Study On Wireless Network Positioning Technology For High-speed Railway

With the development of mobile communication technologies, the position is becoming more and more important. Position can be got with Wireless network positioning technology, which includes Angle of Arrival positioning, Received Signal Strength positioning, cell-ID positioning, time of arrival positioning, time difference of arrival positioning, assisted-GPS positioning and so on. Long Term Evolution (LTE), as3.9G communication technology, improves the performance of cell edge user, increases the capacity, and decreases system delay. In LTE system, wireless positioning technology includes enhanced cell-ID positioning, observed time difference of arrival positioning, and assisted-GNSS positioning. At present, research of wireless positioning is usually on public network, but in high-speed railway, it is still in the initial stage. Railway communication system is now using GSM-R system, which is a2.5G system, and in the near future, LTE technology will be used for railway communication system.In this thesis, it is studied the wireless network positioning technology for high-speed railway user. Main content of this thesis is to research wireless network positioning technology on public network, especially in LTE. On the other hand, study OFDM and MIMO in LTE system. Also learn the structure of LTE downlink physical layer. Then research channel models and choose one which is similar with the high-speed railway environment to be used in simulation. On the basis of research and analysis, establish a TDOA positioning model with two base stations based on the special environment of railway, such as the base stations locates linearly along the railway, and the cell coverage is larger than that in public network, also train can only move along the fixed track. Then, MATLAB is used to set up LTE simulation system with D2a model of WINNER channel, which is a statistical model for high-speed railway environment. Through simulation, we obtain the accuracy of TDOA position scheme in high-speed railway under different conditions. Finally, a TDOA positioning method with more base stations is proposed, usually three base stations, to improve the accuracy of position in high-speed railway.