Outage-optimal power allocation for space-time cooperative network coding with amplify-and-forward protocol

To improve the resource utilisation of traditional two-way wireless relay system, an optimal power allocation (OPA) algorithm for a space-time cooperative network coding scheme employing amplify-and-forward protocol (AF-ST-CNC) is proposed. The system performance in terms of outage probability and its approximation in high signal-to-noise (SNR) regimes are first derived, and with minimising the larger outage probability of the two sources, the optimal power factors are obtained by using an iterative algorithm. Moreover, the closed-form solutions of the optimal power allocation factor under some special scenarios are given. The proposed algorithm only needs the average channel gain information and has low computation complexity, which facilitates the practical implementation. Simulation results show that, the proposed AF-ST-CNC with OPA algorithm outperforms the AF-ST-CNC with equal power allocation (EPA) algorithm and the space-time cooperative network coding scheme employing amplify-and-forward protocol (DF-ST-CNC) with OPA algorithm in terms of outage performance and symbol error rate (SER) performance.