light-emitting diode. A photo-detector on the other end receives the optical signals whereupon they are converted back into standard digital signals. Table 4-6 shows the three general types of optical fiber.

Table 4-6: General types of optical fiber.
 

Type	Diameter Core/Cladding (Micrometers)	NA	Attenuation (dB/km)	Distance-Bandwidth product (MHz-km)
Short Distance, Multimode step-index	100/200	0.3	5-10	20-200
Long Distance Graded Index multimode	50/125	0.2	1-5	500-1500
Single Mode	6/125	0.03	<1	>1000

Source: CORD, 1974, 2000, Tower, 1999.

Some kinds of multimode fiber (such as step index) are used for shorter, local installations, while graded index fiber is used for longer distances. Multimode fiber has reflective walls that move light pulses through the fiber to the receiver, allowing the refraction of multiple light paths through the fiber center core. In addition to the 100/200 core-cladding sizes, multi-mode is available in 62.5/125 (EIA/TIA standard), 100/140, 85/125, and 50/125. The 50/125 multimode is a long distance graded index fiber with the greatest carrying capacity. However, it requires extreme precision during splicing.

NA (Numerical Aperture) is a measure of the light gathering power of fiber. NA refers to an imaginary cone that defines the acceptance region of the core or the ability to accept and carry rays of light. With single mode fiber, light is guided down the center of a narrow core much more precisely (over a single mode or path), with a tighter NA than multimode. Single mode fiber needs precision when connecting and splicing it to the laser source, but the power requirement is lower. Single mode is far more costly than multimode fiber, but is able to support next generation technologies such as SONET OC-12 (622 Mbps) data rates because of the absence of multimodal dispersion.

Signals on fiber-optic cable experience considerably less attenuation while immune to capacitance and electrical interference. For these reasons, fiber greatly surpasses the transmission distances of both twisted pair and coax. In addition, fiber-optic cable is more secure than copper cable since any external tap is easily detected by a reduction in signal strength. The final column in Table 4-6 is " . . . the distance-bandwidth product, expressed in MHz-km. This gives the product of the maximum data-transmission rate and the maximum distance between repeaters. It is a common figure of merit used to characterize system performance." [CORD, 2000, Module 8]

Advantages of fiber optic cable include transmission rates of 100 Mbps and up over strands hundreds of miles long, better security, and the lack of electrical interference. Furthermore, fiber optic is considered to be more secure than coax or twisted pair. Disadvantages of fiber include the high cost, the difficulty in working with it, and need for specialized tools and training. Fiber can be hard to work with because it is inflexible and bulky. Fiber is often used in backbones between buildings and in Token Ring networks. Telcos have deployed it widely to replace coax long-distance trunk lines in the transport level. Cablecos that offer digital TV, high-speed Internet, and telephony use fiber connections to individual homes and businesses.

DWDM (Dense Wave Division Multiplexing) has exponentially expanded the capacity of existing fiber optic networks. Under DWDM, multiple signals are multiplexed onto separate wavelengths of light carried by a single fiber strand. According to the communications research firm Telegeography, all 81.8 billion minutes (over 56 million days worth) of traffic that was carried on the world’s telephone network during 1997 could be sent over a single fiber of the latest-generation fiber optic systems in just eleven days. DWDM can carry up to 25 Tbps (tera, trillion bps).

Guided media such as copper wire, coaxial cable, and fiber optics have five chief physical properties that can vary the capacity and quality of hypercommunications, especially in rural areas where wire distances are longer. These properties have been alluded to in context, but it may help to describe them further. In every case, fiber optic cable is superior to coax, which is superior to twisted pair.

The first physical property of wire is attenuation, a loss of signal strength or amplitude that occurs over distance as the signal passes down conduit. According to Sheldon "attenuation is measured in dB (decibels) of signal loss. For every 3dB of signal loss, a signal loses 50 percent of its remaining strength." [Sheldon, 1998, p. 995] At higher frequencies, skin effect, inductance, and capacitance cause attenuation to increase [RW Cabling Sciences, 1998]. Repeaters (digital), amplifiers (analog), and other devices are used to extend the distance limits caused by attenuation.

The second physical property of guided media is capacitance. Capacitance is a measure of stored electrical charge in a cable or wire. Stored charges can distort transmissions by changing the shape of the signal. Too thick or too closely bundled wires are especially likely to contribute to capacitance. At higher frequencies, capacitance becomes a greater problem, leading to increased attenuation.

The third physical property of guided media is impedance or delay distortion. The impedance value of wire or cable can be measured in ohms. Impedance is a combination of the inductance, electrical resistance, and capacitance of a transmission line. Impedance arises because the propagation velocity is a function of frequency so that only part of the signal arrives at one time at the receiver and part at another time. Impedance is a measure of the opposition offered by the wire to the flow of the carrier wave. Shortening the transmission path distance or lowering the frequency can help reduce impedance. Impedance can be a major problem for digital systems (inter-symbol interference). Abrupt changes in impedance (called discontinuities) distort signals, causing network problems [RW Cable Science, 1998].

The fourth physical property of guided media is noise, an unwanted signal that interferes with, changes, or blocks the transmission and reception of a desired signal. Several kinds of noise can occur, both predictable and unpredictable. Thermal noise occurs across all frequencies. Intermodulation noise happens when frequencies and multiples of their harmonics interfere with the original signal frequency. Impulse (or background) noises include random noises, often of large strength, such as lightning, motors, and elevators. Impulse noise is also generated by adjacent lines and transmitters. Ambient noise can be caused by motors, electronic equipment, nearby radio equipment, electric lines, and fluorescent lights.

The fifth physical property of guided media is inductance or cross talk. Cross talk is a special form of interference (noise) that results from an electromagnetic coupling of one wire with another [REA, 1751-H, 403, p. 9-4]. The number of twists made in a length of wire is one way copper can limit cross talk. Cross talk may be at the near end such as NEXT (Near End Cross Talk) or at a far end such as FEXT (Far End Cross Talk). Shielded twisted pair (STP) is a special kind of copper wire (with aluminum wraps or a copper braided jacket around insulated conductors) used especially in business settings to reduce inductance and crosstalk. It can support transmission over greater distances than unshielded twisted pair can.

Table 4-7 summarizes the general upper theoretical limits of the most frequently used forms of wireline conduit. However, because there are many variants within each of the three main types the table is only a rough guide.

Fiber optic cable is the overwhelming favorite for the transport level and is increasingly used in the access level. Copper twisted pair is still the most frequently used conduit at the access level because of the high cost of replacing the enormous amount that is already present in the telephone infrastructure. Coaxial cable predominates at the customer premise level for data connections, with copper still occupying the leading position for telephone connections. Hybrid fiber-coax and fiber-copper access conduit combinations are becoming increasingly common as telephone companies and cable TV companies compete to modernize their infrastructures so as to offer voice, data, video, Internet, and other high-speed services to residences and small businesses.

Table 4-7: Summary of wireline conduit capacity, cost, and distance.
 

Type	Distance Limit	Bandwidth	Data Rate	Cost
Analog telephone Twisted Pair	30-50,000 feet	0–3.3 Hz, with guardbands	To 56 kbps	$0.11/ft.
Category 3 UTP	6.2 miles (access, w repeaters), 1000 feet on premises	0-1 MHz (106)	up to 45 Mbps	$0.11/ft.
UTP Category 5	800 feet	0-100 MHz (107)	Up to 155 Mbps	$0.12-$0.17/ft.
UTP Category 6	1000 feet	0-350 MHz	1 Gbps	$0.15-$0.22/ft.
Coaxial Cable	Miles	0-1 GHz (109)	Hundreds of Mbps	$0.33-$1.13/ft.
Fiber Optic Cable	Hundreds of Miles	0-1 THz (1012)	hundreds of Gbps	$0.70-$2.80/ft.

 

4.3.2 The Telephone Infrastructure

SEE ALSO: Technical characteristics of the PSTN (3.3), Rural wireline infrastructure history (5.3.1), Hypercommunication Boundaries (6.1)

The telephone plant has evolved from an analog, all-copper conduit system designed to carry voice calls alone to a mixture of digital and analog circuits that carries voice and data traffic over a mix copper wire and fiber optic cable. In the telephone plant, copper conduit is usually found on customer premises and over the access level (especially the local loop). According to Paradyne Corporation, over 95 percent of local access loops are two-wire twisted wire supporting POTS [Paradyne, 1999, p. 5]. Multi-strand cables of up to 500 twisted-wire pairs may be used over the last hop of the access level. The transport level relies almost exclusively on fiber optic backbones and microwave or satellite paths.

AT&T and other telephone company research programs have been behind the invention (and in many cases, the development) of technologies that have made high-speed wireline hypercommunications possible. Digitization resulted in reduced bulk transport costs and better call processing in spite of the fact that digital voice requires more bandwidth than analog does. An important rule-of-thumb that prevailed for years (in the transport network), was that 8kHz was required to carry a 56-64 kbps digitized voice signal using PCM on the same copper conduit that occupied 3.1 kHz on analog lines. New speech codecs are available to reduce the bandwidth requirements, but there is a tradeoff in quality.

While the evolution from analog to digital and from copper to fiber have changed the telephone transport network, the local loop (the access network) typically relies on copper and has remained analog. The copper access network has been designed to handle voice telephone traffic in a narrow bandwidth of approximately 3Hz (see Figure 4-5). As was discussed in the V.90 modem example, under the best conditions (low line noise and subscriber-CO distance of fewer than 30,000 feet), the highest possible data rates would be 33.6 kbps upstream and 56 kbps downstream. In rural areas, (and indeed in many urban and suburban ones), line conditions may not reach anywhere near these capacities.

However, copper wire itself is not responsible for the lack of capacity. Copper wires can be used to extend high speed hypercommunication services thanks to several technologies such as ISDN, DSL, and DS1 (T-1). To understand how these technologies work, it is necessary to examine how the telephone transport and access networks have evolved.

Traditionally, the local exchange was the foundation of a five level hierarchy of exchanges built when AT&T was the national telephone monopoly. While large areas of Florida were served by independent telephone companies before the AT&T breakup the AT&T exchange hierarchy was followed (even by the independents) as the PSTN evolved from analog to digital and copper to fiber. Table 4-8 shows the exchange classes in the hierarchy.

The first stage in the dual evolution from analog to digital and copper to fiber came at the Class 1 level (farthest from subscribers), when traffic between regional centers was digitized and sent over high-speed microwave or satellite links. Then, traffic from sectional to regional centers became digitized and sent over microwave links. By the early 1980's, primary to sectional center traffic was also digitized and sent over microwave links, a technological change that allowed firms such as MCI and Sprint to begin limited competition with AT&T for long-distance customers. Regional centers began to be equipped with fiber optics in the mid-to-late 1980's so they could connect with other regional and sectional centers at record speed [Oslin, 1992]. Coaxial cable, specially conditioned copper loops and, finally, fiber optic cables were used to connect class four and class five exchange offices.

Table 4-8: Telephone transport hierarchy: AT&T exchange classes.
 

Exchange Class	Description	Serving Areas	Function (CLLI)
Class 1	Regional Center	Atlanta center served southeast USA	Switch National and International calls for IXCs
Class 2	Sectional Center	Entire LATA or market area, e.g. Orlando	Switch inter-LATA calls, intrastate calls for IXCs
Class 3	Primary Center	Area code or EAEA. Place where call moves from independent to Bell System, e.g. Eau Gallie.	Switching Center, SAP or EAEA intra-LATA calls from LECS to IXCs
Class 4	Toll Center / Rate Center	Urban-suburban local calling area or group of rural COs.	Main office serving group of LEC COs, local inter-exchange calls
Class 5	End Office/ CO	Rural local calling area or urban NXX group, e.g. Kenansville.	Physical location where local loop begins, local intra-exchange calls

 

After the breakup of AT&T, developments in fiber optic and digital transmission technologies allowed telephone companies to operate digital transport networks. However, in many rural areas, copper or coax transport conduit was still used, even while bulk traffic became digital rather than remaining analog. This was because the fixed cost of upgrading copper transport to fiber could not be offset by revenues in low-density areas. In many areas of Florida, per subscriber revenues in sparsely settled areas are lower than in urban areas, although costs of service are higher.

However, in suburban areas and the urban fringes, it became generally apparent that not all of the local loop would have to be changed from copper to fiber in order to support certain telco carrier services. One option that has been widely deployed by BellSouth in Florida is the DLC (Digital Loop Carrier) which multiplexes many circuits onto a few copper wires or a fiber optic strand. For example, the Northern Telecom Remote Switching Center-S can consolidate the traffic of over 10,000 telephone lines onto 16 T-1 trunks (48 wires) [Nortel, 1998, p. 69]. This allows many traditional CO services to be delivered by telephone companies up to 150 miles away from the subscriber.

By using Remote Access Vehicles (RAVs) and DLCs (Digital Loop Carriers), enhanced telephony services are more available in rural Florida. RAVs are intermediate access level nodes where copper runs to the subscriber and signals are aggregated and back-hauled via fiber optic or enhanced copper from the RAV to the carrier POP. RAVs are especially important in rural areas where the distance from the subscriber to carrier facility exceeds 18,000 feet [Nortel, Telephony 101, 1998, p. 68].

Hence, as Figure 4-24 reveals even though most ILEC COs cover a small geographic fraction of the state's total area, ILECs or competing ALECs could offer most central office traditional telephone services virtually anywhere in the state. However, the same is not true for most kinds of high-speed access provided through the telephone plant using the resulting copper-fiber mix.

In the figure, dots represent an 18,000-foot radius surrounding the location of all COs and wire centers RAVs in Florida as of July 1999. New digital loop technologies allow COs to be served from facilities located hundreds of miles away, meaning that competing traditional telephone service providers would not need to build costly plants all across the state.

Figure 4-24: CO locations in Florida with 18,000 foot distance circle.

However, RAVs (also called DLCs or Digital Loop Carriers) and new switch technologies do not change the basic physical laws governing copper wire regarding enhanced high-speed services (such as data and Internet). The extension of high-speed services requires subscribers be within 18,000 to 35,000 feet of the serving central office or RAV. Many telephone subscribers are outside the 18,000-foot limit. While many RAVs were deployed to provide enhancements to traditional telephone service, only a fraction can be modified to bring high-speed services closer to subscribers. Figure 4-25 focuses on how RAVs represent a recent evolutionary stage in telephone network access.

In Figure 4-25, thicker lines represent trunks and feeder fiber optic cables with multi-gigabit capacities among the central offices. The figure compares CO-1 (non-RAV) at the top with CO-2 (with RAV) shown on the bottom. Features of comparison are numbered. In the CO-1 case, the office building (1) is able to have high-speed T-1 services, as is the farm labeled (2). However, farms labeled (3) are too distant to receive high-speed service. The residences near CO-1 cannot get high-speed services because of limitations in the ratio of high-speed to narrowband copper.

Figure 4-25: RAVs reduce subscriber to fiber distances.

CO-2 has an RAV (and DLC) able to serve more distant areas with more than basic telephone service. With the RAV, farm (2) is able to increase the speed of high-speed service since it is now closer to the fiber to CO connection. Furthermore, farms (3) are now able to access high-speed service. Indeed, as the area grows, new business parks, farms, and homes can be served by high-speed technologies. This is only true if RAV-DLC equipment is compatible with high-speed services. Over half of RAV-DLC equipment deployed by BellSouth in Florida cannot support such services as DSL.

Table 4-9 shows some of the technologies that use the telephone plant to deliver hypercommunication services in Florida. These technologies are described in context in the enhanced telecommunications, private data networking, and Internet sections (4.7-4.9).

Table 4-9: Copper access technologies that use the telephone plant.

Sources: George (1998), Schlegel (1999), Paradyne (1999), FitzGerald and Dennis (1999), REA "Digital Transmission Fundamentals", BellSouth (2000).

The first two rows describe modem technologies, mostly used to allow analog copper lines to transmit Internet and data. It is also possible to use "channel bonding" to combine modems on separate telephone lines (at both ends of a connection) into a single channel to obtain higher data rates. However, analog telephone lines were designed only to accommodate voice conversations over bandwidths that rarely exceed 3.1 kHz.

If bandpass filters and other intermediate equipment (bridged taps, amplifiers, and loading coils) are removed from the lines (a process known as line conditioning), copper is capable of carrying data rates far in excess of 56 kbps modems. The usable bandwidth can rise above 1 MHz, even at distances of two to four miles. However, the availability of this greater bandwidth depends on how close subscribers are to the CO (or suitable RAV) because attenuation and noise increase with distance. Additionally, higher frequencies are inherently more sensitive to noise and interference.

Some of the access technologies shown require individual line conditioning so that only a subset of subscribers along a certain path to the CO will ever be able to obtain high-speed connections. Other copper access technologies require that every line along the entire path to the CO be conditioned so that high-speed services are available to most of the subscribers.

The first digital technology in Table 4-9, ISDN (Integrated Services Digital Network), is both a service and a technology. ISDN was meant as a circuit-switched standard that would overcome problems in the PSTN by creating a way to handle voice, data, and video traffic. There are two kinds of ISDN, ISDN-BRI (Basic Rate Interface) and ISDN-PRI (Primary Rate Interface). ISDN-BRI uses two copper wires and two 64 kbps B channels (that carry communication) and one 16 kbps D-channel (used for signaling or overhead). Both kinds of ISDN operate over the PSTN so both data and voice traffic may pass through the telephone CO, switches, and transport network.

In the late 1980's, ISDN-BRI was expected to replace modems as the copper access technology of choice. This has not ended up coming true, possibly because ISDN connection pricing was metered (per minute). Since then, while ISDN-BRI rates have fallen in many markets, superior copper loop technologies (such as DSL) have become available. ISDN changes asynchronous computer communication into synchronous data streams so computers can use standard COM ports along with a V.120 terminal adapter to communicate. Terminal adapters can tell the difference between data traffic and telephone calls so one channel of the BRI connection can be used for data or Internet while the other B channel is used for telephone calls. ISDN-PRI offers 23 64 kbps B channels and one 64 kbps D channel. Like ISDN-BRI, ISDN-PRI uses telephone switches. Both kinds of ISDN require call set-up and dial access time. Both types of ISDN are given further coverage in 4.7.4.

Another kind of technology that is sometimes called ISDN is B-ISDN (Broadband ISDN). However, B-ISDN is not a circuit-switched ISDN technology but is a protocol for cell-switched ATM (Asynchronous Transfer Mode) technology that operates at speeds of 45 Mbps to 600 Mbps. A close relative of ATM, frame relay, is a frame-switched technology that operates at speeds of 64 kbps to 1.544 Mbps and above. Neither frame relay nor ATM is switched through the PSTN, though they may use copper or fiber from a telephone company (ALEC or ILEC) in the access level. Typically, however, if ATM is the transmission technology, copper can only be used for 300 yards or so on the CPE side. In such a case, access must be by fiber because even CAT 5 UTP cannot handle 155 Mbps longer than that distance [Thorne, 1997]. These technologies (associated with private data networking, but able to support voice) are covered in more detail in 4.8.

The next access technology in Table 4-9 is X-DSL, the first of several dedicated circuit technologies. DSL stands for digital subscriber line and X stands for the over ten different varieties of DSL such as (ADSL, DSL-G-Lite, RADSL). These specific forms of DSL will be discussed in section 4.7.3 with other dedicated circuits. Provision of DSL over the telephone plant requires the absence of bridged taps and loading coils [Paradyne, 1999]. Bridged taps (open ends) are used in many areas so that future telephone subscribers will have lines ready to tap into when new homes or businesses are built in areas where future growth is expected. Loading coils extend the reach of copper in sparsely populated areas on loops over 18,000 feet that do not have RAVs. More than twenty percent of all local loops have loading coils [George, 1998]. Additionally, many DSL varieties cannot be provided over DLCs and RAV equipment.

Also explored in 4.7.3 is DS-0, fractional T, T-1, and T-3 technologies. These are the most common leased or dedicated digital circuit technology in the United States [Tower, 1999]. One use of Ts is to carry multiple voice channels over a single twisted pair or a quad connection. Multiplexing techniques allow T-1s to carry 24 voice channels (each a 64 kbps TDM channel), while T-3s carry 672 voice channels.

Ts may be leased from ILECs or ALECs to access the PSTN for local telephone service (local T). Ts also are leased from an IXC for long-distance service or are leased from an ILEC, ALEC, IXC, or ISP to link corporate data networks nearby or overseas. Ts are also leased from the ILEC or an ALEC and terminated at an ISP for Internet access. T-1s require conditioned lines so that when used with certain signal technologies, repeaters are necessary to regenerate signals every 3,000 to 6,000 feet, with a distance of less than 3,000 feet needed from the demarcation mark and the first repeater [Paradyne, 1999, p. 6]. Newer Ts use a HDSL signaling scheme using quad copper for the full 1.544 Mbps [Sheldon, 1999, p. 942]. HDSL allows two to four times the distance of an conditioned T-1 (AMI) circuit.

T-3s carry DS-3 signals over copper or copper-coax as well, though they are now more likely to be carried by fiber optic cable. A T-3 is the equivalent of 28 T-1s with a total of 672 voice channels and a data rate of 44.736 Mbps. T-3s serve similar purposes as T-1s including voice, data, and Internet access. T-3s are typically leased from ILECs and ALECs, but when Internet is involved, ISPs are also involved as discussed in 4.9.1. Presently, T-3s are not often used as access technologies but are usually used as transport or backbone circuits (mentioned in 4.9.4). However, as agribusinesses require increasingly greater network capacity (especially as Internet, data networking, and Internet access use a single, converged hypercommunications pipeline), T-3s will become more common as access technologies.

4.3.3 Cable TV Infrastructure and Dark Fiber Networks

The telephone infrastructure is not the only way for agribusinesses to access hypercommunication networks. The cable TV plant and dark fiber networks of other potential hypercommunication carriers are additional ways. Cablecos now are focusing on introducing a variety of hypercommunications services primarily for residential suburban Florida. The list of cable services has grown from basic and extended choice television into pay television, audio programming, local telephone service, and high-speed cable modem Internet access.

Electric utilities also have rights-of-way and fiber capabilities over which hypercommunication services are offered. Electric utility fiber is often called "dark fiber" because of the enormous unused capacity in electric company fiber optic networks. There are estimates that as much as 50% of all fiber networks are overbuilt and, hence, dark [Gong and Srinagesh, 1997]. Often, this capacity is sold wholesale to telecommunications carriers. In some cases, such as GRU (Gainesville Regional Utilities) and TECO (Tampa Electric) for instance, electric companies offer data and other hypercommunication services directly to Florida businesses. In some areas, railroads and other firms also have dark fiber capacity.

This section reviews the ability of the cable TV infrastructure to provide hypercommunications access to agribusinesses in Florida. However, generalizations are difficult because of considerable technological variation offered by cablecos in various parts of Florida. In part, the variations in infrastructure are due to the size of cablecos. Cable systems range from with millions of subscribers (such as MediaOne and TCI, both owned by AT&T, and @Home, owned by Time-Warner-AOL) to franchises owned by a single person that serve a few hundred households.

Several observations are in order first. First, cablecos have traditionally focused on serving the residential market, though this is somewhat less important to agribusinesses since many are residences (farms), or are operated in or near residential areas. Second, not all cable systems have upgraded their equipment to provide data and voice services. Third, many rural areas are not served at all by cable television and may never be. Small town cable service is usually available, but conditions vary as to how far out of town the cable travels if at all. Cable TV is a monopoly franchised by cities, counties, and other geographic areas such as subdivisions, with specific service boundaries. Traditionally, state and federal regulations have not equated cable service with telephone service in terms of being a social necessity. Thus, only in localized franchise areas has an attempt been made to provide universal service to all locations.

The main reason cableco networks have become competitive with telco networks is that cablecos have lower costs of upgrading their infrastructure from coax to fiber than telcos do upgrading from copper to fiber. Furthermore, cablecos serve local franchises while ILECs are required to serve all reasonable locations in their larger coverage areas. Estimates differ dramatically on the cost per mile of replacing the local copper telephone loop with fiber.

Upgrading analog copper to FTTH (Fiber to the Home) systems capable of supporting two-way broadband services costs an average of $1,500 to $2,000 per urban ILEC subscriber [Egan, 1996, p. 152]. However, since BellSouth has a $10.4 billion wireline network infrastructure investment now in Florida and an $800 million annual construction budget in the state already, it cannot afford to completely replace access copper with fiber [Ackerman, 2000]. Cable TV providers often have significant cost advantages over ILECs when it comes to upgrading local loops with hybrid copper fiber installations known variously as FTTH, FTTC (Fiber to the Curb), and FTTN (Fiber to the Neighborhood). While expensive, cablecos can upgrade their local loops to fiber at one-fifth the cost telcos can. It will take Cox Cable five years and $400 million to rebuild the 60,000 miles of Phoenix, Arizona's cable system (which passes 1.12 million homes), at $357 per subscriber [Woodrow, 1999].

Figure 4-26 shows the set up for four typical cableco infrastructures. Note on the left the head end. This is similar to the telephone company CO in that it is a physical office where cable company equipment is located and where the cable runs for an area converge. However, the head end is linked to two transport networks (the PSTN and the Internet) and is connected to satellite equipment so TV signals may be downloaded. In digital cable systems, the head end also is equipped for digital cable TV signaling.

Figure 4-26: Cable TV plant showing one-way, FTTN, FTTC, and FTTH distribution.

Regardless of which distribution scheme is used, the head end must be equipped to support Internet and PSTN as depicted. From the head end, a fiber trunk (with power sources required) leads to a node that serves from 500 to 5000 locations. From the node, there are four distribution schemes shown.

The first distribution scheme serves subscribers (s) through distribution coax (top), with amplifiers required to boost the signal enough that it reaches the tap point, from which lower capacity coax is dropped to each home or business. The first distribution scheme may be over 350 MHz coax so that a maximum of 58 TV channels may be received along with download only Internet access. Upload Internet access is via modem over standard analog telephone lines, with downloads accomplished with a one way internal cable modem such as a Surf Board.

The second distribution scheme (bottom, Figure 4-26) is FTTN (Fiber to the Neighborhood). Two-way broadband services could be provided to these subscribers, with fiber optic cable running to a neighborhood pedestal where coax cables distribute amplified signals to homes. A lower capacity (un-amplified) coax leads from the tap point to the service connector(s) within each subscriber’s location. FTTN supports two-way services including Internet, enhanced telephony, and digital cable. Over 100 TV channels may be received via FTTN as well.

The third and fourth distribution schemes, FTTC (Fiber to the Curb or Fiber to the Cabinet for small businesses) and FTTH (Fiber to the Home) are shown on the right of Figure 4-26. FTTC (on the bottom right) uses fiber optic cable to reach curbside tap points and then uses un-amplified drop coax from there to the service point inside each location. Under FTTH (top right), low capacity fiber is run from a neighborhood pedestal to each home. Both FTTH and FTTC can support two-way broadband services including digital cable TV, VOD (Video on Demand), data networking, Internet, and enhanced telephony. Over 120 TV channels may be received using FTTC, with a specialized set top box capable of preprogramming and downloading pay-per-view VOD and pay channels as well as displaying specialized system information.

In FTTN and FTTC, data connections are supported with ordinary 10BaseT-Ethernet cards and connections similar to an RJ45 lead from CPE DTE to on-premise coax and then to tap points. A two-way cable modem (such as the LAN City LANtastic or Toshiba PCX1100) is used with FTTN and FTTC systems. Current FTTH connections use coax inside the home, but fiber to desktop CPE are being introduced. Eventually, FTTH will support bit rates many times that of VDSL (up to 200 Mbps) [Schlegel, 1999].

The capacity of many older analog coax cable systems is 350 MHz and below. However, the latest HFC (Hybrid Fiber Coaxial) voice, data, and TV systems run at 750 MHz and more. A 6 MHz downstream channel capable of 27-36 Mbps is shared among an average of 500 to 2,000 users per node [George, 1998, Table 2-1]. The upstream link of 2-5 Mbps is also shared with other users on the node. However, it would take a critical mass of over 200 simultaneous users per mode for a significant degradation of up or downstream data rates to be experienced with the broadband shared access approach [Reed, 1997].

Because of the shared access broadband signaling inherent in cableco access, it is often not considered a business-class service. Connections can support only up to five computers per location, and there are certain security concerns that require defensive cableco installation. Only a few telephone lines per customer can be supported because of the upstream limitations. However, FTTH applications are being developed that are expected to improve upstream capacity and make cable more attractive as a communications choice for business.

The availability of agribusiness cable access depends on several factors. First, in many areas, the infrastructure does not support even one-way cable modems. Service depends on the infrastructure level the cableco has implemented. Second, the more fiber is used, the more expensive intermediate DCE is required to support the network. FTTH requires that subscribers buy an expensive fiber optic transceiver known as an ONU (Optical Network Unit). With FTTC and FTTN, fiber optic equipment costs are spread among groups of subscribers. Third, telephony implementations are still in introductory stages so that service interruptions and other problems may be common in some areas. Finally, the ability to support the cost of the infrastructure depends vitally on per subscriber revenues. In low-density areas, costs per-subscriber may be too high to extend service and the cableco is rarely required to do so. However, cablecos tend to have better overall infrastructures than telcos for offering cheap, high-speed service in densely populated areas. Telcos have begun to offer cable TV and high-speed hybrid fiber coax services on a limited basis to compete with cablecos. Eventually, cablecos will support multi-telephone lines for small businesses.

Dark fiber networks provided by other carriers such as electric utilities and railroads have the same access and distribution problems that cablecos do. However, the electricity companies have an additional problem caused by the interference of electricity itself. Nortel and other companies have been experimenting with powerline networks where data can be carried within an office through electrical outlets at speeds of up to 1 Mbps, but a variety of technical problems remain. Currently, electric and other dark fiber carriers, tend to wholesale their fiber capacities to transport level carriers and customers, rather than attempt to establish access networks to smaller, local customers. Capacities can range from 45 Mbps to over 100 Mbps, though such speeds are available on a limited basis.

Before moving to transport wireline technologies, it is important to characterize the symmetry and data rates of the wireline access technologies covered thus far in 4.3. When the data rate differs between upload and download (as it does for DSL and V.90 modems), the technology is said to be asymmetric. Indeed, this can be true in some cases due to asymmetric bandwidth, when the upload capacity (in kHz, MHz, etc.) is smaller than the download capacity. The asymmetry is also linked to the use of line codes that take advantage of the fact that for applications such as the Internet, more bits are downloaded than uploaded.

Figure 4-27 compares the data rate symmetries for a voice line with V.90 modem, ISDN-BRI, xDSL, ADSL, T-1, and cable modems. The first column in Figure 4-27, an analog voice line, is asymmetric in that for the 56 kbps modem, download can occur at a rate up towards 56 kbps, while upload can only approach 33.6 kbps. Similarly, the two forms of DSL shown are asymmetric. However, ISDN-BRI, T-1, and ISDN-PRI (not shown, but same data rates as T-1) are symmetric. Cable refers to the data rate of cable modems (covered in 4.3.3).

Figure 4-27: Data rate symmetry among wireline transmission technologies.

4.3.4 Data and Voice Transport, Fiber Optic Backbones

Larger agribusinesses with advantageous locations may be able to gain direct access to the transport network without having to use the access level at all. While this solution is currently an expensive one, it provides the greatest bandwidth possible. Fiber optic connections may be available from ILECs, ALECs, IXCs, cablecos, ISPs, and electric companies. As fiber miles increase and as DWDM increases the capacity of existing fiber optic connections, prices are expected to fall while supply shifts right. However, the results are uncertain.

SONET (Synchronous Optical Network) is an ECSA (Exchange Carriers Standards Association) ANSI standard for fiber optic networks. SONET defines optical carrier (OC) transport standards and STS (Synchronous Transport Signaling) for a hierarchy of fiber optic networks, primarily above the physical layer [Nortel, 1996]. While SONET is covered in more detail in 4.7.3 (as a dedicated circuit technology) and in 4.8.4 (as a private data networking technology), two important features need discussion here.

First, SONET is an "on net" wireline technology that requires direct connection to a backbone network to support a full-range of hypercommunication services. Second, SONET is fast, specifying data rates of from 51.84 Mbps (STS-1, OC-1) to 9.953 Gbps (STS-192, OC-192). Clearly, with these kinds of speeds, present agribusinesses who require SONET "on net" fiber optic connections would be large indeed.

The smallest fiber optic backbone connection is a T-3, the equivalent of 28 T-1s with a total of 672 voice channels and a data rate of 44.736 Mbps. By comparison, an OC-192 has over two hundred times the capacity of a T-3, with a minimum number of voice channels near 150,000. Specialized ONUs, smart building wiring, and other equipment are also needed to support fiber optic access/transport.

Wireless transmission technologies are particularly important for Florida agribusinesses for three chief reasons. First, over 48 million Americans have jobs that require that they be mobile much of the time [Zaatari, 1999, p. 135]. It is likely that this is especially true for the agribusiness sector because of the land-based and international aspects of agriculture. A second reason for the importance of wireless technologies is that wireless can offer cheaper and faster rural access to hypercommunications in unserved areas than wireline. While many promising wireless technologies are being introduced in urban Florida, the advantages of using wireless over wireline technologies have been strongly supported by studies concerning rural access to advanced hypercommunication networks [NTIA, Survey of Rural Information Infrastructure Technologies, 1995, p. 5-8, p. ix].

An understanding of wireless is important to agribusiness for a third reason: wireless technologies are the fastest-growing segment of telecommunications today. According to Core Exchange, Inc., almost eighty percent of U.S. business Internet users will use wireless devices to access data in 2001, up from three percent in the year 2000 [AIM Research Update, 3(8), 2000]. The popularity of wireless may be related to several factors including falling prices, rising QOS, and an array of new services and devices. For example, from December 1997 to January 1999, cellular prices fell at an annualized rate of 8.4 percent while local (wireline) services increased by 2.2 percent. The overall CPI increased by 1.9 percent in the same period [FCC, June 24, 1999, FCC 99-136, p. 22-23].

Wireless technologies are easily confused with the services they deliver. Generally, most of the specific service sub-markets described in 4.6 through 4.9 are available through either guided media (wireline) or unguided media (wireless). Wireless technologies specifically designed to provide a particular service (for example cellular telephone) are given more coverage in the section concerning that service's sub-market. For example, specific wireless technologies used to deliver Internet access (4.9) or enhanced telecommunications services (4.7) are discussed in the sections concerning those sub-markets, along with their wireline counterparts.

This section focuses on wireless transmission technologies in general, especially on the access level. The introduction to electromagnetic spectra in 4.4.1 provides a foundation to understanding wireless technologies. Some examples of wireless spectra (transmission media) include: infrared, laser, microwave, and radio. Each medium (along with variations within that medium) uses a different spectral range constrained by a set of properties that depend on the physics of the electromagnetic waves in that range. Terrestrial wireless technologies (4.4.2) use earth-based wireless equipment to beam communication signals to fixed, nomadic, or mobile users. Satellite wireless technologies (4.4.3) use space-based equipment to beam communication signals to fixed, nomadic, or mobile ground-based receivers. Finally, wireless QOS is addressed in 4.4.4.

The hurried reader may be able to understand the main wireless technologies by consulting Table 4-10 (terrestrial mobile technologies), Table 4-11 (terrestrial fixed technologies), and Table 4-12 (satellite fixed and mobile technologies). Table 4-14 summarizes the QOS concerns related to wireless technologies.

The ability of wireless technologies to provide access to services that previously could only be accessed via wireline technologies led Stone to conclude, " . . . the once sharp division between wire and wireless has now closed. The markets have converged." [Stone, 1997, p. 155] Nonetheless, there are two important divisions in wireless technologies. The first division depends on the type of transmitter (terrestrial or satellite). However, wireless technologies and services have a second division based on how much the user’s location varies. Wireless users may be mobile, nomadic, or fixed. A mobile user is one who travels (often by car) from one point to another within a local coverage area or roams across the state, nation, or world. Nomadic users stay in one localized area of up to a few miles, but require the ability to roam (usually by foot) within that area. A fixed user uses wireless service at one permanent location so that receiving points are stationary, similar to wireline users [Weinhaus, Lagerwerff, Brown, et al., 1999].

Importantly, wireless transmission over the last mile may connect to wireless or wireline CPE at the agribusiness. Similarly, wireline equipment over the last mile may connect to wireless or wireline equipment. Specifically, Figure 4-28 shows a wireless QOS reference model.

Figure 4-28 demonstrates that, like wireline, wireless transmission has three levels: local CPE, access level, and transport level. When the local level is wireless, a wireless LAN or a local nomadic technology (such as a cordless telephone) is being used. For example, LAN wiring may be replaced with infrared signals that create a wireless path from end server (stationary LAN) to nomadic or fixed client devices. When the access level is wireless, a wireless path from customer antenna to wireless POP (base station) is required. For example, the cellular telephone creates a wireless path from a mobile phone to a base station to replace the wireline local loop from subscriber to CO. Finally, if the carrier network is wireless, a wireless transport technology is used. Bulk transmissions of telephone calls commonly use microwave or satellite paths to replace fiber optic cables. As in the case of wireline transmission, wireless transmission technologies may be point-to-point or multipoint. Most applications of wireless technologies involve hybrid wireline-wireless networks because some levels use wireless technologies to establish wireless communication paths, while others rely on wireline technologies to create wireline communication links.

Figure 4-28: Wireless reference model shows local, access, and transport wireless.

The role of DCE and DTE differs from the wireline case. Many wireless devices are both DTE and DCE, with DAC and ADC accomplished through circuitry in the transceiver. A receiver and a transmitter (transceiver) are needed when air is used instead of wire for two-way communications. To transmit successfully, a threshold signal power is needed, while to receive, some form of antenna is required. Wireless communications has two "power challenges". First, path loss occurs when an antenna transmits a signal over air. Unlike guided media, where the entire signal (less attenuation) is received on the other end, the electromagnetic waves of unguided media are scattered through the air on their trip to and from the receiver. Second, power constraints (such as battery life or interference limitations on signal wattage) may prevent devices from transmitting a strong signal [Committee on Evolution of Untethered Communications, NRC, 1997].

Before proceeding to the electromagnetic spectrum discussion in 4.4.1, a short explanation of the generations of wireless technologies puts path loss and power constraints in the appropriate technological context. Most sources argue that there are three generations of wireless technologies, with a fourth yet to be created [NSF, 1998; Zaatari, 1999]. According to Zaatari (1999), in the first generation, analog transmission predominated. AMPS (Advanced Mobile Phone Service) and early CDMA (Code-Division Multiple Access) are two mobile wireless technologies from this era. The CDPD (Cellular Digital Packet Data) standard was established to allow an operational bit rate of 19.2 kbps over the analog AMPS systems, though actual data rates are closer to 5-10 kbps [Telecommunications Engineering Centre, 2000]. Most fixed services (such as microwave relay or fixed satellite) were used only by telephone carriers or TV stations since the technology that supported them was expensive and few other uses existed for high-bandwidth links.

In the second generation, FDMA (Frequency-Division Multiple Access) was originated when digital cellular became a more common wireless service. It was the first of many wireless technologies that allowed multiple mobile users to share the same spectrum. The 200 kHz GSM (Groupe Speciale Mobile) radio band was opened (using a European technology), digital-only service was introduced in the 1900 GHz PCS band, and dual-mode analog cellular technologies began to operate near 800 MHz. Data rates rose to 9.6 kbps and 14.4 kbps.

A scarcity of spectrum limited the extent of the market, so most second generation wireless technologies concentrated on the efficient use of already assigned spectra by increasing capacities of existing (first generation) DCE. In the US, TDMA (Time-Division Multiple Access, IS-4 & IS-136) was developed allowing three times the traffic of its first generation predecessor, AMPS. The European TDMA standard and new iterations of GSM increased existing AMPS capacity by a factor of eight. Another US standard, CDMA (IS-95) allows up to ten times the AMPS capacities using existing spectra. Now, competing carriers use all three in the United States. Fixed and nomadic wireless technologies supported either limited common carrier offerings or private, high-speed digital TV and telephone carrier transport.

In the third generation, three competing standards (backward compatible with existing networks) increase mobile and nomadic data rates even further and allowed deployment of new services. These three are W-CDMA (Wideband CDMA), CDMA-2000, and UWC-136 (Universal Wireless Communications). Third generation wireless technologies will (or are already able to) support Internet access, worldwide roaming, and video conferencing in addition to enhanced wireless voice for mobile users [Zaatari, 1999, p. 133]. All three support mobile data rates of 384 kbps (extended range) and 2 Mbps (mobile, nomadic or fixed, local range). The three competing standards are assigned frequencies in the Broadband PCS and 2 GHz bands.

Another group of technologies of the third generation serve fixed wireless users, offering greater data rates. A promising source of wireless hypercommunication technologies came in the area of wireless "cable" and fixed broadband wireless access. Wireless cable is primarily comprised of MDSs (Microwave Distribution Systems) such as MMDS (Microwave Multipoint Distribution System) and LMDS (Local Multipoint Distribution System). Wireless cable was developed initially to supply cable TV programming to rural locations, thus allowing competition with wireline cablecos. MMDS is the wireless equivalent of broadband communications offering cable TV, Internet, basic telephony, and enhanced telecommunications services.

New technologies and devices have been developed recently to allow LMDS and MMDS to carry two-way data and multiple voice lines. Satellite DBS (Direct Broadcast Systems) offer high-speed Internet access. Wireless LAN technologies allow local CPE networks to function without wires so network users can move about a business’ location with portable computers, telephones, and other devices.

In Figure 4-29 [Adapted from NSF, 1998], the four generations are depicted graphically, summarizing where current wireless transmission technologies fit compared to wireline and future wireless generations. The bottom x-axis depicts the transmission rate (operational bit rate), while the y-axis depicts the degree of mobility. To make comparison easier, at the very bottom (spanning all transmission rates), are boxes containing wireline conduit types.

Figure 4-29: Second, third, and fourth generation wireless services.

The capstone of the third generation will almost certainly be high frequency, fixed wireless technologies that allow two-way access to a full range of hypercommunication services. Concentrated in the SHF (Super-High Frequency) and EHF (Extremely-High Frequency) bands from 3 GHz to 39 GHz third generation services include DEMS (Digital Electronic Message Service), Ka-band FSS-GSO satellite, Big LEO satellite, LMDS, and Winstar’s 39 GHz WLL. Third generation fixed wireless technologies are beginning to provide high-speed services rivaling fiber optic data rates. Power, antenna, and tower relay technologies for some of these services are still under development.

However, the NSF Tetherless T-3 Workshop Report found that the third generation "vision of providing any service to any user at any time anywhere on earth will be only partially achieved by the current technology." [NSF, 1999, p. 2-13] Hence, the development of a fourth generation of wireless technologies is envisioned as necessary for wireless to become a truly mobile, high-speed worldwide method of hypercommunications. Bold isoquant-like curves separate generations in Figure 4-29, with third generation technologies expected to evolve from their introductions in 2000 until the fourth generation begins, sometime near 2010.

4.4.1 Technical overview of electromagnetic spectra

Further clarification of the electromagnetic spectrum will help make the brief, technical introductions to terrestrial (4.4.2) and satellite (4.4.3) technologies more understandable. It is important to note that 4.4.2 and 4.4.3 build on the material presented here in 4.4.1. In this sub-section, the purpose is merely to outline the spectral properties of frequencies associated with wireless technologies. More details about each technology and the services it supports will be found in the sub-sections following.

Physicist James Clerk Maxwell addressed the Royal Society in 1876 with a revolutionary paper showing the existence of the electromagnetic spectrum. Maxwell found that "Electromagnetic fields could be propagated through space as well as conductors" and "light itself was electromagnetic radiation within a certain wavelength" [Stone, 1997, p. 131]. By 1894, English physicist Oliver Lodge came up with systems by which wireless signals were sent and received. However, he could not see any commercial applications. Guglielmo Marconi obtained the first radio patent in 1896 and demonstrated radio’s applicability to navigation. Then in 1901, Marconi transmitted an "s" in Morse code from Cornwall, UK to Newfoundland. Marconi's success led to a scientific race to explain the results, ending in the postulation that layers of the ionosphere refracted short, medium, and long waves to earth [Stone, 1997]. Since that time, as scientists have created new wireless technologies, commercial application has waited for FCC assignment of frequencies and bandwidths for new services, for the perfection of DCE and DTE, and for the launch of new services.

Now, the electromagnetic spectrum consists of:

In wireless transmission, bandwidth has a broadcasting orientation similar to how radio and television channels are defined. Barden defines the bandwidth of a broadcast signal as: "Total width of a radio signal, varying from a few hundred Hz for CW to five or six MHz for TV." [Barden, 1987, p. 109] In general, the wider the bandwidth, the greater the interference. The potential of wireless is especially apparent when the bandwidth of an analog telephone line (3.1 kHz) is compared to WLL upper-band services that reside at 39 GHz, over twelve thousand times larger.

However, the requirements for receiving and sending high-speed wireless hypercommunications traffic vary according to the frequency band, bandwidth, availability of inexpensive equipment, equipment power, antenna type, terrain, and other factors specific to the spectrum used by a particular device. Interference or noise may result from rain, lightning, wind, outer atmosphere conditions, sunspot activity, solar flares, mountains, ground clutter, soil conductivity, interference from other devices, and due to the quality of filtering mechanisms in receiving appliances.

In the US, the FCC allocates spectrum among several groups: scientific interests, governmental and military users, broadcasters, amateur and private operators, and common carriers. Figures 4-30 and 4-32 through 4-33 show some of the more important spectrum assignments resulting from recent FCC licensing, auctions, and legislation. Assignments are far more detailed than those shown [NTIA, 1997; FCC, 1996; Weinhaus, Lagerwerff, and Brown, 1999]. Some wireless services require the action of local governments as well to cross public and private rights-of-way or to compete with wireline cableco franchises [Matheson, 2000].

Figure 4-30: Electromagnetic spectrum (one of three) from AM radio to microwave.

The lower frequencies are familiar since they contain AM radio, FM radio, and VHF and UHF TV bands. Indeed, most first generation and a good part of second generation wireless traffic is carried in the VHF (Very High Frequency) band and sub-microwave part of the UHF (Ultra High Frequency) band, the range shown in Figure 4-30. Beginning at the left, are the AM radio and tropical short-wave bands. The so-called tropical short-wave bands (below 3.950 MHz, wavelength 76 meters) are allocated to countries where interference-causing thunderstorm activity is common. These frequencies have less atmospheric noise due to lightning burst or static noise. Furthermore, since low-power transmitters can be used in those frequencies, radio signals can cover a greater area relatively inexpensively.

Moving to the right of Figure 4-30, other short-wave frequencies are found. It is possible to communicate via SSB (Single Side Band) radio in short-wave bands for thousands of miles to land or sea with specialized radio equipment. Motorola offers radios capable of sending data, voice messages, faxes, and e-mail using SSB paths. Equipment is expensive and interference can be great, so there is no guarantee traffic will get through to the destination.

The VHF band begins just above the CB (Citizen’s Band) at 30 MHz (wavelength, 10 meters). Until 30 MHz, atmospheric noise is plentiful while attenuation is low, meaning short-wave radio signals can be transmitted thousands of miles. Atmospheric noise drops at 30 MHz, but from 30 to 300 MHz, cosmic noise occurs and terrestrial signals cannot be transmitted beyond 50 to 120 miles, depending on terrain. VHF-TV, FM radio, and Little LEO technologies are used to communicate over frequencies in this spectrum. Little LEO systems are used for paging and low-speed data transmissions such as for POS (Point-of-Sale) devices.

From 300 MHz and up, line-of-sight wave propagation occurs [Committee on Evolution of Untethered Communications, NRC, 1997]. While short-waves bounce off levels of the ionosphere to travel hundreds of miles, meter-long (UHF) waves and 0.3 meter microwaves normally do not go beyond the 60 km (37 miles), the line-of-sight from transmitter to receiver [NTIA, 1995]. As frequency rises, coverage distances shrink, though this phenomenon is more pronounced in mobile communications.

Figure 4-31 shows an example of the relationship between the coverage zone of a single transmission tower to an increase in frequency using a mobile radio simulation done by NTIA’s engineering arm, ITS (Institute for Telecommunications Sciences) [NTIA, 98-349, 1998].

Figure 4-31: As frequency rises, coverage zones become smaller.

This physical relationship was behind the development of research on cellular and other mobile wireless coverage. To increase the coverage area for a given frequency, power must be boosted or antennas made taller or an interlocking network of base stations must be established (each with an overlapping coverage zones) or all three tactics taken. By using a combination of methods, the footprint of a particular wireless carrier (sum of individual coverage zones) can grow.

The FCC represents another limitation on coverage zone sizes and footprint areas because it regulates power levels and frequencies used by most wireless spectra. Specific boundaries are discussed in 6.1, but most frequency allocations are assigned on a market by market basis through open auctions or existing licensing regulations.

However, as frequency increases, signals cannot reach places they would have at lower frequencies even with the same signal power and antenna height. Hence, more towers are needed, more closely spaced together as frequencies rise. The irregular shape of the coverage zones in Figure 4-31 is due to terrain differences, water bodies, forested land, and other factors. With fixed services, special gain antennas can be aimed directly at the transmitter, resulting in larger coverage zones (at equal frequencies) than for mobile technologies.

Since satellite signals do not contend with (land-based) horizontal interference because line of sight is defined from outer space, a satellite can cover a vastly larger area than a terrestrial transmitter on the same frequency. However, satellite transmitters need more power to transmit while satellite dishes (designed as cones to increase the gain or signal power) have to be aimed at certain angles to pick up (and transmit) signals from and to outer space. In addition to frequency, antenna type, antenna direction, user mobility, and the specific terrestrial or wireless technology used affect the size of the coverage zone.

Most first generation and some early second generation wireless traffic takes place within the UHF (300 MHz) to 1 GHz (microwave) frequencies shown on the right side of Figure 4-30. Most prominent are UHF-TV, and two forms of cellular service IMTS (analog cellular) and CMRS (digital cellular). The SMR (Specialized Mobile Radio) bands use iDEN™ technology to provide a combination of radio and cellular communications to customers. Narrowband PCS telephones and pagers use this part of the spectrum as do fixed telemetry (remote sensing) devices. The BETRS (Basic Exchange Telephone Radio Service) rural radiophone service also is found here. BETRS offers small, remote communities the opportunity to use a radio transport path for telephone transport when wiring or cable is expensive compared to the subscriber base, impractical, or environmentally unsound. Around one hundred telephones on Dog Island, a small island on the Gulf coast near Carabelle, use this service to connect to the PSTN. ISDN-BRI is available through BETRS [FPSC, Docket 950814-TL, Order PSC-97-1196-FOF-TL, 1997].

Moving up, frequencies above 1 GHz have wavelengths so short they are too small to be called radio waves. Instead, these high frequencies above 1 GHz are called microwaves since they are one-millionth the wavelength of a 1 Hz wave. Figure 4-32 depicts part of the microwave spectrum, from 1 GHz microwaves (300 mm wavelength) up to 10 GHz (30 mm) in the SHF band. Later-second generation and third generation mobile and early third generation technologies that support fixed services operate in this spectral segment.

Figure 4-32: Electromagnetic spectrum (two of three) microwave to 10 GHz.

Two mobile satellite technologies, big LEO (Low Earth Orbit) and GSO (Geosynchronous Orbit), use the spectrum between 1 GHz and the 2.45 GHz frequency (used by microwave ovens), providing telephony and narrowband data communication. Also in this range are broadband PCS technologies, along with two other terrestrial technologies. First, two technologies that support newly auctioned fixed and mobile services at 2 GHz are located there, as is a third technology, MMDS (Microwave Multi-point Distribution System). These three terrestrial technologies are now (or soon will be) capable of providing data rates up to 2 Mbps in localized coverage areas and below 300-400 kbps in extended coverage areas. However, some argue that these promised speeds are higher than reality. For example, mobile users using PCS-1900 standard GPR (General Packet Radio) will have bit rates in extended areas of as low as 115 kbps because of the effect of motion on the radio path [Telecommunications Engineering Centre, 2000].

MSS (Mobile Satellite Service) technologies, fixed satellite, big LEO satellite, and additional point to multi-point terrestrial MMDS technologies have frequency allocations around 3 GHz. In the SHF band from 3 GHz to 10 GHz, several satellite technologies (GWCS or General Wireless Communications Service and other fixed satellite services) operate in frequencies near fixed WLAN (Wireless Local Area Network) technologies.

Figure 4-33 depicts the frequencies from 10 GHz to 59 GHz. From 10 GHz to 20 GHz a variety of satellite technologies share FCC-assigned commercial frequencies. These commercial frequency bands include broadband satellite Ku-band, DBS (Direct Broadcast Satellite), additional Big LEO frequencies, and several other fixed satellite assignments.

Enormous interest exists in development and introduction of services that would use fixed terrestrial technologies to provide services that would operate in the 24 GHz to 39 GHz (upperband) microwave frequencies. Broadband fixed wireless technologies in the upperband range include DEMS, LMDS, MMDS, and WLL. Because wavelengths are smaller, antennas are small enough (15 by 15 cm) that large, expensive rooftop antennas are unnecessary. The short wavelengths of the upperband range are not true line of sight systems because buildings or structures that might normally obstruct signals serve as passive or active repeaters since signals bounce off them or around them [Telecommunications Engineering Centre, 2000].

Figure 4-33: Electromagnetic spectrum (three of three) above 10 GHz.

Hence, while a form of line of sight propagation exists (with smaller coverage zones) above 30 GHz in the EHF band from transmitter to receiver, customers need not resort to large, roof-mounted antennas [Committee on Evolution of Untethered Communications, NRC, 1997]. However, there is a new set of limitations in the upperband. According to the NTIA, "beginning at about 10 GHz, absorption, scattering, and refraction by atmospheric gases and hydrometeors (the various forms of precipitated water vapor such as rain, fog, sleet and snow) become the important limiting factors for electromagnetic wave propagation" [NTIA, 1995, part 2, Ch. 8]. Other important concerns are possible affects on human health of all microwave transmissions, especially those in the upperbands.

Above the range shown in Figure 4-33, lasers and infrared light are also used, mainly for WLAN applications. During every wireless generation, there has been a frequency shortage followed by new technologies (and regulations) that allow ever-higher frequencies to be harnessed for communications. Laser and infrared technologies are currently used for short distances such as within buildings or from one building to an adjoining building for data networking. TV remote controls are examples of laser or infrared devices. Like remote controls, lasers and infrared signals require close, unobstructed ranges to operate.

Figure 4-34 shows how rain, fog, and atmospheric gases (such as water vapor) can limit signal strength (and hence the coverage zone of a single tower) as higher wireless frequencies are used [NTIA, 1995].

Figure 4-34: As frequency rises, rain and other atmospheric conditions lower signal strength.

On the x-axis are frequencies from 5 GHz to 500 GHz, with special attention drawn to the upperband between DEMS and WLL (from 24 GHz to 39 GHz). The y-axis depicts horizontal path attenuation (dB/km), showing how much signal strength is reduced due to various rainfall rates, fog, drizzle, and atmospheric gasses. If every 3 dB of signal loss results in the loss of 50 percent of a signal’s remaining strength [Sheldon, 1998, p. 995]., then the heavier the rain and the higher the frequency, the more likely the signal will suffer. The 3 dB threshold is reached just above 6 GHz for rain falling at a rate of six inches an hour and below 20 GHz for rainfall rates of one inch an hour. The threshold is reached within the upperband with rainfall rates of one-fifth an inch per hour, but not for drizzle. Atmospheric gases cut signal strengths in half only at frequencies well above the 39 GHz band where WLL technology operates.

Upperband technologies can be engineered around these problems through a site specific trial and error approach using early customers as experimental subjects. Nor is there scientific agreement about what kinds of reception problems can be expected. According to NTIA (1995) research, for every km (3280 feet) that an upperband signal travels through rain (falling at a rate of an inch or more per hour) result in as much as a 75 percent signal reduction. Papazian, et al. (2000) found that trees in wind (located near business wireless equipment) could be worse than rain in reflecting or blocking upperband signals.

More generally, path loss, shadow fading, multipath fading, and interference are all problems that affect terrestrial wireless transmission. Path loss equals received power divided by transmitted power and is a function of distance from transmitter to receiver [NRC, 1997]. More formally, path loss, L is given by , where Pr is received power, Pt is transmitter power, f is the center frequency of the signal, and n is the path loss exponent. K is a constant that depends on path loss at a reference distance d₀ from the transmitter, or the antenna far field (approximately 1 m indoors and 0.1-1 km outdoors) [NRC, 1997, p. 2-34].Hence, "received signal power is proportional to the transmit power and inversely proportional to the square of the transmission frequency and the transmitter-receiver distance raised to the power of a path loss exponent." [NRC, 1997, p. 2-34]

Given that the path loss exponent is 2 in free space, but ranges from 3 to 5 in typical outdoor environments, exceeding 8 with dense buildings or trees,

The technical details of wireless transmission are subject to Shannon’s Law, the Nyquist Theorem, and other physical laws governing analog-digital conversions and signal domain as discussed in 4.2. Gilder argues that the future of wireless is "boundless bandwidth, accomplished by the Shannon strategy of wide and weak signals, moving to ever smaller cells with lower power at higher frequencies." [Gilder, 1993, p. 11]

In spite of such a bright future, there are three important differences between wireline and wireless transmission as currently provisioned that should be noted before specific terrestrial and satellite technologies are covered. The first difference is that many mobile wireless CPE devices contain DTE, DCE, and an antenna in one unit. For fixed wireless technologies, there is typically more separation. Figure 4-35 (based on NTIA 98-349, 1998, p.2) shows the components of a general wireless technology, operating at the local network or access level.

DTE perform DSP (Digital Signal Processing), analog-digital conversion (when needed), and interact with the user via display and controls. DCE are transceivers with power settings and electronics components for particular frequencies that send and receive RF (Radio Frequencies), microwaves, infrared, or other wireless signals. Then, for most carrier services, signals are sent over antennas, typically to a base station or tower that has intermediate DCE and antennas of its own. If the opposite end is wireless, the process is reversed. Wireless mobile and nomadic telephones (and other mobile user devices) contain all three components in a single unit.

Figure 4-35: Wireless technology components may be separate or together.

However, fixed wireless connections typically have the antenna separate from the DCE and DTE. When a computer is used for wireless access to a carrier network (or as WLAN station) it serves as the DTE. Typically, in fixed wireless the computer uses a separate DCE (a transceiver) and local conduit to transmit over the antenna. From the antenna, transmissions travel to a carrier tower located at a POP (base station) where they enter a wireline or wireless carrier network (transport level). In a point-to-point system, transmissions do not require a carrier's transport network, since they are beamed directly to another antenna at another location of the business. In the point-to-point case, all equipment may be owned or leased by the agribusiness.

Another way wireless technologies differ from wireline is in the distinction between baseband and broadband. In wireless, baseband is the raw audio or video signal before modulation and broadcast. Thus, the original frequency range before modulation onto a higher, more efficient range is the baseband. For example, most satellite headend equipment uses baseband inputs. The input signal is unfiltered receiver output with FM modulated audio and data sub-carriers. Wireless broadband devices process a signal that spans a relatively broad range of input frequencies.

4.4.2 Terrestrial Wireless Technologies

As has already been mentioned, terrestrial wireless communication may be mobile or fixed. The first and second generations of wireless technology emphasized mobility and lower frequencies since they sought to provide only basic wireless telephony and low-speed data communications. The third generation saw mobile technologies operate in higher frequencies (such as the 2 GHz PCS band) while coverage zones expanded, power needs fell, data rates rose, and more services were supported. Simultaneously, third generation fixed technologies made dramatic leaps into upperband frequencies (24-39 GHz), attaining data rates as high as wireline technologies so as to support a range of hypercommunication services including voice, video, high-speed data and Internet.

In this section terrestrial (non-satellite) wireless technologies are briefly outlined. As with wireline technologies, almost every specific service named in sections 4.6 through 4.9 can be provided by terrestrial wireless technologies. The ability of terrestrial wireless technologies to serve as access paths for hypercommunication services depends mainly on signal frequency, user mobility, and the availability of appropriate antennas, DCE, and DTE. Table 4-10 details terrestrial wireless technologies used to support of mobile and nomadic services.

Typically, mobile user devices include DTE, DCE, and an antenna in a single unit. Mobile services are provided by carriers using a series of overlapping coverage zones (cells) each of which is served by a tower attached to base stations. As subscribers travel in their carrier's local footprint, calls are passed from one cell to another. Subscribers may roam regionally or nationally and use their own (or another) carrier's network if compatible technologies are available in the roamed area.

Mobile wireless voice services are discussed in more detail in 4.7.5, while paging is covered in 4.7.6. Mobile wireless data networking is covered in 4.8.5. Carriers extend service to subscribers based on one or more of the technologies shown in Table 4-10.

Table 4-10: Mobile terrestrial wireless technologies
 

Technology	Market Applications	Freq. & Channel Bandwidth	Data Rate
CDMA (Narrowband PCS)	Two-way paging, digital mobile enhanced telephony	900-941 MHz (25 MHz)	6.4-25.6 kbps
CSCD	Fax, file transfer, Internet	800 MHz Analog cellular (25 MHz)	1.2–9.6 kbps, 14.4 kbps optimally.
CDPD (Analog & early digital cellular overlay)	Two-way paging, POS, data queries, dispatch, on analog cellular line.	800 MHz (12.5-30 MHz)	4.8-12 kbps
Digital Cellular-PCS (IS-136 TDMA, IS-95 CDMA)	Two-way paging, fax, e-mail, enhanced digital telephony.	800,.900, 1900 MHz (25 MHz-200 MHz)	9.6–14.4 kbps (current), 1.2 Mbps (spread spectrum, future)
ARDIS (Motorola DataTAC)	Two-way paging, transportation data support, in-building wireless.	800 MHz (25 MHz)	2.4 kbps (nationwide), 9.6 kbps (limited)
BellSouth Wireless Data (Mobiltex)	Two-way paging, dispatch, database.	900 MHz (12.5 kHz)	4.8 kbps
AMPS cellular Telephone	Mobile telephony, modem applications.	400 MHz (25 MHz)	4.8-9.6 kbps. See also CDPD, CSCD
iDEN (SMR, ESMR)	Enhanced digital mobile telephony, Internet, e-mail, and dispatch.	800-960 MHz (15-30 MHz)	9.6 kbps-64 kbps (Nextel)
GSM-1900, TDMA (Broadband PCS)	Enhanced digital mobile telephony, file transfer, Internet, e-mail.	1.9–2.1 GHz (200 MHz)	300 kbps (extended range), up to 2 Mbps (local CZ)

Sources: FCC 99-136, Hewlett Packard, 1999, Rysavy, 1997, Weinhaus, 1998.

Table 4-11 lists several fixed wireless technologies that are currently or soon to be available in Florida. For each technology, the typical frequency and channel bandwidth, data rate, and services supported are shown. Since fixed terrestrial wireless technologies are works in progress, the table cannot convey more than a broad general categorization. Hence, the specific technologies listed in the table are often imprecise terms, based on a melding of traditional FCC definitions, proposed frequencies, experimental tests, and implementations by carriers.

Table 4-11: Terrestrial fixed wireless access technologies
 

Tech-nology	Market	Typical Frequency (Channel Bandwidth)	Data Rate (Range)
WLAN via infrared	Segments of LANs.	3000-30000 GHz	4-16 Mbps (with token ring card (80 feet)
WLAN via laser	Local Area Network in office or campus.	30-150 THz (800 nm waves)	To 16 Mbps (3280 feet line-of-sight)
WLAN via RF	Local Area Network in office or campus.	5.1-5.8 GHz (30-100 MHz), unlicensed spread spectrum	10-100 Mbps (3280 feet in open, 650 feet in building)
2.4 GHz WCS	WWAN, WLAN, & Internet access.	2.402-2.48 GHz (1-25 MHz per channel), unlicensed spread spectrum	156 kbps to 11 Mbps (Up to 10-25 miles)
DEMS	Broadband microwave access: telephony, WAN, video, Internet.	24 GHz (100 MHz)	Up to 30 Mbps, (2-10 miles)
MMDS	Microwave access: telephony, data, video, Internet.	2-2.6 GHz (190-200 MHz)	Up to 10 Mbps (30-35 miles, one-way; 6 miles, two-way)
LMDS	Broadband microwave WAN & access: data, future telephony, video.	28 GHz, 38 GHz, (150 MHz, B Block, 1.15 GHz, A Block)	Downstream 20-50 Mbps, Upstream 3-10 Mbps, (3-5 miles, possibly 20)
WLL	Broadband microwave WAN & access: data, Internet, ATM, telephony, video.	39 GHz (100 MHz-1.4 GHz)	45-155 Mbps (2-5 miles, possibly 9-10)

Sources: REA (1992); Bezar (1995), Teligent (2000); Rysavy (1997); Molta and Irshad (1999), Mandl (1999).
 
 

The first fixed terrestrial wireless technologies are WLAN (Wireless LAN) technologies. The first type of WLAN is infrared WLAN. Infrared adapters plug into token ring cards to allow localized transmissions (within 80 feet). While infrared can be used between buildings, it is so susceptible to fog, rain, and smog interference (since it is a form of light) that it is usually used for remote controls, wireless keyboards, and wireless computer mice.

The last WAN technology includes the 5.8 GHz spread spectrum technologies that make use of unlicensed spectra to operate on a single premise. Spread spectrum technologies allow low-power operation and reduce interference. In open spaces, 100 Mbps ranges for wireless LANs (such as the Breeze Net Pro.11 product line) can range from 1000m (3280 feet) in open areas to 60-200m (200-650 feet) inside buildings.

WLANs use all-wireless Ethernet and specialized hybrid technologies. An all-wireless Ethernet LAN replaces cabling among computers in a local network with wireless paths, so individual computers require antennas to transmit to the network host. With all-wireless Ethernet technologies, laptop computers connect to the WLAN through antennas in their PCMIA slots and remain portable in the office. Hybrid WLAN technologies use wireline cabling to connect each machine in a particular area to a hub (or other intermediate DCE), but use wireless paths from hub to central server.

The second WLAN technology, WCS, may be particularly useful for agribusinesses seeking to interconnect LANs inside a ten to twenty-five mile radius of a central site (creating WWANs, Wireless WANs), or to obtain Internet access. The 2.4 GHz WCS band is also unlicensed spectrum that can be used on the local or access level. Since spectrum is unlicensed, the FCC requires that spread spectrum technologies be used that make radio signals appear as background noise to unintended receivers. Numerous service providers in many parts of Florida are currently offering wireless Internet access in the 2.4 GHz band. However, interference from garage door openers, baby monitors, and other wireless equipment can occur in the unlicensed frequencies used by WCS. Specific WLAN applications are covered in 4.8.5, while Internet access is the subject of 4.9.1.

DEMS is a two-way all digital system that uses DTSs (Digital Termination Systems) on each end as DCE. An important characteristic of DEMS is proper antenna placement [Weinhaus, Lagerwerff, and Brown, 1999].User stations require directional antennas over a 2-10 mile long path length [REA, 1992].In 1998, Teligent began to provide the first DEMS service in Florida to metro Jacksonville, Tampa, Orlando, Palm Beach County, and Miami-Dade County.

Teligent's DEMS technologies use a two-step wireless layout. In the first step, at the access level, "When a customer makes a telephone call or accesses the Internet, the voice, data or video signals travel over the building’s internal wiring to the rooftop antenna. These signals are then digitized and transmitted to a 'base station' antenna on another building, usually less than three miles away." [Teligent, 2000] The DEMS base station functions as a POP for that area, gathering "signals from a cluster of surrounding customer buildings, aggregates the signals and then routes them to a broadband switching center." [Teligent, 2000]

LMDS and MMDS are similar in that both are multi-point microwave distribution technologies used to provide high-speed hypercommunications access. Both have been used to provide wireless cable TV, but new technologies allow two-way transmission. Some of the differences between LMDS and MMDS are frequency, bandwidth, and cell size:

WLL is another upperband technology christened as fiber in the sky. Wireless POPs are centrally placed in urban areas with access accomplished via MTE (Multi-Tenant Environment, office building) rooftop transmitter to wireless hub paths. Estimates are that only three percent of office buildings have fiber, but that they represent one-third of all business communication lines [Mandl, 1999].WLL is targeted at this three percent (the power users), while LMDS, MMDS, and to a lesser extent 2.4 GHz are aimed at the 97 percent without fiber access, the smaller business customer.

CDMA technology is used to economize on spectrum, so individual clients may maximize data rates. The 39 GHz band in which WLL will operate can carry data rates of up to 155 Mbps over several miles. Winstar is a WLL provider in Florida, with the right to provide coverage from Jacksonville to Miami along the Atlantic Coast and from Citrus County south to Everglades City on the Gulf Coast.

The new upperband technologies are no panacea for rural areas. According to the NTIA, most applications are for dense urban MTE locations.

In spite of predictions by Gilder (1993) and others that wireless bandwidth would be boundless in 2000, InfoWorld has a different prediction for 2001. "Wireless users may hit a speed bump" because of limitations on spectrum and failure to deploy equipment in many areas [InfoWorld, October 29, 1999].While terrestrial wireless technologies are developing slowly, inexpensive, symmetric satellite technologies are coming even more slowly.

4.4.3 Satellite Technology

Until fiber optics, satellite wireless appeared to have the most promise as a high-speed voice transport technology. Early 1960's satellites could carry 480 channels, compared with 256 then carried by telephone cable. By December 1988, TAT-1 the first fiber-optic transoceanic cable became operational and could carry 37,800 voice channels. By 1995, the TAT-12 and TAT-13 satellites (linking Europe and the US) could carry over one million telephone conversations at once [Stone, 1997].At the end of 1997, over 180 communications satellites were in orbit, with industry sources expecting as many as 1700 additional satellites by 2005 [Rysavy, 1997].It remains to be seen if future satellite technologies will carry many times this amount of converged voice and data traffic because of the high cost of orbital launches and the relatively high price of satellite DTE and DCE. However, satellite technology now holds promise in access, point-to-point, and transport levels for businesses regardless of location.

Orbital satellites use an uplink (earth-to-space) and a downlink (space-to-earth) to allow two-way communication. Special bands of the electromagnetic spectrum have been allocated for satellite use. Traditional satellite technologies use the C band and Ku bands. In the C band, 3.4-4.8 GHz is used for downlink and 5.85-7.1 GHz for uplink, while the Ku band uses uplink frequencies of 14-14.5 GHz with 10.7-12.2 GHz for the downlink. A new broadband Ka band of 19.7-20.2 GHz (downlink) and 28.35-28.6 GHz (uplink) is just beginning to see service.

Many satellite technologies are used to deliver wholesale services only to hypercommunication carriers. As with terrestrial wireless technologies, satellite services are classified as fixed or mobile. Fixed means that users on earth do not move, in contrast with mobile services where subscribers move. New technologies are under development by several large consortia to bring broadband (high-speed) services to individual businesses and wholesale customers. However, the costs of deployment and CPE are high enough that progress has been slow.

Table 4-12 shows several satellite technologies capable of providing both mobile and fixed hypercommunication services worldwide, now and in the future. Geostationary orbit (GSO) satellites and geosynchronous (GEO) satellites each orbit at altitudes of 22,300 miles (36,000 km) above the earth, revolving the earth once every 24 hours so they appear to be stationary. GSOs are GEOs that orbit directly above the equator. Geosynchronous satellites transmit both voice and data communications, but long delays are experienced. The delay arises from the fact that the uplink (earth to satellite) and downlink (satellite to earth) portion of the communication each travel at the speed of light. Each step results in a delay of a quarter of a second and up under the best circumstances [IEC, 1998, p. 19].From three to five GSO satellites are deployed to get coverage of almost the entire globe. Larger constellations may be used to obtain faster data rates and greater overall capacity.

GSO technologies include GSO FSS (fixed satellite service) and GSO MSS (Mobile Satellite Service). GSO technologies have been implemented by several systems including Comsat (formerly part of AT&T), Intelsat, and Orion. However, ground equipment (CPE) at the businesses' location is extremely expensive and complicated at this stage. Hence, GSO technologies are normally used by large agribusinesses and other global organizations. Data or voice transmissions may be charged by the minute or by the kilobit.

Table 4-12: Mobile and fixed satellite technologies
 

Satellite System	Services Supported	Altitude (Speed)	Bandwidth (Data Rates)	Frequency	# to cover world
GSO	Voice transport, high-latency data. FSS & MSS	22,300 mi. (11,000 km/hour)	400 MHz -1.1 GHz (variable)	C band (4 GHz), Ku band	3-5
DBS (GEO)	TV, Internet	Same as GSO, but equatorial orbit	0.5 GHz (2 Mbps, downstream, 33.4 upstream)	12.2-12.7 GHz, 17.3-17.8GHz	3-5
MEO	Now: messaging, future: Internet, data networking.	6,250-12,500 mi. (19,000 km/hour)	500-800 MHz (9.6 kbps, 6 Mbps in future)	C band, Ka band (20 GHz)	10-12
Little LEO	Paging, GPS, remote monitoring.	400-1,000 mi. (27,000 km/hour)	25, 85 MHz (up), 25, 1900 MHz (down), (4.8 kbps)	137, 138, 399- 401 MHz	48-66
Big LEO	Satellite telephony, broadband PCS. Future: two-way data & Internet.	400-1,000 mi. (27,000 km/hour)	16.5 MHz (current: 400 kbps, down; 33.4 up via modem; future: 2 Mbps & 6 Mbps )	1-3 GHz (portions)	48-66
Broad-band LEO	Future access to Internet, WAN, converged networks.	150-400 mi. (27,000 km/hour)	.5-.8 GHz: (Future: 64 Mbps down, 2 Mbps up)	Ka band (20, 28 GHz)	200-288
Broad-band GSO & GEO FSS	Future access to Internet, WAN, converged networks.	22,300 mi. (11,000 km/hour)	.5-.8 GHz (Future: 500 kbps up, 3-6 Mbps down)	Ka band (20, 28 GHz)	8-20
MSS	Telephony.	GSO or NGSO	36-72 MHz	2 GHz	varies

Sources: Weinhaus, Lagerwerff, and Brown, 1999; Rysavy (1997); Hudgins-Bonafield (2000).

Advantages to GSO include worldwide coverage even of remote locations far from wireline connections. GSO technologies can also reach ships at sea (Inmarsat), airplanes, and every nation on earth with the satellite serving as access and transport level all in one. While the high latency of GSOs is annoying, echo cancellation and other innovations will improve the quality of GSO voice conversations. GSOs last an average of ten years before they must be replaced, double the length of the next type of satellite technology, NGSO [Hudgins-Bonafield, 2000].

There are several NGSO (Non-Geostationary Orbit) satellite technologies. However, by definition, continuous coverage of any single location on earth requires around the world coverage of similarly situated points. NGSO networks function in a similar way to terrestrial cellular networks in that each satellite has its own coverage zone within a network footprint. However, since the satellites are moving, coverage zones are moving as well whether the user is moving (NGSO MSS) or fixed (NGSO FSS).

DBS (Direct Broadcast Satellites) operate in the 12.2 to 12.7 GHz band (downlink, BSS) and the 17.3 to 17.8 GHz band (uplink, Feeder, FSS). Total bandwidth for uplink and downlink is 0.5 GHz [Weinhaus, 1998, p. 28].DBS satellites are GEOs, so they exhibit high latency. Current systems such as Hughes' DirecPC offer Internet access with download rates of up to 2 Mbps, but require that the upstream end go through a normal telephone modem. Future iterations of DBS technologies are expected to allow a minimal wireless return path, though the emphasis of DBS is on the downstream rate.

MEOs are Middle Earth Orbit satellite systems. Their orbits are from 6,250 miles to over 12,000 miles above earth, in between the orbit of GSOs and LEOs. However, more satellites are needed in a MEO constellation than in GSO or GEO constellations. Between ten and twelve satellites or more are needed for global coverage by a MEO constellation. MEO technologies use up to 500-800 MHz channels in the C and Ka bands. MEO technologies support services ranging from simple messaging (9.6 kbps) to future rollouts of two-way Internet, voice and data networking with data rates of up to 6 Mbps expected. Because a single MEO satellite will be overhead any fixed site for only two to four hours before another orbiting satellite arrives, MEO technologies require coordination among satellites for uninterrupted coverage.

Another NGSO satellite technology is the LEO (Low Earth Orbit) satellite. These orbit from 150 to 1,000 miles above the earth, cutting down on the delay experienced with geosynchronous satellites. However, LEOs are costly to launch and operate because they require a constellation of satellites to cover the earth's surface. For example, the now bankrupt Iridium worldwide network was to have been composed of 66 satellites, while the Globalstar system will have 48.

LEO technology can provide point-to-point or person-to-person services to the entire globe except when atmospheric or solar conditions interfere. There is also significant risk of widespread system damage due to asteroids and meteorites that do not have the atmosphere to burn them up before they hit. LEOs travel at faster rates than MEOs or GSOs, adding to their risk of destruction. LEO construction costs of $6 billion and up per system have led to their development by international consortia, rather than any single firm. For example, (the now bankrupt) Iridium project had Qualcomm, Motorola, and Globalstar as partners.

There are two kinds of LEOs, big LEOs and little LEOs. Little LEOs are used primarily for paging, remote monitoring, vehicle tracking, and other GPS (Global Positioning System) applications. Little LEOs use frequencies from 137 to 400 MHz, offering bandwidths from 0.025 MHz to 0.85 MHz (downlink) and 0.15 MHz to 1.9 MHz uplink. Leo One and Orbcomm are two little LEO systems in common use. Little LEOs offer low-cost, low-speed transmissions of relatively small amounts of data worldwide with higher signal reliability than other space-based systems.

Big LEOs are intended to be the satellite equivalent of terrestrial cellular telephone service. Eventually, big LEO technologies will provide fixed and mobile voice, data, paging, and fax on a worldwide basis, even in rural areas and developing countries at limited data rates. Big LEO technologies use MSS frequencies between 1GHz and 3 GHz, generally around 1610-1625 MHz or 2483.5-2500 MHz, with a bandwidth of 16.5 MHz for each service link [Weisman, 1998, p.39].

Today, big LEO technologies support satellite telephony and broadband PCS. In the future, big LEOs will support two-way data & Internet. Today, Internet data rates from big LEOs are typically around 400 kbps with the return (upstream) signal traveling via wireline telephone modem. Future systems will attain data rates of from 2 Mbps to 6 Mbps. Big LEOs move across the sky quickly, rotating above a single point on earth as many as 14 times per day. Hence, the technology must be flexible enough to allow one satellite to take over from another when the line-of-sight from the first satellite becomes obstructed.

Another type of big LEO satellite technology is broadband LEO. Unlike typical big LEO (and other NGSO) technologies with broadband satellite technology, cells on earth remain fixed, while the network of satellites rotates around earth. The Teledesic satellite network (an NGSO FSS) will be a broadband LEO system capable of offering data rates of up to 64 Mbps (downlink) and 2 Mbps and above (uplink), operating in the Ka band (20 GHz to 30 GHz). Service is anticipated to start in 2004. Broadband LEO systems are seen as an "Internet in the Sky", linking computers worldwide with high-speed connections. The bandwidth of service allocations is 0.5 GHz, with feeder allocations of 0.8GHz. Since they orbit between 150 and 400 miles above earth, broadband LEOs may be over a particular location on earth for only tens of seconds before a new satellite must take over. While broadband LEO technology is engineered to accomplish this, the degree of jitter depends on the total number of satellites in a carrier's constellation [Hudgins-Bonafield, 2000]

Teledesic is an example of an NGSO FSS system, while thirteen GSO FSS systems have been authorized by the FCC including Loral, PanAm Sat, and KaStar [Weinhaus, Lagerwerff, and Brown, 1999, p. 32].Broadband GSO and GEO satellites have higher delays than LEO or MEO, but lower jitter because there is less variability due to handoffs from orbital changes. Both types of broadband FSS operate with channel bandwidths of 500-800 MHz, Future broadband LEOs are expected to feature data rates of up to 64 Mbps downstream with 2 Mbps upstream rates. Broadband GSOs use the same frequencies and bandwidths, but are expected to achieve upload speeds of 500 kbps with 3-6 Mbps download speeds [Hudgins-Bonafield, 2000]

Mobile Satellite Service (MSS) technologies operate near 2GHz, offering a total bandwidth of from 35-72 MHz for uplink and downlink. MSS can be provided by GSO or NGSO technologies. MSS technologies were originated by INMARSAT to enable communication with ships on the high seas [Telecommunications Engineering Centre, 2000]

Advantages of satellite technologies include their lower susceptibility to multi-path fading caused by reflection from objections surrounding the transceiver on the ground [NRC, 1997].By beaming signals vertically, upperband signals show considerably less attenuation than when transmitted terrestrially. They also offer worldwide coverage to rural areas as well as urban ones. It remains to be seen which satellite technologies offer agribusinesses the greatest promise for future hypercommunication needs. For agribusinesses with a need to network directly with rural, third world operations, or foreign customers, satellite technologies may be the only possibility for years to come.

An important physical limitation to satellite technologies is the high path loss. The higher the operating frequency, and the greater the path distance, the more transmit power is needed to compensate. Satellite signals are attenuated by earth’s atmosphere and by cosmic and solar noise. The NRC reports that while satellites offer advantages over horizontal fixed wireless transmission, adverse effects still occur "at frequencies above 10 GHz, where oxygen and water vapor, rain, clouds, fog and scintillation cause random variation in signal amplitude, phase, polarization, and angle of arrival . . . " [NRC, 1997, p. 2-6] High-gain directional antennas help reduce upperband problems, but such high frequency digital transmissions are troublesome given Florida’s climate. High deployment costs are another disadvantage of satellite technologies, with costs of devices and carrier equipment comparatively large.

4.4.4 Wireless QOS

As shown in Table 4-13, QOS in the wireless environment has more variability than in the wireline case. While new wireless technologies are constantly appearing to counteract QOS problems, wireless paths are subject to interference from man and nature. Satellite and mobile services have the more difficulty in establishing guarantees comparable to wireline carriers.

Table 4-13: QOS dimensions and wireless.
 

Dimension	Description	Wireless difference from wireline
Bandwidth	Maximum capacity of path	Bandwidth is a more theoretical concept since capacity varies by path loss, multi-path fading, etc.
Throughput	Transfer speed noticed by users.	Higher error rate, larger jitter, and reception variability can slow throughput.
Bit rate	Variable operational speeds of DCE.	Wireless devices must be flexible enough to adapt to many possible speeds even when multi-path fading causes rapid variations.
Data rate	Actual speed of path.	Larger observed variance. Since error rate is higher, data rates (which are error-free) are affected.
End-to-End delay (latency)	Time a bit takes to go from sender to receiver.	Higher at greater distance (satellite), errors, conversion & encryption increase delay.
Jitter	Variation in delay.	Likely to be much larger.
Connection establishment delay	Time it takes for connection to establish.	Establishment of radio path may take longer with some services, greater variability than in wireline connections.
Connection establishment failure probability	Probability that a given attempt will not establish path.	Chance that sender or receiver cannot establish connection (due to noise, interference, etc.). Most likely for mobile & nomadic wireless.
Network transit delay	Time from transport sender to receiver. (Transport & Access)	As with wireline, varies depending on network load, management. Frequency sharing technologies lower this, but other factors increase it.
Error rate	Fraction of lost or garbled messages in a period.	Interference, loss, fading may cause this to be higher than in wireline. Possibly transparent to user due to slower data rate and throughput.
Security	Ability of others to intercept or copy messages or gain network access.	Inherently easier to eavesdrop on wireless conversations unless scrambling or other techniques are used. Data require encryption, slowing throughput.
Priority classification availability	Ability to create traffic priorities.	No difference.
Resilience	Chance of spontaneous failure at any level.	Wireless equipment is exposed to lightning and weather & has been less thoroughly tested than wireline.
Environmental specifications & safeguards	Effect of power failures, lightning, etc. on communication.	Thunderstorms, solar flares, & even fog can lower data rate or cause the complete interruption of wireless signals.
Overall failure probability	Fraction of time when any QOS dimension fails to reach standard.	The probability of at least one QOS metric being violated is unambiguously higher.

Sources: NRC, 1997; FitzGerald and Dennis, 1999.

There are several physical reasons wireless has QOS disadvantages: frequency, channel width, various kinds of interference, latency, jitter, and tighter technical specifications. As has been mentioned repeatedly, higher frequencies tend to have wider channel capabilities and hence, more bandwidth. This comes at the cost of shorter radio waves that can travel shorter distances, are more prone to interference, and may have negative health consequences. Interference, fading, path loss, and attenuation vary by technology, frequency, and location.

Even with fixed wireless technologies, there is more signal variability than with wireline transmission, propelling error rates higher. Latency and jitter interact with effective bandwidth, data rate, and error rate. Latency or delay depends on distance. Thus, GSO and GEO technologies are most affected followed by MEO and then LEO. All satellite technologies are affected more by delay than earth-based wireless technologies are. Finally, tight technical specifications such as antenna angles, humidity ranges, and antenna type can make wireless services hard to deploy without specially trained carrier and agribusiness personnel.

With few exceptions, wireless QOS is less controllable than wireline. Hence, it may be hard for agribusinesses to gain SLAs (guarantees of service) from wireless providers on par with wireline carriers. Next, the technologies and people needed to operate and interconnect hypercommunication networks are covered.

Support services, facilitation, and consolidation technologies cover a wide territory and there is only space to touch on a bare minimum. Support services (4.5.1) include the human expertise necessary to install, maintain, interconnect, and otherwise assist users and suppliers of hypercommunication technologies and services. Protocols and standards (4.5.2) are the building blocks necessary to improve hypercommunication markets and enable convergence, deregulation, and interconnection. Protocols, standards, and the various standards organizations are hypercommunication facilitation technologies because they create better markets.

Consolidation technologies are known as convergence-enabling technologies since they are examples of areas where convergence will occur. The first consolidation technologies to be covered are wireline-wireless facilitating technologies (4.5.3). Voice-data consolidation technologies (a second type of consolidation technology) are covered in 4.5.4. As both kinds of consolidation technologies become more widely used by agribusinesses, true converged hypercommunication will occur.

Separating support services, facilitation technologies, and consolidation technologies from the services and technologies of specific sub-markets is somewhat artificial. Later, these three subjects are placed in the context of the specific sub-market for specific services and technologies (4.6-4.9). There is an historical component to the separation in that support services are necessary now, facilitation technologies are under constant development, and consolidation technologies are a promising area for the future. However, by separating support, facilitation, and consolidation, agribusinesses will better understand where they will have to invest money, what differences exist among carriers, and where convergence will come from.

4.5.1 Support Services

The dollar cost to business of support services, the human side of hypercommunications, will reach twice the level of equipment costs by 2003. Business expenditures on services to support voice and data equipment are projected to grow at an annualized compound rate of 19.5 percent through 2003 to reach $237.1 billion, more than double the projected $112.6 billion equipment market for 2003 [TIA-MMTA, 2000, p.94].Costs for support and integration services of voice-data communications equipment stood at $116.4 billion in 1999. There are two fast-growing categories of support services.

The first support service category is professional and technical services. This area includes network integration services, consulting, and time and materials for engineers, computer scientists and programmers, and other professionals. In 1999, professional and technical services represented $73.8 billion of the total support service bill for American enterprise. The tab is only expected to grow larger. The second support services category are field maintenance and repair services. In 1999, expenditures here stood at $31.1 billion, with the expectation that the level will continue to rise.

Support services tend to be specific to the services and technologies they support. Thus, some additional coverage occurs in the context of the sub-markets discussed in sections 4.6 through 4.9. Agribusinesses should realize that their CPE and the equipment of their carrier are only as good as the people who service it at the carrier end and the people who use and maintain it at the agribusiness. Furthermore, having employees or consultants whose judgement can be trusted is vital to choosing the right equipment to begin with.

4.5.2 Protocols and Standards for Hypercommunications Networking

Protocols such as (TCP/IP, SS7 signaling, and V.90) may be created through scientific agreement or by government, self-regulatory or independent bodies. Hypercommunications protocols and standards help consumers and suppliers avoid the deadweight loss of endlessly searching technical specifications or creating new ones by establishing mutually agreed upon definitions, along with interoperability and interconnection of technologies and services. This sub-section has three main purposes. First, to classify and explain the sources, bodies, and technical types of standards and protocols. Second, to place hypercommunication standards and protocols in an economic context of interest to agribusinesses. Third, the section outlines a couple of strategic areas where protocols and standards have not yet been agreed upon, placing emphasis on their importance in business settings.

The term protocol is often used interchangeably with standard. According to the FCC, protocol and standard have two separate meanings each. First, protocols are "a formal set of conventions governing the format and control among communicating functioning units". Second, protocols are also "a formal set of procedures that are adopted to facilitate functional interoperation within" a "layered hierarchy" [GSA, FED-STD-1037C, 1996, p. P-25]. The IP (Internet Protocol) is one of the better known examples, underscoring the tendency for protocols to be used in communications networking software and hardware.

Standards are "guideline documentation that reflects agreement on products, practices, or operations." [GSA, FED-STD-1037C, 1996, p. S-26] A second definition of standard as "a fixed quantity or quality" is frequently used [GSA, FED-STD-1037C, 1996, p. S-26].A standard is more likely than a protocol to describe hardware (e.g. wiring standards) or to characterize physical quantities such as specification ranges (e.g. engineering operational standards). While the two terms are used almost interchangeably in this section, precise meanings (when important) should be clear in context.

Economist Paul David established three classes of standards [David, 1987] that some authors consider the "best classification system for telecommunications (standards)" [Stone, 1997, p. 122].Reference standards deal with weights, measures, and other units. These tend to be agreed on by international standards bodies and are generally objective, scientific-based standards. Minimum attribute standards are the minimum acceptable characteristics associated with the deployment of a hardware or software technology. Compatibility standards permit interconnection of CPE and other hypercommunications components such as hardware and software to work in conjunction with an entire network or system.

To these three, security standards could be added. These are standards designed to prevent access to certain information due to privacy, or the desire to sell intellectual property such as hardware, software, or content. Authentication CGI scripts, e-commerce software (such as shopping carts) and hardware (such as secure servers) are common Internet examples. Other computer examples are virus blockers, cookies, automatic registration and upgrading of browser plug-ins, un-uninstallable programs, etc. A particularly controversial case involves cryptography, where e-mail and other communications traffic are sent in coded form that only can be understood with a key at the other end. Federal law enforcement and national security reasons have been given to prevent the export of certain kinds of cryptography software [Internet Week, June, 15, 1998, p.1].

When IAB (Internet Architecture Board) protocols advance to become draft standards, the technical community is on notice that "unless major objections are raised or flaws are discovered, the protocol is likely to be advanced to a standard in six months" [IAB, 1995, p. 2].Protocols and standards have both a state and a status. The state shows at what stage of the standards track (maturity level) a particular protocol has attained. For example, a new protocol occurs after an RFC (Request for Comment) has been issued. In an RFC, users and scientists are asked to comment on a particular proposed protocol. Then, after debate and dialog, that proposed protocol becomes a draft standard, then a required or recommended standard.

Protocols and standards may come from several sources, both formal and informal. There are formal de jure standards and protocols, created and altered by official trade, governmental, or scientific standard setting bodies. In some cases, these formal standards and protocols lag behind technology, while in others they lead technology. In still other cases, de jure protocols and standards describe technologies not yet introduced (and possibly never marketable). Due to the cumbersome process of adopting or altering standards (by international committee), de jure standards are notorious for being time consuming.

De facto standards and protocols arise from informal sources such as the marketplace or a single vendor [Tower, 1999].For example, Microsoft developed MS-DOS, Windows 95, Windows 98, Windows 2000, and NT as de facto, proprietary operating system standards. When the marketplace adopted Windows as a de facto OS standard, it got built-in data communications protocols also developed by Microsoft. Windows data communications protocols are a mix between open, de jure protocols such as IP and TCP and proprietary, de facto protocols such as NetBEUI and Microsoft Front Page extension web hosting. In some cases, de facto standards and protocols become de jure when formal sources adopt them. The de jure adoption (or non-adoption) of de facto standards may occur due to market power and/or technical reasons. A central tenant of network economics is that networks rely on protocols and standards to operate. This reliance is so great that path dependencies occur (see Chapter 3.6) so the economy can veer off an optimal path [Kelly, 1998]

Several examples illustrate the importance of standards. The first two examples concern how changes in standards can completely change the market. The FCC changed FM frequencies in 1945, making FM radio receivers built before then obsolete. Another example came in when a 1963 law mandated that all television sets be equipped with both VHF and UHF channels. In both cases, a change in de jure standards made existing equipment obsolete. The relatively recent struggle to create a de jure 56 kbps modem standard (V.90) from two incompatible de facto, proprietary standards (x2 and K56 Flex) is a further example. In the 56k case, a standard was agreed on that allowed both proprietary technologies to continue under a single unified standard.

Protocols and standards are often behind the confusion between services and technologies. The source of confusion is rooted in data communications according to Klessig and Tesnick:

There are several kinds of standards organizations. The first is the independent testing organization. Underwriter’s Laboratories, Inc. (UL) is an example. These organizations charge vendors a fee to test and certify the safety and sometimes the efficacy of equipment such as conduit and hardware devices. Another kind includes governmental agencies. The FCC imposes de jure standards on communications equipment to prevent interference with other communications and to ensure that connection of a DCE or DTE to a network (either CPE or carrier) does not harm other devices. For example, download speeds of certain 56k modems are restricted to 53 kbps because of FCC regulations designed to prevent excessive power from damaging elements of the telephone network. The third kind of standards organization is the independent national or international de jure standards body. A fourth kind is the scientific society.

In the United States, ANSI (American National Standards Institute) is a membership-supported, non-profit organization founded in 1918 by several engineering societies and US government agencies. ANSI does not develop standards itself, but encourages their development by coordinating communication among stakeholders (qualified engineers, government agencies, and others). ANSI is a member of the ISO (International Standards Organization), an international de jure body. The ISO is an organization similar to the United Nations. The ISO developed the seven layer OSI model discussed in Chapter 3.

Historically wireless standards evolved from the CCIR (International Radio Consultative Committee) which became the first international standards organization in 1927. The 1932 Conference of Madrid replaced CCIR by establishing the ITU (International telecommunications Union), the international body with jurisdiction over communications. ITU became a UN agency after World War II. IFRB (International Frequency Review Board) was part of ITU, until spectrum technologies and use required a new body, the CCITT (International Telephone and Telegraph Consultative Committee), formed in 1956. Intelsat (International Telecommunications Satellite Organization) was formed in 1964 after the U.S. created Comsat (Communications Satellite Corporation).

Many wireline standards and protocols also come from the ITU, which includes representatives from government, telecommunication companies, and industry organizations. Wireline standards include SS7 (Signaling System 7), established by the ITU, RJ-11 telephone cable (ITU), and numerous standards and protocols developed by AT&T's Bell Labs (now part of Lucent), and the RBOC (Regional Bell Operating Companies) successor to Bell Labs, Bellcore, now Telcordia.

Data communication standards and protocols form the basis of hypercommunication networks today. The IEEE (Institute of Electrical and Electronic Engineers) is behind many data communication protocols and standards in the physical and data link layers. IEEE standards include RJ-45 Category 5 cable jacks and Category 5 cable. Other IEEE standards and protocols are numbered such as 802.3 (10 Mbps Ethernet), 802.5 (token ring), and 802.11 (wireless LANs).

The IETF (Internet Engineering Task Force) is the main Internet standard and protocol body. The IETF sets up working groups (whose members are selected from thousands of Internet firms and organizations) to establish proposed standards for the Internet that are then voted on. The IETF established HTTP (web transport), POP (e-mail Post Office Protocol), and TCP/IP (Internet network layer protocols). The idea for TCP came from Vinton Cerf and Bob Kahn's 1974 paper, "A Protocol for Packet Network Intercommunication" [Zakon, 1997, p. 3].TCP and IP together became the protocol of choice for ARPANet (the U.S. DOD precursor of the Internet) in 1982.

Table 4-14 provides an overview of some common interconnection, interoperability, and privacy protocols. For each standard or protocol, the standards body, purpose, and major users are listed. The first of these, SS7 plays an important role in services provided by ILECs and ALECs such as ISDN and advanced telephony. SS7 allows fast call setup and remote database interactions. Without SS7, there would be no "portable" 800 numbers, cellular roaming, caller ID, Enhanced 911, Custom Local Area Signaling System (C/LASS), or Advanced Intelligent Networks (AINs) across CO networks. SS7 is "out of band" signaling, freeing circuits of overhead and extending capacity [Nortel, 1997]

TCP/IP is the main communications protocol of the Internet. The higher-layer, TCP (Transport Control Protocol) divides files (e-mail, HTML, graphic, URL request, etc.) into efficiently sized packets for routing over the Internet. Each packet has the IP address of the destination and can travel a different route to reach that point. Upon receipt at the other end, TCP reconstitutes the file in the correct order. TCP-based protocols include Ping, Telnet, FTP, and HTTP. The lower-layer IP handles the addresses of each packet.

HTTP (HyperText Transfer Protocol) and POP (Post Office Protocol) are widely used in Internet communications. ATM (Asynchronous Transfer Mode) is an increasingly used high-speed transport (and now access) technology to be covered in 4.8. The V.90 modem standard came from a compromise between the K56flex (Rockwell) and x2 (US Robotics/3Com) proprietary standards. HTML is the standard way static web pages are created. Frame relay (covered in 4.8) is used for WAN and Internet access by medium-sized firms provided over copper.

The S.100 interface was created to speed the convergence of voice and data. DSVD is a proprietary standard created by Rockwell and several other companies to allow modem users to remain online while receiving or making telephone calls. SSL (Secure Sockets Layer) is a method of guarding the security of online transactions. CDPD (Cellular Digital Packet Data) is one of several standards created to allow data transmissions over wireless (in this case cellular) connections. H.320 is an umbrella standard that covers the transmission of video over digital connections, such as the Internet.

Protocols and standards provide an important economic benefit: they help to prevent market failure. This is because some degree of uniformity or standardization tends to help markets perform better by accelerating adoption of new technology. This accelerated adoption occurs as compatible DTE, DCE, hardware, and software are purchased by the market.

Table 4-14: Important standards and protocols.
 

Protocol or standard	Body	Purpose	Major Users
Operating Systems (MS-DOS, Windows 3.1, 95 & 98	Private (Microsoft)	Allows computers to operate & software to work on particular computer platforms.	Computer users & software designers.
SS7 telecommunications protocol	ITU	Provides 800 numbers, caller ID, other custom calling services, increases existing transport level capacity.	Network engineers, affects telephone customers.
TCP/IP	IETF	Internet communications protocols. TCP divides files into packets, sends packets to an IP address, then reconstitutes packets into files.	Internet, Intranet, & Extranet users.
HTTP	IETF	Translates alphanumeric WWW addresses to numeric IP addresses.	Web users.
POP	IETF	Protocol for e-mail.	E-mail users.
ATM	ITU	High-speed form of TDM used to send 53-byte information cells (voice, video, data).	Network managers, large businesses.
V.90 Modem Standard	ITU	Allows 56 kbps download over analog telephone lines.	56 k modem owners.
HTML	W3C	Enables creation of hypertext (web pages).	Web designers.
Frame relay	ANSI, CCITT	Data networking & Internet access. Data-link layer fast-packet technology that transmits a set of data packets (frames) in bursts.	Network managers, small & medium businesses.
S.100 interface	ECTF	Allows convergence of telephones and computers.	Expected to see use in converged business networks.
DSVD	Private (Rock-well)	Allow modem users to answer telephone lines, access caller ID, send faxes, etc. while remaining online.	SOHO.
SSL	IETF	Makes e-commerce transactions more secure.	E-commerce website customers.
CDPD	ISO	Allows data to be sent over cellular connections.	Second generation cellphone data users.
H.320	ITU	Umbrella standard for video compression	Used in many web applications.

 

However, in some ways, standards may cause market failure. In the computer networking business standards bodies are manipulated by firms with market power as Saunders points out:

4.5.3 Wireline-Wireless Facilitation Technologies

Technologies used to facilitate hypercommunications between wireless and wireline networks are of two types: PSTN-based and data synchronization. For services that rely on connection to the PSTN, protocols and standards exist to interconnect wireless and wireline networks. These protocols and standards came about based on the desirability of having mobile telephone units able to connect with any other telephone (mobile or wireline) in the world. Since the wireline PSTN was in existence before cellular, PCS, GSM, and other mobile wireless devices were, it was necessary only to connect base stations that received and sent wireless signals to wireline PSTN. Cellular and other mobile wireless carriers also established standards for data transmission using wireless modems so data communications could occur between wireless networks and data networks connected to the PSTN.

One open, wireless-wireline facilitation technology is CDPD (Cellular Digital Packet Data). CDPD was created to "address the need of subscribers to be able to rapidly transmit a small amount of data and not tie up a cellular radio channel for a long period of time" [Harte, Prokup, and Levine, 1996, p. 376]. In 1995, 12,000 cell sites had CDPD capability [Harte, Prokup, and Levine, 1996, p. 377]. By 2000, CDPD was available in every major urban area of Florida.

Another PSTN-wireless facilitation technology is the proprietary iDEN™ (Integrated Dispatch Enhanced Network) standard, an exclusively digital TDMA system, formerly known as MIRS (Motorola Integrated Radio System). Typically used in 800 MHz SMR (Specialized Mobile Radio), MIRS was developed for FleetCall, now Nextel, which had radio coverage of almost all of North America by 1995. Recent iDEN™ technologies allow up to 64 kbps of data on a single 25 MHz radio channel and the simultaneous combination of data and voice. This technology allows both voice and data calls via the PSTN, as well as radio voice and data communications to a private network [Harte, Prokup, and Levine, 1996]. In 2000, Nextel's Florida network covers Tallahassee, Jacksonville, Miami, Palm Beach, Tampa, Orlando, and other urban parts of Florida.

The second type of wireline-wireless facilitation technologies involves device and data network synchronization. Here, the protocols allow wireless and wireline computers, laptops, PDAs (Personal Digital Assistants), mobile telephones, and other devices to synchronize data files and data communication among devices. There are several standards being developed by industry groups, most notably the SyncML Initiative. SyncML is being developed by IBM, Lotus, Motorola, Nokia, Palm Inc., and over 800 other firms. The idea behind SyncML is that networked data on mobile wireless devices needs to be as closely updated (synchronized) as possible with corresponding data on both nearby and remote wireline networks [SyncML, 1999]. Thus, for example, a salesperson's laptop computer would be immediately updated with an inventory change even if the computer were away from the home office. Similarly, if an order were placed at a customer's office, the salesperson would not have to return to company offices or dial-in by modem to place it. SyncML is still being established, but it has great promise for agribusinesses.

Another kind of wireline-wireless facilitation technologies are Bluetooth technologies. Like SyncML, Bluetooth technologies operate with both wireless and wireline equipment. However, Bluetooth technology is meant to facilitate the complete interconnection of fixed and nomadic (rather than mobile) wireless equipment with wireline and wireless devices on a short range, low power basis only. Bluetooth is a consortium led by Ericsson, IBM, Intel, Nokia, and Toshiba charged with designing internetworking standards for all kinds of wireless (and some wireline) devices. Wireless devices will interconnect with each another (and to a main wireline network) at data rates of up to 725 kbps over ranges of up to thirty feet [InfoWorld, 21(33): August 16, 1999]. The market research firm Dataquest estimates that by 2002, 79 percent of digital handsets (and hundreds of millions of PCs) will be Bluetooth-capable.

4.5.4 Voice-Data Consolidation Technologies

Voice-data consolidation technologies support what are variously known as convergent solutions, unified messaging, and FSN (Full-Service Networks). The idea is either to merge voice and data pipelines or converge voice and data DCE or DTE (or both). Voice-data consolidation is already a reality at the transport level, with a data-centric definition of voice expected to predominate. Half of BellSouth's transport network traffic is already data, with the expectation that by the year 2008 less than ten percent will be traditionally defined voice [Ackerman, 1999].

The technologies and economies of scale that are behind consolidation at the transport and access levels are now becoming achievable through new technologies in local networks for small agribusinesses. Voice and data traffic may be merged throughout an agribusiness' operation, only on the carrier side of the demarcation line, or both. While still a relatively new area of technology, voice-data consolidation technologies include advanced call center technologies, CT (computer telephony), VOIP (Voice over IP), VOF (Voice over frame relay), interactive voice, and voice processing equipment.

The ECTF (Enterprise Computer Telephony Forum) is a standards body specifically dedicated to creating interoperability agreements among the hundreds of telephone equipment, PBX, and computer software vendors [ECTF, 1997]. The ECTF is charged with developing APIs (Application Program Interfaces) to allow desktop computers, network clients, and host computers to control incoming and outgoing telephone business calls. The technologies involved include: voice compression/expansion, text-to-speech, voice recognition, fax, fax-to-text, desktop telephony, screen telephones, and hearing impaired devices [ECTF, 1997, p. 6]. The essence of ECTF voice-data consolidation technologies is that all hardware, software, DTE, and DCE within a business would be fully interconnected and interoperable.

An important voice-data consolidation technology is CTI (Computer Telephony Integration). CTI was the fastest-growing category of business telecommunications equipment achieving a 67 percent increase in spending from 1998-1999 [TIA-MMTA, 2000]. CTI is a collection of applications that go beyond the familiar automated attendants, (ACD, Automated Call Distribution), and IVR (Interactive Voice Response) systems that prompt telephone callers for an account number or use speech recognition to connect calls. CTI includes the recording, storing, forwarding, and broadcasting of voice mail, fax-on-demand, automated outbound dialing for telemarketing offices, and inbound "screen pop" applications that enable businesses to pull up a customer's record on the computer screen as calls come in.

CTI requires new hardware, software, and standards to realize convergence of telephone and computer networks. CTI is not new having been introduced to large catalog sales, telemarketing, and other firms in the early 1990's. However, new CTI technologies make CTI affordable even for small businesses, while previously proprietary devices such as PBXs and telephone sets are able to work with computers in novel ways. Two examples merit brief attention.

MVIP (Multi-Vendor Integration Protocol) is an open, de facto standard begun in 1990 that creates a multiplexed digital telephony highway inside a business controlled in one computer chassis, the communications server. MVIP standardizes connection of digital telephone traffic between individual circuit boards so that telephone conversations can be manipulated like any other kind of computer data [GO-MVIP, 1999]. MVIP supports telephone switching using digital switch elements inside the circuit boards of normal PCs. MVIP software standards allow a range of compatible products from compliant vendors worldwide to be used. CTI applications supported by MVIP include call management, fax, voice (live, stored and forwarded), text-to-speech, speech recognition, data and Internet communication, along with digital circuit switching.

The objective of an MVIP bus is to carry telephone traffic. It allows the telephone network connection to be separate from digital voice processing resources, so the telephone connection or PBX may be obtained from one vendor while the voice processing resources are obtained from others, saving businesses money. A single MVIP-90 bus has the capacity of 256 full-duplex telephone channels [EAGLES, 1997, Node 80]

Another de facto voice-data consolidation technology is SCSA™ (Signal Computing System Architecture). Dialogic (a division of Intel) announced the SCSA™ initiative in 1993 along with several dozen other computer telephony vendors. Like MVIP, SCSA™ is a telephony bus. However, SCSA™ can "interface to the public network or the PBX, perform a variety of voice-processing functions, recognize DTMF digits, and then initiate an outgoing call or switch to additional resources (e.g., fax-on-demand service, voice recognition, or text-to-speech)." [Byte Magazine, November, 1996].

According to Dialogic, SCSA™ is a high level call processing architecture with a holistic, multi-layered hardware and software foundation so firms can build call processing systems using standard interfaces but select from a variety of competing technologies. SCSA™ is an open, hardware-independent, software-independent architecture with the objective of providing standards that allow portability, scalability, and interoperability with different software applications [Dialogic, 1997]. An SCSA™ bus has a capacity of 2048 time slots (for a PC) on its bus called Signal Computing Bus so that CT hardware from many manufacturers can be run on a single communications server [EAGLES, 1997].

Taken together, MVIP and SCSA™ are examples of consolidation technologies that are enabling convergence, removing market power of equipment makers, and lowering acquisition costs and recurring expenses of hypercommunications CPE. These and other consolidation technologies are discussed in 4.7.1 and 4.7.2 when enhanced telecommunications CPE and CTI services are covered.

4.5.5 Preface to Specific Sub-Markets: (Sections 4.6 through 4.9)

In sections 4.3 through 4.5, several broad areas of hypercommunication technologies were considered. Before becoming more acquainted with the sub-markets for specific services and technologies, it is important to reiterate that there can be a difference between a service and a technology. According to Dan Lynch in the foreword to Klessig and Tesnick:

The next sections (4.6 through 4.9) cover four specific hypercommunication sub-markets, summarized in the services-market matrix found in Table 4-15. Many services can be provided by multiple markets and multiple transmission technologies (or protocols) covered in 4.3 through 4.5. For example, a local telephone call (a specific service) can be made within three sub-markets: traditional telephony, enhanced telecommunications, and Internet. Physical access to each of these markets may be wireless or wireline.

The first sub-market is traditional telephony services (4.6) such as local and long-distance telephone coupled with related enabling technologies (switches, trunks, and telephone sets). The second sub-market is enhanced telecommunications services (4.7), which include caller ID, CTI services, digital PCS, dedicated circuits, and circuit-switched services. Also given brief coverage are software and hardware technologies (AIN, DMS-100 switching, and SS7 signaling) that enable the enhanced sub-market. The third sub-market, private data networking services (4.8) includes packet and cell-switched services and specific supporting technologies. The fourth sub-market, which includes Internet services (from e-mail to web design), is explored in 4.9.

The row elements of the matrix are specific services an agribusiness might need, while the columns show the sub-markets capable of delivering those services. The sub-markets shown are already collapsing into a single hypercommunication market as convergence occurs. The separation of sub-markets simply demonstrates current market definition and structure. Of course, the expected result of convergence will be a hypercommunication market with an entirely different market structure with profound implications for agribusinesses.

Table 4-15: Services-Market matrix.
 

Sub-market	Traditional telephony (4.6)	Enhanced telecommunications (4.7)		Private data networking (4.8)			Internet access & services (4.9)
Enabling Technologies within markets (columns)
	Analog Wireline	Digital Wireline	Digital Wireless	Digital Wireline	Digital Wireless		Digital Wireline	Digital Wireless
Services (rows)
Local phone (PSTN)	YES	YES	YES	NO		NO	YES	YES
Long-distance phone (PSTN)	YES	YES	YES	NO		NO	YES	YES
Non-PSTN voice	NO	LTD	YES (1)	YES		YES	YES	YES
Conference calls	Limited	YES	YES	YES		YES	PSTN & IP	PSTN & IP
Voicemail	NO	YES	YES	YES		YES	YES	YES
Internet access	via modem	YES	YES	YES		YES	YES	YES
Private data networking	NO	YES	YES	YES		YES	YES- VPN	YES-VPN
Fax machine	YES	YES	YES	NA		NA	NA	NA
Fax server	NO	YES	NO	YES		YES	YES	YES
Video conferences	NO	YES	NO	YES		YES	YES	YES
Interactive video auctions		YES	NO	Intranet, Extranet		Intranet, Extranet	YES	YES
Web design		NO	NO	Intranet		Intranet	YES	YES
E-Commerce		NO	YES	Extranet		Extranet	YES	YES
AIN/CTI	NO	YES	YES				CTI	CTI
Basic 911	YES (3)	YES (3)	YES (2,3)
Enhanced 911	NO	YES (3)	(2,3)
Text paging	NO	YES	YES	LTD		LTD	YES	YES

NOTES: (1) iDEN technology only, (2) not yet location specific, (3) depends on service area.

The extension of hypercommunication services to rural Florida and agribusiness depends heavily on the production economics of the technologies (for carrier and customer alike) used to deploy technologies and deliver the market for services to rural and urban agribusinesses alike. As new services become available, agribusinesses must consider their own needs to see how new choices fit into present or future business strategies.

This section covers the sub-market for traditional telephony services and technologies. There are two parts of the traditional telephony market. First, traditional telephony includes analog POTS (Plain Old Telephone Service) over a local copper loop or trunk. Second, traditional includes long-distance calling, directory, operator, and other services generally available once the December 31, 1983 MFJ (Modified Final Judgement) broke the AT&T Bell System into LATAs and RBOCs. Traditional services are part of a Bell System inspired regulatory mindset (at both the federal and state level) that gave the U.S. monopolized telephone service.

Traditional services originated from what was (before 1984) arguably a textbook example of natural monopoly because of the technologies available then. The high fixed costs of infrastructure investment, engineering, design features of the network, and other factors combined to give AT&T a legally defined natural monopoly, which was regulated by state and federal authorities. From 1984 to 1996 the RBOCs (Regional Bell Operating Companies) such as BellSouth (which resulted from the breakup of AT&T), along with independent carriers such as GTE and Sprint served as local monopolies in non-overlapping service areas within Florida. Several smaller rural telephone companies (such as Indiantown Telephone, Quincy Telephone, and St. Joseph’s Telephone) served rural parts of the state.

Today in Florida, traditional telephone services are provided by LECs (Local Exchange Carriers) and by IXCs (Interexchange Carriers). However, deregulation has changed both the local and long-distance markets from the AT&T days. In the local market, the first kind of LEC, the ILEC (Incumbent Local Exchange Carrier) is the monopoly telco that serves a particular area or exchange. The ILEC is also the owner and builder of the telephone plant (especially the last mile segment). All other LECs are ALECs (Alternative Local Exchange Carriers) established through state and federal de-regulation specifically to compete with ILECs. ALECs can resell ILEC services and offer their own services in addition to exchanges (or parts of exchanges) wherever they choose. ALECs normally use the ILEC's facilities in the access level, though facilities-based ALECs have their own switches, POPs, and transport level equipment. Even after the 1996 TCA, ILECs are legally "carriers of last resort" who must furnish basic telephone service to all reasonable locations within their service territories even if ALECs are unwilling or unable to provide service.

IXCs are long-distance carriers who also use part of the ILEC’s local loop to carry long-distance calls to a POP for transport. While only one ILEC can serve a particular location, 363 ALECs and 988 IXCs offer service in Florida (especially in urban areas) now that traditional services have been de-regulated [FPSC, 2000]. In spite of these numbers, only 4.3 percent of Florida businesses used an ALEC rather than an ILEC for local service as of March 1999 ["You Have to Make the Call on Phone Service", Greg Groeller, Orlando Sentinel, March, 15, 1999].

This section has two sub-sections. The first sub-section (4.6.1) covers traditional services: local calling, other local services, and long-distance services. Then, traditional telephony access technologies and CPE (4.6.2) such as telephone sets, key telephone systems, and PBXs are mentioned. Typically, the access technology used (lines, trunks, PBXs) depend on the POTS equipment selected by a business.

4.6.1 Traditional Telephone Services (POTS)

In 1998, Florida ILECs, ALECs, and IXCs realized $15 billion in telephone revenues, up almost 30% from the 1995 level [FCC, "Telephone Trends", 2000, p.19-7]. It might appear as though revenues from these traditional telephony services (provided by ILECs and IXCs) would consist mainly of charges for local and long-distance telephone calls. In reality, however, the picture is more complicated because local service revenues consist of a mix of PSTN access charges, toll calls, and many miscellaneous revenues. Forty percent of what IXCs collect in long-distance charges goes back to the LEC as access charges.

In fact, as Table 4-16 shows, there is a broad array of traditional business telephony services beyond telephone calls. As the columns show, ILECs may make more money on directory advertising, for example, than they do by providing special local calling services. Indeed, depending on the agribusiness, a larger share of its telephone budget may go towards local calls or directory advertising than is spent on long-distance calling.

The first item in Table 4-16, lineside local telephone service, includes an inbound-outbound voice grade (analog) line or multiple lines, along with local calls. Depending on the local exchange, an agribusiness may be able to choose from using the ILEC or from dozens of ALECs for local telephone service. Typically, unlimited calls to the local exchange together with calls to a group of surrounding exchanges serving nearby areas (the local calling area) are included in a monthly per line rate. However, some new carriers charge for local calls, especially if the line is meant for inbound service only.

Table 4-16: Traditional telephony services.
 

Item	Pricing	Share of bus. phone expense	Share of ILEC revenue	Share of IXC revenue
Lineside local line(s) (voice grade line, local exchange calling, local calling)	SLC, Fixed monthly charge, per line	28%	56%	SLC & US, <5%
Enhanced local, extended local calling, intra-LATA calling	Traffic-sensitive (variable) charges.	> 8%	6%
Operator services (collect, station-station, person-person)	Free or unit-priced.	< 3%	<1%	4%
Repair, installation, line maintenance	Case-by-case.	< 1%	2-3%	Minor
Signaling, touch-tone, tone vs. pulse	No charge or minimal.	Minor-none	Minor	0
Classified directory advertising (Yellow Pages)	Based on ad sizes and categories.	2-3%	over 3%	Minor
Inbound and outbound directory assistance, white pages listings	Unit charges.	<1 %	<1%	Minor
Long-distance telephone service (inter-LATA, intrastate, interstate, and international), IXC trunks	Traffic sensitive: minimum, time-based, step, contractual, & setup.	>38 %	16% IXC access charges	73%
WATS (Inbound and Outbound), FX, 900 number, special prefix	Both per minute & monthly charges.	> 5%	1%	7%
Local & long-distance trunks, multiple trunks.	Per trunk or by bandwidth.	> 12%	over 5%	10.5%

Estimates of revenue shares from FCC, Statistics of Common Carriers, 1999, p.41, pp.166-171; FCC, Telecommunications Industry Revenue: 1998, Table 5 and Table 6, 1999.
 
 

To understand the differences among the local exchange, local calls, enhanced calling zones, and extended local calling zones better, an example should help. Figure 4-36 shows a group of exchanges in Hardee, Desoto, Highlands, and southern Polk counties. Within each local exchange, most local providers offer unlimited calling for a monthly fee. The local exchange may include several RAVs (wire centers), and one or more class five COs (see Table 4-8), each with one or more telephone prefixes (NXXs).

Figure 4-36: Zolfo Springs and surrounding exchanges.

The Arcadia exchange (which covers all of Desoto County) has four NXXs (444, 491, 494, and 993) on one CO. Zolfo Springs has a single NXX (735) in a single CO as does Bowling Green (375). Each exchange has a different kind of FPSC-mandated local calling plan ILECs must offer. Local calling plans are determined by analyzing calling patterns to obtain a PAHS (Probable Area of Highest Service) pattern for calls made from a particular exchange. Local, enhanced local, and extended local calling areas are configured based on the PAHS.

In Arcadia, local calls may be made only within the Arcadia exchange. Calls to Port Charlotte, Wauchula, and Zolfo Springs from Arcadia (extended local calling) are $0.25 per minute for residences, and $0.06 per minute for businesses. The Zolfo Springs exchange can call Bowling Green and Wauchula as a free local call, and can call Arcadia at extended calling rates similar to those for Arcadia to Zolfo Springs ($0.25 and $0.06). Bowling Green customers may call Wauchula and Zolfo Springs as free local calls, but both business and residential calls to Fort Meade (enhanced local calling) are charged a fixed $0.25 fee regardless of length. Calls from these local exchanges to exchanges outside local, enhanced, or extended areas are classified as long distance. ALECs are free to offer larger extended and enhanced calling zones to their customers, providing that LATA boundaries are not crossed. In some cases, if an agribusiness switches to an ALEC that offers a larger calling area significant savings will be achieved.

Local operator services are provided by the local service carrier (ILEC or ALEC) or by any of the 98 operator service providers in Florida [FPSC, 2000]. Long-distance operator service is provided by the presubscribed long-distance carrier (IXC) or by an operator service provider chosen by the IXC. While no charge is assessed for dialing the local operator to report an emergency, a charge may be assessed for other services per call such as emergency line interrupts and line testing. Long-distance operator services such as long-distance call assistance to obtain credit for wrong numbers or to report call quality problems are usually free. Both local and long-distance operators can provide collect, station-to-station, and person-to-person calls. However, local operators (used in this sense) means intra-LATA long-distance only. Charges for operator-assisted calls are up to several times the setup and per-minute rate of direct dial calls.

Repair, installation, and line maintenance are offered by local telephone companies to subscribers who are adding a line, reporting telephone problems, or who want the LEC to be responsible for inside (customer premises) telephone wiring. Installation fees are changed for every line or trunk connected to the PSTN whether or not the LEC actually installs the wiring at the customer’s premises. On-premise wiring and repairs are customarily billed at hourly rates, unless the subscriber pays a monthly inside wiring maintenance charge. In no event are customers supposed to be charged for repairs on the PSTN side of the demarcation line.

Telephone signaling (distinct from the signal that carries the call itself) refers to ringing, dial tone, busy signals, and the dialing technology. An example of extra signaling charges on traditional service includes DTMF (touch-tone) dialing, while custom ringing or stutter dial tone with voicemail are examples of signaling charges for enhanced telecommunications service (explained in 4.7). CPE must be compatible with the serving LEC’s signaling technologies, a problem that can lead to telephones that do not ring or offer dial tone (especially possible with trunkside or enhanced services).

Directory advertising is an especially lucrative source of revenue for ILECs, though court cases allow other firms to publish telephone directories also. The annual cost of listings in various classified categories is usually billed on a monthly basis in the LEC telephone bill. Yellow Page directories (whether ILEC or competing) include a new genre of online electronic listings and search operations where advertisers and/or telephone customers of a particular carrier may receive preferential treatment.

Directory assistance can be inbound or outbound. Outbound directory assistance is offered on a per call basis to callers within the business by the serving LEC, while inbound directory is offered to callers by their own LEC or competing providers. Special white page listings are offered by the ILEC (which is required to publish a telephone directory) and in competing directories. ILECs are required to list customers of ALECs in the local directory (and provide their listing databases to independent directory publishers), though this is sometimes not done in a timely manner. Furthermore, the ILEC or ALEC is responsible for ensuring that white page listings are available nationally and internationally for inbound callers so that prospective customers can find a business.

Inbound and outbound directory assistance services include white pages, 411 (1411), 555-1212, and Internet directory listings. Improved inbound directory assistance services may be a way that rural Florida can see dramatic gains in trade for call center industries, retailers, and certain wholesalers. Currently, inbound directory services covering rural areas exhibit a gap when compared to urban areas. In particular, rural areas may be poorly classified by an ILEC because billing and service addresses are not the same in rural carrier or P.O. box required areas. The location given in the directory is the exchange location, rather than the post office location, which can make searching for a business harder. Changes in directory listings in rural areas may take longer to be updated in inbound and online directory assistance databases than those in urban areas.

Agribusinesses that expect customers to find them in white or classified listings should check them to see that listings are available and correct. One study found that from fifteen to forty percent of directory assistance operator calls found either incorrect numbers or no number at all when one was listed [Seattle Times, May, 15, 1999]. To save money, instead of purchasing directory databases from the ILEC, ALECs and independent directory providers can purchase listing databases from less reliable sources.

There are five categories of long-distance toll service: extended calling zone calls, intra-LATA long distance, inter-LATA intrastate long-distance, interstate long-distance, and international long-distance. The 1996 TCA prohibits RBOCs (but not other ILECs) from offering inter-LATA, interstate, and international long distance under Section 271 of the 1996 TCA. However, RBOCs may offer extended and enhanced toll calling and intra-LATA long-distance as well as local exchange service.

A business must pre-subscribe to a particular IXC or ALEC, but may use a special code to access another carrier on a call-by-call basis if it has lineside long-distance services. Long-distance trunks (trunkside long-distance services) are groups of lines directly connected to a particular IXC's local POP. Calls over LD trunks can be made only through the trunked carrier. Long-distance dedicated circuits are also available for fixed or measured rather than metered (per minute) rates.

To understand long-distance calling (and to understand how many enhanced telecommunication and data networking services are priced), it is important to understand LATAs or (Local Access Transport Areas). LATAs were created in the MFJ (Modified Final Judgement) that broke up the Bell System to differentiate IXC service areas from those where ILECs and LECs could provide long-distance services.

Figure 4-37 shows the LATAs in BellSouth’s service area in the southeast United States.

Figure 4-37: LATAs in the Southeast U.S.A.

Calls placed from locations inside a LATA to other locations within the same LATA (but outside of all local calling areas) are intra-LATA long-distance calls, handled only by LECs and ILECs. Most LECs charge for non-local calls inside the subscriber's LATAs by the minute, though some ALECs allow free or per-call charges for intra-LATA long-distance. Calls from one LATA to another (inter-LATA long-distance), can only be handled by IXCs. Inter-LATA calls may be intrastate (within Florida) or interstate (from Florida to another state). Depending on the rate structure and carriers chosen, intrastate calls may be more expensive than interstate calls. In some cases, intra-LATA calls may be the most expensive of all.

When switching carriers, it is necessary to compare a sample of bills over all types of calls to see if savings will be achieved. Agribusinesses are often tempted by low rate quotes on interstate long-distance to switch to a new carrier. Quite often, their long-distance bill actually rises because of higher intrastate or international rates offered by the new carrier. Furthermore, agribusinesses that direct dial international calls must also consider rates to their most frequently called countries.

A business must choose a different pre-subscribed carrier for inter-LATA long-distance (IXC) than it does for local calling (LEC), and may use still a third pre-subscribed carrier for intra-LATA long-distance. It is a good idea to shop carefully. Because of the complexity of calling plans (and due to the fact that rates are constantly changing), businesses can use special adaptive rate dialing equipment to take advantage of the lowest prices to a particular place at a particular time. An important reason that the telephone transport and Internet are converging into a single hypercommunications network is that savings of from fifty to eighty percent on long-distance calling can be easily realized. This point is discussed further in 4.7.4 (voice-data consolidation technologies) and in 4.9.7 (Internet convergent applications).

Figure 4-38 [FPSC, Division of Communications, 2000] shows a map of Florida's 67 counties, 11 LATAs, and 13 area codes (NPAs). Many area codes contain more than one LATA (such as in the panhandle) but in other cases (such as the Southeast LATA), one LATA contains more than one area code.

Figure 4-38: LATAs (lines) and area codes (shaded) in Florida.

In Florida, area codes cross LATA boundaries in only two cases. First, the 941 NPA is partly in the Tampa market area (LATA) and partly inside the Fort Myers market area (LATA). Second, most of Polk County is in the Tampa LATA, but it is joined in the new 863 NPA by other counties that are inside the Fort Myers LATA. Hence, inter-LATA long-distance and intra-LATA long-distance calls may be in the same or different area codes.

Long-distance tolls are calculated in several ways, depending on whether an agribusiness has a contract to use a minimum number of minutes per month or the IXC charges all calls on an individual basis (open rate). Generally, the calculation depends on three general rate categories: metered (per minute), measured (rate based on lumpy usage categories), or fixed (unlimited calling, charged monthly). Each category can apply to traffic sensitive (TS) and non-traffic sensitive (NTS) service.

The open rate or contract cost of a single long-distance call may include a setup charge, minimum toll, time-increment tolls, and step charges. A setup charge (typically for the first minute) may apply for every completed call, regardless of the call's duration. Setup charges are fixed, TS fees, added to time-based (measured), step (metered), and minimum tolls.

Time-increment tolls apply for each time interval that a call is in progress. They are for metered services and may be per minute or fraction thereof, per second, or based on other time intervals. Step charges apply to all calls until a minimum per-call length (metering threshold) has been reached. After that point, calls are charged in steps governed by blocks of time. For example, if the step increment time is twenty minutes, calls twenty minutes or less are charged at a single block rate. However, calls longer than the step increment time are charged at a different (usually higher) time-increment toll for the full period the call lasts beyond the step time, so the call becomes a mix of measured and metered rates.

Contracts between an IXC and a business may specify minimum toll rates good on all LD time or fixed minute plans. Lower rates are extended for quantity discounts and for customers who sign agreements not to change carriers for from six months to five years or more. Minimum tolls represent the minimum per minute cost of all calls. Typically, contractually based minimum tolls are contingent on whether the customer places enough calls to qualify for a quantity discount over a certain amount of time. The lowest possible time-based toll is applied to all calls in months when a business uses at least the contractual number of minutes. Higher open rates apply for months when the stated quantity of minutes or hours is not used. Under fixed-minute long-distance plans (especially common in the mobile telephony market), customers agree to pay for a particular amount of long-distance (or local) calling whether they use it or not. In some cases, unused minutes may be "banked" or rolled over for use in future months.

While long-distance is covered here under traditional services, it is important to realize that enhanced telecommunications technologies, CTI integration, and the Internet allow adaptive rate systems as well as the traditional open rate (per minute) and contractual long-distance markets. A business can program specialized telemanagement equipment to take advantage of highly fluid demand conditions to use the lowest cost IXC based on the time of day, day of week, destination, and expected length of a call automatically. Larger businesses can even take advantage of forward markets for long-distance bandwidth between points such as the San Francisco-based Rate Exchange.

Free long-distance calls may be placed by callers over computers (without needing a telephone) via their Internet connection to any PSTN telephone throughout the U.S., Canada, or even internationally using free services such as www.dialpad.com. Free Internet calling is underwritten by sales of advertising banners that the call originator sees while in conversation. Call quality is beneath that of pay long-distance, with numerous QOS issues such as connection establishment delay, latency, jitter, and poor voice quality to contend with as well.

Eventually, it is possible that much long-distance calling will become included in fixed rate plans regardless of destination and call length. However, at present, QOS problems limit so-called free calling (actually paid for through a fixed access charge or by the time cost of viewing advertisements). Importantly, there are regulatory barriers as well (mentioned in Chapter 5) that may prevent free long-distance from becoming widely offered.

WATS (Wide Area Telephone Service) lines include both inbound and outbound long-distance. Inbound WATS includes toll free calls to interstate and intra-LATA 1-800, 1-877, and 1-888 numbers from a calling area that can be a single LATA, an entire state, or nationwide. Outbound WATS is a contractual service offered by an IXC to specific area codes or nationwide and even internationally to specific countries. Tolls may be based on the location called (metered distance rates), per call (metered per minute), on a step rate (measured), or on a fixed charge basis, no matter the length of the call or the location called. Businesses can also earn money from 900 number calls where the calling party pays for the call and an extra charge to obtain information or other services.

FX (Foreign Exchange) and special prefix services are similar to WATS because callers do not pay for FX calls. FX is unlike WATS because the call is made to a local number associated with a local exchange, local NPA, and local NXX. The calling party calls a local number and is automatically connected to the business paying for FX service in the next county or next state. Inbound-only FX routes incoming calls through such "virtual" local FX numbers onto to DID trunks (specific lines inside the business that pays for inbound FX). Many different telephone numbers may be mapped to a single DID line.

FX service is often accompanied by specially targeted white and Yellow Page listings so that the FX business appears to be local to the caller. For example, the local exchange name may be used to show a local address rather than use the distant city name and address where the call is received. Charges are made for the FX telephone number, the DID trunk, white and Yellow Page listings in the FX exchange telephone books, and calls typically are subject to long distance tolls as well.

Outbound FX service allows businesses to call numbers in the virtual exchange as if they were local calls. This can result in savings on long-distance calls that would otherwise be charged a higher rate. Other special prefix services use prefixes such as 203 that do not require callers to dial one plus the area code within extended calling areas or LATAs, or even across area codes. In much of Florida, 203 numbers may be called as a local call in every area code. The business would pay for 203 numbers in each area code along with the appropriate open or contract long-distance rate.

The last item in the list of traditional telephony services includes trunkside services (single and multiple trunks). While multiple telephone lines may be charged at a lower per line rate than single lines, many businesses choose to have special groups of lines called trunks attached to a business telephone system that functions as an on-premise telephone network. Trunks and multiple trunks are groups of lines with special rates that connect to specialized CPE such as PBXs thus allowing businesses to be flexible in the number of incoming, outgoing, and long-distance lines. To cover trunkside services adequately, the next sub-section covers telephone systems, PBXs, and other traditional telephony CPE.

4.6.2 Traditional Telephony Access Technologies and CPE

Traditional telephony access for businesses can include multiple line or trunks (groups of multiple lines). The form of access a business chooses (typically a mix of trunks and multiple analog lines is selected) varies based on the telephone system of the business. The form of access also depends on calling patterns, and whether there is a need for specialized lines, extra telephone numbers, or custom call routing.

A business telephone system may be a traditional key system or a Centrex/PBX. Traditional key telephones (now almost extinct) are simple multiple line telephone systems used primarily in small offices that cannot switch calls elsewhere within the business. Key systems are lower-end individual telephone sets that cannot transfer calls within the business or to other locations. Key systems can handle from two to about 100 telephone ports. There is a large difference in capability between traditional key systems and enhanced (or hybrid) key systems to be discussed in 4.7.

Traditional key systems can recognize up to 20 telephone lines on a telephone set that can be individually programmed to recognize calls from certain lines only. Most traditional key sets have hold and volume controls, but typically do not have any kind of computer brain that the next kind of system, a PBX does. Hence, traditional key systems cannot offer voice mail (except on the telephone set itself) or other services. They are able in some cases to offer caller ID, hold, intercom, and speed dialing, but some of these require payment for each service on a per line basis to the LEC. Since traditional key systems are not switches, as PBXs are, businesses that use them use multiple business telephone lines rather than trunks. A single key set can answer multiple lines and transfer calls by using intercom announcements to alert staff members to pick up a particular line, often using lighted signals on the telephone set. Individual telephones may each be programmed to allow long-distance outbound calling and other features, though some key systems have KSUs (Key System Units) to control available features.

PBX stands for Private Branch Exchange. Historically, PBXs consisted of a local loop telephone trunk (group of telephone lines) ending at the PBX, a switchboard, and the copper lines leading from the PBX to individual telephone sets at a business location. In the late 1960's, electronic switchboards replaced electromagnetic switchboards where calls were manually switched by a human operator. By the 1980's, computers began to be used as the "brains" behind electronic switchboards. Traditional PBXs take advantage of line consolidation so that there can be more lines than telephones, saving businesses money. Furthermore, since many calls are within the business, the PBX is a switch for those calls.

Traditional PBXs use proprietary protocols so that additions to the system require that additional equipment be purchased from a particular manufacturer. Furthermore, many traditional PBXs are no longer supported by the manufacturer so businesses must buy new systems since there is no authorized way to replace equipment. Traditional PBXs, even though they used a computer for switching could handle data only at limited rates up to 19.2 kbps, necessitating the use of separate lines for modems and faxes [Tower, 1999]. With a PBX, a single line telephone set can gain access to a pool of outgoing lines (a shared trunk) through users dialing an access code such as 8 or 9 before obtaining dial tone.

Even traditional PBXs support numerous system services such as DID (Direct Inward Dialing), hunt groups, pick-up groups, call detail services, and least call routing for toll calls. DID allows each individual in the business to have his own telephone number without requiring an equal number of telephone lines. The PBX switches the DID number to the appropriate station. Hunt groups allow the PBX to automatically route incoming calls to the first free telephone line in a particular group without a human operator to connect the call. Pick-up groups permit members of a group to answer calls (or have calls forwarded) when a particular telephone is unattended, again without action by a human operator. Call detail services allow logs (even on a per station basis) to be automatically recorded to keep track of long-distance charges, call lengths, and other call management details. More advanced PBXs work with digital and analog trunks that can be dedicated local ISDN-PRIs connected to an ALEC's POP or dedicated long-distance ISDN-PRIs connected to an IXC's POP. These uses are covered in section 4.7.

PBX stations (individual phones) can be programmed from the central computer to allow call waiting, call forwarding, call transfers, speed dialing, voice mail, do not disturb, and automatic callback of busy or no answer numbers. Changes in extension numbers, ringing, hunt groups, and other features are done through the PBX computer rather than by programming individual telephones or rewiring connections. Outbound long-distance and other toll calls can be blocked through the PBX computer for any telephone set or group of telephones in one step. A central PBX or a distributed network of PBXs can be used to link separate buildings or floors. Later versions of PBXs are covered in 4.7 with enhanced services.

Centrex (also known as ESSX^(R) by BellSouth) is a virtual PBX controlled from the telephone company CO. With Centrex service, most traditional PBX services are available for a monthly service charge from the LEC. Centrex service involves leasing a PBX (and often telephone sets) from the ILEC, rather than a PBX that the business owns. Changes to the system must be ordered through the telco (ILEC or ALEC) with separate charges for hold, music on hold, do not disturb, distinctive ringing, and other options that are standard on a CPE PBX.

Some argue that Centrex is gradually becoming a technological legacy of the pre-deregulation era, as even small businesses find that new generation PBXs support special features along with enhanced telecommunications services more affordably. However, Centrex offers higher reliability (designed to be down less than three hours over 40 years) than an in-office PBX, is impossible to outgrow, and does not require the investment cost of a PBX.

As convergence occurs, the overlap among the sub-markets named in sections 4.6 through 4.9 will become ever more substantial. Nowhere is this more the case than when considering how the enhanced telecommunications market overlaps traditional telephony. The two overlap in two ways. First, many enhanced telecommunications services are simply advancements in business telephone equipment such as new kinds of PBXs. These advancements in CPE are summarized in 4.7.1.

The second area of overlap comes because most enhanced telecommunications services are supported by the ILEC copper (or sometimes fiber) infrastructure. Hence, all enhanced telecommunications services have to do with voice communications, though many of the individual offerings also have private data networking and/or Internet applications. Though cablecos and electric utilities have fiber or coax infrastructures that can support enhanced services as well, they are new entrants in a sub-market dominated by telcos. While terrestrial wireless carriers have established presences in paging and mobile wireless telephony, terrestrial fixed carriers (such as WLL and LMDS) and satellite technologies can also (or soon will) support enhanced telecommunications services outside of the mobile market.

In some areas of Florida, ILECs are the only vendor agribusinesses can buy enhanced services from, while in other areas ALECs resell them. In still other areas, even the ILEC is not able (for engineering or marketing reasons) to offer enhanced services. In some cases, ALECs are able to resell unbundled ILEC services when the ILEC cannot profitably introduce service [Ackerman, 1999]. However, some rural areas of Florida may wait years to get particular enhanced services considered vital by urban business.

The enhanced telecommunication sub-market also overlaps both the private data networking and Internet markets. Some of the access services (both dedicated and circuit-switched) mentioned in this section are targeted towards the enhanced telecommunications market, though they can be used as well for data networking or to obtain Internet access. Similarly, certain WAN data networking and Internet offerings can be used for voice though their attention is focused upon the data and WWW side.

There is a subtle evolutionary chain leading from POTS up to enhanced services and then on to both data networking and the Internet that can only be seen through a sequential presentation. The evolutionary stages depend on the needs and sophistication of the agribusiness users. Agribusinesses must adopt POTS before they become customers for enhanced telecommunications. Additionally, private data networking adoption follows enhanced telecommunications as communications sophistication develops with each step beyond POTS the agribusiness takes. Due to the connection between traditional modems and the Internet, its evolution is harder to see because it is associated with POTS and data networking, though enhanced services may be used as combination voice and Internet access loops.

This evolutionary chain is economic as well as technical because as costs fall, choices rise, while reliability varies as communications use progresses from POTS upward. After the sequence of sub-markets has been laid out, the path to convergence is more easily seen by glancing backwards down the evolutionary chain. Furthermore while the overlap exists, the enhanced telecommunication sub-market focuses on common carrier communications, while the data networking sub-market focuses on private connections. Since it is a public data network, the Internet shares some points of similarity with both enhanced telecommunications and data networking. Additionally, the Internet is able to combine features of interpersonal and mass communications to offer lower prices, greater QOS complexity, and the enormous business potential of hypercommunications convergence.

The continuing existence of these separate sub-markets depends importantly on what is an increasingly artificial distinction between voice and data. Enhanced telecommunications offerings put voice first and data second, while private data networking puts data first and (if the network manager looks at voice) it may be put third, behind Internet. However, recent developments in enhanced telecommunications offer a way for agribusinesses to migrate from separate voice and data networks to hypercommunications convergence.

It is important to realize again that line consolidation means that a business will have more telephones that telephone lines. It may choose to have more telephone numbers than telephone lines or telephones as well so that employees may have their own private number without requiring their own private line or for other business reasons. The main idea behind advanced telecommunications services is that line consolidation allows businesses with multiple telephone lines to purchase trunks rather than lines, leading to significant savings on monthly telephone bills. Some trunks can also be used to access private data networks such as WANs or the Internet while carrying telephone calls. Separate trunks may be needed for long distance, WATS, DID, FX, data, and Internet depending on business needs.

Table 4-17 concentrates on voice only or combination voice-data offerings as covered in this section. Some of the services in Table 4-17 will reappear in slightly different contexts in the private data networking section (4.8) and the Internet section (4.9).

Table 4-17: Enhanced telecommunications market offerings.
 

Item	Sec.	Description
Enhanced telecommunications CPE	4.7.1	Telephone and computer equipment (DTE & DCE), software, & protocols needed for enhanced telecommunications services.
CO & AIN technologies, call center services	4.7.2	Enhanced telephony carrier services & technologies necessary to support call centers & CTI
Dedicated circuit services	4.7.3	Joint data and PSTN voice access via T-carrier, x-DSL, cableco & fiber optics.
Circuit-switched digital services	4.7.4	Joint data and voice PSTN access & switching via ISDN-PRI and ISDN-BRI.
Digital cellular & PCS	4.7.5	Mobile telephony & related services.
Paging and wireless messaging services	4.7.6	Handheld one & two-way wireless paging & e-mail.

 

Since BellSouth and other ILECs offer thousands of specific services, this section can only touch generally on a few of the more important enhanced services available to agribusinesses. Importantly, the cost of equipment and services has become more competitive in the new de-regulated environment so that even smaller businesses can now afford enhanced services.

4.7.1 Enhanced Telecommunications CPE

A variety of CPE is available to support enhanced telecommunications services. Table 4-18 shows some of the most important examples. Enhanced telecommunications CPE ranges from PBXs that replace traditional PBXs to DTE and DCE needed to use dedicated or circuit-switched services to fully convergent IP PBXs that merge data and voice together throughout the business.

Because of the sheer volume of new technology, Table 4-18 is incomplete and some entries that have been described elsewhere get no additional treatment here. Since many enhanced services still have a voice focus, the most important piece of equipment is the PBX. As was mentioned in traditional telephony, a PBX is a collection of cards, computers, wiring, and other hardware and software that control switching of telephone calls within a business. Even traditional key telephone systems have become hybrid key-PBXs, able to perform many of the functions that used to require a PBX.

Two new types of PBXs have been developed to support different focuses of enhanced telecommunications services. Before they are covered, it may help to see how the traditional PBX has developed into a LAN-based PBX such as the one shown in Figure 4-39. From the telephone network, trunk lines (switched T-1 or ISDN for local service) and possibly a dedicated LD T-1 or ISDN-PRI trunk lead into the business to a PBX switch, which in turn is attached to the LAN. A fax server and voicemail server can be directly connected to (or part of) the PBX, just as individual telephone sets are directly connected the PBX only. IVR hardware (Interactive Voice Response), predictive dialing equipment, and an e-mail gateway connect to both the PBX and LAN in order to enable CTI applications.

Table 4-18: Enhanced telecommunications CPE.
 

Item	Description	Services used with
LAN-based PBXs	PBXs that use telephone server for brains and some interaction with LAN for CTI use.	Circuit-switched, dedicated circuits, call center, other advanced telephony.
Communications Servers, CT-PBXs & IT-PBXs	Convergent PBX with full CTI, unified messaging.	Above plus full CTI applications over packet-switched, Internet, and cell-switched circuits.
Predictive dialers	Allow outbound calling over cheapest carrier automatically, only answered calls are connected to caller.	Telemarketing, call center, telemanagement, CTI.
IVR systems	Inbound callers use touch-tone or voice responses to make routine inquiries, reach departments, and leave messages.	Call centers, telemanagement, CTI.
DSU/CSUs, NIC-NTs, NIUs	CPE Edge devices that terminate a circuit.	DSU/CSU (T-1, T-3, DS-0), NIC-NT (ISDN, SONET), NIU (DSL).
DACS, channel banks, multiplexors, demultiplexors	Used to configure trunks and split dedicated circuits into multiple channels.	Telephony (T-1 and ISDN-PRI), data networking.
Other DCE	Multiplexors, transcoders, channel banks, routers, gateways, repeaters.	Varies.
Digital telephones	Allows integration of telephone calls with other applications, better call processing, harbinger of move to single network.	Certain PBXs. Reduces need for edge devices on digital lines.
Fax servers	Automate & manage inbound & outbound fax traffic.	Faxes via PSTN, corporate network, & Internet.
Fixed wireless CPE	DCE & DTE that allow wireless local loops to be established. Includes antennas.	WLL, DEMS, MMDS & LMDS access to PSTN, data networking & Internet.
Mobile wireless CPE	Individual combination DTE/DCE devices for mobile users.	Cellular, PCS, paging & wireless messaging.

 

Note that an ISDN-PRI, T-1, or T-3 connection to the PSTN (telephone network) is assumed in Figure 4-39. All voice and data communications flow through the telephone network, while data transfers are accomplished by modem only. Data rates over modem in such a configuration are typically limited to 19.2 kbps because the PBX performs analog and digital conversion slowly.

LAN-based PBXs such as the one in Figure 4-39 use parallel activity architecture [ECTF, 1997, p.15] Also called third-party connection architecture, parallel activity LAN PBXs switch only telephone traffic to terminal devices (DTE). As calls come in to an order or call center in the sales or customer service department, individual computer stations can provide information about callers and open order screens because of equipment that synchronizes telephone calls with computer ordering applications. Calls are answered by an automated attendant (a recording) and an ACD (Automated Call Distributor) routes them to the first available operator. Callers enter the extension or speak the name they want to reach. Often, another part of this system (called more generally IVR for Integrated Voice Response) asks callers for their account number or gives them certain menu options such as the ability to check balances, order status, etc.

Figure 4-39: LAN PBX legacy system

The IVR ACD system may have options asking what department or extension the caller needs as well. If callers know a specific extension, they may dial that extension directly, or automatically reach voice mail or reach a coworker's telephone in a hunt group if the extension is unanswered. Incoming order or information calls can be transferred automatically to a human operator screened for further information by the IVR before transfer. Often, the caller follows a (possibly long) sequence of menu choices or must enter account numbers or other information through the IVR. However, when callers leave the IVR system (by requesting a transfer to a "real person") the information entered through the IVR is not on the computer screen of the "real person" who gets the call. This is because there is no API (Application Programming Interface) to send a record of the IVR session to the answering operator.

More recent LAN-based PBXs have a telephony server-PBX link, with client computers linked to the PBX (via the LAN) and individual telephones linked to the PBX via traditional lines as Figure 4-40 [ECTF, 1997, p. 15] shows. While the server provides the brains for the telephone system and allows some CTI interaction with individual client computers, individual computers are still not directly linked to individual telephones. The PBX does not carry much (if any) data or Internet traffic, since separates circuits (or sets of circuits) are used for data, Internet, and voice.

Figure 4-40: ECTF telephony server, PBX attached.

The ECTF-compatible system shown in Figure 4-40 assumes businesses maintain separate voice and data circuits, but allows them to keep their existing PBX (if it is compatible with ECTF standards). IVR (and other operations) are better synchronized with telephone callers' actions. Incoming PSTN calls come through the PBX where they are transferred to a particular telephone extension or are sent to the telephony server. APIs (Application Program Interfaces) are used to interconnect various kinds of telephones, computers, and servers.

Microsoft's TAPI (Telephony Application Programming Interface) and Novell's TSAPI (Telephony Services Application Programming Interface) are two common de facto API standards. TAPI provides first-party connections (individual telephones are hardwired to an associated PC) while TSAPI provides third party connections (any telephone may be associated with any PC through parallel activity tracking) [Bezar, 1995]. Third party connections have more flexibility since each user has access to the PBX through the LAN.

Previously, such systems were available only to large businesses with mainframe computers or elaborate telephone networks, but new LAN-based PBXs are within the reach of smaller businesses and can be tailored to specific needs. Instead of being forced to use complicated proprietary hardware and software that operate only with equipment purchased from a single vendor, the ECTF standard lets businesses choose from many software manufacturers and PBX makers when they install and upgrade systems.

Newer LAN-based PBXs may be used with circuit-switched or dedicated circuits (such as the T-1 or ISDN-PRI connections as shown) so that call center and advanced telecommunication services are available to all suitably equipped stations [Bezar, 1995]. These services (detailed further in 4.7.2) include caller ID, voicemail, predictive outbound dialing, screen pop inbound call reception, and other features.

Another advantage of newer LAN-based PBXs (such as the ECTF standard shown in Figure 4-40) is that the IVR and other equipment are directly on the LAN so that caller information is more easily seen by employees. Hence, employee time is saved because information that customers have already provided does not have to be reentered. Customers may also be less annoyed, not having to give information twice. Another advantage of LAN-based PBXs is that changes to the telephone system, billing information, and other telemanagement functions can be available to managers throughout the agribusiness without having to be at a particular location. LAN-based PBXs are an intermediate step between traditional PBXs and fully converged CT or IP PBXs.

One step towards a converged voice-data network is to get rid of the PBX. Figure 4-41 shows a telephony server directly attached to the telephone network without a PBX [ECTF, 1997, p. 14].

Figure 4-41: ECTF telephony server, attached to network (no PBX).

This system is perfect for businesses wanting PBX CTI functionality without having to buy an expensive PBX that may become obsolete in just a few years. The ECTF telephony server standard allows software upgrades in the server to support new services or changes in circuits. In this way, the business has more flexibility than it would with a closed, proprietary PBX since PBXs are compatible only with certain telephones, software, hardware, and particular kinds of signaling for access connections to the telephone network, etc. This solution is ideal for a start-up business, for a business that has experienced such rapid growth that it has outgrown its PBX, or for a business that has never used a PBX.

Note from Figure 4-41 that the telephony server has three essential elements: control, switch, and media. In such a distributed architecture, the application servers function as clients of the telephony server The telephony server controls calls and applications that process calls, making the call rather than the application the center of interest. The server is able to switch traffic within the business and may serve as a data switch (able to function as a data edge device as well). The telephony server is able to store, buffer, and switch various message types (media) ranging from telephone calls, voice mail, faxes, e-mail, and video conferencing.

Another kind of PBX (which is not actually a PBX at all, but an all-in-one communications server) is the CT or IP PBX (Figure 4-42). These PBXs also called integrated communications servers, handle more than the telephone switchboard traffic of the telephony server. Voice, fax, video, Internet, and data travel through the same conduit in the business (there is no difference between LAN and telephone wire) and over the same access connection. The communications server is an edge device, router, switch, and other DCE in one unit composed of several modules, such as the applications module shown in the figure.

The CT or IP PBX can represent a tremendous savings in wiring and equipment costs, and allows the agribusiness to pay for only one connection rather than pay for voice, WAN, and Internet access separately. The agribusiness need not have a separate IVR, e-mail gateway, video server, predictive dialer, and voice mail and fax server. Instead these functions are performed by applications on the communications server or hosted elsewhere by an Application Service Provider and accessed via the Internet.

Figure 4-42: Communication server model is a converged network.

The communication server approach uses telephony functions embedded into client computers equipped with voice-data consolidation technologies (4.5.4). Since the telephone operates as a unit with the computer, the complexities of dealing with first-party (standalone) connections and third-party (networked parallel activity) connections are in the past. The DTE client is on a LAN governed by a communications server that controls all incoming, outgoing, and internal voice, data, and Internet traffic. Existing LAN host computers and database servers continue as before, but the LAN host has no communications traffic weighing it down.

CT and IT communication servers are converged voice-data networks with full CTI and unified messaging capabilities. Unified messaging offers the ability to control e-mail, voice mail, and faxes through web browsers, PCS and wireless messaging devices, office telephones, and telephone-computer stations [Riggs, 1999]. Not only can CT and IP PBXs be used with circuit-switched (4.7.4) and dedicated circuits (4.7.3), they may be used over packet-switched (4.8.2) or cell-switched (4.8.3) networks, and even in conjunction with Internet (4.9) connections. The difference between CT and IP PBXs is mainly that IP PBXs can place and receive calls through the Internet, Intranets, extranets, and the PSTN. Users may click on an icon to place telephone calls, get voice mail, and screen both PSTN and IP telephone calls.

Of particular importance, home-based cybercommuters or traveling employees may receive calls made to their office number forwarded anywhere in the world via Internet or Intranet connections, completely avoiding long-distance charges. IP communication server market growth will be driven by long-distance savings of up to 90%. However, even with superior telemanagement, and lower administrative costs, the promise of communication servers depends on whether manufacturers can launch reliable and user-friendly applications [Frost and Sullivan, 2000].

The new convergent PBXs reduce accounting and time costs of businesses in many ways. Employees need not check for voice mail, e-mail, fax traffic, and internal office memos in four separate systems, everything is in one mailbox. Secondly, access to these four kinds of message traffic does not require that any particular device be used or even an employee's presence in the office. Third, the fixed costs of purchasing separate DTE (computers and telephones), separate DCE (data switches, PBXs, Internet routers), expensive stand-alone servers (such as IVR, e-mail gateways, voice mail servers, etc) fall, replaced only by an investment in a communications server. Finally, instead of paying for separate voice, data, and Internet connections each month, agribusinesses have one monthly communications pipeline charge.

To complete the discussion, a return to Table 4-18 shows that the rest of the list would be unnecessary if all businesses have communications servers. However, the communication and telephony server models are hardly available or appropriate for most agribusinesses at this stage of convergence. The rest of the entries in the table include CPE that is still being purchased and probably will be for some time.

DSU/CSUs (Data Service Unit and Channel Service Unit), NICs and NTs are edge devices (DCE) used to terminate dedicated or switched circuits at the demarcation point on the customer premises. Typically, CPE are purchased by the agribusiness or leased from the carrier. Often, CSU/DSU functions are integrated into routers so that convergence is simplified. Other DCE include such items as multiplexors, demultiplexors, transcoders, channel banks, routers, gateways, and repeaters. Many devices may only be used with a particular service, carrier, or technology.

Multiplexors allow agribusinesses to change service channeling, often allowing a more efficient use of bandwidth. For example, a T-1 carries 24 64 kbps voice channels. To carry them over a T-1 carrier, a D4 channel bank is needed to split the DS-1 signal into 24 separate channels. In conjunction with other technologies, multiplexors can lead to greater efficiencies. For instance, an agribusiness could double that number to 48 voice channels using a different voice compression technology than standard PCM in telephone sets and multiplex these 48 channels onto the T-1. A demultiplexor would be needed to reverse the process. Other devices such as DACS allow customers to automatically reconfigure how ISDN-PRI or T-1 trunk channels are allocated so as to allow variations in traffic to accommodate video conferencing, Internet access, or other traffic needing more than one channel.

Digital telephones and other DTE are the devices that interact with users. Digital telephones allow integration of telephone calls with other applications and better call processing, making it easier to migrate towards a unified voice and data network. Digital telephones are DTE and DCE together. Digital phones perform ADC inside the telephone set, directly converting the message from an analog microphone (when the local party speaks) into a digital signal that is sent over an end-to-end digital path. Other "digital" telephones are analog devices that rely on intermediate DCE to perform conversions needed for them to operate over digital PBXs or digital connections. The ultimate digital telephone is a PC or thin client with voice capability.

Fax servers automate and manage inbound and outbound fax traffic. Faxes may be sent or received through the PSTN, corporate data network (WAN or Intranet), and the Internet. Fax servers store incoming and outgoing faxes when the network is congested until conditions allow the faxes to be sent. Faxes are converted into e-mails or e-mails converted into faxes and sent to any PSTN telephone with some fax servers.

Other fixed wireless CPE includes DCE and DTE needed to establish wireless access paths. In addition to DCE and DTE, antennas are needed for wireless communications. Most PBXs are not yet compatible with fixed wireless access to the PSTN. However, carriers offering fixed wireless technologies such as WLL, DEMS, MMDS, LMDS, and broadband LEO are expected to provide access to the PSTN with the necessary CPE, as well as data networking and Internet access over the same wireless path. The wireless industry is developing the necessary CPE to offer support of enhanced services. More information may be found in 4.8.5 (Wireless WANs) and 4.4. Mobile wireless CPE includes combination DTE/DCE devices for mobile users. Services supported include cellular, PCS, and paging or wireless messaging. More information on mobile wireless CPE is given in 4.7.6.

4.7.2 AIN CO Technologies, Call Center Services

This section briefly covers the enhanced telephony carrier services and technologies necessary to support call centers, CTI, and the various levels of business PBX and applications. AIN (Advanced Intelligent Network) CO technologies make possible a variety of enhanced services ranging from caller ID and call waiting to ISDN, DSL, and dedicated digital circuits. It may help to begin by defining call centers and relating them to agribusiness.

Call centers are big business in America. Estimates are that over 60,000 call centers existed in 1998, employing some 3.5 million people, and are responsible for as much as forty percent of all telephone calls. Over seventy percent of customer-business interactions and $840 billion in sales went through US call centers in 1998 [Bernett and Gharakhanian, 1999, p. 107]. In the business-to-business (B2B) arena, call centers accounted for $244 billion or 45 percent of B2B sales in 1996 [Sevcik and Forbath, 1999, p. 2]. Telemarketing, inbound catalog ordering, voice interactive websites, and video interactive websites are some examples of call center services.

Call centers previously required a certain scale and type of business to justify their expense. Until very recently, telemarketing firms, catalog sales companies, and large customer service departments at banks, airlines, cablecos, and telcos have been the largest users of call center technologies. Indeed, these kinds of large retail businesses are starting to use increasingly sophisticated call center services at the high end of this market. However, the cost of software and equipment has fallen so that even small businesses can take advantage of the potential time and cost savings as well as the opportunity to serve customers better and faster than before.

To agribusinesses, call centers can mean the ability to avoid hiring extra employees to cover occasional busy spurts in average weeks or busy seasons. Call center services allow scarce personnel to avoid answering calls over and over regarding business hours, location, account balance, status of shipments, availability of sale merchandise or inventory. Phone system programming can provide premium customer service to large customers and attractive prospects, transfer delinquent accounts to collections, track employee telephone productivity, and display a customer's name and account information via computer the moment he calls (ScreenPop). Call centers can be particularly valuable in small businesses where employees are strapped to keep up with the workload, especially at peak hours. Customers also have access to account information, order status, hours, special offers and other information twenty-four hours a day, 365 days a year.

Table 4-19 shows some of the most important AIN CO technologies along with the call center services and PBX features those technologies support. Not all areas of Florida have access to these technologies because their availability depends on whether the ILEC has equipped the local exchange to support them. However, deployment does not depend solely on the ILEC as cablecos, electric utilities, ALECs, and wireless carriers are often able to provide enhanced services at a far lower cost than the ILEC can.

Table 4-19: AIN CO technologies advanced telephony features and call center services.
 

Item	Acronym or description	Level or Function
AIN	Advanced Intelligent Network	Group of technologies for ILEC COs or ALEC switches, carrier access and transport levels.
SS7	Signaling System 7	Access and transport levels.
Call center services	Inbound, outbound telemanagement, telemarketing	PBX system and telephone station services save time for customers & employees, save on telephone bills, ensure customer service procedures are followed, manage communications.
ACD & IVR	Automatic Call Distribution, Integrated Voice Response	PBX at agribusiness. Routes incoming calls through menu system, allows customer access to automated personalized information.
API	Application Programming Interfaces	PBX, Internet, & LAN interface at agribusiness.
Voice synthesis	Voice-to-text, Text-to-voice	CPE: conversion of voice mail to e-mail, e-mail to voice mail, certain IVR equipment, hearing impaired computing.
PBX system services	System-wide services for PBXs.	DID, FX DID, hunt groups, CDR & SMDR, least cost call (long-distance) routing, call pickup groups, predictive dialing, fraud prevention, voice mail.
PBX telephone station services	Advanced telephony features available in each telephone connected to PBX.	Caller ID, distinctive ringing, DID, FX, conference calling, call blocking, call waiting, call transfer, do not disturb, speed dialing, three-way and conference calling.

 

Savings of fifty percent per month on traditional services with many enhanced services available for free can result in telephone bills up to seventy percent below ILEC carriers for businesses who replace multi-line or Centrex systems with their own PBX. Additionally, the cost of a live telephone transaction (from $25-$35) can be halved using enhanced services-based call centers and cut to $3-$5 on web-based call centers [Sevcik and Forbath, 1999]. However, an agribusiness may need to have eight to twelve telephone lines before those savings can be achieved. Furthermore, some customers are likely to resent systems that make it too hard to reach a "real person", while others will prefer the convenience of not having to wait and the ability to call at any hour.

What follows is a thumbnail sketch of the technologies in Table 4-19. AIN is a term that applies to technologies used in the ILEC local exchange, CO switch, and transport network, including ALEC and cableco switch networks. Network intelligence is distributed under AIN. Therefore, new services can be quickly introduced, service customization is made easier, vendor independence and competition are aided, and open software and hardware interfaces are created [Telcordia, 2000]. AIN means these facilities are equipped with the software and hardware needed to support enhanced telecommunications services, LAN-based or CTI IP PBXs, and call center services.

SS7 is a protocol that enables advanced telephony features (see 4.5.2) through the access and transport levels. ACD and IVR systems were discussed in 4.7.1, as were APIs. Voice synthesis technologies perform voice-to-text and text-to-voice conversions when voice mail must be converted to e-mail, text e-mail converted to voice mail, or allows callers to speak responses to IVR or ACD prompts.

PBX system services have global inbound and outbound capabilities, meaning that they are based on the technology of the access trunks and ALEs (Access Line Equivalents). System services make it easier to perform telemanagement (manage costs, numbers, stations, and users). DID and FX DID are virtual telephone lines that are routed to specific extensions or departments within a business. Hunt groups transfer calls from unanswered or busy telephone lines to the telephone set of the next available group member. CDR (Call Detail Records) and SMDR (Station Message Detail Records) record call information such as length, cost, and extension so telemanagement tracking and fraud prevention can be performed.

Telemanagement reports can be prepared automatically to show long-distance charges, traffic to and from certain numbers or extensions, time on telephone per customer, etc. Least call long-distance routing allows the cheapest long distance carrier at a particular time for a particular call to be selected automatically. Pickup groups are sets of extensions that may be answered by anyone in a certain area. Predictive dialing is an outbound telemarketing service that allows computers to dial calls automatically and connect them to an operator once the call is answered by a human being.

PBX station services are advanced telephony features compatible with the PBX. These include such things as: caller ID, distinctive ringing, DID, FX, conference calling, call blocking, call waiting, call transfer, do not disturb, speed dialing, three-way and conference calling. When the services are purchased on a per trunk basis instead of a per line basis, costs can drop dramatically. Many ALECs and cablecos offer advanced telephony features at no additional charge to local customers in an attempt to woo customers from ILECs. The trunks used by modern PBXs may use dedicated and/or circuit-switched circuits to access the PSTN. The next sections cover access or the OSI physical layer used by enhanced telecommunications services.

4.7.3 Dedicated Circuits

Digital T-1 and ISDN are often both thought of as services and technologies. In reality, they both can function as physical layer (as defined in the OSI model, Figure 3-6) carrier connections that allow agribusinesses access to the PSTN, Internet, or their own private data network. Another dedicated circuit technology, SONET, is a special case since it can be more than simply a physical carrier. As will be shown in 4.7.4, ISDN has such a broad definition that it can be hard to pin down an exact meaning except in context. The main difference between the dedicated circuits covered in this sub-section and the circuit-switched circuits of 4.7.4 (such as ISDN) is that dedicated circuits are not circuit-switched through telco voice switches.

The dedicated circuits shown in Table 4-20 have several things in common with respect to enhanced telecommunications. First, dedicated circuits are leased from an ILEC or ALEC for the sole use of an agribusiness and are available around the clock 365 days each year. Second, they are point-to-point circuits that travel between agribusiness locations (or from an agribusiness to a provider's POP). Typically, dedicated circuits use telco access and transport networks, but do not travel through CO switches.

Hence, in addition to avoiding congestion with PSTN traffic, dedicated circuits avoid the chance of poor connections and other vagaries connected with POTS switches. Most dedicated circuits are "always-on" so there is no connection establishment delay or connection establishment failure. Other QOS variables can be controlled better by carriers since dedicated circuits are engineered to be resilient enough that failure probabilities are extremely low. Charges are a flat monthly fee based on constant use of the entire circuit capacity, whether it is actually used or not. Dedicated circuits that cross LATA boundaries are more costly than inter-LATA dedicated circuits if an ILEC provides them.

There can be significant costs if an agribusiness switches from one carrier to another (but keeps the same type of circuit) or if it switches from one dedicated circuit to another. Such switching costs occur because contracts typically offer the lowest rates the longer the agribusiness is obligated. One to five year terms with a particular carrier at a set price are common. Even if prices fall or new lower-priced carriers begin to serve an area, the agribusiness is obligated by the contract. Furthermore, in many cases, the CPE purchased for use with one carrier's identical service offering will be incompatible with that of another carrier for technical reasons or because carriers make alliances with CPE manufacturers.

Changing from one type of dedicated service to another or adding to existing service (because of business expansion or new needs, etc.) can mean costly rewiring and installation charges and the purchase of new CPE. Service switching costs can even include installation charges for access loops and DCE in the loop such as repeaters or amplifiers, a fact remotely located businesses are already aware of. Thus, networks must be planned carefully with dedicated circuits because capacities must be correctly estimated.

Table 4-20: Dedicated circuit services (voice and mixed voice-data).
 

Circuit	Traffic	Voice capacity	Bandwidth (Code)	Data capacity
Dedicated analog voice grade line.	Analog voice or modem data.	Non-switched leased line from one point to another.	4 kHz (NA)	Modem capacity up to 33.4/56 kbps
DS-0 dedicated digital line or lines (fractional T)	Voice trunk, voice-data mix possible.	Varies by compression, overhead. Typically, 1 digital circuit (voice or data) per 56-64 kbps.	8-40 kHz (PCM)	56-64 kbps per circuit, symmetric.
DS-1, T-1 digital carrier	Voice trunk, Internet, data.	24 channels @ 56 or 64 kbps per digital line.	1.544 MHz (AMI) 2.316 MHz (B8ZS)	1.536 Mbps, symmetric.
DS-1, T-1 (HDSL feeder)	Voice trunk or voice-data mix (Smart T).	Fewer than 24 channels when shared with data.	420 kHz (2B1Q)	1.536 Mbps, symmetric
DS-3, T-3	Multiple voice trunks or voice-data mix.	672 voice channels or mix of voice, data.	67.145 MHz (B3ZS)	44.736 Mbps, symmetric.
DSL	Voice-data mix or data only.	0 to many, depending on variety. (See Table 4-21)	1110 kHz (ADSL)	Differs by DSL variety.
Cableco modem & phone	Internet, enhanced telephony, VPN.	1-3 lines, new technologies may permit more.	360 MHz (QAM, QPSK)	30 Mbps downstream (shared), 768 kbps upstream
SONET self-healing ring	Fiber optic data & multiple voice trunks.	Varies by OC level & compression: 1,000 (OC-1) to 150,000 (OC-192).	To 1 GHz (WDM, DWDM)	Varies by to OC level, OC-1 51.84 Mbps.
Wireless dedicated Ts	Voice, data, or mix.	Varies by service, carrier, and distance.	Varies	Varies

Sources: Tower, 1999; FitzGerald and Dennis, 1999, Hill Associates, 1998.

Analog voice grade dedicated circuits (the first item in Table 4-20) are traditional POTS lines that carry analog voice or data via modem from one point to another over a non-switched route dedicated to the subscriber. Analog leased lines are charged monthly on a per line basis with one voice grade line the usual unit. They may be used for voice intercoms, telephones, or to connect computers at two locations using ordinary modems. Dedicated analog voice grade circuits are also used to connect agribusinesses with ISPs for dedicated Internet connections, links for POS devices, or for remote sensing. The circuit may be open at all times or require connection establishment depending on CPE. Channel bonding is a technology that may be used to combine the bandwidth of two (or more) dedicated analog circuits to create faster data rates and better throughput. However, each end of the connection must have a channel bonding capable modem.

The remaining dedicated circuits are digital. The DS (Digital Signal) hierarchy governs how the next four dedicated circuits in Table 4-20, DS-0, fractional T, T-1 (DS-1), and T-3 (DS-3) are sold. The first DS hierarchy, DS-0 or fractional T circuits, are sold in increments of 64 kbps by ILECs and ALECs. DDS (Digital Data Service) is the name of telco offerings for single 64 kbps circuits. Voice, data, or a voice-data mix may be carried on a single DDS point-to-point line. However, DDS (as the name implies) circuits normally carry data networking or Internet traffic. A CSU/DSU is needed at the customer premises.

T-1 and T-3 dedicated circuits are called T carriers to emphasize the fact that, technically, they are technologies used to carry services. Services such as ISDN-PRI, frame relay, SMDS, ATM, and the Internet may be carried via Ts. However, they are also sold as point-to-point connections for other services such as links in private data networks or for voice telephony use. Typically, voice Ts are switched ISDN-PRI circuits (covered in 4.7.4), but it can often be hard (and sometimes unnecessary) to distinguish T-1s from the voice or data services they carry.

T-1s previously were so expensive that only large corporations could afford them. Hence, fractional Ts (groups of 64 kbps channels such as 128 kbps, 256 kbps, etc.) were introduced for the small business market. Now prices are as low as $100 per month for fractional Ts and even full T-1s are priced from $500 to $1200 per month. Therefore, smaller firms can often save the full monthly cost of the T when they switch from multiple single lines to fractional T-1 or T-1 trunks.

Some IXCs offer dedicated fractional Ts from the agribusiness to the long-distance POP for as few as eight lines, avoiding local service line charges as a full T-1 does, but for much smaller businesses. With a long-distance fractional or full T, long-distance calls are routed directly to the long-distance carrier without having to pay for local loop charges on these lines. Fractional Ts can be used to connect frame relay equipment to other locations in the company WAN or to ISPs. Typically, only one telephone conversation per 56-64 kbps channel can be carried. However, if a voice compression technology other than standard PCM is used, more conversations can be handled in a single channel. Upgrades to full T-1 leased circuits usually involve changing edge devices, but are not likely to require installation fees from the ILEC or ALEC if fractional service has been established.

T-1s transmit point-to-point DS-1 (1.544 Mbps) signals (which carry voice or data or combination traffic) from one point to another. Typically, separate T-1 carrier lines are used for local telephony trunk lines, intra-LATA long-distance trunk lines, inter-LATA long-distance trunk lines, and DID or DID FX trunk lines. Since T-1s feature in-band signaling, each T-1 trunk has 24 channels for individual telephone conversations. Voice-only T-1s are access level connections to local telephone switches of ILECs or ALECs, or to long-distance IXC POPs. Data-only T-1s serve as dedicated links in WANs or as dedicated links to ISPs from an agribusiness location with data rates of 1.536 Mbps. Some Ts (smart Ts) can be used to combine various voice, data, and Internet services in one T. Local T-1 service is available in some areas from cablecos, wireless carriers, and directly on optical fiber networks of IXCs or ALECs. Voice T-1 service differs from ISDN-PRI voice service (carried at T-1 speeds) because switching is not done through the ILEC's voice switch. Often, what is sold as a voice T-1 is technically an ISDN-PRI.

There are several T-1 carrier technologies: AMI/B8ZS, 2B1Q/HDSL T-1, and CAP/HDSL T-1. Before considering what these acronyms stand for and why the type of T-1 carrier technology is important to agribusinesses, realize there are differences that go beyond the three varieties shown in Table 4-20. T carriers differ according to framing, signaling, timing, and whether clear channel capability and customer reconfiguration control (smart Ts) are offered.

Framing concerns the order in which bits and overhead information (signaling) are sent [Hill Associates, 1998, p. 303.2.6]. Framing reduces the usable part of a T-1 circuit to 1.536 Mbps. Two different kinds of framing, SF (Super Frame) and ESF (Extended Superframe) are available. ESF allows both the agribusiness and the telephone company a superior ability to diagnose problems with T-1 lines that otherwise can go undiagnosed for weeks.

The kind of signaling technology affects the circuit's capacity and may determine whether CPE will be compatible with the carrier's hardware and software. Out-of-band or ZCS (Zero Code Suppression) signaling used is with ISDN-PRI (4.7.4), so one of the 24 channels in those circuits carries information about the status and operation of each of the 23 remaining user channels. In-band T-1 signaling lets all 24 voice channels be available to subscribers. Robbed bit in-band signaling (used with voice Ts) allows signaling information to travel over the same channels voice calls do by "robbing bits" from the voice call without affecting call quality [Hill Associates, 1998, p. 303.2.11]. Dial tone, ringing, caller ID, and toll and billing data are examples of voice signaling data.

Timing technologies synchronize bits, maintaining sending and receiving flow control. These background technologies matter to agribusinesses because they determine the distance from CO (or RAV) to customer premises that a T-1 circuit is capable of reaching in addition to the cost of providing the line.

Each T-1 technology has other important differences such as differences in line coding or modulation. The next two figures show the frequency ranges of four different T-1 technologies (AMI, B8ZS, 2B1Q HDSL, and CAP T-1 HDSL). Since each technology has different bandwidth requirements, their ranges vary. Figure 4-43 shows the first part of this relationship, the bandwidth requirement.

Figure 4-43: Bandwidth used by various T-1 and DSL T-1 technologies.

The first T-1 technology, AMI (Alternate Mark Inversion) Ts require expensive repeaters to be spaced 2000- 6000 feet apart over the full length of the loop. Additionally, AMI lines are so noisy that only one may be carried per bundle of 50-100 telephone lines to any one area, making installation difficult in areas where multiple T-1s are to be deployed. B8ZS (Bipolar with Eight-Zero Substitution) supplanted AMI as the most popular line code for T-1 transmission in many areas by the 1990's. B8ZS is AMI with ZBTSI (Zero Byte Time Series Interchange), a method that provides a clearer channel and better timing than AMI. However, standard AMI requires 1.544 MHz of bandwidth (and B8ZS needs 2.316 MHz) which can be a problem because attenuation is greater at higher frequencies.

As can be seen in Figure 4-44 [Adapted from Paradyne, 1999, p.15], B8ZS improved on AMI's range without repeaters. While AMI could reach 6,000 feet, B8ZS AMI could go to just past 13,000 feet. However, note that 2B1Q and CAP (as used in less-costly DSL) transmit 1.536 Mbps for 12,000 and 18,000 feet (respectively) without expensive repeaters or special DCE, as are required with B8ZS. This is primarily due to their efficiency in bandwidth use (as shown in Figure 4-43).

Figure 4-44: Range of various T-1 line codes.

Repeaterless HDSL feeder T-1s such as 2B1Q and CAP are better able to support smart T technology, and less expensive to deploy because repeaters are not needed within 12,000-18,000 feet of the CO. Over 70% of digital Ts now deployed are actually another type of dedicated circuit with superior range, a form of DSL called HDSL [Orckit, 2000] to be covered after T-3 dedicated circuits are mentioned.

T-3 carrier circuits have 28 times the capacity of T-1s. They are generally less expensive than buying from 10 to 15 T-1s separately. T-3 dedicated circuits operate in much the same way as T-1s, though they are mainly deployed over fiber optic lines rather than quad copper unless service is to be provided near the CO or special high-powered repeaters are used. The only way around installation of fiber optic cable for T-3 connections is via a point-to-point microwave path.

Because of the size and capacity of T-3s, there are few agribusinesses with the communications scale needed to demand a full T-3. However, an agribusiness that hosts its own website, owns over a hundred computers (requiring Internet and data network access), and requires as few as one hundred telephone lines could find that it would save money with a converged T-3 connection. By purchasing a single connection, the business would save compared to the cost of paying for separate local trunks, long-distance trunks, and Internet and data connections. Fractional T-3 carriers are also offered.

T-3s with customer reconfiguration control (smart Ts) are perhaps the only current possibility for most agribusinesses other than fractional T-3 connections. A voice-only full T-3 carries 672 voice channels, far beyond the needs of all but large corporations. DCSs (Digital Cross-connect Systems) allow multiple services (various voice trunks, data, and Internet) to be carried over a T-3 between multiple agribusiness locations, sometimes using more than one carrier. However, a smart T-3 connection can take expensive equipment and considerable design and planning. In many cases, telcos design smart T-3s that are somehow not smart enough to be cross-connected with competitors, forcing one-stop shopping for multiple services.

Because they rely on existing copper wire, DSL (Digital Subscriber Line) technologies may be an excellent way for rural Florida residences and small Florida agribusinesses to acquire access to high-speed hypercommunication services. The ILEC's own facilities and existing copper wires are used to deliver voice, data, and Internet service using several DSL technologies. However, the provision of DSL services is highly sensitive to the distance between the subscriber and the serving CO. In some cases, wire centers and RAVs (Remote Access Vehicles) have been implemented that bring DSL closer for customers who are farther than 18,000 feet from a CO. However, DSL faces several technical barriers based on the ILEC wire plant. These barriers include loading coils (used often on longer local loops), bridged taps, and DSL incompatible RAVs. These were discussed in 4.3.2.

Table 4-21 lists twelve varieties of DSL. The full translation of each acronym, bandwidth in Hz (where available), maximum data rate, and maximum range are also shown. For several reasons, the sources used to prepare Table 4-21 showed enormous variability concerning the capabilities of DSL varieties. First, information changes from month to month as new technologies are rolled out and from region to region depending on how local carriers deploy DSL. Second, carriers offer levels of service that include hierarchies of bandwidth for most forms of DSL. For example, BellSouth's FastAccess™ ADSL is 1.5 Mbps upstream and 256 kbps downstream, while GTE's ADSL goes from a bronze level (256 kbps/64 kbps) to a platinum level (1.5 Mbps/768 Kbps). While most DSL CPE operates at several speeds, there can be CPE incompatibilities among line codes or modulation methods. Finally, differences in DSL technologies are responsible for divergent claims regarding the superiority of standards.

Hence, before discussing the varieties of DSL shown by Table 4-21, the problem of comparing different standards with each DSL variety must be briefly addressed. For example, the ANSI and ITU ADSL s