Research On QoS Support Of IEEE 802.11e

The IEEE 802.11e, established by the Task Group E of IEEE 802.11, was issued in October 2005. Supporting local area network applications with quality of service (QoS) requirements, including the transport of voice, audio, and video over IEEE 802.11 wireless local area network (WLAN) is the purpose of IEEE 802.11e. It introduces a new coordination function, called Hybrid Coordination Function (HCF). HCF contains two access mechanisms: the Enhanced Distributed Channel Access (EDCA) and Hybrid Coordination Function Controlled Channel Access (HCCA). After discussing the limitation of the IEEE 802.11 medium access control (MAC), the author gives a comprehensive study of the two access mechanisms of the HCF.First, the thesis researches the characteristic of the EDCA, and the difference between the Distributed Channel Access Function (DCF) and the EDCA. The author presents his development of a four-dimension discrete time Markov chain. The author analyzes mean delay, throughput and drop performance under saturation condition of EDCA. By comparing the result of the calculation with the result of the simulation, the author validates the correctness of the calculation and the QoS support ability of EDCA. This analytical method is a good method for engineering to analyze the ability of wireless network.Second, the author describes the framework for QoS traffic scheduling of the HCCA. The features and functionality of the Simple Scheduler, which is presented in IEEE 802.11e is studied in details. In order to improve the performance of the HCCA scheduler, the author proposes a new scheduler which can achieve more flexible and efficient resource allocation.Third, the New Scheduler is realized using Network Simulator 2. The author analyzes the simulation result of the Simple Scheduler and the New Scheduler.