On the mutual information of relaying protocols

The end-to-end performance metric for a conventional relay network with chase combining is the total Signal-to-Noise Ratio (SNR) delivered at the destination. However, the accumulated mutual information at the destination is the most suitable metric for a relay network which performs code combining (incremental redundancy) instead of chase combining at the destination. This paper investigates the accumulated mutual information acquired at the destination in an Amplify-and-Forward (AF), Decode-and-Forward (DF), and Coded Cooperation (CC) relay network. So far, the analytical comparison of the accumulated mutual information for the different relaying protocols is not reported in the literature. In this paper, it is proved analytically that the mutual information of a relay network with coded cooperation is always greater than or equal to the mutual information of decode-and-forward and amplify-and-forward for the case when all the relays can decode successfully. Moreover, it is also shown that the mutual information of a network with coded cooperation is always greater than or equal to that of a decode-and-forward relay network.