A turbo multiuser receiver for receive diversity CDMA systems over flat Rayleigh fading channel

In this paper we consider an uplink CDMA system employing multiuser detection to suppress multiple access interference (MAI) at the base station. An iterative parallel interference cancellation (PIC) multiuser receiver structure utilizing the minimum mean-squared error (MMSE) detection as its first stage is used, including turbo decoders. We use this structure on a slow, flat Rayleigh fading channel, as well as the AWGN channel, but find that its performance is relatively poor, limited by the single user bound. Accordingly we develop an improved turbo multiuser receiver that can be used in systems with multiple receive antennas. The simulation results demonstrate that this diversity technique allows the turbo PIC receiver to recover its ability to enhance the system performance, even in the presence of severe multipath fading.