Max-Cut based overlapping channel assignment for 802.11 multi-radio wireless mesh networks

Due to the limited number of orthogonal channels in a multi-radio multi-channel wireless mesh network (MR-WMN), overlapping channel assignment (CA) is one of the main factors that greatly affect the network capacity. In this paper, we first propose a model for measuring achieved network capacity in MR-WMNs. Then we prove that finding an optimal overlapping CA in a given MR-WMN with odd number of channels, is equivalent to finding an optimal assignment by only using its orthogonal channels. This theory allows us to use fewer channels to solve complicated CA problems. Third, we prove that in 802.11b/g-based MR-WMN, the simplified optimization problem is a Max-3-Cut problem. Although this problem is NP-hard, it has an efficient approximation algorithm that achieves approximation ratio of 1.19616 probabilistically by using the algorithm for Max-Cut whose approximation ratio is 1.1383 probabilistically. Based on the algorithm for Max-Cut, this paper proposes Max-Cut-based channel assignment (MCCA) which uses a heuristic method to adjust the result produced by the Max-Cut algorithm to achieve an even better result. Finally, we perform extensive simulations to compare the MCCA with a state-of-the-art Tabu-Search based algorithm. The results show that the Max-Cut-based overlapping CA algorithm effectively improves on the network capacity.