Role of Chaos in Spread Spectrum Systems

Abstract

This thesis presents an investigation into the design and performance of chaotic map based interleaver sequence in interleave division multiple access (IDMA) communication scheme, which can be treated as the modified version of a popular spread spectrum system i.e. code division multiple access (CDMA). The primary aim of this thesis is to identify the existing gaps in research and suggesting an appropriate approach for improvement in system performance. newlineInterleave Division Multiple Access (IDMA) based spread spectrum has been recently proposed and found suitable for future radio communication (FRC). In IDMA scheme, interleavers are used to distinguish the different users. This scheme is the improved version of classical CDMA scheme. IDMA inherits all the advantages of CDMA scheme especially it overcomes the major limiting factor of CDMA such as: multiple access interference (MAI) and Inter Symbol Interference (ISI). Interleavers are used to spread the information and to protect these bits from error bursts due to multipath propagation and noise sources. Interleavers should be easy to generate and not to consume large bandwidth, memory and should also be non-colloidal in nature. Many Interleavers were studied and proposed in the literature. Randomly Interleaved sequence can be the good choice of interleaver but the memory requirement in Random Interleaver (RI) is very high. The Nested Interleaver can be good choice but the extra memory requirement limits its performance. The shifting interleaver, Tree based interleaver and many other interleavers were designed and proposed for IDMA. However, still there is the scope of improvement in memory requirement. The limitations of mentioned interleavers motivates for further research. Thus, an efficient interleaver can increase the throughput iterative MUD receivers in IDMA communication newlinesystem and hence the main contribution of this thesis is to resolve the problem of designing of new interleaver for further performance improvement. newlineFurther this thesis extends the an