An efficient soft-in-soft-out multiuser detector for synchronous CDMA with error-control coding

We consider synchronous code-division multiple-access (CDMA) communications incorporating an error-control code (ECC) for improved performance. We describe a reduced-complexity multiuser sequence detector and develop a simple method for computing reliability values for the bit decisions produced by this detector. This reliability information is used by a soft-input Viterbi algorithm to decode the ECC. We compare the uncoded and coded performance of this reduced-complexity detector to those of certain decision-feedback equalizer (DFE) multiuser detectors. Simulation shows that the reduced-complexity sequence detector works better than the DFE detectors.