MBER Turbo Multiuser Beamforming Aided QPSK Receiver Design Using EXIT Chart Analysis

This paper studies the mutual information transfer characteristics of a novel iterative soft interference cancellation (SIC) aided beamforming receiver designed for quadrature phase shift keying (QPSK) modulated systems communicating over additive white Gaussian noise (AWGN) channels. Based on the extrinsic information transfer (EXIT) chart technique, we investigate the convergence behaviour of an iterative minimum bit error rate (MBER) multiuser detection scheme as a function of the system parameters and channel conditions. We also compare the achievable performance and convergence behaviour of different multiuser detectors (MUD) and channel decoders. Our simulation results show that the EXIT chart analysis is sufficiently accurate for reliably predicting the performance of the MBER MUD, despite its potentially non-Gaussian output distribution because we invoke the histogram-based approximation of the true distribution. As expected, the proposed SIC- MBER MUD outperforms the SIC aided minimum mean square error (SIC-MMSE) MUD.