The Research Of Synchronization Techniques In Wireless OFDM Communication System

Synchronization technique is the premise to any communication systems to work effectively. The capability of synchronization directly affects the performance of the whole communication system, no exception for the wide band wireless communication based on OFDM. In recent years, LTE standard attracts great attentions of the people in the industry and academe fields, and it is necessary to do research on the algorithm for the LTE physical layer protocol in which downlink synchronization and cell search play important roles for LTE.This thesis puts forward an improved algorithm based on CAZAC sequence, as well as giving out a whole synchronization solution. Firstly, the properties of the CAZAC sequence are analyzed.Through simulation and theory analysis deduce the rules of frequency offset which affect the autocorrelation of CAZAC sequence. By constructing two training sequences, to make the rules can be illustrated on the timing offset, so that the frequency offset can be detected easily. At the same time, it reduces the computation of correlation. Finally, compared with Schmidl's algorithm, the results of simulation demonstrate that the algorithm has better performance.During the analysis of the synchronization channel in LTE, a feasible solution to LTE downlink synchronization and cell search is detailed. First of all, it detects the physical layer identity and timing synchronization under the aid of primary synchronization sequence, besides, it simplify the computation by taking advantage of the character of the primary synchronization sequence and adds the first path search algorithm in the solution. Then it correlatively detects the secondary synchronization sequence using channel estimation of primary synchronization sequence. And later, physical layer cell identity group search algorithm is introduced, the simulation are carried out to validate the performance of proposed algorithm in the AWGN. The algorithm of residual frequency estimation is detailed, and simulation results verify the proposal algorithm with good performances in both AWGN and multipath fading channel.At the last chapter, the output of the residual frequency estimation and that of the LTE channel estimation can be complete the frequency offset trace and timing trace, simulation shows the solution has its practical value. Finally, the mainly purpose and issue of this thesis are summarized, moreover, it points out potential problems in the future.