Performance analysis of a cooperative retransmission scheme using Markov models

Space-time diversity techniques such as MIMO, space-time coding, and cooperative diversity can significantly improve spectral efficiency. However, they rely on precise instrumentation at the physical layer. In this paper, we propose a simple cooperative retransmission scheme which can achieve space-time diversity without modification to the physical layer. The proposed scheme is implemented at the MAC layer. By monitoring and buffering packet transmissions of neighbors, a node can potentially help to relay an originally failed transmission to its destination, thus providing diverse transmission channels. An analytical model based on Markov chains is used to evaluate the performance of the scheme. Numerical results for a case of two relaying nodes show that the throughput can be improved by as much as 18%. Simulations of larger networks show that the scheme can improve throughput and reduce the average packet delay significantly.