Hidden Station Detection In IEEE802.11Infrastructure Network

In recent years, the Local Area Networks (LAN) and wireless communication technology have got rapid development. WLAN is being favored by many people for its convenience, good mobility and better expansibility. With the expansion and improvement of IEEE802.11standards, WLAN has becoming more and more popular, especially for infrastructure network. At present, more and more cities provide wireless access service. People use PC, PDA and other wireless products to access traditional wired network resources through Access Point.However, the wireless LAN’s characteristic is bound to lead to some problems. These problems have a bad impact on the performance of wireless network, especially hidden stations. Hidden stations make the system potential collision probability increasing. The higher the probability of collision, the lower the system performance is. In order to overcome the adverse of hidden stations, IEEE802.11defines four handshake protocols, which is RTS/CTS exchange. Send the RTS and CTS control packets before data exchange to reduce conflict duration. However, the transmission of control packets will consume bandwidth resources. When there are no hidden stations, using four-way handshake protocol lower channel utilization instead of improving. When the existence of hidden stations, using the RTS/CTS protocol and when no hidden stations using basic protocol, it will help to improve the transmission efficiency of the wireless network system. Moreover, hidden stations will be inevitable in infrastructure network. Therefore, effectively detecting hidden stations has a great significance and practical value for improving the transmission efficiency of wireless network system.In order to solve the problems caused by hidden stations in WLAN, current detection algorithm using the length of idle time of channel after the station receiving a acknowledge frame to judge whether there are hidden stations. Through NS2simulation analysis of its performance in a variety of mobile environments and found that the using of the algorithm has its limitations that It applies to the static environment, but cannot provide good performance in a mobile environment. In order to be able to capture the hidden station changes in a mobile environment, according to the characteristics of basic network, based on the above algorithm, present hidden station dynamic detection algorithm, which is not only applicable to the static environment, and can be used in mobile environment. It is through NS2simulation software to verify its validity. The simulation results show that the proposed algorithm can obtain better performance in a variety of environments. On this basis, analyze some problems such as the movement of hidden stations in Extended Service Set, hidden stations being in power saving mode and hidden stations exiting from the network, which are faced by dynamic detection algorithm, and propose solutions.