Outage performance of relay selection in cooperative wireless networks over Rayleigh fading channels

This paper evaluates the Amplify-and-Forward (AF) and Decode-and-Forward (DF) relay strategies, in which a source node transmits information to a destination node through multiple relays and a direct link. In all-participate (AP) systems, we need N+1 channels (one for the direct link and N for the relays links) to complete the transmission from the source to the destination. We propose a single relay selection strategy for two-hop relay networks based on an outage probability criterion in which the relay with the lowest outage probability is selected for further cooperation in an AF and DF schemes. A method to select the best relay is suggested, wherein the destination node decides to cooperate with a relay node according to which offers the lowest outage probability for each link between destination-relay nodes. In particular, an outage probability closedform expression for the total SNR is derived for the selection AF (SAF) and selection DF (SDF) cooperative techniques. The results show that this method outperforms the AP-AF and AP-DF methods, and that it can maintain a full diversity order.