A comparative study of hybrid relaying protocols for M-PSK modulated signals over Rayleigh fading

The choice of the forwarding protocol to employ at each of the relay nodes in a cooperative communication system not only lowers the complexity of the system, but also greatly affects its performance. While the adaptive decode-and-forward (ADF) protocol provides improved system SER performance, the simplicity of the amplify-and-forward (AF) is unmatched. Hybrid decode-amplify-forward (HDAF) schemes that toggle between ADF and AF allow a cooperative system to make the most of the improved SER performance of the ADF while maintaining the simplicity of the AF. In this paper, we extend the work of [14] for such a HDAF scheme with M-PSK modulated signals. The proposed HDAF schemes for M-PSK are either SNR- or LLR-based. A comparative study is carried out between the proposed schemes and various others, found in the literature, that toggle between the ADF and AF protocols. The effect of relay node location is also investigated and SER curves of the various scheme are compared and contrasted.