Reduced complexity iterative receiver for coded asynchronous DS-CDMA systems over frequency selective channels

We derive a low complexity turbo-detector for coded asynchronous DS-CDMA over frequency selective channels. Our detector is a suboptimal variant of the MAP algorithm based on state-reduction and per-survivor processing. In order to reduce the loss due to state-reduction, we propose to use, as a prefilter for the turbo-detector, a multidimensional whitened matched filter (WMF) which leads to a white-noise "minimum phase" channel model. Simulation results show that the use of the WMF yields significant improvement. Thanks to the iterative turbo processing (detection and decoding are iterated several times), the performance loss due to the use of the suboptimum List-type equalizer is in part recovered.