Abstract: “The most popular and widely used Wireless LAN standard all over the world today is IEEE 802.11. It is likely to play a major role in the next generation wireless communication networks. IEEE 802.11 WLANs has two basic co-ordination functions at MAC layer: DCF (Distributed Coordination function) and PCF (Point Coordination Function). DCF is the basic access function for asynchronous data services and is based on carrier sense multiple access with collision avoidance (CSMA/CA) with a binary slotted exponential contention (back off) algorithm .PCF uses a centralized polling method requiring a node to play the role of a point coordinator (PC) developed for time bounded services. Providing QoS support in IEEE 802.11 is challenging task, as QoS solutions for wired networks cannot be applied out-of-the-box for wireless mobile ad hoc networks, due to specifics of radio networking and mobility. QoS problem has two major perspectives: (1)network perspective (2) application/user perspective. Netw”

Keywords: Quality ,Service, MAC