Performance Evaluation of a Binary Exponential Code Backoff Algorithm for IEEE 802.11

Abstract

IEEE 802.11 is the most widely deployed medium access control (MAC) protocol for wireless access. Simple and efficient, this MAC protocol works well as the last wireless hop and is a key enabler of the widespread success of WiFi. Unfortunately, despite over twenty years of advances in routing algorithms for multi-hop networks, there are no widespread commercial multi-hop networks because IEEE 802.11 delivers poor throughput and fairness on multi-hop networks. This poor performance is due to the hidden terminal often presents on multi-hop networks. In order to address this issue, researchers have proposed numerous new approaches. However, none works well enough to develop commercial multi-hop networks. This work proposes a dynamic hybrid MAC protocol dubbed the Binary Exponential Code (BEC) that adapts to the traffic: in presence of the hidden terminal problem, the MAC assigns reserved CDMA-like channels, otherwise it works like the a contention based protocol (e.g., IEEE 802.11). The scheme is dynamic because the CDMA-like channels support variable bit rates. Formal modeling and simulations are used to validate and evaluate the proposed BEC protocol. The simulation results and mathematical analyses confirm the throughput and fairness improvements achieved by BEC on a variety of topologies and traffic patterns. The network overall throughput is increased by 20% - 40% for UDP applications.