Low-Complexity ICI/ISI Equalization in Doubly Dispersive Multicarrier Systems Using a Decision-Feedback LSQR Algorithm

Taubock, Georg; Hampejs, Mario; Svac, P.; Matz, Gerald; Hlawatsch, Franz; Gröchenig, Karlheinz

doi:10.1109/tsp.2011.2113181

Cited by 34 publications

(13 citation statements)

References 31 publications

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“…We can make a difference between linear equalizers based on zero-forcing (ZF) [7] or minimum mean-square error criterion [8][9][10], and non-linear equalizers based on ICI cancelation or decision-feedback [11][12][13][14][15][16]. Linear equalization requires the inversion of the frequency channel matrix, which is prohibitively complex for large OFDM symbols.…”

Section: Background On Ici Suppressingmentioning

confidence: 99%

Factor graph based detection approach for high-mobility OFDM systems with large FFT modes

Ochandiano

Wymeersch

Mendicute

et al. 2012

J Wireless Com Network

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In this article, a novel detector design is proposed for orthogonal frequency division multiplexing (OFDM) systems over frequency selective and time varying channels. Namely, we focus on systems with large OFDM symbol lengths where design and complexity constraints have to be taken into account and many of the existing ICI reduction techniques can not be applied. We propose a factor graph (FG) based approach for maximum a posteriori (MAP) symbol detection which exploits the frequency diversity introduced by the ICI in the OFDM symbol. The proposed algorithm provides high diversity orders allowing to outperform the free-ICI performance in high-mobility scenarios with an inherent parallel structure suitable for large OFDM block sizes. The performance of the mentioned near-optimal detection strategy is analyzed over a general bit-interleaved coded modulation (BICM) system applying low-density parity-check (LDPC) codes. The inclusion of pilot symbols is also considered in order to analyze how they assist the detection process.

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Section: Background On Ici Suppressingmentioning

confidence: 99%

Factor graph based detection approach for high-mobility OFDM systems with large FFT modes

Ochandiano

Wymeersch

Mendicute

et al. 2012

J Wireless Com Network

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“…This band structure has previously been exploited for similar OFDM equalisation schemes using LDL H [17] or LSQR [14] factorisations of the Hermitian term G n = B n B H n + γ −1 I. Here, we utilise the sparsity of G n to invoke a very recently reported iterative least squares minres (LSMR) approach in [18], which claims to offer lower complexity, higher numerical stability, and faster convergence than the LSQR method.…”

Section: B Low Cost Approachesmentioning

confidence: 99%

“…In all these schemes the equaliser complexity can be reduced by exploiting the approximate band structure of the resulting channel matrix [10,12]. ICI equalisers in [13,14] apply the LSQR algorithm [15,16] which offers a low complexity approach to solve linear systems.…”

Section: Introductionmentioning

confidence: 99%

Low-complexity LSMR equalisation of FrFT-based multicarrier systems in doubly dispersive channels

Solyman

Weiss

Soraghan

2011

2011 IEEE International Symposium on Signal Processing and Information Technology (ISSPIT)

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This version is available at https://strathprints.strath.ac.uk/37915/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. University of Strathclyde, Glasgow G1 1XW, Scotland, UK aaasolyman@Gmail.com,{j.soraghan,stephan}@eee.strath.ac.uk Abstract-The discrete fractional Fourier transform (FrFT) has been suggested to enhance performance over DFT-based multicarrier systems when transmitting over doubly-dispersive channels. In this paper, we propose a novel low-complexity equaliser for inter-symbol and inter-carrier interference arising in such multicarrier transmission system. Due to a lower spreading in the FrFT-domain compared to the DFTchannel matrix as compared to the DFT domain, the equaliser can approximate the fractional-domain channel matrix by a band matrix. Further, we utilise the least squares minres (LSMR) algorithm in the calculation of the equalisation, which exhibits attractive numerical properties and low complexity. Simulation results demonstrate the superior performance of the proposed LSMR equaliser over benchmark schemes. Low-Complexity LSMR Equalisation of FrFT-Based Multicarrier Systems in Doubly Dispersive

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“…A large number of different algorithms have been studied in the last decade for ICI cancellation, e.g., [1][2][3], which take advantage of the banded channel matrix to remove the ICI from neighbouring subcarriers sequentially. Additionally, some techniques in [4,5] exploit the sparsity of the banded matrix to design the OFDM block equalizers. Also, several pre-equalized methods have been proposed in [6][7][8][9][10] to reduce the time variations and obtain a quasi-diagonal channel matrix as convectional OFDM systems over the *Correspondence: huangyao@cuit.edu.cn Chengdu University of Information Technology, Sichuan, China slowly time-varying channels.…”

Section: Introductionmentioning

confidence: 99%

Multi-segmental OFDM signals equalization with piecewise linear channel model over rapidly time-varying channels

Hua

Yao

et al. 2017

J Wireless Com Network

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For rapidly time-varying channels, the performance of (orthogonal frequency division multiplexing) OFDM systems with the conventional one tap equalizer will be significantly degraded. Because the orthogonality between subcarriers is destroyed, the conventional way to combat the inter-carrier interference (ICI) is employing the banded minimum mean square error (MMSE) equalizer, which can save computational efforts introduced by a large number of subcarriers. However, the width of the banded channel matrix is mainly determined by the normalized Doppler frequency in the sense that with the high Doppler frequency the complexity of equalization for one OFDM block will significantly increase with the band width D. In order to reduce the equalization complexity, the authors proposed multi-segmental OFDM signal equalization method with piecewise linear model (PLM) to approximate the time variations and mitigate the corresponding ICI. Its complexity is significantly reduced with the small segments. Furthermore, an alternative MMSE method with the iterative rank-1 matrix updates is proposed to further reduce the complexity. We also derive the theoretical pre-equalized and equalized signal to interference ratio (SIR) for different normalized Doppler frequencies and segment numbers, which implies that the larger segment number can achieve the better performance. Simulation results demonstrate that the proposed method outperforms the conventional banded MMSE equalizer and the partial fast Fourier transform (FFT) method in terms of bit error rate (BER) with almost the same complexity.

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Low-Complexity ICI/ISI Equalization in Doubly Dispersive Multicarrier Systems Using a Decision-Feedback LSQR Algorithm

Cited by 34 publications

References 31 publications

Factor graph based detection approach for high-mobility OFDM systems with large FFT modes

Factor graph based detection approach for high-mobility OFDM systems with large FFT modes

Low-complexity LSMR equalisation of FrFT-based multicarrier systems in doubly dispersive channels

Multi-segmental OFDM signals equalization with piecewise linear channel model over rapidly time-varying channels

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