Quality of Service in Wireless LAN Using Opnet Modeler

Abstract

Abstract

Wireless local area networks (WLANs) are in a period of great expansion and there is a strong need for them to support multimedia applications. Wireless networks are becoming more and more popular in recent years, ranging from digital cellular telephony up to satellite broadcasting. With the increasing demand and penetration of wireless services, users of wireless networks now expect Quality of Service (QoS) and performance comparable to what is available from fixed networks. Providing QoS requirements like good throughput and minimum access delay are challenging tasks with regard to 802.11 WLAN protocols and Medium Access Control (MAC) functions. This research is done to study, the presently implemented schemes (the Point Coordination Function (PCF) of IEEE 802.11, the Enhanced Distributed Coordination Function (EDCF) of the proposed IEEE 802.11e extension to IEEE 802.11), solves these issues and what can be done to improve them further. The metrics used were Throughput, Data Drop, Retransmission and Medium Access Delay, to analyze the performance of various MAC protocols in providing QoS to users of WLAN. During the evaluation of EDCF, the performance of various access categories was the determining factor. Two scenarios, with same Physical and MAC parameters, one implementing the DCF and other EDCF, were created in the network simulation tool (OPNET MODELER) to obtain the results. The results showed that the performance of EDCF was better in providing QoS for real-time interactive services (like video conferencing) as compared to DCF, because of its ability to differentiate and prioritize various services. Whereas the DCF’s overall performance was marginally better for all kinds of services taken together. In a network environment, where support for realtime interactive services is required, EDCF protocol should be used.