The aim of this book is to regale the reader with an overview of some of the technologies peculiar to wireless communications. I have addressed what I believe are important aspects of the subject. The material is tailored for technical personnel working in the field of wireless, who are seeking additional information on the technologies in this area. The practicing engineer will find the text to contain useful information concerning the design of wireless systems. The material presented is also suitable for senior undergraduate or graduate students majoring in communications. The prerequisite knowledge is a first course in communication theory, some exposure to probability and random noise theory, and a nodding acquaintance with matrices.
Wireless communications have consistently exceeded the capacity of available technology. The exponential increase in voice service (mobile in particular), together with the evergrowing demand for data services, have pushed current systems beyond their capacities. There is therefore a continuous pursuit to satisfy these burgeoning demands and for advancing the technological frontiers.
The coverage in this book is broad, encompassing subjects from signal formats to smart antennas, with the latter developing in the continuous pursuit of more capacity. The material is not rigorous, but is readerfriendly with a tutorial slant. The text is complemented with numerous figures to make the presentation more lucid.
The various technologies described in this book are as follows: The first two chapters deal with spectral efficiencies and power efficiencies within Shannon bounds. Providing wireless service in a spectrum where there is paucity of spectrum is an everpresent challenge. Chapter 3 discusses various higher order modulation methods in the presence of limited bandwidth, which can achieve increased spectral efficiency (b/sHz), but with a concomitant increase in power requirements. Chapter 4 deals with modulation methods which provide high spectral efficiency and robustness in a stressed environment. The latter includes fading induced amplitude fluctuations in the received signals and nonlinearities in the communications channel, and hence permits the utilization of efficientC amplifiers. This is followed by Chapter 5, which deals with errorcorrecting codes with coding gain a necessary adjunct in wireless to cope with the fading signal environment and other deleterious interference. Both random and bursty errors are generated, which are combatted by various coding schemes. Chapter 6, Trellis Coded Modulation, is a compliment to the coding chapter. This modulation type provides coding gain without sacrificing additional bandwidth and is truly a breakthrough in coding theory.
Chapter 7, Spread Spectrum Communications, describes a cellular standard now used in the U.S. This standard mitigates interference from systems using cochannel operation by tagging each channel with its unique identifying orthogonal code. Each signal channel sees the other channels as adding noiselike interference to its channel (which puts a bound on capacity). It potentially can significantly increase capacity to cellular systems, even though this has yet to be established.
Chapter 8, Terrestrial Cellular Communications, presents some of the concepts used in terrestrial cellular, including the various signal formats and performance specifications used by various standards, which have been developed and used globally.
The next few chapters deal with the evolution of smart antennas. These antenna systems use phased arrays to produce beams in space which can increase the capacity of a system. Chapter 9 starts with a discussion of the Butler matrix, which is an integral component of some smart antennas. The Sidelobe Canceller, discussed in Chapter 10 had its origin in radar and was used to reduce interference coming into radar antenna sidelobes. It has few applications in cellular, but is presented for historical value and lays the groundwork for smart arrays. Chapters 1113 deal in more detail with the two basic types of smart arrays that is, switchedmultiple beam and adaptive array configurations. The attributes and shortcomings of both are given. The last chapter, Chapter 14, is a summary of smart antennas and where they are going in cellular communications.
All chapters are complemented by a list of references through which the reader may seek additional information.