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Takumi Ishihara

Publications
28
Citations
448
Publications by Year
20162024
Co-Authors:
Show All Co-Authors (9)
Image of author Takumi Ishihara

Takumi Ishihara

Affiliation

Institute of Industrial Science
The University of Tokyo
Tokyo, Japan

Publication Topics

Biography

Takumi Ishihara (Member, IEEE) received the B.E., M.E., and Ph.D. degrees in computer and information sciences from the Tokyo University of Agriculture and Technology, Koganei, Japan, in 2016, 2017, and 2020, respectively. From 2020 to 2022, he was a Post-Doctoral Research Fellow with the Institute of Industrial Science, The University of Tokyo, Tokyo, Japan, where he is currently an Associate Research Fellow. His research interests include faster-than-Nyquist signaling. He was a recipient of the IEEE VTS Tokyo Chapter 2019 Young Researcher’s Encouragement Award, the Yasujiro Niwa Outstanding Paper Award in 2019, and the 33rd Telecom System Technology Award (Honorable Mention) from the Telecommunications Advancement Foundation in 2018. He w...
Publications
28
Citations
448
Publications by Year
20162024
Co-Authors:
Show All Co-Authors (9)
Author's Published Works

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Differential Multi-Carrier Faster-Than-Nyquist Signaling in Doubly Selective Fading Channel

Takumi Ishihara;Shinya Sugiura

IEEE Transactions on Vehicular Technology
Year: 2024 | Volume: 73, Issue: 1 | Journal Article |
Cited by: Papers (2)
In this article, we propose a novel concept of differentially encoded multi-carrier faster-than-Nyquist (DMFTN) signaling with noncoherent detection, which is robust against a detrimental doubly selective fading channel. In the proposed scheme, by approximately diagonalizing the FTN-specific inter-symbol interference (ISI) and noise correlation matrices, the traditional differential encoding and n...Show More

Differential Multi-Carrier Faster-Than-Nyquist Signaling in Doubly Selective Fading Channel

Takumi Ishihara;Shinya Sugiura

Year: 2024 | Volume: 73, Issue: 1 | Journal Article |

Precoded Filterbank Multicarrier Index Modulation With Non-Orthogonal Subcarrier Spacing

Prakash Chaki;Takumi Ishihara;Shinya Sugiura

IEEE Transactions on Communications
Year: 2023 | Volume: 71, Issue: 2 | Journal Article |
Cited by: Papers (1)
In this paper, we propose a novel precoded non-orthogonal frequency division multiplexing (NOFDM) with subcarrier index modulation (SIM) to increase spectral efficiency for multicarrier systems. The proposed NOFDM-SIM scheme is constituted by a filterbank multicarrier system under reduced subcarrier spacing, where precoded index modulated symbols are mapped onto the subcarriers. The detrimental ef...Show More

Precoded Filterbank Multicarrier Index Modulation With Non-Orthogonal Subcarrier Spacing

Prakash Chaki;Takumi Ishihara;Shinya Sugiura

Year: 2023 | Volume: 71, Issue: 2 | Journal Article |

Precoded Non-Orthogonal Frequency Division Multiplexing with Subcarrier Index Modulation

Prakash Chaki;Takumi Ishihara;Shinya Sugiura

2022 IEEE 95th Vehicular Technology Conference: (VTC2022-Spring)
Year: 2022 | Conference Paper |
Cited by: Papers (2)
In this paper, we propose a novel precoded non-orthogonal frequency division multiplexing (NOFDM) with sub-carrier index modulation (SIM) to increase spectral efficiency for multicarrier systems. The proposed NOFDM-SIM scheme is constituted by a filterbank multicarrier system under reduced subcarrier spacing, where precoded index modulated symbols are mapped onto the subcarriers. The detrimental e...Show More

Precoded Non-Orthogonal Frequency Division Multiplexing with Subcarrier Index Modulation

Prakash Chaki;Takumi Ishihara;Shinya Sugiura

Year: 2022 | Conference Paper |

FFT-Spread Faster-Than-Nyquist Signaling in Frequency-Selective Fading Channel

Takumi Ishihara;Shinya Sugiura

ICC 2022 - IEEE International Conference on Communications
Year: 2022 | Conference Paper |
Cited by: Papers (2)
In this paper, we propose novel reduced-complexity fast Fourier transform (FFT)-spread faster-than-Nyquist (FTN) signaling with optimal power allocation for a frequency-selective fading channel. The information rate of the proposed FTN signaling is approximately derived by relying on the circulant approximation of the FTN-specific intersymbol interference matrix and noise covariance matrix. This a...Show More

FFT-Spread Faster-Than-Nyquist Signaling in Frequency-Selective Fading Channel

Takumi Ishihara;Shinya Sugiura

Year: 2022 | Conference Paper |

Precoded Faster-Than-Nyquist Signaling for Doubly Selective Underwater Acoustic Communication Channel

Jingwen Zhou;Takumi Ishihara;Shinya Sugiura

IEEE Wireless Communications Letters
Year: 2022 | Volume: 11, Issue: 10 | Journal Article |
Cited by: Papers (5)
In this letter, we propose faster-than-Nyquist (FTN) signaling transmission that is robust for an underwater acoustic (UWA) doubly selective channel. Owning to the explicit benefits of a reduced symbol interval specific to FTN signaling, the detrimental effects of a time-selective channel are significantly relaxed. Furthermore, upon introducing single-carrier transmit precoding and equalization, t...Show More

Precoded Faster-Than-Nyquist Signaling for Doubly Selective Underwater Acoustic Communication Channel

Jingwen Zhou;Takumi Ishihara;Shinya Sugiura

Year: 2022 | Volume: 11, Issue: 10 | Journal Article |

Eigendecomposition-Precoded Faster-Than-Nyquist Signaling With Index Modulation

Prakash Chaki;Takumi Ishihara;Shinya Sugiura

IEEE Transactions on Communications
Year: 2022 | Volume: 70, Issue: 7 | Journal Article |
Cited by: Papers (5)
In this paper, we propose a precoded faster-than-Nyquist (FTN) signaling technique for time-domain single-carrier index-modulated symbol transmission. More precisely, eigenvalue decomposition (EVD) precoding is adopted for the FTN transmission of data bits modulated by single-carrier time-domain index modulation (IM). While the FTN scheme increases the spectral efficiency and data rate by increasi...Show More

Eigendecomposition-Precoded Faster-Than-Nyquist Signaling With Index Modulation

Prakash Chaki;Takumi Ishihara;Shinya Sugiura

Year: 2022 | Volume: 70, Issue: 7 | Journal Article |

Reduced-Complexity FFT-Spread Multicarrier Faster-Than-Nyquist Signaling in Frequency-Selective Fading Channel

Takumi Ishihara;Shinya Sugiura

IEEE Open Journal of the Communications Society
Year: 2022 | Volume: 3 | Journal Article |
Cited by: Papers (9)
In this paper, we propose novel reduced-complexity fast Fourier transform (FFT)-spread multicarrier faster-than-Nyquist (MFTN) signaling with power allocation for a frequency-selective fading channel. The information rate of the proposed MFTN signaling is derived by relying on the circulant approximation of the FTN-specific intersymbol interference matrix and noise covariance matrix. This allows u...Show More

Reduced-Complexity FFT-Spread Multicarrier Faster-Than-Nyquist Signaling in Frequency-Selective Fading Channel

Takumi Ishihara;Shinya Sugiura

Year: 2022 | Volume: 3 | Journal Article |

Eigendecomposition-Precoded Faster-Than-Nyquist Signaling With Optimal Power Allocation in Frequency-Selective Fading Channels

Takumi Ishihara;Shinya Sugiura

IEEE Transactions on Wireless Communications
Year: 2022 | Volume: 21, Issue: 3 | Journal Article |
Cited by: Papers (12)
In this paper, we propose eigenvalue decomposition (EVD)-precoded faster-than-Nyquist (FTN) signaling with power allocation in a frequency-selective fading channel. More specifically, we derive the mutual information associated with the proposed FTN signaling. Then, the optimal power coefficients are calculated such that the derived mutual information is maximized. Our analytical performance resul...Show More

Eigendecomposition-Precoded Faster-Than-Nyquist Signaling With Optimal Power Allocation in Frequency-Selective Fading Channels

Takumi Ishihara;Shinya Sugiura

Year: 2022 | Volume: 21, Issue: 3 | Journal Article |

Eigenvalue Decomposition Precoded Faster-Than-Nyquist Transmission of Index Modulated Symbols

Prakash Chaki;Takumi Ishihara;Shinya Sugiura

2021 IEEE International Symposium on Information Theory (ISIT)
Year: 2021 | Conference Paper |
Cited by: Papers (5)
In this paper, we propose a precoded faster-than-Nyquist (FTN) signaling technique for time-domain single-carrier index modulated (IM) symbol transmission. More precisely, eigenvalue decomposition precoding is adopted for the FTN transmission of data bits modulated by single-carrier time-domain IM. While the FTN scheme increases the spectral efficiency and data rate by packing more transmit symbol...Show More

Eigenvalue Decomposition Precoded Faster-Than-Nyquist Transmission of Index Modulated Symbols

Prakash Chaki;Takumi Ishihara;Shinya Sugiura

Year: 2021 | Conference Paper |

Precoded Faster-than-Nyquist Signaling with Optimal Power Allocation in Frequency-Selective Channel

Takumi Ishihara;Shinya Sugiura

2021 IEEE International Conference on Communications Workshops (ICC Workshops)
Year: 2021 | Conference Paper |
Cited by: Papers (5)
In this paper, we propose eigendecomposition-precoded faster-than-Nyquist (FTN) signaling with power allocation in a frequency-selective fading channel. More specifically, we derive mutual information associated with the proposed FTN signaling. Then, the optimal power coefficients are calculated such that the derived mutual information is maximized. Our analytical performance results show that the...Show More

Precoded Faster-than-Nyquist Signaling with Optimal Power Allocation in Frequency-Selective Channel

Takumi Ishihara;Shinya Sugiura

Year: 2021 | Conference Paper |

The Evolution of Faster-Than-Nyquist Signaling

Takumi Ishihara;Shinya Sugiura;Lajos Hanzo

IEEE Access
Year: 2021 | Volume: 9 | Journal Article |
Cited by: Papers (42)
The fifty-year progress of faster-than-Nyquist (FTN) signaling is surveyed. FTN signaling exploits non-orthogonal dense symbol packing in the time domain for the sake of increasing the data rate attained. After reviewing the system models of both the conventional Nyquist-based and FTN signaling transceivers, we survey the evolution of FTN techniques, including their low-complexity detection and ch...Show More

The Evolution of Faster-Than-Nyquist Signaling

Takumi Ishihara;Shinya Sugiura;Lajos Hanzo

Year: 2021 | Volume: 9 | Journal Article |

Non-Orthogonal Frequency-Division Multiplexing Based on Eigenvalue Decomposition

Seichiroh Osaki;Takumi Ishihara;Shinya Sugiura

2020 IEEE 92nd Vehicular Technology Conference (VTC2020-Fall)
Year: 2020 | Conference Paper |
Cited by: Papers (3)
This paper proposes a novel ultra-dense non-orthogonal frequency-division multiplexing (NOFDM) transmission, where subcarrier spacing is set significantly lower than that of OFDM. Eigenvalue-decomposition-aided precoding is conceived for eliminating the detrimental effects of NOFDM-specific inter-carrier interference and correlated noises. The classic capacity formula is extended to that supportin...Show More

Non-Orthogonal Frequency-Division Multiplexing Based on Eigenvalue Decomposition

Seichiroh Osaki;Takumi Ishihara;Shinya Sugiura

Year: 2020 | Conference Paper |

Effects of Eigenvalue Distribution on Precoded Faster-than-Nyquist Signaling with Power Allocation

Keita Masaki;Takumi Ishihara;Shinya Sugiura

2020 IEEE 92nd Vehicular Technology Conference (VTC2020-Fall)
Year: 2020 | Conference Paper |
Cited by: Papers (2)
In this paper, we investigate the achievable performance of precoded faster-than-Nyquist (FTN) signaling with truncated power allocation from the information-theoretic perspective. More specifically, the effects of the eigenvalue distribution of the FTN-specific inter-symbol interference (ISI) matrix on the information rate were investigated. In order to evaluate the effects of significantly low e...Show More

Effects of Eigenvalue Distribution on Precoded Faster-than-Nyquist Signaling with Power Allocation

Keita Masaki;Takumi Ishihara;Shinya Sugiura

Year: 2020 | Conference Paper |

Tradeoff Between Calculation Precision and Information Rate in Eigendecomposition-Based Faster-Than-Nyquist Signaling

Keita Masaki;Takumi Ishihara;Shinya Sugiura

IEEE Access
Year: 2020 | Volume: 8 | Journal Article |
Cited by: Papers (9)
This study measured the achievable performance of the recently developed precoded faster-than-Nyquist (FTN) signaling scheme with truncated power allocation from an information-theoretic perspective. More specifically, the effects of the eigenvalue distribution of the FTN-specific inter-symbol interference matrix on the information rate were investigated. To explicitly evaluate the effects of sign...Show More

Tradeoff Between Calculation Precision and Information Rate in Eigendecomposition-Based Faster-Than-Nyquist Signaling

Keita Masaki;Takumi Ishihara;Shinya Sugiura

Year: 2020 | Volume: 8 | Journal Article |

Variable-Block-Length Joint Channel Estimation and Data Detection for Spatial Modulation Over Time-Varying Channels

Yuya Akiba;Takumi Ishihara;Shinya Sugiura

IEEE Transactions on Vehicular Technology
Year: 2020 | Volume: 69, Issue: 11 | Journal Article |
Cited by: Papers (4)
We propose novel variable-block-length joint channel estimation and data detection for spatial modulation over time-varying channels, where the data frame is divided into multiple blocks, and channel state information (CSI) is estimated in a block-by-block manner. More specifically, in each block maximum-likelihood-based data detection and channel estimation are iteratively carried out, where the ...Show More

Variable-Block-Length Joint Channel Estimation and Data Detection for Spatial Modulation Over Time-Varying Channels

Yuya Akiba;Takumi Ishihara;Shinya Sugiura

Year: 2020 | Volume: 69, Issue: 11 | Journal Article |

Eigenvalue-Decomposition-Precoded Ultra-Dense Non-Orthogonal Frequency-Division Multiplexing

Seichiroh Osaki;Takumi Ishihara;Shinya Sugiura

IEEE Transactions on Wireless Communications
Year: 2020 | Volume: 19, Issue: 12 | Journal Article |
Cited by: Papers (8)
This paper proposes a novel ultra-dense non-orthogonal frequency-division multiplexing (NOFDM) transmission, where subcarrier spacing is set significantly lower than that of orthogonal frequency-division multiplexing (OFDM). In order to eliminate the detrimental effects of NOFDM-specific inter-carrier interference and correlated additive noises, eigenvalue-decomposition-aided precoding is conceive...Show More

Eigenvalue-Decomposition-Precoded Ultra-Dense Non-Orthogonal Frequency-Division Multiplexing

Seichiroh Osaki;Takumi Ishihara;Shinya Sugiura

Year: 2020 | Volume: 19, Issue: 12 | Journal Article |

Optimal and Suboptimal Power Allocation for SVD-Precoded Faster-than-Nyquist Signaling

Takumi Ishihara;Shinya Sugiura

2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall)
Year: 2019 | Conference Paper |
Cited by: Papers (1)
This paper proposes a precoded faster-than-Nyquist (FTN) signaling scheme based on singular-value decomposition (SVD) with optimal power allocation. An information-theoretic analysis is conducted on the proposed SVD-precoded FTN signaling architecture. Analytical performance results demonstrate that the proposed optimal scheme outperforms its conventional Nyquist-criterion- based counterpart and t...Show More

Optimal and Suboptimal Power Allocation for SVD-Precoded Faster-than-Nyquist Signaling

Takumi Ishihara;Shinya Sugiura

Year: 2019 | Conference Paper |

SVD-Precoded Faster-Than-Nyquist Signaling With Optimal and Truncated Power Allocation

Takumi Ishihara;Shinya Sugiura

IEEE Transactions on Wireless Communications
Year: 2019 | Volume: 18, Issue: 12 | Journal Article |
Cited by: Papers (27)
This study proposes a precoded faster-than-Nyquist (FTN) signaling scheme based on singular-value decomposition (SVD) with optimal power allocation. An information-theoretic analysis is conducted on the conventional and proposed SVD-precoded FTN signaling architectures. The associated information rate bound is derived in a closed-form by extending the classic Shannon capacity to support the SVD-pr...Show More

SVD-Precoded Faster-Than-Nyquist Signaling With Optimal and Truncated Power Allocation

Takumi Ishihara;Shinya Sugiura

Year: 2019 | Volume: 18, Issue: 12 | Journal Article |

Differentially Modulated Spectrally Efficient Frequency-Division Multiplexing

Seichiroh Osaki;Miyu Nakao;Takumi Ishihara;Shinya Sugiura

IEEE Signal Processing Letters
Year: 2019 | Volume: 26, Issue: 7 | Journal Article |
Cited by: Papers (8)
This letter proposes a differentially modulated non-orthogonal spectrally efficient frequency-division multiplexing (D-SEFDM) architecture, which allows us to dispense with any pilot overhead needed for channel estimation at the receiver, while increasing the bandwidth efficiency in comparison to the orthogonal frequency-division multiplexing counterpart. While it is a challenging task to carry ou...Show More

Differentially Modulated Spectrally Efficient Frequency-Division Multiplexing

Seichiroh Osaki;Miyu Nakao;Takumi Ishihara;Shinya Sugiura

Year: 2019 | Volume: 26, Issue: 7 | Journal Article |

Performance Analysis and Constellation Optimization of Star-QAM-Aided Differential Faster-Than-Nyquist Signaling

Chie Sagayama;Takumi Ishihara;Shinya Sugiura

IEEE Signal Processing Letters
Year: 2019 | Volume: 26, Issue: 1 | Journal Article |
Cited by: Papers (5)
In this letter, motivated by the recent differential faster-than-Nyquist (DFTN) signaling concept, we propose an improved 16-point double-ring star quadrature amplitude modulation (QAM)-aided DFTN signaling transmission, which allows us to attain a higher bandwidth efficiency as well as a simple receiver based on noncoherent detection. We derive an analytical error-rate bound for the proposed star...Show More

Performance Analysis and Constellation Optimization of Star-QAM-Aided Differential Faster-Than-Nyquist Signaling

Chie Sagayama;Takumi Ishihara;Shinya Sugiura

Year: 2019 | Volume: 26, Issue: 1 | Journal Article |

Faster-Than-Nyquist Signaling with Differential Encoding and Non Coherent Detection

Takumi Ishihara;Shinya Sugiura

2018 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)
Year: 2018 | Conference Paper |
Cited by: Papers (2)
In this paper, we propose a novel differential faster-than-Nyquist (DFTN) signaling scheme, which allows us to dispense with any channel estimation at the receiver while benefiting from the rate boost of faster-than-Nyquist (FTN) signaling. At the transmitter, differentially modulated binary phase-shift keying (DBPSK) symbols are transmitted with the symbol interval that is smaller than that defin...Show More

Faster-Than-Nyquist Signaling with Differential Encoding and Non Coherent Detection

Takumi Ishihara;Shinya Sugiura

Year: 2018 | Conference Paper |

Differential Faster-Than-Nyquist Signaling

Takumi Ishihara;Shinya Sugiura

IEEE Access
Year: 2018 | Volume: 6 | Journal Article |
Cited by: Papers (17)
In this paper, we propose a novel differential faster-than-Nyquist (DFTN) signaling concept that allows us to dispense with any channel estimation at the receiver, while benefiting from a rate boost specific to faster-than-Nyquist (FTN) signaling. More specifically, at the transmitter, differentially modulated phaseshift keying (DPSK) symbols are transmitted with a symbol interval that is smaller ...Show More

Differential Faster-Than-Nyquist Signaling

Takumi Ishihara;Shinya Sugiura

Year: 2018 | Volume: 6 | Journal Article |

Dual-Mode Time-Domain Index Modulation for Nyquist-Criterion and Faster-Than-Nyquist Single-Carrier Transmissions

Miyu Nakao;Takumi Ishihara;Shinya Sugiura

IEEE Access
Year: 2017 | Volume: 5 | Journal Article |
Cited by: Papers (23)
In this paper, we propose a novel dual-mode time-domain single-carrier (SC) index modulation (DM-SCIM) scheme, where the combination of two constellation modes carries information bits further to modulated symbols, hence increasing the transmission rate. Accordingly, the proposed DM-SCIM scheme is capable of attaining a higher transmission rate than the conventional SC and SCIM schemes, without im...Show More

Dual-Mode Time-Domain Index Modulation for Nyquist-Criterion and Faster-Than-Nyquist Single-Carrier Transmissions

Miyu Nakao;Takumi Ishihara;Shinya Sugiura

Year: 2017 | Volume: 5 | Journal Article |

State-of-the-Art Design of Index Modulation in the Space, Time, and Frequency Domains: Benefits and Fundamental Limitations

Shinya Sugiura;Takumi Ishihara;Miyu Nakao

IEEE Access
Year: 2017 | Volume: 5 | Journal Article |
Cited by: Papers (88)
In this paper, we provide a comprehensive review of diverse index modulation (IM) architectures that operate in the space, time, and frequency domains, as well as their related technologies. We clarify that several IM-specific characteristics have explicit advantages over those of the conventional bandwidthefficient counterparts, such as spatial multiplexing, orthogonal frequency division multiple...Show More

State-of-the-Art Design of Index Modulation in the Space, Time, and Frequency Domains: Benefits and Fundamental Limitations

Shinya Sugiura;Takumi Ishihara;Miyu Nakao

Year: 2017 | Volume: 5 | Journal Article |

Faster-Than-Nyquist Signaling With Index Modulation

Takumi Ishihara;Shinya Sugiura

IEEE Wireless Communications Letters
Year: 2017 | Volume: 6, Issue: 5 | Journal Article |
Cited by: Papers (35)
In this letter, we propose a novel faster-than-Nyquist (FTN) transmission scheme relying on the time-domain single-carrier index-modulation (IM) concept. In the proposed FTN with IM (FTN-IM) transmitter, a subset of time-domain FTN symbols are activated, where the combination of the activated symbols conveys additional information further to the classic amplitude phase shift keying. Owing to the e...Show More

Faster-Than-Nyquist Signaling With Index Modulation

Takumi Ishihara;Shinya Sugiura

Year: 2017 | Volume: 6, Issue: 5 | Journal Article |

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