Research And Implementation Of LTE Synchronizaton

In order to satisfy people's increasing demand for high data transfer rate, the 3rd Generation Partnership Project (3GPP) designed the Long Term Evolution (LTE) standard of universal mobile telecommunication system. LTE wound become the dominant technology of broadband mobile communication in the future. The multiple access technology of LTE is based on Orthogonal Frequency Division Multiplexing (OFDM). As a multi-carrier transmission technology, OFDM is very sensitive to time and frequency offset, so an accurate synchronization of OFDM system is very important.This paper mainly discusses the algorithm and procedure of LTE downlink and uplink synchronization, analyzes and simulates the cell search algorithm in LTE, and presents an implementation scheme based on multi-core DSP. Firstly, OFDM system model and the impact of time and frequency errors on the performance of OFDM system are summarized; two classical OFDM synchronization algorithms are reviewed, while is based on pilot symbols or CP respectively. Secondly, the properties of Zadoff-Chu sequences, which are widely used in LTE, are expounded; the design of LTE synchronization signals and Physical Random Access Channel (PRACH) are introduced; the basic principles of LTE downlink and uplink synchronization are studied, the procedures of cell search and random access are presented, and the PRACH detection method for uplink synchronization is discussed. Thirdly, the paper analyzes the cell search algorithm in detail and the performance is verified by simulation:the received signal is transferred to a low-pass filter and then down sampled; coarse timing synchronization information is acquired by computing the cross-correlation value of time domain PSS and the received signal; based on of the phase difference between the first half and the second half of the time domain received PSS, coarse frequency offset estimation could be calculated; after FFT operation to the received signal which has been compensated for frequency offset, a frequency domain channel estimation according to PSS is adopted, which is used to do SSS coherent detection in frequency domain. The simulation results show that this algorithm can be applied in real system.This paper also designs a cell search implementation scheme based on picoChip multi-core DSP:on basis of the introduction of chip structure, the parallel processing characteristics, data transmission pattern and the development flow of picoChip multi-core DSP, this paper presents the function division, data processing flow, hardware resources usage and port rate setting for each child module. The test results indicate this scheme can fulfill the function and time delay requirements of the system. This paper is significant to the research and implementation of LTE synchronization.