802.11 MAC protocol based QoS research
|School||Kunming University of Science and Technology|
|Course||Communication and Information System|
|Keywords||802.11e quality of service EDCA WME|
WLAN is the product of combination of computer network and wireless communication, which shucks people off the bondage of wire. After ten years of development, IEEE 802.11, derived from mature Ethernet, has distinguished itself from all kinds of WLAN standards and entered home, office, airport and other areas and become the wideband technology of "last one hundred meters".While enjoying the convenience of wireless, people also expect that WLAN may provide the same reliable service as LAN. At the same time, with the development of mobile communication, 3G traffic is evolving from traditional voice to Internet access and multimedia. As the efficient complement of 3G, WLAN must suit for the demand of safe authentication, roam and QoS and so on aspects.Because of our life, study and work are more and more relying on WLAN, the research of QoS based on IEEE 802.11 has extensively applied value. This thesis modeled the EDCA mechanism of 802.11e standard approved last year. Analyzed the throughput by mathematic means and created a delay analytical model and designed a set of systemic parameter.In chapter one, multi-access technique is narrated and random competing multi-access protocol’s history and four progressive directions was introduced, emphasis was focused on the research background based on 802.11 media access control layer and the advantage of WLAN. In the last, the applied foreground of the research was illuminated.In chapter two, IEEE802.11 documental series were consulted. Firstly, introduction of main standards of IEEE802.11 series were simply presented and some main technology of physical layer were mentioned. After the introduction of common network frame of IEEE 802.11, detail description of DCF and PCF mechanism was presented and assisted with picture.In chapter three, the draft 9.0 of IEEE802.11e was consulted. The shortcoming of 802.11 MAC layer about QoS was introduced. And then, detail development process about 802.11e workgroup was presented and all kinds of recommendation wasmentioned. In this chapter, the most important presentation was EDCA mechanism of D3EE802.11e, and the introduction of HCCA was incidental. At last, the real applicative model——WME protocol was presented.In chapter four, the Markov chain model of EDCAF was constructed and Giuseppe Bianchi’s research work about saturated throughput formula was adopted, then simulation was made with 802.11b parameters. On the basis of the above, simple Markov chain model of EDCA mechanism was constructed. At last, Markov chain model of approximate EDCA mechanism was constructed.In chapter five, Markov chain model of backoff relay and Markov chain model of collided relay were constructed by author, and, by the means of simulation, important conclusion was that the relay brought by collision could be omitted. The author designed a set of systemic parameter showed in table 4-2 in chapter four. Then it was experimented in simple EDCA mechanism and approximate WME (EDCA) mechanism and the result of simulation showed that the given parameter set contented the realtime demand of audio and video frequency.In chapter six, the summary of this thesis was made. Not only the research production was discussed, but also the problem lied in this thesis was pointed out. At last, the author narrated the experience of research and the direction of further reaserch.