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Joint Frequency Offset and Channel Estimation for OFDM Systems Using Pilot Symbols and Virtual Carriers

Cui, Tao and Tellambura, Chintha (2007) Joint Frequency Offset and Channel Estimation for OFDM Systems Using Pilot Symbols and Virtual Carriers. IEEE Transactions on Wireless Communications, 6 (4). pp. 1193-1202. ISSN 1536-1276. doi:10.1109/TWC.2007.348312.

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We consider joint estimation of carrier frequency offset and channel impulse response (CIR) for orthogonal frequency division multiplexing (OFDM) systems with pilot symbols and virtual subcarriers (VCs). We derive the receive-signal correlation structure due to the pilots and VCs, give the evidence of joint multivariate Gaussian distribution of the received samples, and derive an approximate maximum likelihood (ML) frequency offset estimator. We also derive the asymptotic mean-square error (MSE) and an approximate Cramer-Rao bound (CRB) and establish the asymptotic unbiasedness. Without pilots, in high signal-to-noise ratio, our estimator is equivalent to Liu and Tureli's estimator with Nv virtual carriers. When the pilot number (Np) is greater than the channel length L, our estimator acts as a subspace-based estimator with Nv + Np - L virtual carriers. A decision-directed joint ML estimator is derived to iteratively update the estimates of frequency offset, data symbols and CIR. The optimal pilot and virtual carrier placement strategies are also discussed. The resulting decision-directed joint estimator performs within 0.8 dB of the ideal case even when the frequency offset is as large as 20%.

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Additional Information:© Copyright 2007 IEEE. Reprinted with permission. Manuscript received July 26, 2005; revised June 30, 2006; accepted October 24, 2006. [Posted online: 2007-04-23] The associate editor coordinating the review of this paper and approving it for publication was R. Fantacci. This work has been supported in part by the Natural Sciences and Engineering Research Council of Canada, Informatics Circle of Research Excellence and Alberta Ingenuity Fund. This paper has been presented in part at the IEEE Vehicular Technology Conference 2004-Fall, Los Angeles, CA, USA, September 2004.
Subject Keywords:Channel estimation, frequency offset, OFDM, maximum likelihood
Issue or Number:4
Record Number:CaltechAUTHORS:CUIieeetwc07b
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8387
Deposited By: Archive Administrator
Deposited On:02 Aug 2007
Last Modified:08 Nov 2021 20:50

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