Combined decision-feedback multiuser detection/soft-decision decoding for CDMA channels

This paper evaluates the performance of decision-feedback multiuser detectors with coding for CDMA channels. A combined multiuser detection/soft-decision Viterbi decoding scheme is proposed (for asynchronous CDMA channels with convolutional coding) which allows total control over the reliability of decision-feedback mechanism. Its performance is compared to that of conventional detection and linear-decorrelation detection with soft-decision decoding. Simulation and analysis is undertaken for synchronous CDMA channels. It is found that the scheme works very well especially for weak users and when multiuser interference is large. However, strong users do not gain much with this scheme over a linear-decorrelation detector.