User-relay assignment for amplify-and-forward cooperative communication systems

In this paper, we study the low complexity user-relay assignment problem in amplify-and-forward (AF) cooperative communication systems, where multiple users compete for the same group of relays. In order to reduce the great computational complexity of the exhaustive user-relay assignment algorithm which provides the best performance in multi-user multi-relay environment, we propose a suboptimal low complexity user-relay assignment algorithm. The proposed algorithm can also optimize the achievable system average sum rate and improve the system outage probability. Simulation results and analysis demonstrate the efficiency and superiority of the proposed algorithm in average system sum rate and outage probability of the worst user. The complexity of the proposed algorithm is increased linearly with the number of the users and the relays.