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A Scattered Pilot OFDM Receiver Employing Turbo ICI Cancellation in Fast Fading Environments
IEICE TRANSACTIONS on Communications
Publication Date: 2005/01/01
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Multi-carrier Signal Processing Techniques for Next Generation Mobile Communications--Part 1)
Category: Interference Canceller
OFDM, mobile communications, scattered-pilot, turbo cancellation, decision directed channel estimation, digital terrestrial television broadcasting,
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This paper proposes a scattered-pilot-OFDM reception scheme employing turbo inter-carrier interference (ICI) cancellation in the fast varying fading environments of mobile communications. In the OFDM transmission, the orthogonality among the subcarriers cannot hold due to large Doppler shift, and the OFDM signal suffers from severe degradation due to ICI. The proposed receiver carries out two modes: (i) a coherent detection (CD) mode, and (ii) a turbo ICI cancellation (TC) mode. Initially, the receiver performs the CD mode. When any decision errors are detected, it shifts from the CD mode to the TC one that carries out both the ICI cancellation and the channel estimation by using the decoder output (the log likelihood ratio). In addition, the iteration of the TC mode can improve the accuracy of the channel estimation and ICI cancellation ability. Computer simulations following specifications for the mobile reception mode in the digital terrestrial television broadcasting demonstrate that the receiver can effectively cancel ICI due to the fast varying fading, and that its average BER performance is much better than that of CD.