An Admission Control Method For IEEE 802.11e Contention Access Mechanism

Abstract

IEEE 802.11 Wireless Local Area Network (WLAN) is a shared medium communication network that transmits information over wireless links for all 802.11 stations in its transmission range to receive. The support of audio, video, real-time voice over IP (VoIP), and other multimedia applications over 802.11 WLAN with Quality of Service (QoS) requirements is the key for 802.11 WLAN to be successful in multimedia home networking and future wireless communications. Recently, the IEEE 802.11 task group E specified a distributed access approach, called Enhanced Distributed Coordination Access (EDCA), which supports service differentiation in the Medium Access Control (MAC) layer. However, no assurance can be given to higher priority traffic in terms of throughput and delay performance. The problem is especially apparent when the wireless channel is overloaded causing the bandwidth share of each flow to diminish. In this research, a simple measurement based admission control method is proposed to enhance the QoS of EDCA network when it is heavily loaded. The proposed method is implemented in Network Simulator ns-2. The results have shown that the proposed method can protect the QoS of high priority applications but sacrifice the QoS of low priority flow at a moderate level.