Amplify-and-Forward Space-Time Coded Cooperation via Incremental Relaying

User cooperation can provide spatial transmit diversity gains, enhance coverage, and potentially increase capacity. In this paper, incremental relaying protocol is developed. This protocol uses a limited feedback from the destination to transmitters to choose between direct transmission or cooperation. The incremental relaying protocol is examined in a space-time coded cooperation under the amplify-and-forward model. The exact bit error rate of the system is derived. Furthermore, the bit error rate of amplify-and-forward based space-time cooperation is derived, when the source-destination link is considered in both phases. Simulations demonstrate that the proposed scheme can substantially improve the spectral efficiency of the system comparing to the conventional two-phased cooperative schemes. Moreover, it is shown that the proposed scheme can achieve an outstanding coding gain in comparison to direct transmission.