Research On LTE Wireless Positioning System In Multipath Environment

With the rapid growth of LTE and the demand for location services, the research of LTE wireless location system has been a hot research topic. Because of the low requirement of environment and the terminal, OTDOA positioning technology becomes the mainstream positioning technology in LTE positioning system. However Because of the environment of the mobile user terminal is often the multipath environment, the location signal is affected severely by the multi-path effect and NLOS. It is a huge challenge for LTE positioning system to overcome the multipath effect and NLOS interference. So it is very important to study and improve the performance of the LTE system in multipath environment.This paper first introduces the characteristics of LTE positioning system and summarizes the LTE positioning technology to provide theoretical knowledge for the research of LTE wireless location system, including its positioning protocol and positioning method, and then the main factors affecting the terminal positioning accuracy are studied. The next work is finding a feasible way to improve the accuracy of positioning On the basis of the previous research. Considering the multipath environment there may be the case of the main path is not the first arrive path, the positioning accuracy will be caused error if the first time delay is not accurately estimated. So, we start with improving the first arrive path delay estimation in multipath environment. Firstly study the multipath delay estimation algorithm of the traditional LTE positioning system terminal, and analyze its shortcomings. Then some classical TDOA localization algorithm is deduced, and the performance of the positioning algorithm is verified by simulation. At the last, take advantage of the channel estimation, using multipath channel impulse response contains the pulses of multipath, an improved algorithm for TOA estimation in multipath environment is proposed. Setting a search window, and then add up the power of the pulse in the window to forward search the delay of first arrive path, and then fixed the initial time delay estimation, and get more accurate time delay estimation, which can improve the accuracy of positioning.The improved algorithm in this paper simulated and compared with other algorithm by modeling multipath channel with MATLAB simulation. The result of simulation verifies the improved algorithm has a very high probability of detection for the first path delay when the first path energy is not the strongest, and practical application value to improve the positioning performance.