Time Domain Feedback Equalizer for Fast Fading Channel in OFDM with Scattered Pilot

Yutaro NAKAGAWA  Yukitoshi SANADA  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E93-A   No.12   pp.2691-2695
Publication Date: 2010/12/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E93.A.2691
Print ISSN: 0916-8508
Type of Manuscript: Special Section LETTER (Special Section on Wideband Systems)
Category: 
Keyword: 
OFDM,  ISDB-T,  scattered pilot,  ICI,  Doppler shift,  feedback equalizer,  

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Summary: 
In this letter, a new feedback equalization scheme to suppress inter-carrier interference (ICI) in an OFDM system using scattered pilot is investigated. On a fast fading channel severe ICI occurs due to a Doppler shift and it deteriorates a bit error rate (BER) seriously because of small subcarrier spacing. In an ISDB-T receiver the equalization is mainly processed in a frequency domain because the scattered pilot is transmitted over the subcarriers. However, the frequency domain equalization may not suppress severe ICI in the case of the fast fading channel with a large Doppler shift. The proposed equalization scheme uses the scattered pilot symbols transformed in a time domain as the reference signal for feedback taps. Numerical results through computer simulation show that the proposed scheme improves the BER performance especially with low carrier-to-noise ratio (CNR) conditions.