Fair throughput assignment in multi-cell WLANs with hidden terminals

In this paper we study the problem of client association, jointly with airtime sharing and contention resolution in a multi-cell WLAN with hidden terminals with the objective of achieving proportional fair download bandwidth allocation to the clients. We first formulate the problem as a utility maximization problem, which, due to the integral nature of association turns out to be a 0-1 (NP-hard) programming problem, then by studying its structure, we decompose it into two subproblems: the client association problem on one hand, and the joint airtime sharing and contention resolution problem on the other. We show that, for each fixed association pattern, the corresponding joint airtime sharing and contention resolution problem can be solved in polynomial time, then focus on solving the client association problem, via a greedy algorithm designed based on our observations from our previous work. In this algorithm, each AP associates with all the non-associated clients in its neighbourhood, based on a priority ordering of the APs determined so as to enable each AP to either be associated with as many clients as it can, or as few clients as it can, which will have the effect of reducing hidden nodes collisions. The simulation results show that, the proposed algorithm achieves a near-optimal performance.