Enhancement of IEEE 802.11 WLAN MAC using EDCF Protocol

Abstract

IEEE 802.11 Wireless LAN is one of the most deployed wireless technologies all over the world and likely to play a major role in the next generation wireless communication networks. In the present 802.11 WLAN two basic co-ordination functions exists. DCF (Distributed Coordination function) and PCF (Point Coordination Function). DCF is responsible for Asynchronous data services and the PCF was developed for time bounded services. Although IEEE 802.11 is most widely used WLAN today, it cannot provide QoS(Quality of Service) Support for the increasing number of the multimedia applications typically for time bounded service such as video/audio conferencing which require some level of specified bandwidth and delay. So a new protocol called EDCF (Enhanced Distribution Coordination function) is being introduced in IEEE 802.11e standard which supports the QoS requirements to a certain level. Even though EDCF protocol supports many QoS requirements, it has some drawbacks like static values assignment of CW size. In this work I had analyzed the various QoS limitations of the DCF and QoS Support of EDCF. Then I had enhanced the EDCF protocol to support the Adaptive technique in assigning the values of Contention Window size. The simulational analysis of these protocols is done in NS2 (network simulator 2). The NS2 is a open source software embedded with rich set of network protocols at different layers and is used for simulation purposes with real time environment. The basic structure of ns2 and the networking protocols are realized in C++ programming language where as the simulations are controlled by script language TCL (Tool Command Language).