Joint Frequency Assignment and Optimal Association of Stations to Access Points in IEEE 802.11 WLAN

摘要

Frequency channels are allocated to the access-points (APs) subject to an acceptable co-channel interference level in an IEEE 802.11 WLAN. Due to limited number of the non-overlapping frequency channels, all APs in a given area may not be activated simultaneously. Therefore which subset of the APs to select for activation is a major concern. Given a set of selected APs, often a station (STA) can potentially associate with more than one AP. The association of an STA to an inappropriate AP will not only lead to degraded service for the concern STA but also may pull down the throughput of the other STAs associated with that AP. Thus finding the optimal association between STAs and APs is another important concern. We argue that treating these two issues in succession may lead to suboptimal solutions, whereas, ignoring the co-channel interference may result over estimation of the throughput. In this paper, an integrated model based on integer programming and an efficient greedy algorithm are proposed that address both aspects simultaneously and maximizes the overall throughput while taking care of load balancing across different APs. Computational results show that indeed the integrated approach is superior to both two-step approach and methods that ignore the interference.