Application Research On Timing And Frequency Synchronization Technology In OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technology, which improves the spectrum utilization and can greatly increase the system capacity, is becoming the core of next generation mobile communication technology. However, there are well-known shortcomings of OFDM technology: the timing offset and frequency offset is very sensitive. Timing offset causes inter-symbol interference, and frequency offset would destroy the orthogonality between subcarriers, causing ICI, which lead to a sharp decline in overall system performance. Therefore, it is necessary to research the effective timing synchronization algorithm and frequency synchronization algorithm to estimate and compensate for timing offset and frequency offset effectively, and try to minimize the negative impact on system performance. Therefore, research of this topic is necessary, and this paper is of great important academic value and practical significance.Firstly, the academic research value, the practical significance, the OFDM synchronization technology and the recent status were analyzed, and the basic principle of the OFDM system and synchronization were briefly introduced, And then the influence to the system performance of the symbol timing offset, carrier frequency offset and the sampling timing offset was analyzed in detail, at last, simulated and analyzed use computer to show the importance of the synchronization for OFDM systems.Secondly, the timing synchronization algorithm for OFDM systems and frequency synchronization algorithm were researched. After reading a lot of literature and analyzing the research on the current situation at home and abroad, this paper selects the data-aided algorithm class representative Schmidl&Cox algorithm and the Minn&Letaief algorithm to research. And then this paper studied the training symbol based on the improved timing synchronization algorithm, which adopts the relevant treatment methods. and can achieve accurate symbol synchronization compared with the previous algorithm. The simulation results demonstrate that the improved algorithm improves blurred phenomenon in the Schmidl&Cox timing estimation, greatly improves the precision of time estimation.Finally, improved frequency synchronization algorithm based on training signs is studied. By improving the function of frequency offset sentence and the structure of training symbols, the improved frequency synchronization algorithm improves the frequency offset estimation accuracy, and reduces the calculation cost. The simulation result shows that the frequency synchronization algorithm is of higher precision and of lower bit error rate under the same conditions compared with the Schmidl&Cox frequency synchronization algorithm. So, the improved algorithm can improve system performance.