Joint Estimation of Carrier Frequency Offset and Channel and Symbol Timing for OFDM

Shaopeng WANG  Shihua ZHU  Yi LI  

IEICE TRANSACTIONS on Communications   Vol.E92-B   No.6   pp.2247-2250
Publication Date: 2009/06/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.2247
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Transmission Systems and Transmission Equipment for Communications
OFDM,  carrier frequency synchronization,  timing,  channel,  iteration,  

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A method that jointly estimates the carrier frequency offset (CFO), channel and symbol timing for orthogonal frequency division multiplexing (OFDM) is proposed in this letter. Based on the characteristic of cyclic training symbols in the frequency domain, the joint estimation is divided into three separate estimations. The CFO and equivalent channel impulse response (CIR) are first estimated by an iterative joint maximum likelihood estimation (JMLE), then the symbol timing offset (STO) is obtained by the assistance of equivalent CIR, finally the CIR is calculated based on the equivalent CIR after known STO and CFO. In our proposed method, the effect of imperfect CIR is considered in the CFO estimator. Moveover, a procedure, which eliminates the inverse operation of a covariance matrix at each iterative process, was adopted to reduce the complexity of our proposed method. Simulations show that the proposed method is capable of retaining the same bit error rate as joint CFO and CIR maximum likelihood estimation without symbol timing error.