Maximum-Likelihood Estimator for Coarse Carrier Frequency Offset Estimation in OFDM Systems
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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.
KeywordsCarrier frequency offset (CFO) OFDM Coarse estimation Maximum-likelihood estimation
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- 1.Standard, E. T. (1994). Radio broadcast systems; digital audio broadcasting (DAB) to mobile, portable, and fixed receivers. preETS 300 401, Tech. Rep., March 1994.Google Scholar
- 3.IEEE Std. 802.11a. (1999). Wireless LAN medium access control (MAC) and physical layer (PHY) specifications: High-speed physical layer extension in the 5-GHz band. IEEE, 1999.Google Scholar
- 4.Khun-Jush, J., Schramm, P., Wachsmann, U., & Wenger, F. (1999). Structure and performance of the HIPERLAN/2 physical layer. In Proceedings of Vehicular Technology Conference (Vol. 5, pp. 2667–2671). Amsterdam, The Netherlands.Google Scholar
- 13.Nogami, H., & Nagashima, T. (1995). A frequency and timing period acquisition technique for OFDM systems. PIMRC ’95, (pp. 1010–1015). Toronto.Google Scholar
- 16.Kay, S. M. (1998). Fundamentals of statistical signal processing, detection theory, (Vol. II). Prentice Hall.Google Scholar