A low-complexity iterative multiuser receiver for turbo-coded MC-CDMA system

A low-complexity iterative multiuser receiver is proposed using groupwise maximum likelihood sequence estimation (MLSE) combined with a modified interference cancellation scheme in a turbo coded MC-CDMA system. It is based on grouping the active users according to their signal strengths and computing the log-likelihood ratios by MLSE among each group of users at the first iteration. For subsequent iterations, a modified interference cancellation scheme that can benefit from code extrinsic information available through decoding is used, for lower complexity. Simulation results are presented in a Rayleigh multipath fading environment for a typical data transmission scheme. Comparisons are made with iterative receivers using the maximum a posteriori (MAP) criterion and soft interference cancellation. Performance very close to that of a MAP based iterative receiver is achieved by this novel scheme within a few iterations, with much lower computational cost. This approach also performs significantly well under near-far conditions.