A New Perspective on the Unfair Channel Access Phenomenon in Wireless LANs

Wireless LAN, based on the IEEE 802.11 standards, has been extensively studied since its release. The topic of several of these research papers was the discrepancy of delays and buffer overflow probabilities experienced by the Access Point on one hand and the stations on the other hand. This is widely referred to as the unfair channel access phenomenon. A related issue that has not yet been investigated is another kind of unfairness resulting from different collision probabilities. Interestingly, the latter unfairness favors the Access Point, contrary to the former. In this paper, we present an extensive simulation study of this problem and validate the results by means of analytical models. Here, mainly bi-directional voice traffic and TCP traffic flows are considered. The results reveal how pronounced this unfairness is and how the recent introduction of the Quality-of-Service extension exacerbates the unfair channel access phenomenon.