Effective AP selection and load balancing in IEEE 802.11 wireless LANs

IEEE 802.11 wireless LANs have been widely deployed. How to efficiently balance the traffic loads among Access Points (APs), which will lead to improved network utilization and higher quality of user experience, has become an important issue. A key challenge is how to select an AP to use during the handoff process in a way that will achieve overall load balance in the network. The conventional approaches typically use Signal-to-Noise Ratio (SNR) as the criterion without considering the load of each AP. In this paper, we propose two effective new AP selection algorithms. These algorithms estimate the AP traffic loads by observing and estimating the IEEE 802.11 frame delays and use the results to determine which AP to use. The algorithms can be implemented in software on mobile stations alone. We will show that better performance can be achieved when the APs provide assistance in delay measurements; however, the improvement is not significant. There is no need to exchange information among APs. The proposed algorithms are fully compatible with the existing standards and systems and they are easy to implement. We will present extensive simulation results to show that the proposed algorithms can significantly increase overall system throughput and reduce average frame delay.