PrefaceIn the 1970's and 1980's, we saw phenomenal advancement in nonlinear science, which had led to many important discoveries that greatly improve our understanding of the physical world. Among them, the discovery of chaos in deterministic systems is unarguably one of the most revolutionary scientific findings. We are now able to explain the apparent complexity and subtle order exhibited by many physical systems under the unified framework of chaos theory.The past decade has seen heightened interest in the exploitation of chaos for useful applications in engineering systems. One application area that has attracted a great deal of attention is communications. Chaotic signals, by virtue of their wide band characteristic, are natural candidates for carrying information in a spread-spectrum communication environment. The use of chaotic signals in communications thus naturally inherits the advantages that are currently being offered by conventional spread-spectrum communication systems, such as robustness in multi path environments, resistance to jamming, low probability of interception, etc. In addition, chaotic signals are easy to generate and hence offer a potentially low-cost solution to spreadspectrum communications.Although many practical problems need to be solved before chaos-based communications can be realized in practice, the field has advanced rapidly during the past few years and it now reaches a point where abstract concepts from physics and mathematics have been fruitfully ported to techniques that allow information to be carried by chaotic signals.This book is intended to address the basic system design, operation, analysis, and performance evaluation of a few selected chaos-based digital communication systems. We put emphasis on the analytical approach taken to study chaos-based communication systems, and focus our attention on a few performance aspects that are of practical importance. In particular, we discuss in this book the modulation techniques, error rate calculations, anti-jamming capabilities, and coexistence with conventional communication systems. We believe that the materials covered in this book will be useful to graduate students, researchers, communication engineers and technology developers who wish to exploit chaos for communication applications.viii We begin in Chapter 1 with an overview of spread-spectrum communication systems and the potential benefits of carrying information with chaotic signals. In Chapter 2 we introduce chaos-based digital modulations and discuss the salient concepts in encoding information with chaotic signals. A review of the various modulation schemes is given. Chapter 2 also contains a discussion on the use of equivalent discrete-time baseband models for studying chaos-based digital communication systems. This kind of models will be used throughout the book. Chapters 3 and 4 provide an indepth treatment of analytical techniques for calculating bit error probabilities of chaos-based digital communication systems. Both single-user and multi-user systems are...

Abstract-The performance of the noncoherent differential chaos-shift-keying (DCSK) communication system over a multipath fading channel with delay spread is evaluated. Analytical expressions of the bit error rates are derived under the assumption of an independent Rayleigh fading two-ray channel model. Analytical and simulated results are presented and compared. The multipath performance of the DCSK system is also compared with that of the coherent CSK system as well as conventional generic waveform communication schemes.Index Terms-Chaos communications, delay spread, differential chaos shift keying (DCSK), multipath Rayleigh fading channel.

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Low-density parity-check (LDPC) codes have attracted much attention in the past two decades since they can asymptotically approach the Shannon capacity in a variety of data transmission and storage scenarios. As a type of promising structured LDPC codes, the protograph LDPC codes not only inherit the advantage of conventional LDPC codes, i.e., excellent error performance, but also possess simple representations to realize fast encoding and efficient decoding. This paper provides a comprehensive survey on the state-of-the-art in protograph LDPC code design and analysis for different channel conditions, including the additive white Gaussian noise (AWGN) channels, fading channels, partial response (PR) channels, and Poisson pulse-position modulation (PPM) channels. Moreover, the applications of protograph LDPC codes to joint sourceand-channel coding (JSCC) and joint channel-and-physical-layernetwork coding (JCPNC) are reviewed and studied. In particular, we focus our attention on the encoding design and assume the decoder is implemented by the belief propagation (BP) algorithm. Hopefully, this survey may facilitate the research in this area.

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