We propose a method for dynamic load balancing in wireless LANs (WLANs), which adapts association topology dynamically based on traffic conditions, while keeping the handoff overhead negligible using virtualized wireless network interfaces (WNICs). In large-scale WLANs, there are many locations that each station (STA) can discover multiple access points (APs). In these locations, the conventional approach to the AP selection in which each station connects to the AP with the strongest Received Signal Strength Indication (RSSI) may suffer from imbalanced load among APs. To address this issue, a number of AP selection schemes have been proposed, which achieve load balancing by changing some STA-AP associations. However, since stations cannot communicate during handoff, frequent changes of STA-AP associations will result in serious deterioration of the communication quality. Therefore, in the existing schemes, we face a problem that it is difficult to decide appropriate timing of association changes. Nevertheless, this problem was not considered as a major concern in the literature. In this paper, we propose a method for trigger-based dynamic load balancing in WLANs. In the proposed method, to minimize the handoff overhead, the WNIC on a station is virtualized and connected to multiple APs simultaneously. Using this approach, we propose a method that continuously monitors changes in traffic conditions and that switches STA-AP associations at appropriate timing based on the monitored results. We evaluate the effectiveness of our method in terms of aggregated throughput and fairness using the ns-3 simulator. Compared with the result in the traditional AP selection method, aggregated throughput is improved by about 11%, while increasing the Jain's fairness index by about 19% in our method.
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