The Research Of Timing And Frequency Synchronization Technology In LTE-A

In recent years, the LTE-A technology is widely researched around the world, as the subsequent evolution of LTE, LTE-A has superior performance, it has higher data transmission rates, higher spectrum efficiency and system throughput. It supports flexible spectrum bandwidth configuration and has great research value. In the global commercial LTE-A technology and at the same time, China’s high speed railway has been growing rapidly, and the number of mobile users is increasing, too. So, people have higher requirements with the application of mobile communication in high speed environment.In LTE-A system, before the UE is dispatched, the first thing is to complete the uplink time synchronization process, and then, the uplink data can be transmitted. During the transmission, the system should ensure proper frequency offset estimation and correction of the received signal, thus to ensure the accuracy of the data transmission. Under the environment of high speed railway, due to the high speed of the train, there is great Doppler frequency shift and time offset between the terminal and the base station, which will seriously affect the performance of the receiver system. Therefore, uplink synchronization technology under high speed scenarios is of great research significance.Combined with the actual research project and on the basis of studying uplink physical layer key technology in LTE-A, LTE-A uplink PUSCH synchronization procedure simulation platform is built, the work includes:(1) Studying the LTE-A system performance index and the key techniques in the uplink, researching and designing the PUSCH transmitter and receiver scheme. Compared to LTE system, adding multi-carrier aggregation technology in LTE-A, simulation shows that the multi-carrier aggregation technology can aggregate several LTE bandwidth into100M. thus meeting the demand of LTE-A peak rate and can also be compatible with LTE.(2) Analyzing the characteristics of the environment of high speed channel. setting up a high speed channel model, and simulating the difference between common channel and the high speed channel.(3) The frequency offset estimation technology are studied in high speed scenarios, analyzing the defects and advantages of the existent time synchronization technique in high speed scenarios. By jointing DFT channel estimation techniques and DMRS estimation technology, an improved time offset estimation algorithm that is suitable for the high speed scenarios is proposed. We carry out simulation to improve the effectiveness and the reliability of the algorithm under high speed scenario.(4) Researching frequency offset estimation techniques in the high speed scenarios. Through combining the CP and the DMRS frequency estimation techniques, an improved algorithm against the scenes of Doppler shift frequency deviation estimation techniques is proposed. Simulation shows that the algorithm has a larger estimation range, can be effectively used in high speed environment against the Doppler frequency.