Overview

When we completed the first edition of Modern Cable Television Technology, we described the major characteristic of the technologies covered as accelerated change. That has proven to be true, with so many major changes taking place since 1999 that a second edition was required to catch up. Even the book’s title is really obsolete, since so-called “cable television” systems have moved far beyond simply transporting video entertainment to the development of scalable-bandwidth, multi-service platforms supporting virtually every wired communications service desired by individuals and small businesses.

Among other changes since the first edition was published have been great progress in standards and practices for delivery of high speed data, home networking, IP-based voice, optical dense wavelength division multiplexing, new video compression techniques and integrated voice/video/data transport. With the help of a fourth author and a lot of industry professionals, we have attempted to update the previous material and add new material on emerging technologies on the same consistent, applications-oriented level as the first edition. Our aim has been to give the working engineer the information needed to understand the fundamentals of all the technologies used to build and operate a cable television system, while avoiding the detailed minutiae best left to designers of the hardware and software involved.

Intended Audience

The target audience includes several constituencies. Most important are our colleagues in the industry, particularly the members of the Society of Cable Telecommunications Engineers (SCTE). It is our intention that this book serve not only as a day-to-day reference, but also as the most useful tool for those preparing for the SCTE’s certification examinations. The cable industry is made up of those who build cable systems, operate them, connect to them, and supply the equipment used in them. All are part of the intended audience. The consumer electronics industry produces products that are connected to these systems. A better understanding of cable technology can facilitate equipment and system designs that will interwork seamlessly to the mutual benefit of operators, manufacturers and end users. An ever increasing percentage of the information that moves through cable systems is digital and cable system staffs now typically include technologists whose previous experience is limited to data networks. We hope to provide a mutual education vehicle between those whose backgrounds are in the broadband, linear world and those who think of information in a baseband, digital format. Similarly, the traditional telecommunications carriers heavily use optical fiber to carry digitally modulated signals. We hope to provide a tool for telecom engineers to understand the critical differences when linearly modulated signals are carried over optical networks. Others who should find material of relevance include operators of campus networks, regulators seeking a better understanding of the industry, telecom operators seeking to expand their service offerings, the emerging fiber-closer-to-the-home network architects, and private network operators. Lastly, we hope that the general technical fraternity might find satisfaction for a curiosity about the technology behind cable television.

Although we have not dealt thoroughly with metric measurements, PAL and SECAM analog video formats, and non-U.S. regulations, the technology differences are relatively minor, and most of the material should be of interest and value to non-North American audiences.

Fitting the material to the audience is a challenge when readers come with widely different experiences and pre-existing knowledge bases. Some will be experienced engineers from related fields who are unfamiliar with the details of cable television transmission technology, but intimately familiar with television. Others will be familiar with various methods of transporting signals, but not with some of the signal types carried over our networks. Still others will be experienced with radio frequency techniques, but not with optical transport. Finally, some will be equipment designers who are intimately familiar with their market niche, but need an understanding of how and whether their products fit into the business of cable television. Though some will be engineers with graduate degrees, others will be self-taught. Even those who have previously studied these topics may benefit from the refreshing.

Another aspect of the problem is to fit the scope of interest. Some may find the history of the industry fascinating, while others have no interest at all. Some want to know details, others want the shortest path to useful results. Our task was to organize and present the material at a level that is most useful to the majority of readers, while providing references to more-detailed treatments for those needing it. We also faced an ultimate restraint on the size of the book — you have to be able to lift it without requiring assistance! Our advice is to boldly skip over what is beyond your interest, use referenced material for more details where needed, and seek us out at the next convention to ask about what is missing.

Approach

The general level of the book is intended to be appropriate for a competent technologist who understands the basics and wants to understand cable television technology or who already understands some aspects of the business, but needs to expand his scope. Mathematics is held to the minimum needed to understand apply the technologies presented, rather than to rigorously prove each theory, with the hope of building a practical and useful understanding of the technology. It is not our purpose to develop concepts from first principles or to be scientifically “pure.” In that regard, we have tended to use common engineering units, as opposed to scientific units, in formulas even when that results in the inevitable correction factors. Our intention is to create a text that will have lasting value in an era of rapid technological change. This requires an emphasis on the fundamentals that are the basis upon which the advanced technology is built.

The general flow of the material here roughly parallels a “downstream” flow towards the end user. We begin with the signals, then consider the headend where those signals are received or generated and processed, then the transmission system that carries them throughout the served community. Finally, we deal with the terminal equipment and various compatibility and security issues involved.

Content

Cable television networks were originally designed for the purpose of delivering analog, broadcast-format television to widely dispersed viewers with a quality level that competed with alternate technologies and met FCC requirements. As other signals have been added to these networks, they have benefited by being transmitted through the very clean, low-distortion channels required for analog television, but also been constrained by the historically-based requirement of conforming to the 6-MHz television channelization. Thus, the book begins with a brief history of the industry, followed by analog television. It then deals with other signal formats and modulation types. With that background, it then deals with the central signal processing center (the “headend”), the distribution systems, and the subscriber end of the network.

The book is organized into six major parts:

The parts, and even the chapters, stand alone reasonably well. Dependencies of material from other chapters are clearly indicated. The reader having specific needs or a generalized knowledge of cable is invited to dive directly into the chapters of interest. A newcomer to the industry is advised to approach the process iteratively. First a light treatment, then more detail from a sequential reading of the chapters. Even so, skipping a chapter of little interest shouldn’t create a serious continuity problem.

Part 1, Once over Lightly, consists of a single chapter that gives a casual review of cable technology, business, regulation and history. This should be easily readable, even for those with no technology background.

Part 2, The Signals, covers in five chapters the technical details of the signals currently being transmitted over cable networks. These networks are inherently service-agnostic, however, so a reading of this section will also serve to inform the creator of a new service class about the transmission channel parameters to be expected. Chapter 2, Analog Television, covers the signals that drove the early development of the industry (and the only signals whose minimum performance level is specified by the Federal Communications Commission). The technical history of analog television is traced from the original black-and-white format through the additions of color, stereo sound and ancillary signals. Chapter 3, Digitally Compressed Television, covers the processes of digitizing the original analog signal, compressing it by removing redundancies, formatting it, and preparing it for transmission. Both standard-resolution and high-definition formats are covered. Chapter 4, Digital Modulation, covers all aspects of modulating an RF carrier with a baseband digital stream so that it can be transmitted through a shared, broadband, linear distribution network. This is an important chapter for those with a baseband, digital background, as the transmission channel conditions are considerably different in cable’s frequency-division-multiplexed (FDM) environment when compared with the traditional telecom time-division-multiplexed (TDM) channels. Chapter 5, Cable Networking Protocols, covers all aspects of transmitting high-speed data through cable net-works. In particular, the Data Over Cable System Interface Specification (DOCSIS) is covered in detail, as are non-DOCSIS protocols of interest to cable operators. Chapter 6, Cable Telephony, covers the technology required to carry digitized voice signals over these shared networks. Both proprietary switched-circuit TDM and newer Voice-over-IP (VoIP) protocols are covered.

Part 3, Headends covers, at a system engineer level, the originating and processing of signals in the headend. The three chapters cover reception, processing and headend operations. Chapter 7, Signal Reception, covers all aspects of receiving signals, including satellite, off-air and direct cable or fiber paths. Chapter 8, Headend Signal Processing, covers analog and digital modulation, handling of off-air digital signals (which are in a different modulation format than usually used for cable digital signals), ad insertion and server-based services such as video-on-demand (VOD). Chapter 9, Headend Operation, covers the overall RF spectral planning, RF and Optical signal management in the headend, and signal quality tests.

Part 4, Broadband Distribution Systems, covers in seven chapters the technologies used to transport signals throughout service areas. Chapter 10, Coaxial RF Technology, covers the linear, RF technology that forms the “last mile” of the hybrid fiber/coaxial (HFC) networks that are almost universally the backbone of modern cable systems. Chapter 11, Coaxial Distribution System Design, shows how that technology is used to design and specify coaxial networks. Chapter 12, Linear Fiber-Optic Signal Transportation, discusses the basics of transporting RF FDM spectra through use of linearly modulated optical transmitters. Chapter 13, Wavelength Division Multiplexing, expands on Chapter 12 to discuss and calculate the tradeoffs when transmitting multiple optical signals on different wavelengths of light through shared fibers. Chapter 14, Broadband Amplitude Modulated Microwave Links (AMLs), covers the use of microwave to transmit wideband FDM spectra where the use of cabled media are not practical. Chapter 15, End-to-End Performance, covers the total cascaded performance of the optical-plus-RF distribution path, with an emphasis on downstream transmission. Chapter 16, Upstream Issues, covers the unique aspects of signals that are transmitted from end users towards the headend.

Part 5, System Architecture, covers in four chapters how the network elements go together to form a complete system, starting with requirements, through design principles to expected reliability. Chapter 17, Service-Related Architecture Requirements, examines each current or contemplated cable-delivered service and examines its requirements in terms of signal quality, bandwidth, scalability and reliability. Chapter 18, HFC Architectural Elements and Examples, covers the principles of service-related overall design, including how the headend and distribution system interrelate. It gives examples of various architectural alternatives. Chapter 19, Fiber-Deep Systems, covers emerging network architectural alternatives in which all, or nearly all, the distance from headend to subscriber is through optical fibers. Chapter 20, Network Reliability and Availability, covers the process of designing distribution systems to meet defined goals for failure rate and availability.

Part 6, Customer Interface Issues, covers in five chapters issues associated with delivering services to customers at their homes. Chapter 21, Program Denial Technologies, covers the processes used to selectively deliver analog video programming to subscribing customers, while protecting them from unauthorized reception. Chapter 22, Digital Video Reception, covers the issues related to real-time customer interaction with headend equipment that delivers digital video programming. Chapter 23, Consumer Electronics Interface, covers the operational issues that arise when customer-owned equipment is connected to cable systems, while Chapter 24, Equipment Compatibility, covers the technical compatibility issues. Chapter 25, Home Networks, covers issues of interconnecting data equipment within customers’ homes.

In addition to the text, various appendices are included for reference. Appendix A, Channel Allocation, is a partial reprint of CEA/ANSI 542-B, the U.S. standard for downstream channelization in cable systems. Appendix B, Video Waveforms is based on EIA/TIA 250C and contains details of analog NTSC video waveforms and timing information. The Glossary contains an alphabetized listing of acronyms used throughout the book and should remove the necessity for a reader to search through the text for the first usage of a term when coming across it later in the book.

Background

We, the authors of this book, have written hundreds of technical papers and trade magazine articles, delivered countless presentations, and presided over dozens of technical conference sessions during combined activities exceeding a century in the cable industry. Some of us have also taught and lectured both within and outside the industry. In the process, we have certainly developed individual styles. We also have overlapping, but distinct, areas of expertise. Those who know us well can thus make a good guess as to which author made the primary contribution to each chapter. Every chapter, however, has had the benefit of mutual author review, independent review by outside authorities in each subject matter, and stylistic review by Morgan Kaufmann’s own copy editors. Hopefully, the result has a consistent feel for the reader.

The seed of the first edition was a monograph written by Walt Ciciora when he was with American Television Communications (the predecessor of Time Warner Cable). After extensive revision, that became a CableLabs publication. Morgan Kaufmann Publishers asked if it could be expanded into a book. Walt initially enlisted Dave Large to assist, and when the effort was about to overwhelm the two of them, they shanghaied Jim Farmer and among them, the First Edition was born with little resemblance to its ATC/CableLabs parent. Published in late 1999, it has been very well received by the cable technical community and was honored as the recipient of the Cable Center’s 2000 Cable Book Award.

Things are changing quickly in cable-related technology, however, and by mid-2001 we were already discussing the need for a second edition and sketching a revised table of contents. This time we were happy to add Michael Adams to the team (especially because of his expertise in digital video), while Walt Ciciora has served as a general consultant, rather than an active author. Chief among new material that needed to be covered were the emerging digital standards for voice, data, video and multi-media. On the distribution side, wavelength-division multiplexing had become a mainstream technology and several vendors were proposing various fiber-deep architectures. At the same time, a few existing technologies were beginning to fade, among them analog scrambling methods. We hope you find that we have achieved a balance between covering everything that needed to be included in a comprehensive book on cable technology, while turning out a book that is still lighter than the average spectrum analyzer!

Acknowledgments

Given the breadth of cable technology, there are no four people who can hope to be sufficiently familiar with it all to have written this book. We have relied on both the published materials of many others and, on a more direct level, the second edition has benefited, as did the first edition, from the specific contributions and review of many. We have, we hope, properly credited information gleaned from previously published works.

Special acknowledgment goes to Mary Philips for advice, draft review and use of her published material, all of which greatly aided our treatment of dense wavelength-division multiplexing. New material was contributed and reviewed by Erich Arnold (Arris Interactive), Tom Carr, (Wave7 Optics), Bob Gaydos (Concurrent Computer), Dean Stoneback (Motorola), and Ned Mountain and Louie Lividitis (both Wegener Communications). Ned even picked up the check for lunch! John Kenny (now Wave7 Optics), who was most helpful in the first edition, again contributed his proofing ability (and his insistence that power, not energy, is present at an interface). Kinney Bacon and Tony Wasilewski (both Scientific-Atlanta), Julius Bagley (consultant), and Jeff Reidmiller, (Dolby Labs) contributed their expertise. Consultant Charles Poynton was preparing his Morgan Kaufmann book about digital video while we were writing. He excerpted it for a tutorial at the IEEE International Conference on Consumer Electronics, which was so good he found himself pressed into service answering a lot of questions for us, and then proofing one chapter.

The cover art for the second edition originated with a series of pictures taken by Fred Spencer and Carolyn Terry of Altrio Communications, who are not only superb technologists, but competent photographers.

Much of the material from the first edition, while updated, has been retained largely intact. That edition reflected the contributions of many, including the following proposal reviewers (with their then-current affiliations): Alex Best (Cox Cable), Rex Bullinger (Hewlett Packard), Keith Cambron (Pacific Bell), Jim Chiddix (Time Warner Cable), Brian Colbry (Bell Labs), Joseph Glaab, (General Instrument Corporation), Andrew Glasspool (Farncombe Technologies, UK), Paul Shumate (Bellcore), and Archer Taylor (The Strategis Group).

Chapter reviewers included: George Abe (University of California, Los Angeles), Tim Brophy (General Instruments Corporation), Bob Dickinson (Dovetail Surveys, Inc.), John Carlucci (MystroTV), John Coppola (Cox Communications), Craig Cuttner (HBO), Keith Fleming (Antec), Joseph Glaab, Kenneth Gould (Time Warner Cable), David Grubb (General Instrument Corporation), Dan Harris, PhD (Corning Glass), Ted Hartson (Scottsdale Television Labs), Jud Hoffman (Panasonic), Steve Hughey (Antec), Doug Jones (U.S. West), John Kenny (Antec), Keith Kreager (Antec), Bill Lagoni (Thomson Consumer Electronics), Tom Lookabaugh (University of Colorado at Boulder), Michael Maslaney (Arris Interactive), M.C. “Mitch” Matteau (Arris Interactive), Marv Nelson (SCTE), Jim Raiser (Scientific Atlanta), Gerald Robinson (Scientific Atlanta), Blair Schodowski (Antec), Oleh Sniezko (TCI Cable), S.V. Vasudevan (BigBand Networks), Merrill Weiss (Merrill Weiss Group), and Norman Woods (Cable AML Inc.).

Special acknowledgments went to: Andrew Large, for the treatment of user-perceived reliability; Nick Hamilton-Piercy, for the contribution of recent failure analysis data; Ted Hartson, for additional help on the fine points of the history of television technology; and Dr. Francisco Bernues of Cable AML for providing the approach used for estimating microwave rain fade outage probability. For help with various technical details, we were grateful for the assistance of: Vic Williams and Dave Womble (Scientific Atlanta), Scott Ramsdell and Keith Kreager (Antec), John Vartanian (Viewers’ Choice), Mitch Matteau and Mark Bugajski (Arris Interative). Archer Taylor was a remarkable contributor, both as a reviewer, and in sharing his extensive knowledge and experience in the industry. He provided a number of interesting historic notes and also suggested a notation for the addition of cascaded noise and distortion in distribution systems.

The first edition was shepherded through Morgan Kaufmann by Jennifer Mann who was editor, friend and, occasionally, stern taskmaster, aided by Karyn Johnson our editorial assistant and Cheri Palmer, our production editor.

Rick Adams of Morgan Kaufmann spearheaded the effort that led to the second edition, working with the authors to architect a revised book that covered the new material, while staying within a reasonable size constraint. Karyn Johnson has done the heavy lifting of bringing together all of the updated and new material and overseeing the process of making a cohesive whole out of it. Angela Dooley and Elliot Simon had the unenviable task of fixing all the authors’ grammatical and style errors. As always, the folks at MKP have been an author’s dream to work with.

Our heartfelt thanks to all the contributors to both editions. If we have failed to thank someone for his or her assistance (or misspelled a name or publication, despite our best efforts), we apologize. If we have misinterpreted your suggestions or stubbornly refused to take your good advice, we take full responsibility for the result.

Lastly, we wish to thank those in the industry we have been privileged to know, our colleagues, and those who have gone before us and left us with a rich legacy of tools with which to further build. We have enjoyed the adventure and look forward to years of further challenges.