Research On Time And Frequency Synchronization Algorithm Of LTE In The Urban Railway Environment

In 2006,the Qinghai-Tibet railway firstly has applied transport based on GSM-R(Global System Mobile for Railway)system to realize train control information transmission between train and ground in our country,but it only possesses 4 MHz frequency bandwidth.In 2014,at the meeting of Chinese wireless technology and application,Ma Fang said that GSM-R is considered as narrow communication system which is difficult to adapt the transportation of railway information and next generation railway wireless system will evolve directly from GSM-R system to 4G LTE-R(Long Term Evolution-Railway).OFDM(Orthogonal Frequency Division Multi-plexing)transportation technology was applied to LTE-R system.With the increase of training speed,multi-path delay and Doppler Effect have great influence on the performance of railway wireless communication system which will seriously affect the railway traffic safety and transport efficiency.Therefore,it is of great significance for railway wireless communication system to study the symbol timing synchronization and carrier frequency synchronization of OFDM system.Training symbol completing OFDM system's time and frequency synchronization algorithms are analysed in the thesis.OFDM system's time and frequency synchronization algorithms by classic structure of training symbol are analysed and studied,the structure of training symbol is improved and time and frequency synchronization is put,which will combine symbol timing synchronization with carrier frequency synchronization in order to achieve accurately OFDM system's time and frequency synchronization.Firstly,OFDM system theory and wireless communication theory is studied and symbol timing synchronization error and carrier frequency synchronization error is analysed,which will cause what kind of influence for OFDM system.Training symbols are proposed to complete symbol timing synchronization and decimal times carrier frequency offset of subcarrier interval in the time domain and integral times carrier frequency offset of subcarrier interval in the frequency domain,in order to reduce effectively the error of symbol frequency synchronization and carrier frequency synchronization.Then,various typical training symbols of completing OFDM system's symbol timing synchronization algorithm are analysed and all kinds of symbol timing synchronization are compared.On typical training symbol basis,the better relevant training order for searching for the location of FFT window is structured.Various symbol timing synchronization of OFDM system are tested and verified in AWGN communication route and under the multi-path Rayleigh channel in the urban railway environment.Finally,various typical training symbols of completing OFDM system's carrier frequency synchronization algorithm are analysed.Frequency estimation and compensation of decimal times sub-carrier interval is estimated in the time domains.Frequency estimation and compensation of integral times sub-carrier interval is estimated in the frequency domains.Various kinds of carrier frequency synchronization algorithms of OFDM system are tested and verified.Various carrier frequency synchronization of OFDM system are tested and verified in AWGN communication route and under the multi-path Rayleigh channel in the urban railway environment.