“Another book on digital communications?” will likely be the reaction of many readers upon seeing this work. Indeed, as more and more applications of digital communications become commonplace, the literature has thoroughly covered the subject matter.

What distinguishes this 500-page book from many others on the subject is its comprehensive treatment of communications theory in a textbook specifically intended for senior- and graduate-level students. The author has also made a conscious effort to base the theory upon strong mathematical foundations. Thus, the book assumes that the student has a fairly solid background in applied mathematics. Although its title refers to the design of digital systems, it is definitely not a design handbook, nor would the book be appropriate as an introductory primer on digital communications. Roden has stressed the theory underlying the techniques and applications of digital communications rather than dwelling on the applications themselves.

Several features of the book enhance its usefulness as a study tool. Each chapter has a brief introduction and a summary and concludes with problems based on the text. Unfortunately, only about 30 percent of the problems are accompanied by solutions. Sample problems and their solutions are also sprinkled throughout the text.

One drawback of the book is its skimpy treatment of protocols and standards; no study of digital communications would be complete without adequate coverage of the roles and some of the basic conventions of communications standards and protocols. Based on his cursory review of the OSI model and the X.25 standard, one cannot help but feel that Roden is paying lip service to the subject. I hope that future editions of the book will correct this deficiency.

A more general problem is the book’s overemphasis on theory at the expense of practice. The author’s several attempts to show practical examples (e.g., a review of some commercial integrated circuits in Section 3.2.5) are not enough. Similarly, Section 11.5, “Design Considerations,” reviews the basic trade-off considerations in system performance and starts to treat some of the more practical aspects of system design, but it barely scratches the surface.

Notwithstanding the above comments, the text covers a lot of ground. Chapter 1, “Introduction and Background Material,” briefly discusses the elements of digital systems and reviews some basic mathematical theories related to numbering systems (e.g., modulo arithmetic), probabilities, and Fourier transforms. Chapter 2, “The Channel,” examines signal distortion, channel bandwidth, and random noise. Chapter 3, “Source Encoding,” begins by presenting Shannon’s sampling theorem and proceeds to review the techniques of pulse code and delta modulation. Chapter 4, “Channel Encoding,” reviews classical information theory, including Shannon’s channel-capacity theorem, coding schemes, and error-correcting codes.

Chapter 5, “Data Transmission and Reception,” discusses various signal formats (e.g., non-return to zero) and matched filters. It also reviews concepts of mathematical decision theory and its application to digital signals within noise. Chapter 6, “Timing,” examines symbol and frame synchronization and considers trade-offs in designing a synchronization system. Chapter 7, “Baseband Systems,” focuses on system performance calculations such as the selection of waveform shapes in low-frequency baseband signals.

Chapters 8 (“Amplitude Modulation”), 9 (“Frequency Modulation”), and 10 (“Phase Modulation”) explore three methods of formatting the baseband signal to make it suitable for transmission. Chapter 11, “Design Considerations,” examines various trade-off decisions concerning the type of modulation, system performance, signal-to-noise ratio, and construction cost. Chapter 12, “Secure Communication,” explores common techniques for preventing unauthorized use of data. These techniques include spread spectrum, frequency hopping, and traditional cryptography schemes.

Chapter 13, “Computer Communications Networks,” concludes the book and contains a brief review of concepts and on-going efforts in computer networking. The discussion begins with a review of switched systems (i.e., circuit, message, and packet switching) and proceeds with a brief description of several popular data communication protocols (e.g., the seven-layer International Standard Organization approach and X.25). Local area networks and the integrated services digital network (ISDN) concepts are also described. The chapter then concludes with a brief review of several large computer networks, including ARPANET, ALOHA, and Ethernet.

In conclusion, I recommend the book as a text for more advanced students who possess a good mathematical foundation. Some practitioners who need to brush up on the theoretical foundations of digital communication will also benefit from it. Nevertheless, this book falls short of bridging the gap between theory and practice.