In this paper, we analyze and compare the outage probabilities of selection relaying protocols for cooperative communications in wireless networks. Depending on the quality of the source-relay channel, the relay may choose either Decode-and-Forward (DF), Amplify-and-Forward (AF), or Direct-Transmission (DT) to forward signals. It turns out that in terms of outage probability, two selection relaying protocols are better than others: either selection between DF and AF protocols (DF-AF) or selection between DF and DT protocols (DF-DT). We show that with an equal power allocation at the source and the relay, both the DF-AF and DF-DT selection protocols have the same asymptotic outage probability. However, with an optimum power allocation strategy, the DF-AF selection is in general better than the DF-DT selection. Simulations are also presented to validate the analytical results.
展开▼