Research On Timing And Frequency Offset Estimation Algorithm In OFDM System

OFDM, a multi-carrier transmission solution, has been widely utilized in high-speed wireless data transmission systems such as wireless local area network (WLAN) due to its fairly strong anti-multipath delay capability and quite high utilization efficiency for frequency spectrum. It is also been regarded as the core technology for the fourth generation mobile communication technology.As a result of OFDM system's high sensitivity to synchronization difference, the existence of synchronization difference would greatly low down OFDM's working efficiency. Among synchronization difference, its time difference will lead to inter-symbol interference, while its frequency difference would lead to inter-channel interference, therefore, an accurate synchronization algorithm become an extremely important part in OFDM system.In this thesis, it firstly described the development process of OFDM technology, the research background and meaning for synchronization algorithm as well as the principal and feature for OFDM system; and then it analyzed the influence that time difference,frequency difference and sampling difference have in OFDM system, lastly, via simulation, it explained the signal to noise ratio loose condition while synchronization difference existed.In the following, this thesis paid much attention on the research and analysis of the four types of OFDM timing synchronization algorithms. Of the four types of algorithms, MLE algorithm is based on non-data-aided, while the S&C algorithm, Minn algorithm and Park algorithm are based on the data-aided method. Through abundant of simulation, this thesis analyzed the advantage and disadvantages for each algorithm. When refer to the peak plateau-like effect for S&C algorithm, it simulated a windowing S&C algorithm that can effectively eliminate the peak plateau-like effect of S&C algorithm.In the following, it made an improvement for Park algorithm based on the idea that to increase the complexity but not change the structure for the training symbol. In the meantime, it also made the synchronization algorithm possess stronger pertinence. It was also proved through simulation analysis that the improved algorithm has only a single peak value, thus overcame the demerits of S&C algorithm, Minn algorithm and Park algorithm, which therefore improved the timing precision.In the last, this thesis mainly researched and analyzed the OFDM frequency synchronization algorithm. It firstly analyzed the basic theory for data assistance based frequency synchronization algorithm, including Moose algorithm, S&C algorithm and M&M algorithm. Then researched the non date assistance based algorithm:MLE frequency synchronization algorithm. Basing on theory analysis, it made quite a few simulations for those three frequency synchronization algorithm and compared their advantages and disadvantages.