Improving fairness in IEEE 802.11 using enhanced carrier sensing

Fair access of the shared wireless medium among different contending stations is a very important issue, especially when Quality of Service needs to be provided. In CSMA/CA-based IEEE 802.11 protocol, Carrier Sensing (CS), Collision Avoidance (CA), and Contention Resolution (CR), the three main components, affect its fairness. While the influences of CA and CR on the fairness have been emphasized in the literature, to the best of our knowledge there is no research-work taking into account CS's influence. In this paper, we focus on the CS part to improve the fairness. In the current IEEE 802.11 standards, whenever a node detects a Sensing Range (SR) frame on the medium, it defers the transmission by a fixed duration. We show that this duration is sometimes smaller and sometimes larger than the desired period by which the transmission should be deferred, and it is the main cause of the unfairness in some cases. We propose an enhanced carrier sensing (ECS) scheme, which distinguishes among the SR frames based on their lengths and defers the transmission accordingly. Simulation results show that the ECS improves the fairness substantially. 1