Spectrally-efficient relay selection based on ARQ protocol and Opportunistic Relaying

A novel spectrally-efficient relay selection algorithm based on ARQ protocol and Opportunistic Relaying is presented in this paper. The multiplexing loss in decode-and-forward (DF) relay networks is recovered by applying the ARQ protocol to wireless cooperative networks. The collision probability in opportunistic relay communications is decreased by introducing a channel gain threshold to restrict the number of contending relays and exploiting control channels in cooperative networks. Theoretical analysis and simulation results both show that spectral efficiency and collision probability get significantly improved comparing with Opportunistic Relaying Selection (ORS). Meanwhile, comparing with Incremental Opportunistic Decode and Forward (IODF), the proposed algorithm obtains more power gains and lower collision probability.