In this paper, an optimization model for solving the channel assignment problem in multi-cell WLANs is proposed. This model is based on maximizing the minimum distance between access points (APs) that work on the same channel. The proposed model is formulated in the form of a mixed integer linear program (MILP). The main advantage of the proposed algorithm is that it ensures non-overlapping channel assignment with no overhead power measurements. The proposed channel assignment algorithm can be implemented within practical time frames for different topology sizes. Simulation results indicate that the proposed algorithm exhibits better performance than that of the pick-first greedy algorithm and the single channel assignment method.