Improving voice capacity in IEEE 802.11 WLAN

Nowadays IEEE 802.11 Wireless Local Area Networks (WLANs) become pervasive driven by huge demands for portable access to the Internet. Meanwhile, Voice over Internet Protocol (VoIP) is one of the fastest growing Internet applications because of its high resource utilization and low cost. This paper focuses on the combination of these two technologies. Aiming to support more voice calls in IEEE 802.11 infrastructure networks, voice capacity in IEEE 802.11 WLAN is studied. Through simulation, it is found that Access Point (AP) is a bottleneck that limits the number of concurrent voice calls. This is because in infrastructure networks, all frames must go through the AP so that the AP has much more traffic, but the AP has no advantage on accessing the medium. In this paper an enhanced DCF protocol is proposed to give AP higher priority to access wireless medium and mitigate AP bottleneck effect. In proposed scheme, AP's priority is adjusted dynamically by changing some Distributed Coordination Function (DCF) parameters according to the length of the AP queue. Simulations in various scenarios well verify the improvement achieved with increased voice capacity and decreased access delay.