Multiple-relay cooperative MIMO designs

We consider the problem of designing a cooperative multiple-input multiple-output (MIMO) wireless network, where a multi-antenna source-destination communication link is assisted by several multi-antenna amplify-and-forward (AF) relays. Assuming either full or partial channel state information (CSI) at the relays, we propose an optimization framework for joint design of the source precoder, the AF relaying matrices, and the destination equalizer. Starting from the minimum-mean-square-error (MMSE) criterion with a transmit power constraint at the source and a global power constraint at the output of the relays, we relax the original nonconvex optimization problem to derive closed-form solutions in both full and partial CSI scenarios. The bit-error-rate performance of the proposed designs is numerically evaluated and compared with competing approaches.