Quiet ACK: ACK Transmit Power Control in IEEE 802.11 WLANs

With increasing demand for wireless connectivity, IEEE 802.11 WLANs have become ubiquitous and continue to grow in number. This leads to high density of basic service sets with the significant co-channel interference (CCI) among them. This paper sheds light on the CCI caused by 802.11 MAC ACK frames, which has been less studied than the CCI caused by data frames. Based on stochastic geometry analysis, we propose Quiet ACK (QACK), a dynamic transmit power control algorithm for ACK frames. Fine-grained transmit power adjustment is enabled by CCI detection and CCI power estimation in the middle of a data frame reception. Our prototype using software-defined radio shows the feasibility and performance gain of QACK, i.e., 1.5x higher throughput than the legacy 802.11 WLANs. The performance of QACK is further evaluated in more general WLAN environments via extensive simulations using ns-3.