Stochastic Geometry Analysis of Individual Carrier Sense Threshold Adaptation in IEEE 802.11ax WLANs

This paper discusses the impact of spatial reuse and carrier sense threshold (CST) optimization on the performance of wireless local area networks using stochastic geometry analysis. The adjustment of the CST is a promising approach to improve spatial reuse, and has been proposed for the IEEE 802.11ax standard. Considering the situation where each access point (AP) individually adjusts its CST based on the individual received power, this paper derives the probability of transmission success and the density of successful transmissions (DST). The evaluation results of these metrics reveal that the optimal setting is to increase the CST linearly (in terms of dB) with respect to the average received signal power. Because the maximization of the DST causes unfairness from the viewpoint of success of transmission, the maximization of the product of the transmission success probabilities is proposed to improve the performance of the entire system and restrain unfairness. Using the trend of the optimal CST function, the impact of the density of APs on the optimal CST function is determined. Moreover, individual CST adjustment is found to improve spatial reuse compared with identical adjustment, i.e., setting the CST of all APs to an identical value.