A pilot-based fast algorithm for joint estimation of frequency offset and channel in OFDM

Efficient estimations of the carrier frequency offset (CFO) and channel are vital to orthogonal frequency division multiplexing (OFDM). In this paper, a new fast algorithm is proposed for estimating the CFO based on the pilot structure in [M. Morelli, U. Mengali, An improved frequency offset estimator for OFDM applications, IEEE Commun. Lett. 3(3) (1999) 75-77; H.K. Song, Y.H. You, J.H. Paik, Y.S. Cho, Frequency-offset synchronization and channel estimation for OFDM-based transmission, IEEE Commun. Lett. 4(3) (2000) 95-97]. The new method first identifies a coarse estimation of the CFO and then refines it by a least square (LS) method. It always gives a more accurate estimation than the multistage method in [H.K. Song, Y.H. You, J.H. Paik, Y.S. Cho, Frequency-offset synchronization and channel estimation for OFDM-based transmission, IEEE Commun. Lett. 4(3) (2000) 95-97] and is better than the method in [M. Morelli, U. Mengali, An improved frequency offset estimator for OFDM applications, IEEE Commun. Lett. 3(3) (1999) 75-77] at low SNR. It only slightly worse than the maximum likelihood estimator at high SNR. Furthermore, the proposed method can be used for CFO tracking. Also, in this paper, channel estimation by using the same pilot block is considered. The best values for the non-null subcarriers are found to optimize the channel estimation and peak to average power ratio (PAPR) simultaneously. Simulations demonstrate that the proposed methods are effective. (c) 2006 Elsevier B.V. All rights reserved.