A nearly optimal amplify-and-forward relaying scheme for two-hop MIMO multi-relay networks

This letter proposes a nearly optimal amplify-and-forward (AF) relaying scheme for two-hop and half-duplex distributed relay networks with one source, one destination, and multiple relays, each equipped with multiple antennas. The system mutual information is first analyzed under the assumption of known channel state information (CSI), revealing that it is possible to maximize the information rate by designing properly the relay precoder as a block-diagonal matrix. Then, the maximum transmission rate issue is investigated under a total relay power constraint, leading to an optimal relaying scheme for moderate to high levels of total relay power. A simulation study is undertaken to show the effectiveness of the proposed solution.