BER performance analysis of multistage PIC scheme in an asynchronous DS-CDMA system with long scrambling codes

We tackle the problem of theoretical evaluation of the multistage parallel interference cancellation (PIC) scheme in a DS-CDMA system with orthogonal modulation and long scrambling codes. The studied system operates on the reverse link in a time-varying multipath Rayleigh fading channel. By applying the central limit theorem to multiple access interference (MAI) and intersymbol interference (ISI), as well as identically distributed chips from a single interferer, the bit error rate (BER) performance of the PIC scheme at any stage can be recursively computed from the signal-to-noise ratio, number of users, the number of paths per user, processing gain of the CDMA system, as well as the average received power of each path. The proposed approximative analysis is validated by Monte-Carlo simulations and proved to be accurate, and it gives insight into the performance and capacity one can expect from the PIC based receivers under different situations.