Low complexity power allocation for hybrid amplify-and-forward opportunistic relay ordering cooperation

In this paper, to enhance the robustness against link imbalance, a hybrid cooperative protocol is proposed for amplify-and-forward (AF) opportunistic cooperation, where opportunistic relaying and multi-hop cooperation with relay ordering (RO) are dynamically selected to maximize the end to end signal-noise ratio (SNR), and the power allocation coefficient is optimized under total power constraint accordingly. Furthermore, a suboptimum allocation scheme with low complexity is proposed by employing the upper bound of harmonic mean. Simulation results show that the proposed scheme outperforms conventional AF opportunistic cooperation in variety of line type topology. Moreover, the efficiency of the proposed suboptimum allocation is also validated in large SNR region.