Adaptive contention control for improving end-to-end throughput performance of multihop wireless networks

In multihop wireless networks, packets of a flow originating from a source node are relayed by intermediate nodes (relay nodes) and travel towards their destination along a multihop wireless path. Since the traffic forwarding capability of each node varies according to its level of contention, ideally, a node should not transmit more packets to its relay node than the corresponding relay node can forward. Instead, each node should yield its channel access opportunity to its neighbor nodes so that all the nodes can evenly share the channel and have similar forwarding capabilities. In this manner, nodes can utilize the wireless channel effectively, and further increase the end-to-end throughput of a multihop path. We propose a fully distributed contention window adaptation (CWA) mechanism, which adjusts the channel access probability depending on the difference between the incoming and outgoing traffic at each node, in order to equate the traffic forwarding capabilities among all the nodes in the path. We implement the proposed adaptive contention algorithm on Madwifi Linux kernel driver for Wi-Fi interface with Atheros chipset and carry out an empirical study in our division building. The experiment results demonstrate how the proposed mechanism can improve end-to-end throughput performance in the multihop wireless networks.