Research On Synchronization Algorithms In OFDM System

Orthogonal Frequeney Division MultiPlexing(OFDM)is the key technique of the fourth generation mobile communieation,it is regarded as one of the best transmission method in the future wireless broadband communication.It solves the problems of multipath fading channel and bandwidth efficiency well.Timing synchronization and frequency synchronization are the key effects which influence the performance of OFDM system. This paper introduces the synchronization algorithms in OFDM system thoroughly and comprehensively.In this thesis,the OFDM features and its principle are analysised firstly in brief,then Analysis the effeets of frequeney offset and timing offset in OFDM system,and in-depth researeh on symbol timing synchronization and frequeney synchronization algorithms of OFDM system. The typical timing synchronization and frequency synchronization algorithms based on training sequence and cyclic prefix are detailed and compared,some improved algorithms based on cyclic prefix are also presented. The improved timing algorithms uses autocorrelation ,so timing recovery of the proposed is robust to carrier frequency offset and multipath.Simulations results illustrate The improved timing algorithms have a peak, overcome the shortcomings of the phantom which result in ambiguity of timing estimation and multi-peak would occur in the shortcomings of the conventional method. The improved frequeney algorithm uses the training sequence which are used for timing recovery. The repeating of reference symbol in training symbols extend the rang of frequency estimation. As the improved algorithm is executed in time domain, the carrier frequency acquisition can be fasted. Simulations show the improved frequeney algorithm could reaeh smaller MSE.