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| Channel Estimation of Rapidly Time-Varying Channels for OFDM Systems |
| Hu Die①; He Liang-hua②; Yang Lü-xi① |
| ①Department of Radio Engineering, Southeast University, Nanjing 210096, China;②School of Electronics and Information Engineering, Tongji University, Shanghai 200092, China |
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Abstract In Orthogonal Frequency-Division Multiplexing (OFDM) systems, how to estimate rapidly time-varying channels exactly is a challenge issue. In this paper, relying on a basis expansion channel model, a channel estimation scheme of rapidly time-varying channels is proposed for OFDM systems. Along with the channel estimation scheme, the optimal pilot sequence and optimal placement of the pilot tones are also derived with respect to the mean square error (MSE) of the channel estimate. It is shown that the optimal pilot sequence consists of some adjacent equipowered and equispaced subsequences, and each of them is constrained by certain phase conditions. Simulation results demonstrate the effectiveness of the proposed channel estimation scheme in rapidly time-varying scenarios and the superiority of using the derived optimal pilot sequences.
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Received: 12 May 2005
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2007, Vol. 29 
