SmartCAC: Call Admission Control scheme to guarantee QoS for Voice over IEEE 802.11 WLANs

Abstract

Most of the wireless LANs deployed today are IEEE 802.11b/g compliant. Since IEEE 802.11 standard specifies a contention based MAC-DCF, it cannot support QoS requirements of real-time traffic like voice or video. Thus these WLANs are not suitable for supporting real-time voice traffic. In this paper we propose an admission control scheme "SmartCAC", which without modifying the basic access mechanism of IEEE 802.11 tries to guarantee QoS for voice traffic. SmartCAC is a channel BW allocation scheme; in which most of the available BW is reserved for real-time voice traffic and remaining small amount is allocated to non real-time data traffic. Moreover, the BW allocation is not static; rather it can be dynamically changed depending on traffic conditions. If the voice traffic is lightly loaded then rather than wasting the greater BW share allocated to voice, it is made available for non real-time traffic sources momentarily. Our ns-2 simulations result show that the proposed SmartCAC scheme can support strict QoS requirements such as high throughput and low delay (<150ms) required for voice over IP.