| With the rapid development of commercial computer networks, more and more researchers have been studying on computer networks'Quality of Service (QoS). The wireless LAN was the combination product of computer network and wireless communication technology in the 1990's. It provided the access to network via wireless channel, thus it could be a potential method for the future telecommunication: mobility, personality and multimedia application, it also came to be an efficient broad-band wireless access mechanism. Researching on QoS based on IEEE802.11 MAC layer has become a very active field in recent years.As a convenient communication method, distributed wireless LAN (DWLAN) became more and more popular by the virtue of its inherent advantages on flexible and rapid networking. The main task of medium access control (MAC) protocol is to efficiently share limited wireless channel among distributed stations. Conventional MAC mechanism can hardly provide good performance in a complex environment of distributed networks. Based on fairness performance analysis of 802.11DCF protocol, this dissertation focuses on fairness performance of MAC technologies for DWLAN.At the basis of any access to the channel in IEEE802.11 is the so-called distributed coordination function (DCF) which adoptes BEB algorithm. DCF has an advantage in increasing the network throughput, but it can bring unfairness among different nodes. In short, when there are N network nodes competing with each other, the backoff algorithm adopted by IEEE802.11 tries to adjust the channel access attempt probability of each node such that it approaches the optimal (theoretical) success probability of 1/N, within the shortest possible time interval, thus effectively achieving very high throughput. When the traffic load is... |
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