A low-complexity iterative multiuser receiver for turbo-coded DS-CDMA systems

We propose a low-complexity iterative multiuser receiver for turbo-coded DS-CDMA systems. The proposed iterative multiuser receiver consists of a modified decorrelating decision-feedback detector (MDDFD) and K single-user turbo decoders, where K is the number of CDMA users. The MDDFD is derived on the basis of maximizing a likelihood probability and has the feature that it uses the reliability information from turbo-decoder output. In addition, the MDDFD delivers interference-cancelled soft-outputs to the turbo decoders where transition metrics calculations are appropriately modified. Both performance analysis and computer simulation results have indicated that the reliability information from turbo-decoder output can enhance the multiuser detection capability of the MDDFD. Computer simulations have shown that the proposed iterative multiuser receiver significantly outperforms the conventional DDFD-based multiuser receiver in terms of bit error probability.