Hybrid Demodulate-Forward Relay Protocol for Two-Way Relay Channels

Two-Way Relay Channel (TWRC) plays an important role inrelay networks, and efficient relaying protocols are particularly importantfor this model. However, existing protocols may not be able to realizethe potential of TWRC if the two independent fading channels are notcarefully handled. In this paper, a Hybrid DeModulate-Forward (HDMF)protocol is proposed to address such a problem. We first introduce thetwo basic components of HDMF - direct and differential DMF, and thenpropose the key decision criterion for HDMF based on the correspondinglog-likelihood ratios. We further enhance the protocol so that it can beapplied independently from the modulation schemes. Through extensivemathematical analysis, theoretical performance of the proposed protocolis investigated. By comparing with existing protocols, the proposed HDMFhas lower error rate. A novel scheduling scheme for the proposed protocolis introduced, which has lower length than the benchmark method. Theresults also reveal the protocol’s potential to improve spectrum efficiencyof relay channels with unbalanced bilateral traffic