Improved partial parallel interference cancellation for MC-CDMA uplink systems

This paper presents a new low-complexity method for realizing the main partial parallel interference cancellation (PPIC) operations proposed by Divsalar et al for multicarrier code division multiple access (MC-CDMA) systems. Based on this approach, K multiplications of the original scheme are replaced with K additions for each interference cancellation (IC) stage and two equivalent PPIC-based multiuser detectors of lower complexity are presented. Also, a new bit estimator is derived for PPIC-based multiuser detectors to reduce the variances of the final signal estimates. The bit estimator linearly combines soft information of each IC stage using weighting factors derived from those for PPIC. Computer simulation results show that a PPIC-based multiuser detector with the bit estimator has performance gain over the original one.