Adaptive Cooperative Space-Time Block Coding with Amplify-And-Forward Strategy

Cooperative space-time block codes (STBC) can be applied to exploit the spatial diversity among several single antenna users. Because of its simplicity, amplify-and-forward strategy is often used at relay. In such cases, the additive noise at the relay is also forwarded to the destination. Therefore, it will degrade the received signals from both the relay and the source, due to the receiver structure of STBC. In this paper, we examine the effect of the forwarded noise and propose a condition, under which the relay should stop forwarding the signal. Based on this condition, adaptive cooperative STBC schemes are proposed. The performances of these schemes are studied and the exact bit error probabilities are obtained in closed form.