Relay Selection with Constellation Rearrangement for Superposition Modulation Cooperative Relay

In this paper, we consider a multi-relay Demodulate-and-Forward (DMF) cooperation system, in which the high order superposition modulation (SM), superposition 16-QAM modulation (16-QAM SM), is employed. For the given system, a new relay selection scheme with constellation rearrangement (CR) technique is proposed, which is based on the optimal total mutual information (MI) criterion. Firstly we find the optimal bit-symbol mappings for all the relays. And then the source chooses the best relay, which maximizes the MI, to cooperate with. We assume that all the channel state information (CSI) is available. A variety of simulations are performed and show that they match exactly with analytic ones. In addition, the result shows that our new strategy utilizing high order superposition modulation with CR outperforms the classical SM cooperation scheme and traditional DMF scheme for about 1.5 dB and 2.5 dB, respectively. Meanwhile, it improves spectrum efficiency with the same complexity.