Blind Carrier Frequency Offset Estimation for OFDM Systems with Constant Modulus Constellations

This paper proposes a blind carrier frequency offset (CFO) estimation scheme for OFDM systems. In the proposed scheme, the covariance matrix of the received signal is obtained through the circular shifts of OFDM blocks in the time-domain. From the fact that the covariance matrix has a banded structure in the absence of CFO, we estimate CFO through minimizing the powers of the elements that are outside the band. We show that the proposed scheme is better than the conventional schemes through simulations.

I. Introduction

Orthogonal frequency division multiplexing (OFDM) systems are very sensitive to carrier frequency offset (CFO), which results in inter-carrier interference (ICI) and deterioration of performance [1]. Therefore, the estimation and compensation of CFO have to be performed prior the fast Fourier transform (FFT). To preserve the bandwidth efficiency, blind CFO estimation schemes have been proposed for the continuous transmission systems such as DVB and DVB [2]. In [2], the kurtosis-type cost function is proposed by exploiting non-gaussianity of the received signal. Likewise, the variance scheme to exploit the interference between subcarriers is used to set up the cost function, which is the same as the kurtosis-type cost function [3]. To overcome the drawback of the kurtosis-type cost function in multi-path channels, the spectrum-smoothing (SPS) scheme which uses similarity of the frequency response between two adjacent subcarriers has been proposed [4], [5]. In [6], the powers of the non-diagonal elements are used as the cost function based on the diagonality criterion. However, the scheme in [6] requires a large number of OFDM blocks and the schemes in [4], [5] suffer from performance degradation in severe frequency selective channels.