A fixed backoff-time switching method for wireless mesh networks: Design and Linux implementation

As a flexible and cost-efficient scalable Internet access network, we have studied architectures, protocols, and design optimizations of the Wireless Internet-access Mesh NETwork (WIMNET). WIMNET is composed of wirelessly connected access points (APs), where any host can basically access to the Internet through multihop communications between APs with IEEE 802.11 standard. In WIMNET, undesirable situations can often happen such that some links dominate the bandwidth while others become insufficient due to the limited shared bandwidth. However, the contention resolution mechanism using a random backoff-time in the CSMA/CA protocol of 802.11 standards is not sufficient for handling real-time traffic in multihop wireless communications. Previously, we have proposed the concept of the CSMA-based Fixed Backoff time Switching (CSMA-FBS) method for WIMNET to improve the performance by giving necessary link activation chances for multi-hop communications. We implemented our proposal on the QualNet simulator, and verify its effectiveness through simulations. In this paper, we present an implementation of the FBS method in Linux kernel to show its practicality and investigate the performance in a real network. Our design consists of implementations or modifications of the five programs: Kernel configuration, Debugfs, Minstrel, iw, and FBSdaemon.