Joint Linear Filter Design in Multi-User Non-Regenerative MIMO-Relay Systems

This paper addresses the filter-design issues for multi-user non-regenerative MIMO-relay systems. Based on the perfect channel state information (CSI), optimal joint linear filter schemes at the base station and the relay are derived, aiming to minimize the mean squared error (MSE). We first propose the joint optimal filter scheme in the downlink scenario along with a more practical suboptimal scheme, and then a closed-form optimal solution in the uplink scenario is exploited. Numerical results show that the proposed joint schemes can reduce the bit error rate (BER) significantly, especially for the high SNR case.