Demand-Aware Load Balancing in Wireless LANs Using Association Control

The densely deployed Access Points (APs) have overlapping coverage areas. In the hotspot area, a user can usually receive signals of more than ten APs. The signal-based association in IEEE 802.11 may result in significant unbalanced loads among APs. Moreover, diverse user demands on bandwidth further exacerbate the load unbalance. Some APs are too overloaded when multiple high-demand users gather on them due to the strongest signal, while the others are light-loaded with a few low-demand users associated to them. The severe load unbalance degrades the user performance. In this paper, by adding different user bandwidth demands as new constraints, we formulate the joint AP association and bandwidth allocation problem. We comprehensively analyze the solution space of optimal bandwidth allocation while satisfying the time-based fairness among users. We develop a 1/2-approximation algorithm to solve the problem. Our extensive trace- driven evaluations show that our algorithm achieves better load balance. As a result, it greatly improves the aggregated throughput and provides better user fairness than conventional association schemes.