Frequency Synchronization Technique Using Replica Created by Mutual Correlation Value for Classifying the Weight in Autocorrelation Operation

摘要

In an orthogonal frequency-division multiplexing (OFDM) system, a method based on the autocorrelation of two consecutive known symbols is proposed in order to estimate the frequency offset. In this system, the autocorrelation is calculated for all samples in a symbol. When the products of samples are summed and averaged, the product of each sample is weighted by the absolute amplitude of the received sample. Consequently, a sample which exhibits large received absolute amplitude due to the effect of noise is given a large weight. Since the product of samples given a large weight has a large effect on the estimation, it may degrade the estimation accuracy. Based on this idea, this paper proposes a method of reducing the effect of noise in frequency offset estimation, in which a replica constructed on the basis of information concerning the arrival time, the power, and the phase rotation of each path contained in the cross-correlation is used to determine the weights used in the calculation of the autocorrelation. It is shown by computer simulation that the proposed method can improve the accuracy of frequency offset estimation in the region where the carrier-to-noise ratio (CNR) is low.