High throughput path selection for IEEE 802.11s based wireless mesh networks

The IEEE 802.11s draft is the first attempt to develop a standard fully intended for the rapidly growing Wireless Mesh Networks (WMNs). Performance of a WMN is largely affected by the design of routing protocol and the associated metric. The recent version D2.02 of 802.11s has defined Hybrid Wireless Mesh Protocol (HWMP) and Airtime as the default path selection protocol and metric, respectively. However, Airtime and other well known existing routing metrics do not consider the impact of backoff delay and queueing delay, and hence, ignored some important factors like transmission time of the contending nodes, their loads and densities which might hinder the network performance. In this paper, we first identify the parameters that affect the forwarding time of a packet and then, design a new routing metric referred to as EFD (Expected Forwarding Delay) that estimates the forwarding time of a packet of particular traffic class in a node and selects the best path (high throughput) having minimum cumulative expected forwarding delay. We also made changes to the path selection criteria, metric propagation and route update intervals of HWMP, so that more stable paths can be chosen. Finally, we incorporate our new metric with the modified HWMP and study the performance through extensive simulations. Results indicate that the proposed mechanism outperforms others in terms of average network throughput, end-to-end delay and packet loss rate.