CoRex: A Simple MAC Layer Cooperative Retransmission Scheme for Wireless Networks

Wireless link is not reliable and has a time-varying quality. When a link quality is bad, all transmissions over the link are not successful and persistent retransmissions of the failed packet over the same link are not productive. Consider the broadcast nature of radio communications, a packet that fails to reach its intended receiver may be successfully received by neighbors. The idea of cooperative retransmission suggests that a neighbor should help in retransmitting an overheard packet to its intended receiver, instead of letting the original sender to persistently retransmit the failed packet. This paper proposes a simple MAC layer cooperation retransmission scheme, called CoRex. The proposed scheme deals with the three critical issues, namely relay selection, packet selection and fairness, all together. The performance of CoRex has been analyzed theoretically and evaluated through random event simulations. The results show that CoRex always outperforms the non-cooperative scheme in terms of throughput without compromising fairness.