A distributed on-off amplify-and-forward protocol for the fading parallel relay channel

A single source-destination pair communicating via a layer of two parallel relay nodes under slow fading is considered. The bit error rate (BER) performance of Alamouti-Coded Amplify-and-Forward (ACAF) transmission protocol under different power control strategies is investigated. The optimal power control rule is analytically derived and two distributed approximations to this rule are proposed. The optimal rule reveals an interesting fact: The transmission of each relay is on-off in nature. Simulation results show that our proposed distributed approximations improve the BER performance significantly.