Contention Window Size Control for QoS Support in Multi-hop Wireless Ad Hoc Networks

IEEE 802.11 MAC protocol for medium access control in wireless Local Area Networks (LANs) is the de facto standard for wireless ad hoc networks, but it does not necessarily satisfy QoS requirement by users such as fairness among flows or throughput of flows. In this paper, we propose a new scheme aiming to solve per-flow fairness problem and achieves good throughput performance in IEEE 802.11 multi-hop ad hoc network. We apply a cross-layer scheme, which works on the MAC and link layers. In the link layer, we examine each flow and choose suitable contention window for each output packet from the flow. The aim of the mechanism is achieving per-flow fairness. In our proposed scheme, the MAC layer of each station tries to evaluate network condition by itself then adjust channel access frequency to improve network utilization and ensure per-node fairness. Performance of our proposed scheme is examined on various multi-hop network topologies by using Network Simulator (NS2).