Load Balancing in Wireless LAN using Optimal Association Control Algorithm

In wireless LAN technology, access point selection at each station is a critical problem in order to obtain satisfactory throughputs. The traffic load of wireless LANs is often unevenly distributed among the Access Points (APs), which results in unfair bandwidth allocation among Mobile Users. We argue that the load imbalance and consequent unfair bandwidth allocation can be greatly reduced by intelligent association control. In a large wireless network with multiple collocated Access Points (AP), a load balancing policy is necessary for the distribution of the Mobile User (MU) to the APs, so  the network performance to be maximized. Already proposed algorithms, which are based only on the Received Signal Strength Indicator (RSSI) and Association Control Algorithm (ACA), may cause all the MU to be associated to a single or to a very few number of APs, and result in an overall network performance degradation. In this paper, we present an efficient solution to determine the MU-AP associations for bandwidth allocation. In this paper, we propose a load balancing procedure namely Optimal Association Control Algorithm (OACA), which acts in two separate levels. First, the APs are either distributed across the channels (if the number of APs is small) or located in the same channel that is specified by taking into account the channel-location and the received RSSI of the neighbor AP. Second, the APs are distributed across all the available MUs, if any MUs relieved from the APs, based not only on RSSI measurements but also on the number of MUs already associated to the AP and other link quality measurements. Besides, in this paper we describe the signaling extension needed for the implementation of the proposed load balancing procedure.