Cooperative communications with selfish busy relay´s source selection: Whether to cooperate and whom to cooperate with

In this paper, an evolutionary game based relay assignment algorithm is proposed for a cooperative network consisting of multiple source users (SUs) and multiple selfish busy relay users (RUs) with their own packets to transmit. Each RU can select either non-cooperative mode (i.e., direct transmission with its own receiver pair) or cooperative mode (i.e., relay transmission for the SUs). Thus, for the relay assignment, there exists an inevitable problem for all RUs: whether to cooperate and whom to cooperate with. Considering all RUs´ different individual channel conditions, a variable-population evolutionary game model is formulated to analyze the cooperation possibility and relay competition among all selfish RUs, which is performed in a distributed manner. Moreover, this algorithm is shown to improve the entire network´s performance and compared with the centralized optimal relay assignment algorithm.