Subframes Discrimination and Time Synchronization Methods in LTE-V2X System

L TE- V2X system is developed based on L TE system and their synchronization methods are similar. In this paper, the content of physical layer of L TE sidelink system is analyzed. Based on the characteristics of channels and symbols, a method to identify subframe types by symbol periodicity is proposed, which can effectively distinguish data frames from broadcast frames. On the basis of traditional L TE synchronization algorithms, two new synchronization algorithms are proposed for L TE sidelink system. One is subframe synchronization method based on cyclic prefix autocorrelation and the other is PSSS synchronization method for sidelink broadcast frames. The simulation results show that the synchronization performance of the subframe synchronization algorithm, which integrates multiple symbols' correlation results, is significantly better than that of the traditional auto-correlation algorithm. The synchronization miss detected ratio is reduced to 0% when SNR is more than 4dB, which is barely affected by frequency offset. PSSS synchronization algorithm is applied to broadcast frames and its synchronization RMSE value is only 0.1 % of the subframe synchronization algorithm, when the SNR is less than 2dB. Even under the influence of frequency offset, the miss detected ratio of this algorithm is 50% lower than that of subframe synchronization algorithm.