Fast power control for amplify-and-forward multiple-antenna bidirectional relays

Cooperative relay communication is an interesting area of research, since it is to enhance data rate and coverage in wireless networks. In this paper, we propose a method to optimize power allocation strategy in an amplify-and-forward relay system. Our objective is to attain a max-min fairness within co-channel users. To reduce the complexity we maximize the upper bound on the performance. The reason is that this bound is observed to be tight in low noise conditions. Therefore, one achievement of this work is separating the problem of relay pre-coding design from power allocation. Then, the power control is done iteratively via the proposed low-complexity algorithm whose convergence is proven. The relay precoder can be subsequently designed via existing methods, such as semidefinite programming, nonetheless, it is beyond the main focus of the current work. The optimality of the proposed power allocation algorithm is very hard to mathematically prove. Yet, the simulation results are promising.