A relay preselection and contention-based cooperative MAC for wireless networks

Cooperative communication is proved to effectively mitigate fading, achieve high spectrum efficiency and improve transmission capacity for wireless networks by means of spatial diversity. Recently increasing work is extended to cooperative medium access control (MAC) protocol design. A relay preselection and contention-based cooperative MAC (RPCB-CMAC) protocol is proposed to alleviate the negative effect of low rate nodes which take more time to transmit the same data than high rate nodes. In the protocol, the sender preselects two candidate relays through its local relay-information table, and sets different priorities to these two candidate relays by relay utility which reflects how much time can be saved per packet. After the handshake between the sender and the receiver, two candidate relays can obtain rate information among the sender, the receiver and themselves to judge whether they can provide cooperation gain. If they can, then they contend to become the final relay based on their priorities. Simulation results show that compared to basic RTS/CTS scheme and CoopMAC, the proposed protocol can improve the network performance.