A Dynamic Load Balancing Scheme for VoIP over WLANs

Abstract

Coverage areas of WLAN access points (APs) are usually overlapped so a WLAN station (STA) might find several APs to attach in a WLAN hotspot. Generally speaking, a WLAN STA associates with an AP with the maximal signal strength, and requests the bandwidth of the AP for establishing network connections. However, this kind of STA-centric association and bandwidth request policy may introduce unbalance loads of APs, and the utilizations of APs in a WLAN hotspot cannot be maximized. This unbalance load problem for a WLAN hotspot becomes one of the critical issues for the commercial deployment of WLAN services such as voice over IP (VoIP) over WLAN (VoWLAN) which needs to guarantee the Quality of Service (QoS) and also to satisfy the maximal number of subscribers. In this work, a novel dynamic load balancing scheme that works together with a network-assist association policy is proposed for a VoWLAN system. The network-assist association policy first advices an STA to request a VoWLAN session through an AP with the minimal load. In case the APs that the STA can attach are all overloaded, the proposed load balancing scheme further rearranges the serving VoWLAN STAs between APs in order to spare enough resources to service that new request. Simulation results demonstrate that the utilizations of APs in a WLAN hotspot are improved by applying the proposed scheme.