Joint association control, airtime sharing and contention resolution in multi-cell WLANs with directional antennas

In this paper we study the problem of joint client association, airtime sharing and contention resolution in IEEE802.11 multi-cell WLANs with directional antennas with the goal of achieving optimal fair throughput. We formulate the problem as a non-linear programming problem and solve it under the network utility maximization framework. Using simulation, we demonstrate that i) the association pattern should try to balance the number of clients associated with each AP to use the capacity of more APs; ii) clients in the same transmission range of an antenna should always be associated with the same AP to avoid hidden node collisions.