Research On OFDM Synchronization Algorithm Based On Training Sequence And FPGA Implementation

Orthogonal Frequency Division Multiplexing (OFDM) technology is the main technology for the the fourth generation communication system, with a high spectrum efficiency and strong resistance to the multipath fading. As a multi-carrier modulation technique, OFDM is very sensitive to synchronization errors, so synchronization is a very important issue. This paper has a deep reasearch on OFDM synchronization technique based on the training sequence, and designs synchronization algorithm based on FPGA. The main research works are listed as follows:(1). For the frame synchronization, the timing metric function is improved based on Schmidl algorithm to improve timing accuracy of frame synchronization; The frame structure which is superimposed PN sequence in time-domain is researched, and a new timing metric function with weighted by PN correlation peaks is designed. This new method can eliminate the effects of vice-peak completely, and produce sharp correlation peaks. To improve transmission efficiency, this paper researches the synchronization algorithm based on Park frame structure, and the improved method of fractional frequency offset estimation is designed based on least squares to improve the accuracy of carrier frequecy deviation estimation. For the sampling synchronization, an improved sampling offset estimation algorithm is designed based on slow time-varying fading channel. The improved algorithm can reduce the computational complexity of the original algorithm.(2). For realizing the synchronized algorithm, this dissertation firstly researches various synchronizations using numeric principle, and improves the realization structure of matched filter. Moreover a new method to achieve least square method is designed using FIR structure. This method can make FPGA logic resources and computational rounding errors compatible. Then the implementation structures of synchronized algorithms are designed based on FPGA. At last, this paper apply simulation tools such as Matlab,ModelSim to verify the validity of algorithm implementation structure.