Outage optimal relay selection and power allocation for amplify-and-forward relaying networks

In this paper, we consider the relay selection and power allocation problem in an amplify-and-forward relaying network, the objective is to minimize the outage probability given that only mean channel gain information is known. We firstly show that relay selection is important in achieving the global optimal solution in addition to the power allocation. Based on this argument, we then propose to decompose the problem into two parts: relay selection and power allocation. For the relay selection problem, a novel scheme is designed to incrementally select relays according to their ordering of mean channel gain. Then for the given set of relays, the optimal power allocation for the source and relays are obtained by exploiting the special structure of the problem. Simulation results show that the proposed scheme outperforms existing schemes without relay selection, which is also very efficient since the results obtained by this scheme are very close to the optimal results achieved by exhaustive search.