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Reviewer: Charles Kenneth Davis

There is an interesting anomaly in the public networks that wireless communications may eventually resolve. Essentially all of the longer-distance communications provided by telephone companies (telcos) are using high-speed digital transmission and switching. Furthermore, corporations and other large-scale users have been installing telephone switches (PBXs) and local area networking facilities in their buildings and offices for years. These facilities also utilize fast digital transmission and switching. Digital computers (and even networks) are also infiltrating homes at an amazing rate. But the interconnections between these longer-distance digital services and the digital local equipment at a telco customers home or office are still analog, and far too slow to support modern multimedia applications. These interconnection circuits are called “local loops.” They connect homes and office buildings to the telco “end office exchanges,” which provide basic network access. Across the country, local loops have been creating and continue to create bottlenecks that retard the implementation of the new computing and networking technologies. Like the proverbial chain, the network overall is only as strong as its weakest link. The local loops are the weakest link in todays networking chain. Think about major old cities like Boston, New York, or Philadelphia. Older twisted-pair cable and analog transmission and switching abound. The investment in these local loops by the telcos is enormous, and the cost to replace them, with a mixture of fiber optics and better-quality copper cable, for example, would be simply staggering. This is a major problem. Because it is expensive, the transition to modern technology in the local loops will happen slowly—at a snails pace compared to the rapid-fire developments that are happening in the underlying networking technology itself. Modern telecommunications technology is not delivering all it is capable of delivering to the common user, in large part because of these local loops. Table 1: Descriptive data Bates Feher Pahlavan and Levesque Pelton Viterbi Number of pages 295 524 572 277 245 Number of chapters 11 9 12 10 6 Number of appendices 0 4 2 3 0 Everyone in the industry is talking about the virtues of high-speed digital networking for multimedia applications, emphasizing high-quality video and imaging. The applications themselves are increasingly and ever more widely available. The ability to use these applications within our companies is well established. The problem is that multi media cannot be made available to the average citizen across the “plain old telephone” network for applications dealing with electronic commerce, online entertainment, distance learning, video telephones, and so on until local loops can be significantly re-engineered and upgraded. Enter wireless communications. Wireless will undoubtedly be an increasingly important component in the next generation of networking architectures. A mixture mostly of fiber optics and wireless holds the promise of rectifying this antiquated local loops situation. Certainly in the longer term, as wireless communication improves in reliability and transmission quality, it will become the local loop of choice because it is convenient and flexible to use and easy to maintain. Consequently, it is clear that every conventional telecommunications technician, analyst, and manager should make the effort to review the basics (or even the esoteric details) of wireless communications. The five books reviewed here all cover the same material, but each book has a different focus so that, collectively, they cover the topics very well. Most of them are very readable and understandable, even for the wireless novice who is willing to study them carefully. As Table 1 shows, three of the books are of similar length, while those by Feher and by Pahlavan and Levesque are substantially longer. The number of chapters varies between 6 and 11, with, at most, four appendices included. Viterbi is the shortest book, with fewer chapters and appendices than the others. Table 2: Coverage of topics Bates Feher Pahlavan and Levesque Pelton Viterbi History of wireless Minimal Adequate Extensive Adequate None Cellular communications Adequate Extensive Adequate Minimal Minimal Personal communications Extensive Adequate Extensive Extensive None Modem techniques Minimal Extensive Extensive None Extensive Spread spectrum systems Minimal Extensive Extensive None Extensive Policy & management Minimal Minimal Minimal Extensive Minimal Regulatory issues None None Adequate Extensive None Industry standards None Minimal Extensive Adequate Minimal Future applications Minimal Minimal Adequate Extensive None Bates, Pelton The focus of each of these books is very different. Managers interested in background reading in this area will probably find Bates and Pelton the most interesting. Bates focuses on the concepts underlying the technology and its implementation. Peltons tutorial approach to satellite and wireless technology deals simply with matters dear to most managers hearts (for example, policy issues, regulations, standards, and the future of wireless). Neither of these books is overly technical for the average motivated and careful reader. Viterbi, Feher Both Viterbi and Feher focus on the technology of spread spectrum communications, a wireless communications technique that uses a transmission bandwidth many times greater than the information bandwidth (or data rate) for any specific user. Spread spectrum is important because it exhibits the following characteristics: high tolerance of interference, high signaling accuracy, low detectability of signal by unintended receivers, and multiple access by a number of simultaneous users (increasing in proportion to the spreading factor, that is, the ratio of bandwidth allocated to the number of bits per second transmitted). Spread spectrum can achieve considerably higher transmission capacities than other wireless multiple access techniques. The Viterbi book is a different kind of book from the others reviewed here. As Table 2 illustrates, it is essentially a technical reference manual, specifically for constructing and maintaining communications systems based on spread spectrum technology. It is amply interspersed with what one of my friends calls “beta-wiggles” and “gamma-wiggles,” that is, mathematical formulas used to describe and engineer communications networks. Feher, on the other hand, focuses more on applications using spread spectrum. It is much easier to read and has more of the flavor of a college textbook. It, too, relies on mathematical presentations at times, though not as much as Viterbi. Feher also includes a disk with a PC software package, CREATE-1, that allows creation of a baseband waveform and simulated testing of a modem that uses that baseband signal. Pahlavan and Levesque Pahlavan and Levesque is the most thorough of the five books reviewed here. It is essentially a graduate-level university textbook. It is well organized and clearly presented. While some math is included, the detailed mathematical derivations characteristic of many other texts are not included. Pahlavan and Levesque focus on four main areas: wireless standards with descriptions of systems and products; measurement and modeling of radio and optical wave propagations; wireless transmission techniques; and wireless multiple access techniques. Comparison In closing, it is important to note that all five of these books have merit. Each has a different focus, as explained above. Because of the complementary structure of the five individual books, this collection would constitute an outstanding reference library for individuals interested in mastering topics in wireless communications technologies. Each book emphasizes different important aspects of this technology. This fact is illustrated by the matrix in Table 2, which includes key topics down the left column, followed by an assessment of the degree to which each book addresses these topics in subsequent columns. For the interested technically oriented reader with a minimal background in wireless communications, the Pahlavan and Levesque and the Feher texts are probably the most suitable.