Research Of QoS In Subway Mobile Wireless Local Area Network System

The network access isn't limited by physics circuit any more for the technology of wireless LAN. The embedded technology makes the communication device become more microminiaturized with lower power consume and stronger function. The subway wireless WLAN system researched in this paper is precisely an integrated application model of the wireless LAN and the embedded technology.Quality of Service is one of the most important skills of WLAN. It is an important and hot problem to make QoS suits multi-operation that WLAN can be advance. The subject matter of this thesis is to improve the thuoughput and decrease the handoff dalay of the Subway Mobile WLAN System.There are four processes to research the QoS of Subway Mobile WLAN System. First of all, analyse the states of current Subway Mobile WLAN System by several test data to get the limitation of thuoughput and handoff, and get the reasons. The second, optimizing the data receiving process of wireless device driver to resolve the data loss which can promote the thuoughput distinctly. Third, a solution of MAC layer and network layer handoff is produced according the characters of the Subway Mobile WLAN System. Arithmetic of determining a time to trigger the handoff is developed and a threshold value of signal strength is determined by the mobile node's speed and angle and the handoff time. Contraposing the stable position of AP and simple line of mobile node, a method of hiting dynamic handoff queue to determine NAP is carried out to decrease handoff delay. At last test the result of solution with full-scale methods. The test results indicate that the solutions of thesis have good promotions to the QoS of Subway Mobile WLAN System.