Optimizing Aggregate Throughput of Upstream TCP Flows over IEEE 802.11 Wireless LANs

This paper via analysis and simulation revisits the interaction between MAC contention and TCP congestion control over IEEE 802.11 WLANs, misled in the previous efforts. The results reveal that the effective number of contending wireless stations is not proportional to the number of wireless stations with an upstream TCP flow in IEEE 802.11 wireless LANs. Thus, we propose a new scheme called TCP ACK priority (TAP) in which, by allowing an access point to transmit TCP ACKs at the highest priority, the optimal number of competing stations are allowed to contend for media access to utilize link bandwidth efficiently. We use an ns-2 simulator to evaluate the performance of TAP with the IEEE 802.11 DCF. The results show that there is an improvement in network performance without the loss of fairness between upstream TCP flows. The extensions for IEEE 802.11e/n are also considered.