WLAN Mesh Network Interference Management Using FSO Link Deployment

Frequency channels are assigned in wireless LAN mesh networks subject to strict co-channel interference constraints. Since Wi-Fi may be freely used by other networks, added interference may eventually invalidate the original frequency assignment, making full link activation impossible. In this paper we address this problem by selectively installing supplementary free space optical (FSO) links when RF link performance has deteriorated. We first formulate the channel assignment problem with the objective of maximizing the number of simultaneous link activations while satisfying cumulative RF interference constraints. A proof is given for the NF-completeness of the joint frequency assignment and FSO link placement problem. We then propose an efficient heuristic to solve the channel assignment problem using a genetic algorithm. Our comparisons show that the proposed algorithm gives good results compared with computed bounds.