Research Of Data-aided OFDM System Synchronization Algorithm

Orthogonal frequency-division multiplexing (OFDM) is a kind of multi-carrier digital modulation technology. It has many advantages, such as anti-jamming and anti-multipath capability, high utilization of the spectrum and so on. For these advantages, it is used in the fourth generation mobile communication systems with other technologies. But the disadvantage of OFDM is that this system is very sensitive to timing synchronization error and carrier frequency offset. Timing synchronization error can make phase rotate, and carrier frequency offset can destroy the orthogonality of subcarriers, and the system performance can rapidly deteriorate. So the accurate timing and frequency synchronization plays an important role in promoting the property of OFDM system.This article studies data-aided OFDM system synchronization algorithms, and mainly studies the optimization method of symbol timing synchronization and carrier frequency synchronization. Firstly this article introduces the domestic and international research status of OFDM synchronization technology, the principle and system model of OFDM, the principle and processing procedure of synchronization. Then it analyses the influence of symbol timing error and carrier frequency offset to OFDM system in detail.For another, this article further studies synchronization algorithms based on PN sequence, and analyses Schmidl & Cox algorithm and Minn algorithm of them. In allusion to the plateau phenomenon of Schmidl & Cox algorithm and the biggish correlation peak in Minn algorithm, this article presents a kind of timing and frequency joint synchronization algorithm. The improved project brings pseudo random weighting factor in redesigning training symbol, and then presents the corresponding timing metric used of autocorrelation of pseudo random sequence and mirror symmetry structure of training symbol, and proceeds symbol timing synchronization and implements carrier frequency synchronization. Through the experiment simulation in AWGN channel and multi-path Rayleigh fading channel, and the comparison with Schmidl & Cox algorithm and Minn algorithm, this article proves the superiority of the improved algorithm.At last, based on the analysis of CAZAC sequence characters and Park synchronization algorithm, this article presents the Park synchronization algorithm based on CAZAC sequence. And in allusion to the disadvantage that the timing measurement curve emerges correlation peaks in improved Park algorithm, this article also presents a kind of timing synchronization algorithm based on CAZAC sequence. Through the experiment simulation under different cyclic prefix lengths, this article compares and proves the advantage that the improved algorithm enhances the timing accuracy effectively.