An iterative multiuser receiver using groupwise MLSE and interference cancellation in a MC-CDMA system

We propose a low-complexity iterative multiuser receiver using groupwise maximum likelihood sequence estimation (MLSE) combined with interference cancellation for 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 using MLSE in each group at the first iteration. For subsequent iterations, a modified interference cancellation scheme that can benefit from code extrinsic information available through decoding is used. Simulation results are presented in a Rayleigh multipath fading environment for a data transmission scheme. Comparisons are made with iterative receivers using maximum a posteriori (MAP) criterion and soft interference cancellation. Performance very close to that of MAP based iterative receiver is achieved by this novel scheme within a few iterations, with much lower computational requirements. This scheme performs significantly well also under the near far conditions.