Delay Fairness in IEEE 802.11 WLANs

In IEEE 802.11-based WLANs, nodes sharing an access point (AP) have equal opportunity to access the link (or channel) via a random access MAC protocol. As a consequence, a node sending more packets shows a longer delay than other nodes sending a lower number of packets. This is fair enough for besteffort service, since the communication cost is not determined by the amount of traffic sent. In a commercial service with per-packet based payment, however, this may be unfair for nodes sending more packets, since each packet has the same transmission cost, and the payment is proportional to the amount of traffic. In this paper, we address this unfairness problem in IEEE 802.11 and propose a modification of the current standard MAC protocol to achieve a fair delay regardless of the amount of packets sent. It can be implemented with both notificationbased and estimation-based approaches. We show via simulation that both approaches can achieve weighted delay fairness among nodes with different access priorities and sending rates.