Blind Carrier Frequency Offset Estimators Based on Variance for OFDM Systems

Carrier frequency offset (CFO) estimation is critical in practical orthogonal frequency-division multiplexing (OFDM) systems. In this paper, we propose two novel blind CFO estimators named the variance estimator (VE) and the approximate variance estimator (AVE) respectively with high bandwidth efficiency. Both of them are based on minimization of the variance of the received symbols on each subcarrier, but the AVE only utilizes a half of OFDM symbols needed in the VE at the cost of a little degradation in performance. Simulation results show that the proposed estimators are attractively efficient for the future wireless communications.

I. Introduction

Orthogonal frequency-division multiplexing (OFDM) has been widely used in various communication systems, such as the asymmetric digital subscriber line (ADSL), the digital audio broadcasting (DAB), the terrestrial digital video broadcasting (DVB-T), and the wireless local area networks (WLANs). Now, OFDM is considered as a highly recommendable candidate for future communications. However, OFDM is extremely sensitive to the carrier frequency offset (CFO), which is caused by Doppler shift or the mismatch of the oscillators in the transmitter and the receiver. CFO destroys the orthogonality among subcarriers and results in significant performance degradation. Therefore, CFO estimation is of critical importance in OFDM systems.