| Recently indoor wireless broadband accessing has been an importantmethod of accessing network. Future wireless communication systems are expected to provide convenient broadband services for different customers using the minimum possible resources (power, complexity). Toward this trend, an appropriate transmission and medium access technique that matches the indoor wireless multipath channel characteristics is required. IEEE 802.11b based wireless LAN is one of the promising techniques that meet such requirements with reasonable complexity, and its medium access technique provides a fine supporting platform for data services of upper layers. Wireless LAN has recently achieved much popularity due to its desirable properties, such as its high data rate transmission capability, its robustness to multipath fading, and so on.However, there are many key problems of a wireless LAN system and solutions of these problems must be available before the system can be used in future wireless communications system as a promising and practical technique, such as the wireless network QoS (quality of service). This thesis mainly aims at obta-ining a better QoS performance in a wireless network based on the IEEE 802.11b standard, by reconfiguring its back-off algorithm.Following a brief discussion of the background, key techniques and trends of wireless LAN in the first chapter, as well as some basic knowledge about W-LAN QoS, detailed discuss on binary exponential backoff is carried out in the n-ext part, and a certain modified algorithm will be brought forward. At the end of this paper a simulation will be made to testify whether the modified backoff algorithm has the better performance than before. |
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