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Practical Resource Management in Wireless Systems [Book Review]

One cannot imagine any communications systems that have not been affected by the unavoidable natural phenomenon known as interference. Interference can usually be introduced to any communication systems internally through electronic systems and externally through propagation media. The unfortunate fact about interference is that it cannot be removed entirely. One can find ways to reduce the effects of interference and must live with the rest of it. There are several ways to reduce interference and improve the signal-tonoise ratio of the system. If conditions are minimal, a small increase in this ratio can result in a dramatic decrease in errors as well as a considerable rise in communication speed. Chapter 1 provides an overview of wireless communications systems. It talks about the first-, second-, and thirdgeneration communication systems and their specifications. The mobile communications concepts of frequency reuse, handover/handoff, and cell splitting are briefly touched upon. Satellite systems, mobile satellite systems, wireless local loops, Bluetooth, WLAN, HIPERLAN, wireless data networks and wireless broadband mobile communications systems are discussed at the level of basic understanding in this overview chapter. Chapter 2 is about the characterization and coding of the wireless channel. Wireless channels are analyzed for slow and fast fading for narrowband and wideband conditions. Channel coding techniques are also discussed here. Codes like block codes and their examples (e.g., Hamming codes, Hadamard codes, Golay codes, cyclic codes, BCH codes, and RS codes), and conventional codes and their generation and decoding are given in this section. Chapter 3 sheds light on the performance of transmission systems in the presence of interference. The discussion of analog transmission and its related properties (the various modulation methods, effects of interference), and digital transmission and the various modulation techniques associated with it are presented in an easily understandable fashion. Spread spectrum techniques are also referred to in this context. Another positive point about this chapter is its precise description and comparison of the various access techniques: frequency(FDMA), time(TDMA), code-divsion multiple access (CDMA), frequency(FDD) and timedivision duplex (TDD). Orthogonal frequency-division multiplexing (OFDM) techniques are also discussed here. Chapter 4 is devoted to analysis of the techniques used for investigation of wireless system behavior when the interference environment is fading due to multipath interferers. The various properties of the received signals in terms of the probability density function, average BER under fading, and various fading related techniques and parameters are discussed here. The various diversity and diversity combining techniques associated with wireless systems are also described in this section. Finally, frequency selective fading and a comparison of the compensation algorithms are also subjected to scrutiny. Chapter 5 illustrates the analysis of various interference cases. It discusses cochannel interference, adjacent channel interference, intermodulation interference, intersymbol interference, and nearend to far-end interference. It also gives a detailed interference analysis methodology for an analog system in particular, and for digital systems for several wireless systems and specifications. In Chapter 6, the results of Chapters 4 and 5 are reviewed and used to develop interference suppression techniques, and it is shown how they can be used in real implementation. Methods are proposed here to mitigate the effects introduced by interference. They include indirect reduction methods, direct reduction methods, and nonlinear methods, with several practical cases that are possible. Several methods of interference avoidance are also illustrated to increase the signal-to-interference ratio (SIR). Chapter 7 covers the actual interference cancellers used in real designs that utilize most of the techniques presented in the previous chapters. Several applications are discussed here. An interference-canceling equalizer for mobile radio communication, a linear interference canceller with a blind algorithm for CDMA systems, an indirect cochannel interference canceller, and adaptive interference cancellers are among them. Intersymbol interference and cochannel interference canceller combing adaptive array antennas and the Viterbi equalizer in a digital mobile radio are also studied here. Several other algorithms are also subjected to study for interference cancellation. The book provides in-depth studies and analysis of the suppression of interference in any communication system. The earlier parts of this book are devoted to brushing up on the details of earlier telecommunications systems, starting from the first-generation system on. Then it works through the associated parameters that affect the performance of a wireless system. Slowly the book talks about how to reduce the effects to maximize the original signal. This systematic approach makes this book an interesting read and research material for people working in this area.