Feasibility Analysis And Test Of WLAN In UMT Environment

With the high-speed development of economic, the traffic is more and more crowed, especially in the big cities; the need of traffic is go up quickly, the conflict of supply and need is protruding increasingly. Because of the city orbit traffic have many advantages, such as, passenger transport is generous, high-speed, safe, saving energy sources, less disturb and so on. The effect on relax the city traffic conflict is more and more in evidence.The CBTC (Communication based Train Control) adopt high precision train orientation and continuous, high, bidirectional data communications; via vehicle equipment and ground safe equipment achieve the control on train. It's not only reduce the investment of hardware equipment, but also can cut the traveling crane distance, increase the move speed and system safety on the old lines. The channel,in which the data is transferred in the CBTC system,is called DCS(Digital Communication System).DCS is the core part of CBTC. According to characteristic of the CBTC system, CBTC can make good use of city orbit traffic environment.WLAN (Wireless Local Area Network) is a local network which established by the use of wireless communications technology, is the result of combining the computer network and wireless communication technology, It make the users achieve broadband Internet access at anytimeand anywhere, WLAN is easy to build, expand, manage, maintenance, high mobility, keep seceret and the confidentiality of strong anti-interference, and other characteristics. Therefore, the study of Feasibility Analysis of WLAN in UMT Environment has very important significance.First of all, By introducing research background, paper expounded the requirements of wireless communications for DCS subsystems on CBTC system ,and summarized the historical development of WLAN for leading to the purpose and significance of the topics. Then we studied and analyzed the performance of WLAN, investigated the key characteristics and key technology of IEEE802.11b, a, g's standard physical layer. By using the result of the simulation in physical layer of 11g and 11b, as well as the CBTC system requirements for the wireless communication system, we analysed the feasibility of the usage of 11g and 11b in the urban rail transport enviroment. The simulation results showed that: the speed of the train had a certain influence on wireless communications systems, so IEEE802.11b and 11g can better support in the low-speed (under 90km/h) in the mobile access, and they meet the requirements of wireless communication system of CBTC.Then the paper studied the WLAN's requirements of CBTC DCS subsystem from the actual situation. After that, paper designed a wireless communication network based on DCS subsystem of WLAN's requirements and istablished an actual test project. And then three conditions of actual environment from open space, tunnel and waveguides are tested for wireless communication system. With the testing result, we think the WLAN can be used in urben railway transport enviroments.