Maximum-Likelihood Estimator for Coarse Carrier Frequency Offset Estimation in OFDM Systems |
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| Authors: | Feng Yang Zhenrong Zhang Yifan Chen |
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| Affiliation: | (1) Research and Innovation Center, Alcatel Shanghai Bell Co., Ltd., Shanghai, People’s Republic of China;(2) School of Computer, Electronic and Information, Guangxi University, Guangxi, People’s Republic of China;(3) School of Engineering, University of Greenwich, Kent, UK |
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| Abstract: | Orthogonal frequency division multiplexing (OFDM) systems are more sensitive to carrier frequency offset (CFO) compared to
the conventional single carrier systems. CFO destroys the orthogonality among subcarriers, resulting in inter-carrier interference
(ICI) and degrading system performance. To mitigate the effect of the CFO, it has to be estimated and compensated before the
demodulation. The CFO can be divided into an integer part and a fractional part. In this paper, we investigate a maximum-likelihood
estimator (MLE) for estimating the integer part of the CFO in OFDM systems, which requires only one OFDM block as the pilot
symbols. To reduce the computational complexity of the MLE and improve the bandwidth efficiency, a suboptimum estimator (Sub
MLE) is studied. Based on the hypothesis testing method, a threshold Sub MLE (T-Sub MLE) is proposed to further reduce the
computational complexity. The performance analysis of the proposed T-Sub MLE is obtained and the analytical results match
the simulation results well. Numerical results show that the proposed estimators are effective and reliable in both additive
white Gaussian noise (AWGN) and frequency-selective fading channels in OFDM systems.
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| Keywords: | Carrier frequency offset (CFO) OFDM Coarse estimation Maximum-likelihood estimation |
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