An Efficient Relay Selection Strategy for High Speed Users in Cooperative Diversity Systems

Cooperative diversity has been proposed to form virtual antenna arrays in order to obtain spatial diversity gains. Various relay selection strategies in cooperative diversity systems were proposed but they are efficient for static or low speed users. An efficient relay selection strategy for systems with high speed users is presented in this paper by dividing users into three groups according to their moving speeds and directions. The relays for cooperation are selected from the same group with the source user. Simulation results show that the proposed strategy can increase duration of cooperation, as well as decrease the partner handoff times and probability of unsuccessful partner selection, and the same energy gain can be obtained.