Nonlinear multistage multiple access interference cancellation receiver for asynchronous DS/CDMA communication systems

A nonlinear multistage receiver employing parallel interference cancellation (PIC) is investigated for an asynchronous direct-sequence code-division multiple-access (DS/CDMA) channel in additive white Gaussian noise (AWGN). The cancellation processing simultaneously removes from each user the interference produced by the remaining users accessing the channel. Additionally, partial cancellation is also considered, which involves the splitting of the corresponding bits of the interfering users into two parts, with reference to the desired user, and estimating these two parts separately before attempting cancellation. The bit-error rate is analysed as a function of the signal-to-noise ratio (SNR) for different user populations. Furthermore, comparisons are made between the proposed partial PIC algorithm, the full-bit PIC and the conventional matched filter receiver. Simulation results demonstrate the advantage gained in performance by using the proposed partial PIC.