Interference Avoidance through Frequency Assignment and Association Control in IEEE 802.11 WLAN

Very often a denser deployment of APs is required to increase the coverage and capacity in IEEE 802.11 WLAN. It increases the number of APs with overlapping coverage areas. Such overlapping eventually makes more and more clients to fall in the common coverage area of several APs. Interfering APs require different frequency channels for operation in order to avoid the co-channel interference between the APs. Two clients receiving down-link data from two non-interfering APs operating on the same frequency, may also suffer from interference, if both the clients present within the intersecting coverage area of their associating APs. This type of client interference is very common, as the number of available frequency channels is very limited. Ignorance of both types of interference may significantly overestimates the network performance while independent consideration of the frequency assignment and the association control to deal with such interferences, may lead to a sub-optimal solution. In this paper we argue that both the frequency assignment and the association control play an important role and they should be considered simultaneously to improve the overall network performance. We propose an efficient greedy algorithm that jointly deals with the frequency assignment and association control to maximize the aggregate down-link throughput while avoiding both type of interferences. Through simulation, we have shown that our proposed approach is superior than both the traditional approach of dealing with these interferences and the approach that ignores these interferences altogether.