Power Efficient Relay Selection and Diversity-Multiplexing Tradeoff in Two-way Relaying Networks

—Two-way amplify-and-forward (AF) relaying networks have been widely studied because of its simplicity and high spectral efficiency. In this paper, we investigate the relay selection problem and the diversity-multiplexing tradeoff (DMT) for two-way AF relaying systems over independent flat Rayleigh fading channels. We first derive the closed-form expression of the minimum total transmit power under the predefined data rate requirements. Based on the minimum total transmit power, we propose a simple relay selection which only requires user-relay channel state information (CSI). We proved that the proposed relay selection scheme can achieve the same DMT performance as obtained by the popular outage-optimal two-way opportunistic relaying scheme. Simulation results demonstrate that the proposed scheme can significantly decrease the power consumption compared with random relay selection and other schemes.