The Implementation And Performance Analysis Of IEEE802.11 Rate Adaptation Algorithms

Wireless mesh network, as a new type of access network technology, is developping quickly and has become the focus of research community in recent years because it has advantages such as flexible network architecture, mobility, and easy to deploy. At the same time, geometric growth rate of wireless multimedia network applications request wireless mesh network to have better performance. The current growth rate of network resources is slower than network applications, so a realistic solution is to improve the existing network performance sufficiently. Throughput is a main measure of network performance, and how to maximize network throughput performance is one of the problems which need to be solved in time.Studies show that choice of data transmission rate can influence network throughput performance, in other words, there is a best data transfer rate which can maximize network throughput performance. In IEEE802.11 serials, physical layer can support various data rate transmission, but the IEEE802.11 does not specify any schemes to efficiently utilize multiple transmission rates, so rate adaptation is in the spotlight.The thesis is organized as follows: Firstly, the existing study of rate adaptation algorithm is summarized. Secondly, physical layer protocol and MAC layer DCF mechanism in IEEE802.11 are researched, and relation between transmission rate and network throughput performance is confirmed, then the structure and characteristics of the wireless Mesh network are summarized. Thirdly, through analyzing main flow of classical rate adaptation algorithms, a new adaptation algorithms is proposed, which calculates the Frame Success Rate(FSR) for each rate and map the estimated FSR values to the transmission time using DCF Markov chain model, so a specified rate with the smallest transmission time is selected for next frame delivery. Fourthly, Mesh test-bed is constuctd and the novel rate control algorithm is implemented on madwifi driver of Mesh test-bed. Finally, through several real-world measurements under different test environments, experimental results demonstrate that novel rate adaptation algorithm outperforms three existing algorithms of Madwifi in the test.