Digital Transmission Systems

580 Pages·1985·17.744 MB·English

by  David R. Smith (auth.)

Digital
Transmission
Systems
DAVID R. SMITH
Chief, Transmission System Development Division
Defense Communications Engineering Center
Associate Professorial Lecturer
Department of Electrical Engineering and Computer Science
George Washington University
LIFETIME LEARNING PUBLIC AT IONS
~
SPRINGER SCIENCE+BUSINESS MEDIA, LLC
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© 1985 by Springer Science+Business Media New York
Originally published by Wadsworth, Inc. in 1985
Softcover reprint of the hardcover 1st edition 1985
All rights reserved. No part of
this book may be reproduced, stored in a retrieval system, or
transcribed, in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without the prior written
permission of the publisher.
1 2 3 4 5 6 7 8 9 10--88 87 86 85
Library of Congress Cataloging in Publication Data
Smith, David R. (David Russell), 1945-
Digital transmission systems.
Includes index.
1. Digital communications. I. Title.
TK5103.7.S65 1985 621.38 84-27049
ISBN 978-1-4757-1187-5 ISBN 978-1-4757-1185-1 (eBook)
DOI 10.1007/978-1-4757-1185-1
To my wife, Carolyn, and our children
Christy, Stacy, Allison, and Andrew.
Preface
In the development of telecommunication networks throughout the
world, digital transmission has now replaced analog transmission as the
predominant choice for new transmission facilities. This trend began in
the early 1960s when the American Telephone and Telegraph Company first
introduced pulse code modulation as a means of increasing capacity in their
cable plant. Since that time, digital transmission applications have grown
dramatically, notably in the United States, Canada, Japan, and Western
Europe. With the rapidity of digital transmission developments and imple
mentation, however, there has been a surprising lack of textbooks written on
the subject.
This book grew out of my work, research, and teaching in digital
transmission systems. My objective is to provide an overview of the subject.
To accomplish this end, theory has been blended with practice in order to
illustrate how one applies theoretical principles to actual design and imple
mentation. The book has abundant design examples and references to actual
systems. These examples have been drawn from common carriers, manufac
turers, and my own experience. Considerable effort has been made to
include up-to-date standards, such as those published by the CCITT and
CCIR, and to interpret their recommendations in the context of present-day
digital transmission systems.
The intended audience of this book includes engineers involved in
development and design, system operators involved in testing, operations,
and maintenance, managers involved in system engineering and system
planning, and instructors of digital communications courses. For engineers,
managers, and operators, the book should prove to be a valuable reference
v
Vi • PREFACE
because of its practical approach and the insight it provides into state-of
the-art digital transmission systems. In the classroom the book will allow the
student to relate theory and practice and to study material not covered by
other textbooks. Theoretical treatments have been kept to a minimum
by summarizing derivations or simply stating the final result. Moreover, by
consulting the extensive list of references given with each chapter the
interested reader can explore the theory behind a particular subject in
greater detail. Even so, to gain from this book the reader should have a
fundamental knowledge of communication systems and probability theory.
The organization of this book follows a natural sequence of topics:
• Chapter 1: Historical background and perspective on worldwide dig
ital transmission systems
• Chapter 2: System design including services to be provided, parame
ters used to characterize performance, and means of allo
cating performance as a function of the service, media, and
transmission equipment
• Chapter 3: Analog-to-digital conversion techniques, starting with the
most commonly used technique, pulse code modulation,
and ending with specialized voice coders
• Chapter 4: Time-division multiplexing using both asynchronous and
synchronous techniques
• Chapter 5: Baseband transmission including coding, filtering, equaliza
tion, and scrambling techniques
• Chapter 6: Digital modulation, starting with binary (two-level) forms
and generalizing to M-ary forms, showing comparisons of
error performance, bandwidth, and implementation com
plexity
• Chapter 7: Digital transmission over the telephone network, from
voice-channel modems for low data rates to wideband
modems for high data rates
• Chapter 8: Digital cable systems for twisted-pair, coaxial, and optical
fibers, showing design and performance
• Chapter 9: Digital radio systems including propagation and interfer
ence effects, radio equipment design, and link calculations
• Chapter 10: Digital network timing and synchronization, describing
fundamentals of time and frequency and means of network
synchronization
• Chapter 11: Testing, monitoring, and control techniques used to
measure and maintain system performance
• Chapter 12: Assessment of the future of digital transmission services
and technology, together with a look at the emerging
integrated services digital network (ISDN)
PREFACE • Vii
The material presented in Chapters 3 through 8 has been used for a
graduate course in digital communications at George Washington Univer
sity. The contents of the entire book form the basis for a short course on
digital transmission, also offered by George Washington University.
David R. Smith
Acknowledgment
I first wish to acknowledge the support of my colleagues at the Defense
Communications Agency, especially K. R. Belford, J. J. Cormack, W. A.
Cybrowski, B. S. McAlpine, T. L. McCrickard, J. L. Osterholz, M. J.
Prisutti, D. 0. Savoye, D. 0. Schultz, P. S. Selvaggi, S. Soonachan, and
H. A. Stover.
My graduate students at George Washington University used early
versions of chapters of this book and made many helpful contributions.
Participants in numerous short courses offered encouragement and sug
gested improvements. I am indebted to all those who have taken my courses
and at the same time helped me with the writing of this book.
I would like to pay special thanks to Dr. Heinz Schreiber of Grumman
Aerospace Corporation and the State University of New York, who care
fully reviewed the entire manuscript and provided many valuable com
ments.
In writing a book of this size, I have made considerable use of the open
literature, especially the IEEE Transactions on Communications, the Bell
System Technical Journal, and proceedings of various technical conferences.
In describing standards applicable to digital transmission systems, I have
extracted from the reports and recommendations of the CCIR and CCITT. *
Finally, I would like to express my thanks to Linda Thomas who
diligently typed the original and revised versions of the manuscript.
*The reproduction in this book of material taken from the publications of the International
Telecommunications Union (ITU), Place des Nations, 1211 Geneva 20, Switzerland, has been
authorized by the ITU.
ix
Contents
Preface v
Acknowledgment ix
1 Introduction to Digital Transmission Systems 1
1.1 Historical Background 1
1.2 Present-Day Digital Transmission 4
1.3 Digital Transmission Standards 8
1.4 Digital vs. Analog Transmission 10
1.5 A Simplified Digital Transmission System 12
1.6 Summary 13
2 Principles of System Design 17
2.1 General Plan 17
2.2 Transmission Services 19
2.3 Hypothetical Reference Circuits 26
2.4 Performance Objectives 31
2.5 Summary 59
3 Analog-to-Digital Conversion Techniques 63
3.1 Introduction 63
3.2 Pulse Code Modulation 64
3.3 Differential PCM and Delta Modulation 89
3.4 Comparison of OM, DPCM, and PCM 104
3.5 Voice Coders (Vo coders) 114
3.6 Summary 120
xi
Xii • CONTENTS
4 Time-Division Multiplexing 127
4.1 Introduction 127
4.2 Frame Synchronization 131
4.3 Pulse Stuffing 152
4.4 Multiplexing of Asynchronous Data 168
4.5 Digital Multiplex Hierarchies 171
4.6 Statistical Multiplexing and Speech Interpolation 181
4.7 Summary 184
5 Baseband Transmission 189
5.1 Introduction 190
5.2 Types of Binary Coding 190
5.3 Power Spectral Density of Binary Codes 198
5.4 Error Performance of Binary Codes 203
5.5 Pulse Shaping and Intersymbol Interference 207
5.6 Multilevel Baseband Transmission 210
5.7 Partial Response Coding 212
5.8 Eye Patterns 221
5.9 Equalization 223
5.10 Data Scrambling Techniques 228
5.11 Summary 235
6 Digital Modulation Techniques 239
6.1 Introduction 239
6.2 Binary Amplitude-Shift Keying (ASK) 245
6.3 Binary Frequency-Shift Keying (FSK) 248
6.4 Binary Phase-Shift Keying (BPSK) 251
6.5 Comparison of Binary Modulation Systems 254
6.6 M-ary FSK 256
6.7 M-ary PSK 260
6.8 Quadrature Amplitude Modulation (QAM) 266
6.9 Offset QPSK (OQPSK) and Minimum-Shift
Keying (MSK) 270
6.10 Quadrature Partial Response (QPR) 275
6.11 Summary 279
7 Digital Transmission Over the Telephone Network 283
7.1 Introduction 283
7.2 Frequency-Division Multiplex (FDM) 284
7.3 Transmission Parameters 290
7.4 Conditioning 294
7.5 Voice-Band Modems 296
7.6 Wideband Modems 300
7.7 Transmultiplexers 305