Pilot Cluster ICI Suppression in OFDM Systems Based on Coded Symbols

Yong DING  Shan OUYANG  Yue-Lei XIE  Xiao-Mao CHEN  

IEICE TRANSACTIONS on Communications   Vol.E101-B   No.11   pp.2320-2330
Publication Date: 2018/11/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2017EBP3473
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
orthogonal frequency division multiplexing (OFDM),  channel estimation,  pilot cluster ICI suppression,  coded symbol,  alternating iterative optimization,  

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When trying to estimate time-varying multipath channels by applying a basis expansion model (BEM) in orthogonal frequency division multiplexing (OFDM) systems, pilot clusters are contaminated by inter-carrier interference (ICI). The pilot cluster ICI (PC-ICI) degrades the estimation accuracy of BEM coefficients, which degrades system performance. In this paper, a PC-ICI suppression scheme is proposed, in which two coded symbols defined as weighted sums of data symbols are inserted on both sides of each pilot cluster. Under the assumption that the channel has Flat Doppler spectrum, the optimized weight coefficients are obtained by an alternating iterative optimization algorithm, so that the sum of the PC-ICI generated by the encoded symbols and the data symbols is minimized. By approximating the optimized weight coefficients, they are independent of the channel tap power. Furthermore, it is verified that the proposed scheme is robust to the estimation error of the normalized Doppler frequency offset and can be applied to channels with other types of Doppler spectra. Numerical simulation results show that, compared with the conventional schemes, the proposed scheme achieves significant improvements in the performance of PC-ICI suppression, channel estimation and system bit-error-ratio (BER).