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Since the fourth edition of The Irwin Handbook of Telecommunications was published in 2000, wireless communications, high-profile mergers, broadband, Ethernet, and more have transformed the telecom industry. In this comprehensively revised and updated fifth edition, veteran telecom authority James Harry Green helps you understand the new concerns regarding wireless networks and security, covers new wiring standards and changes to the National Electric Code, evolving Ethernet and Local Area Network (LAN) standards, the transition toward converged voice and data, and much more.
Then, in a series of court cases, AT&T's monopoly collapsed, and the result reverberated around the world as postal, telephone, and telegraphs (PTTs) gradually privatized their telephone systems to keep pace. Not coincidentally, the collapse of the monopoly coincided with the rise of the semiconductor industry. No longer was the design and manufacture of telecommunications equipment specialized. The electromechanical apparatus that served the industry for its first century was displaced by equipment that shares its technology with the computer industry. Half of the companies producing telecommunications equipment today weren't even formed when the first edition of this book was published in 1986. The Internet was the exclusive terrain of a selected group of users and experimenters, and most of today's transport control protocol/ internet protocol (TCP/IP) experts hadn't even heard that term then. In 1986 a router was something you used to gouge holes in wood, and a bridge was used for crossing streams.
If someone were setting out today to build a new telecommunications infrastructure, it wouldn't much resemble what we have in place. The industry has well over a century of history, and several key events during that time have shaped the industry into the structure it has today. Governments have by no means been passive participants. In most of the world the government owns most, or all, of the telephone system, operating it as part of PTT operations. In most of North America ownership has been private, except for a short time during World War I when the U.S. government nationalized the telephone system. Nationalized telecommunications systems are now rapidly becoming a thing of the past. Governments are recognizing that their information systems must be freed from the sluggish responsiveness that often results from public management. Consequently, many of the major European and Asian economies have either privatized their telecommunications systems or are in the process of doing so.
In this chapter we will examine the major events that have shaped telecommunications as it is today. Much of this will focus on the United States, which has led the rest of the world in information system and telecommunications development. We will also look at some of the standards and regulatory agencies that develop and promulgate standards and otherwise shape the industry.
A Short History Of The Bell System
No organization in the world has influenced telecommunications to the degree that the Bell System did. The Bell System traced its roots back to Alexander Graham Bell's invention of the telephone in 1876, and survived for nearly 110 years until the Department of Justice broke it up in 1984 following a protracted antitrust case. For six decades prior to the 1984 dissolution of the Bell System, American Telephone and Telegraph Company (AT&T) operated as a regulated monopoly, but it wasn't always so.
The early days of the telephone were characterized by freewheeling and open competition. Following expiration of Bell's patents in 1893, small companies cropped up in every locale to provide switching services. The process was manual, handled from switchboards such as the one shown in Figure 1-1. Subscribers signaled the central office by lifting the receiver or turning a crank. The operators recognized the request for service by a lighted lamp on the switchboard or a magnetic flap that dropped down when ringing current was detected. By the turn of the twentieth century, some 4000 independent telephone companies served the United States, representing about 40 percent of the telephones in the country. AT&T, which was incorporated in 1885, owned the rest. During the first 35 years following Bell's invention of the telephone, AT&T acquired franchise rights to provide telephone service in most of the metropolitan areas of the United States.
The Principle of Regulated Monopoly
Finally, concerned about AT&T's monopolistic tactics, the Department of justice stepped in. In 1913 AT&T signed an agreement with the Department of justice that it would refrain from purchasing any more independent telephone companies. This agreement, called the Kingsbury Commitment, left the country with the configuration that persists today: a core metropolitan area in most major cities that traces its roots back to the Bell System. A non-Bell company often serves the suburban areas. In 1918, in the middle of World War I, the federal government nationalized the Bell System. For a brief 1-year period, the nation's telephone system was under government control. The AT&T president at the time, Theodore N. Vale, proposed to the government the principle of regulated monopoly. In exchange for freedom `to retain the telephone system in private ownership, Vale agreed to submit AT&T and its operating companies to government regulation. The theory was that utilities, such as water, electricity, and telephone, were natural monopolies. The public interest would not be served in having duplicated facilities because the additional investment required would drive prices up. Furthermore, utilities rely on the public right-of-way to deliver service, and the needs of the public are not well served by having multiple utilities digging up the streets and installing pole lines.
At the conclusion of AT&T's negotiations with the government, the principle of regulated monopoly was established as an alternative to government ownership, at least in the United States and most of Canada. Regulation was divided into two parts. The Interstate Commerce Commission regulated the interstate portions of telephone service while the intrastate elements were left to the states. Some states formed statewide regulatory agencies, while others left regulation to municipalities.
ICC regulation continued until 1934, when Congress passed the original Telecommunications Act. This act, among other provisions, established the Federal Communications Commission, and gave it responsibility for regulating interstate communications. In addition, the FCC was charged with regulating the use of the airwaves.
Universal Service and Subsidies
It is important to understand that, during this period of regulation, the operation of the nation's telephone system was driven by a quest for universal service. The value of every telephone, the argument went, was enhanced by the number of telephones that could be reached. It was logical, therefore, for urban users, where the cost per subscriber was low, to subsidize high-cost rural users. Also, it was logical for basic service rates to be kept low and to be subsidized by optional services. The method of pricing services was pegged to the value to the subscriber, and had little to do with the carriers' cost of providing it. Under regulation, the telephone companies and the utility commissions shared several joint objectives. For one, the cost of basic service would be held to a minimum, with revenues made up through discretionary services. Since a large portion of the carriers' expense was depreciation, the regulatory commissions had every incentive to keep this expense low, which they could do by extending the service life...
|Ch. 1||A brief history of telecommunications||3|
|Ch. 2||Introduction to the public switched telephone network||21|
|Ch. 3||Introduction to data communications||35|
|Ch. 4||Data communications principles||55|
|Ch. 5||Pulse-code modulation||73|
|Ch. 6||Data communications protocols||93|
|Ch. 7||Outside plant||111|
|Ch. 8||Access technologies||125|
|Ch. 9||Structured cabling systems||139|
|Ch. 10||Local area networks||155|
|Ch. 11||Network equipment||173|
|Ch. 12||Signaling systems||195|
|Ch. 13||The PSTN and quality requirements||215|
|Ch. 14||Circuit switching systems||239|
|Ch. 15||The integrated services digital network||261|
|Ch. 17||Optical networking||289|
|Ch. 18||Microwave radio systems||309|
|Ch. 19||Satellite communications||327|
|Ch. 20||Mobile, cellular, and PCS radio systems||343|
|Ch. 21||Wireless communications systems||365|
|Ch. 22||Video systems||387|
|Ch. 23||Station equipment||405|
|Ch. 24||Customer-premise switching system features||419|
|Ch. 25||TDM customer-premise switching systems||437|
|Ch. 26||IP customer premise equipment||455|
|Ch. 27||Automatic media distribution systems||475|
|Ch. 28||Voice-processing systems||497|
|Ch. 29||Electronic messaging systems||519|
|Ch. 30||Facsimile systems||535|
|Ch. 31||Enterprise networks||551|
|Ch. 32||Metropolitan area networks||569|
|Ch. 33||Wide area networks||587|
|Ch. 34||Frame relay||605|
|Ch. 35||Asynchronous transfer mode||619|
|Ch. 36||IP networks||633|
|Ch. 37||Network testing||647|
|Ch. 38||Network management systems||661|
|Ch. 39||Telecommunications convergence||677|
|Ch. 40||Future developments in telecommunications||691|
Before the breakup of the Bell System, telecommunications was in a technology-push situation rather than demand-pull. Most developments originated in the Bell Labs and were released to the field only after they were thoroughly tested. Development cycles of 4 or 5 years were not uncommon. Then in the late 1970s came a fabulous development that is invisible to most people, but which has revolutionized telecommunications: fiber optics. Bell Laboratories did most of the research on fiber and the lasers that make information transferpossible, but other companies rapidly picked up on the technology, and demand exploded. Fiber optics was probably the first real demand-pull product that hit the telecommunications market. Fiber optics is still, by far, the most dynamic and influential of all the telecommunications technologies. In a little more than two decades, strands of fiber have girdled the world and its capacity is practically unlimited. Production equipment can reach speeds of 10 gigabits per second (Gb/s) now, and that is still not the top limit. Dense wavelength division multiplexing divides the medium into 40 different "colors," each capable of carrying a 10-Gb/s signal. Undersea cables have, for all practical purposes, replaced satellites as transcontinental telephone media, but satellites are experiencing a new rebirth with low earth-orbiting vehicles that eliminate the delay inherent in geosynchronous devices. These make it possible to place a telephone call from virtually any place on the face of the earth.
New technology has flourished since divestiture, but perhaps a better indicator of the wisdom of the consent decree that broke up the Bell System is the fact that all parties remained dissatisfied. The regional Bell Operating Companies chafed at the long-distance restrictions the agreement imposed upon them. The interexchange carriers (IXCs) complained about access charges, which they deemed excessive, and a host of would-be competitors complained about the local monopoly. Congress entered the picture and, responding to multiple pressures, created the Telecommunications Act of 1996. The act uses both carrots and sticks to reshape the local telephone market from government regulation to competition. At the time `this is written, the Telecommunications Act has resulted in few of its intended outcomes. Business subscribers in larger cities all have options for local dial tone provided they purchase enough lines to make it worth the while of competitive local exchange carriers (CLECs) to serve them.
Few residences have a choice of telephone service, but they are still saddled with increased costs. The Telecommunications Act requires carriers to contribute to a Universal Service Fund to subsidize rural and low-income consumers. Congress decided that schools, libraries, and rural health care organizations were also entitled to subsidies. The carriers passed their increased costs through to consumers in the form of surcharges and directly allocated costs, even while they were enjoying reduced access charges. The act required that local telephone numbers be portable between carriers, the costs of which are being pushed directly onto consumers who don't even enjoy the possibility of reduced rates from competitive carriers. The impact of these regulatory fiats has been negative for most consumers even though it may prove beneficial in the long run.
Mergers and acquisitions have changed the landscape in ways that we can't begin to grasp yet. The seven regional Bell Operating Companies have dwindled to four-probably three by the time you read this. GTE will merge into Bell Atlantic, which already has absorbed Nynex. Southwestern Bell has assimilated Pacific Telesis and Ameritech. US West announced its intention to join in a "union of equals" with Global Crossings, a Bermuda-based firm that has a corporate history stretching all the way back to 1997. Global Crossings has already acquired Frontier Communications and the undersea cable operations of Cable and Wireless, a British firm. Before the deal could be consummated, Qwest, another newcomer to the industry, offered a more attractive proposition. As this is written, regulatory approval is still pending. After flirting briefly with British Telecom, MCI, which was a major player in triggering the collapse of the Bell System, allowed itself to be acquired by WorldCom, another corporate newcomer. The MCI WorldCom combination, which is the second largest IXC in the United States, is attempting to get approval to aquire No. 3 Sprint.
AT&T, which fought to keep its manufacturing and customer premises equipment business intact at divestiture and then launched a hostile takeover of NCR, suddenly dismantled its empire of its own volition. After setting free NCR and spinning off its manufacturing operations into Lucent Technologies, AT&T then set about to acquire Teleport Communications Group, a competitive local exchange carrier, and TCI and Media One, two of the country's largest cable providers, with the announced intention of delivering Internet and telephone services over cable. On the European continent, Deutsche Telekom and Telecom Italia have joined forces. Will all of these mergers and acquisitions work to the benefit of the users? The room for doubt is more than ample.
Much has been written about the convergence of voice and data. Accompanied by loud fanfare, products are beginning to appear, but the technology is yet in its infancy. A host of other products is appearing on the horizon and potentially will further alter the shape of telecommunications, but it's too early to tell. Wireless has the potential to break some of the stranglehold that the incumbent local exchange carriers (ILECs) have by virtue of their cable plant. At the same time, the ILECs are attempting to deploy a variety of digital subscriber line techniques to relieve some of the bottlenecks users experience in accessing the Internet. Cable companies, led by AT&T's acquisition of TCI, hope to grab some of the market for both dial tone and Internet access as they upgrade their older coaxial systems to fiber optics.
Another dramatic development was the cell phone, which happened about the same time as fiber optics. The development cycle of this product was astounding: the concept was born in 1947-before it was technically feasible. The Bell System demonstrated its feasibility in the 1970s, but the FCC camped on it for years, reluctant to grant the airwaves to a monopoly. Finally, they settled on a duopoly. Half of the frequency spectrum was awarded to the traditional wireline carrier in each market. The other license was granted to competitors for the asking. As cellular hit the market, demand exploded and the cost of cell phones dropped, but the legislated competition didn't do much else for the consumer. The FCC learned from its mistakes and divided the market more intelligently with personal communications services (PCS). Instead of a duopoly, the band is divided into six segments, and the FCC auctioned off the spectrum.
The Internet itself is nothing short of phenomenal, and it is just getting started. It is sparking not only information and entertainment pastimes, it is also fueling a whole new way of doing business, and offering ways for companies to link themselves together by building secure tunnels through a chaotic and insecure network.
All of this makes plenty of grist for a book that has the aim of helping people to make sense of the confusion. With the possible exception of health care, no other industry in the world has undergone such a radical and wrenching change in the past 20 years.
And more is yet to come.
Unquestionably, the confusion still exists, and the pace of change is accelerating. Since the third edition was published, the Internet has exploded, bringing the most far-reaching effects of any telecommunications development in our lifetimes. The "information superhighway" is no longer theoretical. The underlying technologies have been developing for decades and now they are converging into a network that is compelling in its simplicity and in its ability to link people with a cost and convenience that changes the foundation of our lives. Commerce is shifting to the Internet, altering conventional methods of doing business. Teaching and learning methods are changing, entertainment patterns are shifting, time spans are compressedas we no longer have to wait for information delivery, and even traditional telephone service is moving from the confines of narrow-band copper wire to broadband facilities.
The Handbook of Telecommunications has undergone regular revisions to keep pace with the changes in the industry. The third edition was written during the period when the Telecommunications Act of 1996 was passed, but its effects had not been felt. Now, competitive local service is available in most metropolitan areas and prices are dropping for multiline businesses. The structure of the telephone business is being challenged as voice and data converge over packet networks and cable television providers offer dial tone and Internet access over their facilities. The industry has evolved from staid predictability into one where chaos reigns. My aim in writing this book is to provide, in language that anyone with an interest in the subject can understand, an overview of how each of the telecommunications technologies works. Obviously, some very complex concepts have been simplified. Each chapter would easily require several volumes for a full treatment. For those who want more detail, the bibliography lists many excellent books on the subject.
With this edition, much is changed besides just an update to include new developments. First, in addition to the primary audience of business telecommunications managers, several colleges and universities have used this book as a text. Consequently, with this edition, an instructor's manual is available through normal university channels.
The second change involves giving the book a more international flavor. The first three editions dealt primarily with the North American network. While this is still the primary focus, additional emphasis has been given to international issues. Where the technology and terminology differ in other countries, these are discussed.
Over the course of four editions, the references to proprietary protocols and interfaces are gradually giving way to International Telecommunications Union standards. Most chapters reference the predominant standards applying to the technology under discussion. Standards have always been a wild card in the world of telecommunications, and the problem isn't getting better. The permutations and combinations of standards aren't quite infinite, but they are coming close and new ones are announced regularly. The Internet hasn't helped. Ironically, although the growth of the Internet was fueled by internet protocol (IP), the most open standard of all, its shortcomings have inspired a barrage of modifications, some open and some proprietary.
The structure of the book is modified somewhat from the third edition. It is divided into the same five parts as in previous editions, corresponding to major divisions in telecommunications equipment. The introductory chapter in Part One covers both voice and data. The remainder of Part One is devoted to concepts that are common to the industry. In Part One, we discuss voice and data fundamentals, pulse code modulation, outside plant, structured wiring, local area network principles, and the other building blocks of telecommunication networks. Part Two covers circuit switching concepts. It begins with a discussion of signaling followed by three chapters that explain in overview how local and toll switches function. Circuit switching has been at the heart of the telephone industry for more than a century. Although it is being challenged by packet switching, it retains a stability and service quality that packet technologies cannot yet provide.
Part Three covers transmission equipment. Separate chapters discuss the fundamental technologies of fiber optics, microwave radio, satellite transmission, cellular and PCS radio systems, and video. Video has evolved the least of all telecommunications technologies over the past half century. Although color has been added, television signals still use the same techniques that they did when the first broadcast stations went on the air, but that is about to change. High-definition television is just entering the market, and as with other technologies the signals are changing to digital. Digital cable transmission systems will begin to compete with the conventional telephone system for carrying Internet and telephone traffic. Part Four discusses customer premise equipment. We begin with an explanation of station equipment, followed by key telephone equipment and private branch exchange (PBX). Ancillary equipment, such as automatic call distribution, voice processing, and computer-telephony integration, are covered in separate chapters. Other chapters discuss electronic messaging, facsimile, and Centrex, which is the central office equivalent of a PBX.
Part Five pulls together the building blocks we have discussed in the earlier chapters into completed and functioning networks. This part illustrates the tremendous variety of alternatives that are available and discusses how and where they are applied. We begin this part with the discussion of enterprise networks, Which is a blanket term covering the type of network large organizations use to link the company together. Following that, other chapters cover broadband protocols such as switched multimegabit data service, gigabit Ethernet, Fibre Channel, and fiber distributed data interface. We discuss frame relay, asynchronous transfer mode, the integrated services digital network, and wide area data networks. Other chapters deal with internetworking and convergence, which is one of the hottest topics in the industry today. The book concludes with a discussion of network management systems and how they are used to enable humans to cope with the complexity. The final chapter in the book looks ahead a few years with a view of where telecommunications technology is headed.
Readers of previous editions will find that some information has been omitted to make space for new developments. Previous editions included a buyer's guide at the end of each chapter and an appendix listing addresses and telephone numbers of telecommunications manufacturers and service providers. With the number changes that result from new area codes, these lists are frequently outdated. Therefore, we have instead included a list of Web sites of the telecommunications firms that we were able to identify. This list is posted on Pacific Netcom's Web site where it will be kept updated. Manufacturers who have been omitted from this list may send me an e-mail (firstname.lastname@example.org) and you will be added. The list in Appendix A does not include distributors, software developers, and the like, but the Web site does. We hope to develop this into a comprehensive list of telecommunications-associated organizations.
As a guide to decoding the countless acronyms that have crept into the telecommunications vocabulary, this book contains an appendix that should be helpful. Appendix B lists the principal acronyms and what they stand for. In addition, a glossary is provided that defines terms that are used in this book. We have endeavored to either define the term in context, in the glossary, or both. Some material, primarily transmission principles and an explanation of how to use network design formulas and techniques were to some degree duplicated in The Handbook of Telecommunications Management. These are omitted from this volume, and will be updated in the third edition of that book. In previous editions we've included an explanatory section on the fundamentals of electricity that are necessary for understanding some of the technical concepts presented in the book. That information is also omitted from this edition, but it is available for download along with other white papers on Pacific Netcom's Web site, which may be found at www.pacificnetcom.com. We also invite readers to offer corrections or suggestions for changes on the same Web site.