An Introduction to Digital Communications / Edition 1

by Jack Kurzweil

Overview

An Introduction to Digital Communications focuses on the central theoretical and practical issues involved in modem design. It is intended for a two semester course at the graduate or advanced undergraduate level. The first half of the book deals with the basic issues of baseband and passband data transmission and contains descriptions of applications to specific digital transmission systems. The second half is more specifically addressed to design issues including timing and carrier recovery, channel characterization, adaptive equalization, and trellis coding. Although application oriented, the text is sufficiently rigorous to provide an entry point into current research.

Product Details

ISBN-13:	9780471157724
Publisher:	Wiley
Publication date:	11/18/1999
Pages:	560
Product dimensions:	7.20(w) x 10.00(h) x 1.10(d)

About the Author

Jack Kurzweil is the author of An Introduction to Digital Communications, published by Wiley.

Table of Contents

Fourier Series and Transforms.

Spectral Analysis of Data Signals and Noise.

Baseband Data Transmission.

Bandpass Data Transmission.

Maximum Likelihood Signal Detection and Some Applications.

Carrier Phase and Timing Recovery.

Channel Models for Communication Systems.

Channel Capacity and Coding.

Trellis Coding and Multidimensional Signaling.

Equalization of Distorted Channels.

Adaptive Equalization and Echo Cancellation.

Index.

Preface

This textbook is being published at a moment when the 56 Kbps modem has reached the limit of data transmission on the Plain Old Telephone System (POTS) and the attention of the industry and academic researchers has long since turned to the high-speed digital subscriber loop, coaxial cable, and wireless transmission. This is accompanied by technological changes that make it possible to incorporate the digital signal processing necessary to support high-speed data transmission onto special-purpose chips. Nevertheless, the new technology relies on theory that has been accumulated over decades; indeed, in some instances, it requires the rediscovery of theory that has lain dormant for decades.

Every textbook tells a story that comes from the accumulation of the author's experience. My experience started with some years at Racal-Vadic in Sunnyvale, California, working on the V.22 (bis) modem. This book evolved from developing a two-semester graduate-level course in digital communications at San Jose State University. Since the book comes from my syllabus, it includes only material that I have actually taught. This choice of material is consequently incomplete but does represent one viewpoint of what should go into such a course. This book deals with adaptive equalization, carrier recovery, and timing recovery in greater depth than most other digital communication texts. A central portion of the presentation is the development of simulation programs for testing the performance of different modulation techniques and equalization strategies. On the other hand, there is hardly any discussion of channel coding except in relation to understanding the meaning of channel capacity. There is considerable discussion of the time-domain characterization of channels, because that is the basis for adaptive equalization, but little discussion of continuous-phase modulation. There is no discussion of spread spectrum, satellite communications, or communications protocols. This book asks students to understand the code of the simulation programs and even write some code for the implementation of particular algorithms rather than using communications simulation packages, because it is at the code level that the student is required really to understand how the algorithm works.

In short, I have written this as a relatively focused book that is both theoretical and design-oriented. It is aimed toward graduate students or those advanced undergraduates who are prepared to engage in a combination of somewhat involved mathematics and computer simulation. All students taking the course are assumed to have a background in spectral analysis, z-transforms, Laplace transforms, and probability theory.

I have typically covered the first five to six chapters in the fall semester and the remainder in the spring. It is reasonable to tread lightly over Chapter 1, Fourier Series and Transforms, if the students are well prepared. The review of probability theory in Chapter 2, Spectral Analysis of Data Signals and Noise, is very modest and the discussion of random processes centers on communications applications. Of particular interest is the use of the Matlab Symbolic Toolbox for analyzing Markov processes. Chapter 3, Baseband Data Transmission, and Chapter 4, Bandpass Data Transmission, should be covered in their entirety because they form the basis for understanding most of the modulation techniques currently in use. There is an emphasis on the development of a simulation model for a communication system. An instructor may choose to be selective with Chapter 5, Maximum Likelihood Signal Detection and Some Applications, but I would urge careful attention to the development of the Viterbi Algorithm. This might allow time to begin Chapter 6, Carrier Phase and Timing Recovery. I would urge that this chapter be covered in some detail in the spring semester. The major or purpose of Chapter 7, Channel Models for Communication Systems, is to establish the sampled impulse response model for a communication channel and give a brief view of how different channels can be modeled in this way. Extensions and variations of the material in this chapter are an excellent source of ideas for term papers and projects. In Chapter 8, Channel Capacity and coding, I have attempted to provide some kind of intuitive understanding of what the issue of capacity is about. I have also pointed to derivations of the capacity of some channels such as the Digital Subscriber Loop, in which the design of modems to come near achieving capacity continues to be an active project. Chapter 9, Trellis Coding and Multidimensional Signaling, develops the basic ideas of combined modulation and coding and examines a few codes in detail. A deeper look at these codes might very well be part of a separate course on algebraic coding theory. Chapter 10, Equalization of Distorted Channels, deals in detail with baud-rate, fractionally spaced, and decision-feedback equalizers. The performance of these equalizers is derived mathematically and simulated through Matlab scripts. Chapter 11, Adaptive Equalization and Echo Cancellation, examines the LMS algorithm for equalizer convergence as well as algorithms for rapid convergence. A program that simulates convergence for various equalizer structures and convergence algorithms is included.

Anyone who has designed modems owes an immense debt of gratitude to the extraordinary collection of researchers at Bell Labs who essentially invented the bulk of the theory. An examination of the references at the ends of the chapters shows these names repeated many times over. In particular, I have been heavily influenced by the work that culminated in Data Communication Principles, by Richard Gitlin, Jeremiah Hayes, and Stephen Weinstein, Plenum, 1992. As my book was taking shape, theirs was the assigned text for my course.

Since no single textbook can adequately address all of the issues of digital communications and each of them has something unique to offer, the reader will not be surprised to find references to the many fine books in this area by E. Lee and D. Messerschmitt; J. Proakis; B. Sklar; D. Smith; I. Kom; S. Benedetto, E. Biglieri, and V Castellani; R. Zeimer and R. Peterson; A.P. Clark; and J. Bergmans.

I want to thank Kim Maxwell and John A.C. Bingham for taking the risk of bringing a somewhat theoretical and abstract academic into the R&D process at Racal-Vadic. John Bingham has, over the years, been a technical sounding board as well as a friend. His two books on modem design as well as his papers are prominent among the references. Every fumbling engineer needs a great technician and I was particularly blessed with Duane Marcroft, who guided me in the translation of ideas into reality.

My friends Steve Willet and Bill Swanson were always there to help with programming problems. Carlos Puig, lent a hand with problem solutions and many excellent ideas and insights. John Cavalli produced many of the simulations. Jack Stotes Berry kept my computer running.

I did not actually have the idea of translating my notes into a book until a Wiley representative wandered into my office with the innocent-sounding question, "Are you working on anything?" The Wiley staff have been most helpful and, when appropriate, firm in bringing this project to fruition. I would like to thank Bill Zobrist, Penny Perrota, Jennifer Welter, Robin Factor, and Andrew Wilson. I also want to thank the reviewers for their very helpful suggestions and insights: S. Hossein Mousavinezhad, Western Michigan University; James S. Kang, California State Polytechnic University; John R. Barry, Georgia Institute of Technology; Haniph A. Latchman, University of Florida, Rich S. Blum, Lehigh University; Vijay K. Bhargava, University of Victoria; and Upamanyu Madhow, University of Illinois. San Jose State University allowed me to make a major leap in transforming a set of notes into a book by granting me a sabbatical leave. I hope that the errors in this book are few and not very serious. They are, of course, entirely my responsibility.

On a more personal note, thanks go to Jennifer, Joshua, and Shoshana, who seemed to grow from adolescence to adulthood as this project proceeded, for their wonderful support. Finally, I want to pay tribute to Dr. Claudette Hoover, Professor of Literature and Women's Studies, my wife and strongest advocate, who passed away on December 21, 1997.