New Adaptive 802.11 MAC Protocol to Enhance Throughput and Fairness in Multihop Wireless Networks

Multihop Wireless Networks (MWNs) suffer from contention over the medium between nodes, resulting in a decrease of end-to-end throughput. Also, nodes with multiple hops away from the gateway experience additional throughput degradation caused by high collisions from competing nodes, resulting in more packet loss. It has been shown that packets' fragmentation at the (Medium Access Control) MAC layer plays an important role in improving nodes' throughput. Inspired by this idea, we propose an algorithm to estimate more suitable fragmentation threshold for various nodes in the network based on their locality. Although various fragmentation thresholds achieve better end-to-end throughput, it does not improve the fairness problem in such networks. To address the fairness problem, we propose changing also the transmission rates to nodes across the network. In this work, we propose a new scheme called Adaptive Transmission Rate and Fragmentation Size (ARFS) that can be implemented on top of the 802.11 MAC protocol. ARFS computes the collision probability of each node based on its interfering range and its distance from the gateway. It then uses these values as weights to compute new fragmentation threshold and transmission rate of each node in the MWN. We show that ARFS significantly outperforms the standard 802.11 MAC protocol in regarding fairness and end-to-end throughput.