(A) low complexity adaptive interference cancellation scheme for CDMA systems

Abstract

This thesis proposes an adaptive parallel interference cancellation scheme for code-division multiple-access (CDMA) systems. The scheme allows users to overcome the near/far effect and reduces the degradation effect of the interference from other users who share the same channel. Different from previous methods, the proposed receiver has a double-substage structure. In the first substage, we decide reliable signals which need no interference cancellation through a threshold method and in the second substage, for unreliable signals interference cancellation is performed based on an adaptive approach. In the second substage, the weights are derived by minimizing the mean square error between the received signal and its estimate. The computational complexity of the proposed adaptive parallel interference cancellation scheme is much lower than that of the conventional adaptive interference cancellation. The performance of the proposed interference cancellation scheme is investigated through computer simulations, particularly in those cases for which the analysis is too complex. An analytical approach is also presented in the appendix in order to evaluate the bit error rate performance.