The Wlan's Adaptive Access Technology Of The Embedded Mobile Station

The research status of Wireless LAN technology in the embedded system platform application was summarized, then the access mode of existing wireless LAN and the Traditional switch mechanism ware analyzed. Meanwhile, the framework of Wireless adaptive embedding technology, which possesses Network scanning against detective, adaptive access analysis, seamless switch function module and so on, was constructed in the ARM9 embedded processor platform. At last, the Processing and achievement of the Adaptive Access and seamless handover was put forward, and two kinds wireless LAN access improvement were proposed:At first, For the signal analysis of WLAN in moving state was most correlated with the signal intensity, the moving speed,the network coverage and the position features, based on the FFT signal attenuation detection algorithm, a variable step size LMS prediction algorithm was proposed. On one hand,the algorithm proposed can help to improve the method of analyzing the signal moving speed, so that the moving speed can be estimated more precisely, on the other hand, until the signal attenuation leads to the signal communication failures, it would switch the signal. The experimental results show that, the signal-to-noise ratio was increased and mean square error was reduced, and it shows the superiority and of the feasibility of the algorithm.Secondly, Comparing the advantages and disadvantages of several network-layer roaming handoff mechanisms, such as hard handoff mechanism, semi-soft handoff and so on.According to performance requirements of the network handoff in WLAN, using the variable step size LMS prediction algorithm, a new seamless handoff based on the prediction forwarding was proposed. The handoff delay and the packet loss rate of the new seamless handoff was emphatically analyzed. The experimental results indicate that seamless handoff based on the algorithm can decrease handoff delay and packet loss rate.At last, the principle and achievement of the adaptive access was introduced, the processing of the adaptive access and seamless handoff was analyzed, as well as the design model in ARM9 platform.