An End-to-end Delay Metric for Multi-rate Wireless Mesh Networks with Cooperative Retransmission

The IEEE 802.11 MAC protocol performance degrades severely as the number of stations in the collision domain increases in a saturated network. Employing cooperative retransmission at the MAC layer provides a way to work around the performance limitations by exploiting the broadcast nature of wireless communication. This paper presents a new routing metric, termed Expected Cooperative Forwarding Delay (ECFD), with the aim of selecting a minimum end-to-end delay path for multi-hop multi-rate wireless mesh networks. Different from previously proposed cooperative-aware routing metrics such as ORETT, the ECFD metric is based not only on expected cooperative transmission time but accounts for queueing and backoff delays in the path selection process. We describe the design and implementation of ECFD, and conduct extensive simulation experiments in random topologies showing that, under various realistic network traffic patterns, the use of ECFD instead of ORETT and ETT significantly improves both end-to-end delay and throughput.