Providing Delay Fairness in IEEE 802.11 WLANs

In IEEE 802.11 based WLANs, nodes sharing an access point (AP) have the equal opportunity to access the link (or channel) through a random access MAC protocol. In consequence, a node sending more packets observes longer delay than other nodes sending less packets. It would be fair enough for best-effort service since the communication cost is not determined by the amount of traffic sent. In a commercial service with perpacket based payment, however, it may be unfair for the nodes sending more packets since the transmission cost for each packet is the same, and the payment is proportional to their amount of traffic. In this paper, we address this unfairness and propose a modification of the current standard MAC protocol for providing fair delay regardless of the amount of packets to be sent. It can be implemented with both centralized and decentralized fashions, and through simulation, we show that both can achieve delay fairness among nodes with different sending rates.