Understanding Digital Subscriber Line Technology

by Starr, Thomas; Cioffi, John M.; Silverman, Peter J.

• ISBN13: 9780137805457
• ISBN10: 0137805454
• Edition: 1st
• Format: Paperback
• Copyright: 1998-12-29
• Publisher: PEARSO

Summary

Visionaries have spoken of a future where the common person has instantaneous access to data spread around the globe. Engaging in a live videoconference, or perhaps watching a personalized newscast are just two of examples of many. For this vision to become reality, a global broadband information infrastructure must be built that provides low-cost access to the consumers and sources of information. What connects to virtually every home and business in the industrialized world? Phone lines connect to 700 million sites today. Data rates of several kilobits per second are possible over phone lines using dial-up modems. This is enough to spark the appetite of the Internet surfer but is not nearly enough to satisfy the desire for immediate information on demand. Similarly, video and audio applications at dial-up modem data rates leave users demanding more.

Digital subscriber line (DSL) technology enables high-speed digital transmission on conventional telephone lines. A global broadband information infrastructure based on telephone lines is emerging, and it relies on DSL technology. The transformation of the telephone line access has begun; it is progressing with the addition of over one billion U.S. dollars worth of DSL equipment each year. Accomplishing the impossible is an engineer's greatest reward. Digital subscriber line development has been most rewarding. In 1975, it was believed that 20 kb/s was the highest data rate that could be transmitted via telephone lines. Then, breakthrough concepts in digital transmission were enabled by enormous advances in very-large-scale integrated (VLSI) circuits and digital signal processing (DSP). Transceiver designs of breathtaking complexity (at that time) provided 144 kb/s basic rate ISDN (BRI) transport via most telephone lines. Experts then said that this was very near the capacity limit of telephone lines. This barrier was demolished by the 1.5 Mb/s high bit rate DSL (HDSL). The breakthrough cycle was repeated by 6 Mb/s asymmetric DSL (ADSL), and then 52 Mb/s very-high bit rate DSL (VDSL).

This book explains and details the key concepts for DSL technology and its applications. The reader will attain a strong familiarity with the crucial aspects and technical jargon of the DSL field. The scope encompasses applications, network architecture, network management, network operations, communications protocols, standards, regulatory issues, and the underlying technologies. This book was written to assist engineers and marketing managers - whether new to DSLs or experts in need of a convenient reference. Background regarding voice-band transmission via telephone lines may be found in the excellent books by Witham Reeves on subscriber loops.

Acknowledgments

The authors thank Jim Loehndorf for assistance with the sections on data communications protocols, and Kim Maxwell for providing his input regarding voice-band modems and other sections.

The authors would also like to sincerely thank Dr. Kiho Kim, Richard Goodson, and Dr. Martin Pollakowski for their review of this material and their helpful comments and suggestions.

The second author, John Cioffi, especially would like to thank the following people (in alphabetical order) for their significant discussions and direct assistance on specific topics of this book: Mike Agah, John Bingham, Jacky Chow, Peter Chow, John Cook, Joice DeBolt, Kevin Foster, Mathias Friese, Richard Goodson, Werner Henkel, Atul Salvekar, Jose Tellado, Po Tong, Craig Valenti, Jean-Jacques Werner, and George Zimmerman. He further wishes to thank Dr. Joe Lechleider for enticing him into DSL in 1987, and thanks beyond measure the outstanding technical staff of Amati (1989-1997, now Texas Instruments), and the first to believe: his past and present students at Stanford.

Thanks also go out to Steve Blackwell and Kevin Schneider of Adtran, who kindly offered the use of their good summary of HDSL2 work in the T1E1.4 Working Group. The first author, Tom Starr, has had the pleasure of chairing the T1E1.4 Working Group for over ten years. Thanks to the professionalism, dedication, and expertise of its members, T1E1.4 has done more than merely write the industry's DSL standards. Multidisciplinary collaboration has allowed T1E1.4 to set the industry's objectives and chart the course to meeting these objectives. There have been moments of agony and disappointment but, on the whole, serving as T1E1.4 chair has been rewarding. Thank you, members of T1E1.4, for being the world's foremost creators of DSL technology.

The views expressed in this book are those of the authors and do not necessarily reflect the views of their employers or the organizations in which the authors hold office.

Thomas Starr John M. Cioffi Peter Silverman

Author Biography

Thomas Starr develops and manages new local access technologies for Ameritech. He also chairs ANSI's T1E1.4 working group, which develops XDSL standards for the United States. Mr. Starr also serves as a member of the Board of Directors of the ADSL Forum.

JOHN CIOFFI is the founder of Amati Inc., the company that wrote most of the ADSL standard. He is an associate professor of electrical engineering at Stanford University.

Table of Contents

Preface	xv	(1)
Acknowledgments	xvi	(1)
About the Authors	xvii
Chapter 1 DSL Fundamentals	1	(22)
1.1 Alternatives to DSLs: Fiber, Wireless, and Coax	2	(1)
1.2 Worldwide Extent	2	(1)
1.3 Voice-Band Modems and DSLs	3	(5)
1.4 Transmission Modes	8	(4)
1.4.1 Direction	8	(1)
1.4.2 Timing	9	(1)
1.4.3 Channels	10	(1)
1.4.4 Single and Multipoint Topologies	11	(1)
1.5 DSL Terminology	12	(1)
1.6 Rate Versus Reach	12	(1)
1.7 Crosstalk	13	(3)
1.8 Enabling and Disabling Forces	16	(1)
1.9 Applications	17	(4)
1.10 Evolution of Digital Transmission	21	(2)
Chapter 2 Types of DSLs	23	(30)
2.1 DSL Design Margin	23	(1)
2.2 DSL Precursors	24	(1)
2.3 Basic Rate ISDN	25	(5)
2.3.1 ISDN Basic Rate Origins	25	(1)
2.3.2 Basic Rate ISDN Capabilities and Applications	26	(1)
2.3.3 Basic Rate ISDN Rate Transmission	26	(1)
2.3.4 Extended-Range Basic Rate ISDN	27	(2)
2.3.5 Digital Added Main Line	29	(1)
2.3.6 IDSL	30	(1)
2.4 HDSL	30	(11)
2.4.1 HDSL Origins	30	(1)
2.4.2 HDSL Capabilities and Application	31	(1)
2.4.3 HDSL Transmission	32	(3)
2.4.4 Second-Generation HDSL	35	(6)
2.5 ADSL	41	(8)
2.5.1 ADSL Definition and Reference Model	41	(1)
2.5.2 ADSL Origins	42	(1)
2.5.3 ADSL Capabilities and Application	43	(1)
2.5.4 ADSL Transmission	43	(3)
2.5.5 ADSL's Future	46	(3)
2.6 VDSL	49	(4)
2.6.1 VDSL Definition and Reference Model	49	(2)
2.6.2 VDSL Origins	51	(1)
2.6.3 VDSL Capabilities and Applications	51	(2)
Chapter 3 Twisted-Pair Transmission	53	(80)
3.1 Twisted-Wire-Pair Origins	53	(1)
3.2 Telephone Network and Loop Plant Characteristics	53	(10)
3.2.1 Feeder Plant	54	(1)
3.2.2 Digital Loop Carrier	54	(2)
3.2.3 Distribution Plant	56	(1)
3.2.4 Wire Gauge	56	(1)
3.2.5 Bridged Tap	57	(1)
3.2.6 Loaded Loop	58	(1)
3.2.7 Loop Length Distribution	59	(1)
3.2.8 Customer Premises Configuration	60	(3)
3.3 Line Powering	63	(1)
3.3.1 Activation/Deactivation	63	(1)
3.4 Sealing Current	63	(1)
3.5 Transmission Line Characterization	64	(21)
3.5.1 "ABCD" Modeling	64	(3)
3.5.2 Transmission Line RLCG Characterization	67	(7)
3.5.3 Characterization of a Bridged-Tap Section	74	(1)
3.5.4 Loaded Coils -- Series Inductance	75	(1)
3.5.5 Computation of Transfer Function	75	(3)
3.5.6 Measurements for Computation of RLCG Parameters	78	(6)
3.5.7 Balance -- Metallic and Longitudinal	84	(1)
3.6 Noises	85	(12)
3.6.1 Crosstalk Noise	86	(6)
3.6.2 Radio Noise	92	(2)
3.6.3 Impulse Noise	94	(3)
3.7 Spectral Compatibility	97	(8)
3.7.1 Interference Between DSLs and Multiplexing	98	(1)
3.7.2 Self-Interference	99	(1)
3.7.3 Crosstalk FEXT and NEXT Power Spectral Density Models	100	(4)
3.7.4 Emissions from DSLs	104	(1)
3.8 More Two-Port Networks	105	(14)
3.8.1 Reciprocal and Lossless Two-Port Circuits	106	(1)
3.8.2 Analog Filter Design and T(s)	107	(6)
3.8.3 Lossless Realization of H(s)	113	(1)
3.8.4 Frequency/Magnitude Scaling and Frequency Transformations	114	(2)
3.8.5 Active Filters	116	(3)
3.9 Three-Port Networks for DSLs	119	(10)
3.9.1 POTS Splitters	120	(8)
3.9.2 Hybrid Circuits	128	(1)
References	129	(4)
Chapter 4 Comparison with Other Media	133	(6)
4.1 Fiber-to-the-Home	133	(1)
4.2 Coax and Hybrid Fiber Coax	134	(2)
4.3 Wireless Alternatives	136	(1)
4.4 Satellite Services	137	(1)
References	137	(2)
Chapter 5 Transmission Duplexing Methods	139	(8)
5.1 Four-Wire Duplexing	139	(1)
5.2 Echo Cancellation	140	(2)
5.2.1 Adaptive Echo Cancellation	142	(1)
5.3 Time-Division Duplexing	142	(1)
5.4 Frequency-Division Multiplexing	143	(1)
References	144	(3)
Chapter 6 Basic Digital Transmission Methods	147	(36)
6.1 Basic Modulation and Demodulation	147	(8)
6.1.1 The Additive White Gaussian Noise Channel	150	(4)
6.1.2 Margin, Gap, and Capacity	154	(1)
6.2 Baseband Codes	155	(17)
6.2.1 The 2B1Q Line Code (ISDN and HDSL)	155	(4)
6.2.2 Pulse Amplitude Modulation	159	(2)
6.2.3 Binary Transmission with DC Notches	161	(5)
6.2.4 4B3T Line Code	166	(2)
6.2.5 4B5B Modulation	168	(1)
6.2.6 Successive Transmission	169	(3)
6.3 Passband Codes	172	(8)
6.3.1 Quadrature Amplitude Modulation	173	(1)
6.3.2 Carrierless AMPM	174	(1)
6.3.3 Other Quadrature Modulation Schemes	175	(1)
6.3.4 Constellations for QAM/CAP and Relation to VSB	176	(2)
6.3.5 Complex Baseband Equivalents	178	(2)
References	180	(3)
Chapter 7 Loop Impairments, Solutions, and DMT	183	(114)
7.1 Intersymbol Interference	183	(22)
7.1.1 Quantifying ISI	184	(2)
7.1.2 Equalization	186	(10)
7.1.3 Transmit Equalization	196	(4)
7.1.4 Partial-Response Detection	200	(2)
7.1.5 Maximum-Likelihood Detection (Viterbi Algorithm)	202	(3)
7.2 Multichannel Line Codes	205	(51)
7.2.1 Capacity of the AWGN Channel	205	(1)
7.2.2 Basic Multichannel Transmission	206	(2)
7.2.3 Loading Algorithms	208	(9)
7.2.4 Channel Partitioning	217	(11)
7.2.5 Equalization for Multichannel Partitioning	228	(7)
7.2.6 ADSL T1.413 DMT	235	(1)
7.2.7 Clipping and Scaling (Peak-to-Average Issues)	236	(6)
7.2.8 Fast Fourier Transforms for DMT	242	(5)
7.2.9 Multiplexing Methods for Multicarrier Transmission	247	(4)
7.2.10 Narrowband Noise Rejection	251	(5)
7.3 Trellis Coding	256	(8)
7.3.1 Constellation Partitioning and Expansion	256	(6)
7.3.2 Enumeration of Popular Codes	262	(1)
7.3.3 Shaping Effects	262	(1)
7.3.4 Turbo Codes	263	(1)
7.4 Error Control	264	(24)
7.4.1 Basic Error Control	265	(5)
7.4.2 Reed-Solomon Codes	270	(4)
7.4.3 Interleaving Methods	274	(3)
7.4.4 Concatenated Coding and Multilayer Coding	277	(1)
7.4.5 ADSL Special Case	277	(4)
7.4.6 CRC Checks	281	(4)
7.4.7 Scramblers	285	(3)
References	288	(9)
Chapter 8 Initialization, Timing and Performance	297	(58)
8.1 Initialization Methods	297	(17)
8.1.1 Activation	297	(2)
8.1.2 Gain Estimation	299	(3)
8.1.3 Synchronization (Clock, Frame)	302	(1)
8.1.4 First Channel Identification	303	(8)
8.1.5 Channel Equalization	311	(3)
8.1.6 Secondary Channel Identification and Exchange	314	(1)
8.2 Adaptation of Receiver and Transmitter	314	(10)
8.2.1 Receiver Equalization Updating	315	(3)
8.2.2 Transmitter Adjustment	318	(6)
8.3 Measurement of Performance	324	(13)
8.3.1 Test Loops and Noise Generation	325	(8)
8.3.2 Measure of Performance	333	(4)
8.4 Timing Recovery Methods	337	(15)
8.4.1 Basic PLL Operation	337	(4)
8.4.2 Open-Loop Timing Recovery	341	(3)
8.4.3 Decision-Directed Timing Recovery	344	(2)
8.4.4 Pointers and Add/Delete Mechanisms	346	(2)
8.4.5 Frame Synchronization	348	(1)
8.4.6 Discrete-Time VCO Implementation	349	(3)
References	352	(3)
Chapter 9 Operations, Administration Maintenance, and Provisioning	355	(8)
9.1 OAM&P Features	358	(2)
9.2 Loop Qualification	360	(3)
Chapter 10 DSL in the Context of the ISO Reference Model	363	(6)
10.1 The ISO Model	363	(2)
10.2 Theory and Reality	365	(1)
10.3 The Internet Protocol Suite	365	(1)
10.4 ATM in the Seven-Layer Model	366	(3)
10.4.1 Physical Layer Functions	367	(1)
10.4.2 Link and Higher-Layer Functions	367	(2)
Chapter 11 ADSL: The Bit Pump	369	(12)
11.1 ADSL System Reference Model	369	(1)
11.2 ATU-C Reference Model	370	(2)
11.3 ATU-R Reference Model	372	(1)
11.4 Specific Configurations to Support ATM	373	(1)
11.5 Framing	373	(4)
11.5.1 Superframe Structure	375	(1)
11.5.2 Fast Data Buffer Frame Structure	375	(1)
11.5.3 Interleaved Data Buffer Frame Structure	376	(1)
11.6 Operations and Maintenance	377	(1)
11.7 Initialization	378	(1)
Reference	379	(2)
Chapter 12 ATM Transmission Convergence on ADSL	381	(4)
12.1 Functions of ATM Transmission Convergence	381	(1)
12.2 Transmission Convergence in an ADSL Environment	382	(2)
Reference	384	(1)
Chapter 13 Frame-Based Protocols over ADSL	385	(6)
13.1 PPP over a Frame-Based ADSL	385	(3)
13.1.1 RFC 1662 -- PPP in HDLC-Like Framing	386	(1)
13.1.2 RFC 1661 -- The Point-To-Point Protocol	387	(1)
13.2 FUNI over ADSL	388	(1)
13.2.1 FUNI Frame Structure	388	(1)
13.2.2 Encapsulation	389	(1)
Reference	389	(2)
Chapter 14 ADSL in the Context of End-to-End Systems	391	(20)
14.1 An Overview of a Generic DSL Architecture	394	(4)
14.1.1 The Customer's Premises	394	(1)
14.1.2 The DSL Loop	395	(1)
14.1.3 Termination of DSL in the Carrier's Central Office or Remote Site	395	(1)
14.1.4 The Carrier's Back-End Data Network	396	(2)
14.1.5 The Interface to the Service Provider's Network	398	(1)
14.2 Potential ADSL Services and the Service Requirements	398	(1)
14.3 Specific Architectures for Deploying ADSL in Different Business Models	399	(3)
14.4 Several ADSL Architectures	402	(8)
14.4.1 A Packet-Based Architecture for Small Deployments	402	(1)
14.4.2 ATM Access Networks	403	(2)
14.4.3 RFC 1483	405	(2)
14.4.4 PPP over ATM	407	(1)
14.4.5 Tunneled Gateway Architecture	408	(1)
14.4.6 PPP Terminated Aggregation	409	(1)
References	410	(1)
Chapter 15 Network Architecture and Regulation	411	(8)
15.1 Private Line	411	(1)
15.2 Circuit Switched	411	(1)
15.3 Packet Switched	412	(1)
15.4 ATM	413	(1)
15.5 Remote Terminal	414	(1)
15.6 Competitive Data Access Alternatives	414	(2)
15.7 Regulation	416	(3)
Chapter 16 Standards	419	(14)
16.1 ITU	420	(1)
16.2 Committee T1	421	(2)
16.3 ETSI	423	(1)
16.4 ADSL Forum	424	(1)
16.5 ATM Forum	424	(1)
16.6 DAVIC	425	(1)
16.7 IETF	425	(1)
16.8 EIA/TIA	426	(1)
16.9 IEEE	426	(1)
16.10 The Value of Standards and Participation in Their Development	427	(1)
16.11 Standards Process	428	(5)
16.11.1 When to Develop a Standard	429	(1)
16.11.2 Is a Standard Needed?	430	(1)
16.11.3 Standard or Standards?	431	(2)
Appendix A Glossary	433	(10)
Appendix B Selected Standards and Specifications	443	(4)
Appendix C Selected T1E1.4 Contributions and ADSL Forum Technical Reports (found on CD-ROM)	447	(18)
Index	465

Excerpts

Visionaries have spoken of a future where the common person has instantaneous access to data spread around the globe. Engaging in a live videoconference, or perhaps watching a personalized newscast are just two of examples of many. For this vision to become reality, a global broadband information infrastructure must be built that provides low-cost access to the consumers and sources of information. What connects to virtually every home and business in the industrialized world? Phone lines connect to 700 million sites today. Data rates of several kilobits per second are possible over phone lines using dial-up modems. This is enough to spark the appetite of the Internet surfer but is not nearly enough to satisfy the desire for immediate information on demand. Similarly, video and audio applications at dial-up modem data rates leave users demanding more. Digital subscriber line (DSL) technology enables high-speed digital transmission on conventional telephone lines. A global broadband information infrastructure based on telephone lines is emerging, and it relies on DSL technology. The transformation of the telephone line access has begun; it is progressing with the addition of over one billion U.S. dollars worth of DSL equipment each year. Accomplishing the impossible is an engineer's greatest reward. Digital subscriber line development has been most rewarding. In 1975, it was believed that 20 kb/s was the highest data rate that could be transmitted via telephone lines. Then, breakthrough concepts in digital transmission were enabled by enormous advances in very-large-scale integrated (VLSI) circuits and digital signal processing (DSP). Transceiver designs of breathtaking complexity (at that time) provided 144 kb/s basic rate ISDN (BRI) transport via most telephone lines. Experts then said that this was very near the capacity limit of telephone lines. This barrier was demolished by the 1.5 Mb/s high bit rate DSL (HDSL). The breakthrough cycle was repeated by 6 Mb/s asymmetric DSL (ADSL), and then 52 Mb/s very-high bit rate DSL (VDSL). This book explains and details the key concepts for DSL technology and its applications. The reader will attain a strong familiarity with the crucial aspects and technical jargon of the DSL field. The scope encompasses applications, network architecture, network management, network operations, communications protocols, standards, regulatory issues, and the underlying technologies. This book was written to assist engineers and marketing managers - whether new to DSLs or experts in need of a convenient reference. Background regarding voice-band transmission via telephone lines may be found in the excellent books by Witham Reeves on subscriber loops. Acknowledgments The authors thank Jim Loehndorf for assistance with the sections on data communications protocols, and Kim Maxwell for providing his input regarding voice-band modems and other sections. The authors would also like to sincerely thank Dr. Kiho Kim, Richard Goodson, and Dr. Martin Pollakowski for their review of this material and their helpful comments and suggestions. The second author, John Cioffi, especially would like to thank the following people (in alphabetical order) for their significant discussions and direct assistance on specific topics of this book: Mike Agah, John Bingham, Jacky Chow, Peter Chow, John Cook, Joice DeBolt, Kevin Foster, Mathias Friese, Richard Goodson, Werner Henkel, Atul Salvekar, Jose Tellado, Po Tong, Craig Valenti, Jean-Jacques Werner, and George Zimmerman. He further wishes to thank Dr. Joe Lechleider for enticing him into DSL in 1987, and thanks beyond measure the outstanding technical staff of Amati (1989-1997, now Texas Instruments), and the first to believe: his past and present students at Stanford. Thanks also go out to Steve Blackwell and Kevin Schneider of Adtran, who kindly offered the use of their good summary of HDSL2 work in the T1E