Analysis of Successive Interference Cancellation in M-ary Orthogonal DS-CDMA System with Single Path Rayleigh Fading

Compensating for near/far and fading effects is critical for satisfactory performance of DS/CDMA systems. So far, practical systems have used power control to over come fading and near/far effects. Another approach which has a fundamental potential in not only eliminating near/far effects but also in substantially raising the capacity, is the multiuser detectors and interference cancellers. Various optimal and sub-optimal schemes have been investigated. These schemes, however, get too complex even for considerably simple systems. Previously, we analyzed a simple successive interference cancellation scheme for a simple coherent BPSK modulation scheme. We now extend the simple successive interference cancellation scheme to a more complex (robust) modulation scheme, namely, M-ary Orthogonal modulation. We analyze the performance of the successive IC scheme under Rayleigh fading, where the order of cancellation changes as fast as fading (of the order of every 1 ms). The analysis indicates that the successive IC scheme not only increases the mean post-cancellation SNR (signal to noise ratio), but also lowers the coefficient of variation of the SNRs. This translates to lower BER, increased capacity and near far resistance.