The Research Of OFDM Synchronization Technology In LTE Downlink

"For communication, the first synchronization", the synchronization plays a vital role in a communication system, and it’s the premise to restore the correct transmission signal. LTE adopts OFDM technology as its downlink transmission scheme, as a high-speed multi-carrier system, OFDM is very sensitive to frequency offset and timing error caused by the crystal frequency inconsistent and the Doppler effects. Which will introduce inter-symbol interference(ISI) and inter-carrier interference(ICI), destroy the orthogonal relationship between the subcarriers, thereby greatly reducing the system performance. So an accurate estimate and compensate for the frequency offset and timing error is needed. The main work of this paper is study the synchronization technology.Firstly, this paper analyzed the synchronization technology in OFDM system and the synchronization error’s impact on system performance. Then pay more attention to the synchronization algorithm in traditional OFDM system, Including the ML algorithm based on cyclic prefix and the algorithms based on training sequences, such as SC, Minn and Park. By analysis the simulation results, we found the performance of the Park algorithm is superior to SC algorithm and Minn algorithm.Secondly, combined the MIMO technology with the OFDM technology, focus on the synchronization algorithm in centralized and distributed MIMO-OFDM systems, and do a simulation to verify the performance of the distributed system.Finally, Take the LTE physical layer standards into consideration, learned the Primary synchronization signal and secondary synchronization signal’s generation methods. Focus main attention on the downlink synchronization algorithm in TD-LTE system, and improved the coarse timing synchronization algorithm and the coarse frequency offset estimation algorithm. Take the original algorithm and improved algorithm for simulation, the results show that the improved algorithm have a good performance.