BOOK REVIEWS

cation theory to describe signals, while statistical concepts were appropriated later to characterize noise. This situation proved quite satisfactory for most purposes, but later Weiner and Shannon showed that randomness is a necessary feature of communication signals as well as noise. In fact, Bennett.him- self helped popularize this notion. Since Davenport and Root’s classic text, it has become customary for most books on communication to contain some discussion of signals as random processes. Bennett, however, has tacitly decided that at the level of his text there is no need to include the idea of the inherent randomness of communication signals. His phi- losophy is that communication systems designed to operate well with sine waves in certain frequency bands will also work well with communication signals. There is no discussion of Weiner’s or Shannon’s work-the index does not even contain the word information. Some will find this an asset of the book, others may feel it is a liability.

The strongest point of this book is that, unlike other books of this type, this one covers specific communication signals and not just communication systems. There are separate chap- ters on speech, telegraph signals, and television. One of my most frustrating experiences was to be thrust, upon graduation with a degree in electrical engineering, into a world of Vu, dB, dBRNO, and lately dBBFLS! Bennett devotes some, though not enough, effort into explaining terms like these, which are the parlance of the speech communication business, but which are almost never mentioned in communication textbooks. His chapter on television signals is much too short and sketchy. Furthermore, none of these three chapters is referenced very well so that someone wanting a deeper understanding of these topics would not know where to turn. But the idea of includ- ing chapters on these three important communication signals overshadows any imperfections in their coverage. I hope this is the beginning of a tradition.

This book is at its best when the author draws upon his ex- perience to discuss in somewhat philosophical terms the real issues and history of communication theory and practice. Pas- sages with this philosophical flavor are interspersed throughout the text and their subjective nature lends this book a sense of character lacking in other books in this area. His discussion of the history of PCM theory and practice is especially rewarding. With an iconoclastic flare of good-natured oneupmanship, Bennett attributes the invention of PCM to Paul M. Rainey in a 1926 patent rather than to ITT’s venerated Alec H. Reeves, who received a medal of the Franklin Institute for this invention.

Finally, who will use this book? I feel that this book would be appropriate for a one-semester course offered to seniors and first-year graduate students interested in communication. To do this, material would have to be left out and I suggest the following outline for such a one-semester course.

Chapter 1 Representation of Signals. Chapter 2 Representation of Noise. Chapter 3 Baseband Transmission of Telephone Signals. Chapter 4 Baseband Transmission of Telegraph Signals. Chapter 5 Baseband Television Signals. Chapter 6 Basic Principles of Modulation. Chapter 10 Digital Transmission of Analog Signals (PCM).

This would be a total of 173 pages. An ambitious instructor might want to include chapter 9, Multiplex Transmission. I feel that chapter 7, Linear Operations on Signals and Side- bands, and chapter 8, Nonlinear Analog Modulation, are sec- ondary to the others. A course with this design would empha- size modulation at the expense of random signals. Such a

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course, I feel, would be suitable as a final course in communi- cation for students interested in a cursory knowledge of this subject or as a background course for students intending to take more advanced work. This book may also have some value for those who need to learn something about communi- cation on their own. The book is probably too elementary to be of much use as a reference to experienced communication engineers. ,

J. B. O’Neal, Jr., was born in Mason, Ga., on October 15, 1934. He received the B.S. degree from the Georgia Institute of Technology, Atlanta, in 1957, the M.S. degree from the University of South Carolina, Columbia, in 1960, and the Ph.D. degree from the University o f Florida, Gainesville, in 1963, all in electrical engineering. He is currently an Associate Profes- sor in the Department of Electrical Engineering, North Caro- lina State University, Raleigh.

Theory of Synchronous Communications-J. J . Stiffler (Engle- wood Cliffs, N.J.: Prentice-Hall, 1971, 562 pp., $16.95).

Communications engineers have long recognized the inade- quacies of coding and information theory as it applied to the problems of synchronization. This is the first book written to remedy this situation. To quote the author in the preface, “This book is concerned with synchronization in communica- tion systems. . . . The aim of the book is to present the basic theory of the operation and performance of synchronous com- munication systems and, at the same time, to exhibit the con- clusions of this theory in a form useful to the communication system designer.”

Dr. Stiffler’s book is more self-contained than most treatises on communication systems in that the fundamentals of statis- tical decision‘ theory, modulation theory, optimum filter theory, and the principles of phase-lock loops are carefully de- veloped in Part I of the book. This material supplies the neces-’ sary background to handle Part 11, titled “Synchronization.”

In Part I1 the author applies machinery, related to radar de- tection theory, namely, various detection and estimation tech- niques, to the problem of detecting and locking onto a signal train. Many of these methods are derived from the maximum likelihood approach, yielding the matched filter detection and estimation of epoch for both single symbols and words. Other techniques relate to sequential detection and search.

Generally, to receive information on a real communications channel one proceeds first to a synchronization of the carrier, next to symbol epoch determination and sampling, then finally to a word framing and decoding. Dr. Stiffler treats with equal depth all three of these aspects of the communica- tions problem. The latter problem is dealt with in the final third of the book, entitled “Coding.”

In Part 111 a large number of coding techniques are devel- oped to achieve word synchronization to tolerate noise and to transmit information efficiently. Efficiency is achieved in the noiseless case by minimizing the average number of bits needed to encode the source symbols, assuming a known source probability distribution. Error tolerance is accom- plished with error-correcting codes. Finally word sync is made possible by the use of a variety of synchronizable codes,

1048 IEEE TRANSACTIONS ON COMMUNICATIONS, OCTOBER 1912

such as comma-free codes, synchronizable error-correcting codes, etc. Dr. Stiffler presents a comprehensive study of cod- ing theory as it relates to synchronization.

Undoubtedly this book will become an important text for future graduate courses in communication theory and systems. To the engineering world it is an excellent scholarly study of communication theory and practice. It certainly has no equal in its treatment of receiver synchronization of messages.

Irving S. Reed was born in Seattle, Wash., on November 12, 1923. He received the B.A. and Ph.D. degrees in mathematics from the California Institute o f Technology, Pasadena, in 1944 and 1949, respectively. He is currently a Consultant to the Rand Corporation and a Professor o f Electrical Engineering at the University of Southern California, Los Angeles, with inter- ests in mathematics, computer design, coding theory, stochas- tic processes, and general information theory.

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