A novel selective relaying protocol for wireless networks

For a three-node cooperative network model we propose a novel relaying strategy, referred to as selective decode-and-forward/ampliy-and-forward (selective DF/AF), and analyze its symbol error rate (SER) performance. In the proposed scheme, the relay always cooperate: when it is able to decode correctly the transmitted information symbols it forwards the decoded information to the destination, when it fails to correctly decode the information symbols, rather than staying idle, it amplifies and forwards the received signal from the source to the destination. The performance of selective DF/AF scheme is compared against that of selective DF/idle scheme, in which the relay is idle when it is unable to decode the source message reliably. The selective DF/idle scheme has been investigated in [1, 2], however, it remains unclear whether it is the optimal selective relaying protocol. Using high SNR approximation of SER as the performance metric, we show that both schemes harvest full diversity, when the destination employs maximum ratio combining (MRC) to combine signals received from the source and the relay, while the proposed scheme provides higher cooperative gain.