列车高速运动过程中多普勒频偏及误码率分析

Analysis on the Doppler Frequency Offset and Error Rate during the High-speed Running of Train

在列车高速行驶过程中,由于多普勒效应的影响,会对数据传输过程中的误码率产生影响。本文从单基站、多基站情况下列车直行过程中的多普勒频移分析到曲线行驶过程中的频移分析,推导出具体的定量频移公式,获得行车过程中的频偏变化规律,可用于无线通信多普勒频偏的矫正。在不考虑气候、地形等因素条件下,构建GSM-R网络无线信道传输误码率仿真模型,利用matlab的simulink工具箱对高速列车行驶过程中数据传输误码率变化进行仿真。发现靠近基站时,多普勒频偏值会减小,误码率呈振荡减小的趋势。该趋势得到武广线实测数据的支持,而且通过对比基站与钢轨距离不同时的情况,得出基站距钢轨越远,低误码率区越大的结论,为基站选址提供了依据。

Due to the impact of Doppler effect, the Error rate produced in the data transmitting process will be influenced when a train runs on high-speed railway lines. By means of analysing the Doppler frequency offset at single base station and multiple base stations in traffic from straight lines to curves,we deduced the formula of Doppler frequency offset and obtained the changing law of frequency shifts when the train was running. That can be applied in the correction of Doppler Frequency offset in wireless communication. In addition, taking no account of other factors such as weather and geography,we built a simulating model of data-transmitting error rates of the GSM-R wireless network . By using the simulink tool-box belonging to matlab,we discovered that the Doppler frequency was decreasing gradually and the error rate was oscillating in a descending tendency when the train was running closer and closer to the base station. The descending trend was supported by measured data of the Guangzhou-Wuhan Railway. By comparing the different distancs between the base station and rail, we got to know that the longer the distance, the larger the low error rate area. That provides basis for site selection of base stations.