Uncovering a Hidden wireless menace: Interference from 802.11x MAC acknowledgment frames

Previous work on 802.11x (Wi-Fi) power control have focused almost exclusively on the mitigation of interference from data frames. Since Wi-Fi wireless access points are increasingly ubiquitous, it is now common for an 802.11x client to be able to receive signals from more than 10 APs simultaneously in a modern urban operating environment. At such high densities, we found that the interference from the MAC acknowledgment (ACK) frames can potentially reduce throughput by several fold. We show that by dynamically adjusting the transmission power of the ACK frames, a simple ACK power control algorithm, which we call MinPACK, can significantly mitigate interference and increase throughput by a median of 31%, while simultaneously improving fairness. MinPACK is complementary to existing data frames power control algorithms, and adapts rapidly to dynamic environments.