Researches Of Rate Adaptation Technology In Wireless Local Area Networks

With the development of wireless communication technology, WLAN (Wireless Local Area Network) has been widely used because of its access flexibility, low cost, wide coverage, easy to extend etc. So far, the optimization of the throughput of the WLAN has attracted more and more attention in academic circles. On the one hand, according to characteristics of wireless channel at the time, frequency and space, adaptive transmission links can adjust the transmission parameters adaptively to ensure the accuracy of the received information. On the other hand, WLAN can not only meet the Qos requirements of different business, but also improve the average bandwidth utilization and transmission rate to increase the system capacity.Rate adaptation is one way to achieve adaptive transmission links. The estimation of channel quality and the selection of transmission rate are important parts of the rate adaptation. In the thesis, rate adaptation using adaptive modulation coding in WLAN is studied and the existing problems are solved by analyzing and comparing the performances of open-loop rate adaptive algorithm with that of the closed-loop.The contents of the thesis are as follows:1,WLAN based on the IEEE802.11 is researched. The basic principles and method of rate adaptation in transmission link adaptation are elaborated and the effect of different rate selection strategy on the throughput of system is analyzed in detail.2,The characteristics of closed-loop algorithm is summarized by analyzing the performance and technical features of typical closed-loop rate adaptation algorithm, such as RBAR,OAR, etc.3,The characteristics of open-loop algorithm is summarized by analyzing the performance and technical features of typical open-loop rate adaptation algorithm, such as ARF,ARE series and RRAA, etc.4,An anti-jitter EN-CARA algorithm is proposed by analyzing the effect of hidden terminal on the throughput of WLAN and improving the CARA algorithm. The algorithm using hidden terminal detection mechanism can avoid the RTS oscillating effect, reduce the probability of collision effectively, and improve system performance. The CARA algorithm and new algorithm are analyzed in the randomly generated topology. Simulation results show that the new algorithm performs well...