Abstract:
This thesis presents the analysis of chaos-based direct sequence code division multiple access (DS-CDMA) systems under imperfect channel estimation environments. Chaos-based CDMA systems are studied extensively in the last few decades, but their performances under imperfect channel estimation conditions are never studied. The main motivation of the thesis is to fill this research gap under various possible conditions. The thesis focuses on three main objectives. The first objective is to determine the effect of spreading sequences in channel estimation processes. Here performances of channel estimators in the presence and absence of chaotic spreading sequences are investigated. The second objective is to study the performances of imperfect channel estimations in chaos based CDMA systems under various fading conditions. This part mainly focuses on the various factors which deteriorate the performance of the systems. The third objective focuses on the various techniques which can improve the performances of the systems. In this part various available techniques for CDMA systems are studied under imperfect channel estimation environments. It is concluded that performances of all the available chaos based CDMA systems significantly depend on performances of channel estimators. Analytical simulation results in the thesis show that performance degradation in available systems due to various fading channels can be significantly improved by using channel estimators.
