A Study On MAC Technology Of The WLAN

In recent years, the wireless local area network (WLAN) market is experiencing explosive growth, and the IEEE 802.11e task group is currently working on a standard to meet the increasing demand for supporting quality of service (QoS) in IEEE 802.11 WLANs. IEEE 802.11e provides a channel access function called the hybrid coordination function (HCF) to support applications with QoS requirements, which include both contention-based access mechanism called the enhanced distributed coordination function (EDCF). EDCF endows different preferential deals with different completive parameter, such as inter-frame space (IFS), minimum and maximum back off window, with purposes to offer QoS various deals. Contention-based access mechanism embodies the real and simple characteristics, and EDCF has brought the WLAN fields great attention.The present thesis has theoretically analyzed Enhanced Distributed Coordination Function in 802.11e. Based on the option and the influence of network function, we attentively discuss the different effects on using TXOP (transmission Opportunity) and unideal channel conditions, and then put forward an ideal controlled calculation and research onto the access project of CC-CMDA. The main task goes as followings.1.We analyze the system's throughput and access delay of EDCF of the IEEE802.11e, discuss error codes of a channel and the EDCF performance after adopting TXOP especially. On this basis, a kind of new EDCF algorithm of accessing and controlling, which meet synchronously the different QoS requirements of various throughputs and access delay indices, is proposed then.2.Based on analysis of avoiding conflicting access mechanism of CC-CMDA, we put forward a new spread frequency scheme. The premise of keeping the access request data package in orthogonal having been established, the system's complex is reduced and the system's efficiency is promoted.