Two-way relaying for energy constrained systems: Joint transmit power optimization

We consider an energy constrained two-way wireless relay system, where a bidirectional connection between two terminals T_A and T_B is established via one decode-and-forward (DF) relay R. We study the optimal power allocation that minimizes the total transmit power consumption, under given requirements on the end-to-end bit error rate (BER) at T_A and T_B. By approximating the non-convex BER constraints, we formulate a convex optimization problem and provide closed form solutions for the optimal power assignment problem. Comparing the resulting overall transmit power consumption with that achieved through the individual link requirement strategy (where power is assigned under a per-link BER constraint), we show that the proposed power allocation scheme can achieve a maximum of 50% power reduction.