Integrated interference cancellation and decoding for CDMA systems using turbo code

Interference cancellation and turbo code are two very promising techniques for performance improvement in CDMA systems. The former significantly reduces most of the multiple access interference (MAI) while the latter provides very strong error correcting capability against residual interference and background noise. As both interference cancellation and turbo decoding are iterative multi-stage algorithms, we combine the two multi-stage algorithms into an integrated interference cancellation and decoding algorithm in which each stage consists of a interference cancellation iteration and a turbo decoding iteration. The performance of this integrated approach is compared to the usual concatenation approach where all the multi-stage interference cancellation iterations are completed first before starting the turbo decoding iterations. Even though both approaches have the same amount of complexity, we find that significant performance gain is achieved when the iterations are integrated and this performance gain increases with the number of users.