An iterative multiuser receiver using partial parallel interference cancellation for turbo-coded DS-CDMA systems

A low-complexity multiuser receiver for turbo-coded DS-CDMA systems is presented to perform jointly iterative multiuser detection and turbo decoding. The proposed approach consists of a new multistage partial parallel interference cancellation (NPPIC) detector and K single-user turbo decoders, where K is the number of active CDMA users. The NPPIC detector is derived based on the single-user maximum a posteriori criterion and has a similar simple structure to the conventional partial parallel interference cancellation scheme presented by Divsalar et al. (see IEEE Trans. Commun., vol.46, p.258-268, Feb. 1998). A prominent feature of this detector is that it delivers interference-cancelled soft outputs to the turbo decoders and utilizes the soft information from the turbo decoders´ output. Extensive computer simulations demonstrate that the cooperation between NPPIC and turbo decoding offers significant performance gain over the traditional non-iterative receivers and performs comparably to some existing iterative schemes of much higher complexity