The Research Of Frequency Offset Estimation And Channel Modeling Of LTE System In High Speed Railway Environment

The construction of China’s high speed railway is in a very high speed. According to theplan, by the end of2012,there will be5000km railway completed for the train at speeds of250km/h， and8000km railway completed for the train at speeds of350km/h. Comparedwith the traditional low-speed railway，in the highs-speed railway environment, there ishigher requirements for the wireless communication system. Wireless communicationtechnology plays a role in the railway system as follows:1) Tourists need mobilecommunication service in their trip. They want to make a phone, surf the internet and so on.2)The modern railway control system is based on the wireless communication system. Thewireless system transfers the control and dispatch signal which ensure the security of thehigh-speed train.At present the main railway communication system used in China is GSM-R(GlobalSystem Mobile for Railway). This digital system is based on the common GSMcommunication system, and designed some special function for the railway application.However it’s a trouble that GSM-R is based on a2G communication system, which meansthat it has very big deficiency to the latest3G/UMTS system. As the latest3G also has itsown problem like very high construction cost and less improvement in voice quality, the mostpopular research direction is evolution from2G GSM to4G LTE.Because the high-speed environment will cause serious Doppler Shift phenomenon,which will make neighbor symbols lose their orthogonality, and it will lead to serious ICI.This paper discuss the ICI’s effect under high-speed railway environment and its BER loss,we give a new receiver technology based on cyclic cumulant and it BER improvement curve.This paper also discusses the channel model under high-speed railway environment. Wemainly work on path loss and Multi-path modeling. To get suitable path loss for high-speedenvironment, we collect the data provided by ZTE company, and improve the parameters ofCOST and SCME model. As time delay parameters will not be fit for the high-speed railwaysystem, this paper will analyze performance of models from different international standardsto select the best models. Based on the analysis result. This paper will propose an improvedHST model and give its simulation curve.