Joint MMSE Transceiver Design for Closed-Loop Non-Regenerative MIMO Relaying Systems

In this paper, as a extended structure of the existing relay-destination joint minimum mean square error (MMSE) design, we propose a new source-relay-destination joint MMSE design strategy allowing the channel state information (CSI) additionally at the source node. Instead of conventional singular value decomposition based methods, we address the problem for joint MMSE design in a different approach using the Wiener filter solution which leads to the simple derivation of the optimal MMSE design. From our design strategy, we also observe that compared to conventional non-regenerative relaying systems, the source or the destination only needs to know the CSI corresponding to its own link such as the source-to-relay or the relay-to-destination for minimizing the mean square error. Furthermore, numerical results show that the proposed design gives about 7.5 dB gains at a bit error rate (BER) of 10^-4 over existing relay-destination joint MMSE schemes.