Research Of QoS In Wlan MAC Layer

With the recent development of wireless technology and Internet, the requirementsof portable computers are fast increasing. And WLAN (Wireless Local Area Network)is used widely to meet these demands because of its high flexibility and robustness.There are many existing standards now, such as IEEE802.11, HiperLAN andBluetooth etc, but IEEE802.11 is most widely used. With the increasing demand ofquality, the ability of WLAN to support real-time traffic with stringent quality ofservice requirements has come into fore.In this thesis, author briefly introduces the overview of Wireless LAN, networkstructure, transmission means and characteristic, also gives out the series protocols ofthe wireless LAN. After that I major analyzed MAC layer mechanism of IEEE802.11in details --DCF medium random access protocol and IEEE802.11e MAC layermechanism --EDCA medium random access protocol, and analyzed the improvementin IEEE802.11e protocol for the request of users' service quality against IEEE802.11protocol. Based on this, author completes the module and innovation of the protocol.The main work: first author programs the mechanism of IEEE802.11e MAC layer--EDCA, and estimates performance of QoS in infrastructure network structure andAD HOC network structure;Secondly basing on the EDCA module, author putsforward a new mechanism --DDTA (Distribution of Dynamic Traffic Attribution,DDTA) to improve the capability of network. During the simulation, authorconfigures different parameters to simulate IEEE802.11 protocol and IEEE802.11eprotocol. After comparing the throughput, media access delay and competitionwindow etc in these protocols, we get the conclusion: IEEE802.11e uses differenttraffics with different priority level, for example, priority levels of voice and video arehigh while that of data is low, the traffic of high level will get a good QoSperformance with decreasing the quality of low level traffic to meet user's request onvoice and video effectively;also uses different parameters to simulate DDTA, theresults show the new mechanism can improve the QoS performance of voice, videoand data effectively and utilize wireless channel resources more effectively.Finally with our analysis we prospect the future of IEEE802.11e.