Non-Data Aided EM-Based Channel Estimation for OFDM Systems with Time-Varying Fading Channels
In this paper, a computationally efficient algorithm is presented for maximum a posteriori (MAP) channel estimation for OFDM systems employing M-PSK modulation scheme with additive Gaussian noise, based on the Expectation Maximization (EM) method. A non-data-aided scheme is considered for the estimation of a multipath time-varying channel by averaging over the M-PSK signal constellation. For this, an EM algorithm is derived which estimates the complex channel parameters of each subcarriers iteratively in frequency domain and which converges to the true MAP estimation of the unknown channel. The algorithm requires a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve orthogonal expansion. The algorithm is applied to the QPSK modulated OFDM systems and efficiency of the method proposed is shown by the computer simulations.
KeywordsFading Channel Channel Estimation Channel State Information ExpectatIon MaXI1111zatlon Algorithm Pilot Symbol
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- R. Van Nee and R. Prasad, OFDM Wireless Multimedia Communications’, in Artech House Publishers, 2000.Google Scholar
- J.-J. van de Beek, O. Edfors, M. Sandell, S.K. Wilson, and P.O. Borjesson, “On channel estimation in OFDM systems”, Proc 45.th IEEE Vehicular Technology Conf(VTC’96), Atlanta, GA, April 1996.Google Scholar
- M. Siala and D. Dupontiel, “Maximum A Posteriori Multipath Fading Channel Estimation for CDMA Systems”, Proc IEEE Vehicular Technology Conference (VTC’99), 1999.Google Scholar
- A. T. Huq, Panayirci and C.N. Geoghiades, “Non-data-aided ML carrier frequency and phase synchronization in OFDM systems”, European Transactions on Telecommunications (ETT), vol. 12, no. 2, pp. 83–94, March-April 2001.Google Scholar
- E. Panaylrcl and C. N. Georghiades, “Carrier phase synchronization of OFDM systems over frequency selective channels via EM algorithm”, Proc. IEEE Vehicular Technology Conference (VTC99), May 16–20, 1999, Houston, Texas, USA.Google Scholar
- R. Steele, Mobile Radio Communications, New York, IEEE Press, 1974.Google Scholar
- W.C. Jakes, Jr., Ed., Microwave Mobile Communications, NewYork: Wiley, 1974.Google Scholar