A Dynamic Adaptive QoS Guaranteeing Scheme Based On Admission Control In IEEE802.11e WLAN

Wireless Lan adapting IEEE 802.11 protocol is extensively applied worldwidely owing to its simple deployment,efficiency,agility,and low price.But legacy IEEE 802.11 protocol can't satisfy QoS requirement of current ever-growing multimedia traffic such as VoIP,Video Conference which need severe delay,jitter,drop rate and throughtput guarantee.After several amendment, IEEE 802.11 Working Group finally released a new protocol-IEEE 802.11e in October 2005.The release of IEEE 802.11e Standard make it possible to provide different QoS request of traffic flow within Wireless Lan at the same time. The main QoS facility of IEEE 802.11e is Hybrid Coordination Function(HCF) mechanism . The HCF uses both a contention-based channel access method,called the Enhanced Distributed Channel Access(EDCA) mechanism for Prioritized QoS sevrices,and a controlled channel access method,referred to as the HCF Channel Access(HCCA) mechanism for Parameterized QoS services. HCCA is a central controlled method ,which is hard to implement and does not adequate for market request.On the contrary, contention-based EDCA is more popular.It improves DCF mechanism,supply different prioritized AC,and implement sevice differentiation.But it can not provide QoS guarantees based on traffic streams.Howerver,owing to the characteristic of Wirless Lan and traffic streams,it is uneasy to completely guarantee the QoS.In addition,the maximization of network resource utility rate is also the target that we pursue.The main task of the thesis is concentrated on the EDCA mechanism of IEEE802.11e.In my paper,I summarize the primary task of the direction and provide a new QoS mechanism based on 802.11e protocol in the changeful WLAN environment which can optimize network utility rate as far as it can.All the task of the paper is completed based on DCF mechanism of 802.11 and EDCA mechanism of 802.11e.The main work in my thesis include as follows:(1) The thesis firstly analyze and illustrate the basic principle and mechanism of the legacy IEEE 802.11 and updated IEEE 802.11e.(2) It utilize NS2 to simulate 802.11 and 802.11e scenario.By the simulation result comparison between 802.11 and 802.11e,the thesis analyze the 802.11e efficiency in the capability of QoS differentiation. Meanwhile, by the simulation experiment based on dynamic network scenario,it also point out the deficiency of 802.11e protocol.(3) It lists current materials in the direction and summarize their characteristic.Then it provide a new algorithm based on adaptive contention window.And we implement the algorithm and AEDCF algorithm in NS2.By comparing the experiment result of the proposed algorithm,AEDCF algorithm and standard with the same network scenario,we can show our scheme feasibility and efficiency.(4) It classifies the up to date admission control algorithms. Then we give a simple admission control algorithm based on above the algorithm. Lastly,we present a admission control model in IEEE 802.11.