Source and Relay Precoder Designs to Maximize Sum Rate in Two-Way Relay System with Multiple Sources

We propose the source and relay precoder designs to maximize sum rate under individual power constraints in two-way relay system with one relay and multiple sources. However, it is difficult to directly solve the sum rate maximization problem. For this reason, we establish the relationship between sum rate and weighted mean square error(WMSE), and show that the solution of the sum rate maximization problem can be also the solution of the WMSE minimization problem if the weight matrices are properly chosen. Then, based on the relationship between sum rate and WMSE, the sum rate maximization problem is equivalently formulated as the WMSE minimization problem. We finally propose an iterative algorithm for WMSE minimization problem. Simulation results show that the proposed scheme has better sum rate performance than conventional scheme at all SNR regimes.