Evaluating spatial reuse in 802.11ax networks with interference threshold adjustment

The sixth generation of Wi-Fi standards, denoted as IEEE 802.11ax, is gathering research interest as the first Wi-Fi standard to address the Quality of Experience (QoE) in dense environments. Members of the Task Group AX have proposed several solutions for improving spectrum efficiency in high density scenarios. In this paper we analyze efficiency of Basic Service Set (BSS) color, one of those solutions proposed for spatial reuse and improvement of area throughput. Using ns-3 network simulator, we model a hotspot scenario consisting of 7 overlapping basic service sets, implementing BSS color to identify the source of detected transmission. Nodes in each BSS use two Carrier Sense Thresholds (CSTs) for sensing the channel, where the higher threshold value is being applied for detection of inter-BSS frames. We show that, by selecting higher threshold for detecting frames from other access points (foreign frames), spectrum efficiency can be improved and area throughput can be increased. However, if the value of this threshold is too high, it can have a counterproductive effect, as it increases interference and probability of error in reception. Therefore, we present the upper limit value of CST, which should not be exceeded in the presented communication scenario, as well as a range of threshold values that enables improvement of area throughput.