Superposition coding cooperative relaying communications: Outage performance analysis

User cooperative is a powerful tool to combat fading and to increase robustness for communications over wireless channels. For cooperative relaying communications, the outage probability and the expected rate (throughput) can be greatly improved when the superposition coding relaying (SC‐relaying) strategy is employed. Under the assumption of high signal‐to‐noise ratio (SNR), this work contributes to a comprehensive investigation on the outage probability and the throughput of cooperative relaying communications system with only two‐level rate SC. Through strict mathematical process and deduction, the approximated close‐form expressions of the outage probabilities and the throughput of system are obtained for the first time. Based on the results, the impact of power and channel allocation fractions on system performance is carried out. With the aim of maximal throughput, a set of optimal solutions of system parameters are obtained by employing difference evolution arithmetic. The comparative numerical analyses show that the approximation results are feasible and correct. Copyright © 2010 John Wiley & Sons, Ltd.