Frequency Offset Estimation for OFDM in Frequency Selective Channel Using Repetitive Sequence

Yinsheng LIU  Zhenhui TAN  Bo AI  

IEICE TRANSACTIONS on Communications   Vol.E94-B   No.4   pp.1033-1042
Publication Date: 2011/04/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E94.B.1033
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
carrier frequency offset,  frequency selective channel,  maximum likelihood,  OFDM,  

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Repetitive synchronization sequences in the time domain can be used to estimate Carrier Frequency Offset (CFO). The Un-Guarded Maximum Likelihood (UGML) estimator and Guarded ML (GML) estimator of CFO in the frequency selective channel are proposed in this paper. The results of theoretical analysis show that the UGML estimator is hard to implement if the channel response is not known while the GML estimator can be easily implemented due to inserted guard sequences. The guard sequences can be easily implemented as Cyclic Prefix (CP) in OFDM system. Therefore, the UGML estimator is only suitable for the systems where the channel response can be predetermined. This paper also gives a comparison with the existing CFO estimator. Theoretical and simulation results show that both the proposed estimators outperform the existing estimator.