JITSUMATSU YUTAKA | Last modified date：2024.06.03 |

Associate Professor /
Mathematical Informatics

Department of Informatics

Faculty of Information Science and Electrical Engineering

Department of Informatics

Faculty of Information Science and Electrical Engineering

Graduate School

Undergraduate School

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Homepage

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Phone

092-802-3624

Fax

092-802-3624

Academic Degree

Ph. D (Engineering)

Country of degree conferring institution (Overseas)

No

Field of Specialization

Information Theory, Communication Theory, Signal Processing

ORCID(Open Researcher and Contributor ID)

https://orcid.org/0000-0003-3056-2402

Total Priod of education and research career in the foreign country

00years09months

Outline Activities

Mathematical aspects of issues emerged in telecommunication and signal processing, such as a tradeoff between the data transmission rate and quality of communication, analog-to-digital converter and dynamical systems, random number generation, and channel impulse response estimation based on a compressed sensing theory.

I have several international conference presentation every year. I also attend domestic conference.

I teach signals and systems (2nd grade, 2nd semester) and information theory (3rd grade, 1st semester).

I have several international conference presentation every year. I also attend domestic conference.

I teach signals and systems (2nd grade, 2nd semester) and information theory (3rd grade, 1st semester).

Research

**Research Interests**

- Acceleration of acquisition of MRI images using deep neural networks

keyword : MRI, Deep Learning, Deep Neural Networks, Image Super Resolution

2017.04～2020.03. - Computation for error exponent in Converse Theorem for discrete memoryless channels

keyword : Correct decoding Probability, Error exponent, Iterative Algorithm

2014.03～2017.03. - Signal Processing for RADAR system based on Compressed Sensing

keyword : Compressed Sensing, Rate of Innovation, Prony's frequency estimation method

2014.04～2017.03. - quantization error of beta-encoders

keyword : analog-digital/digital-analog converters, beta-expansion, pulse code modulation (PCM), sigma-delta converter, quantization error

2012.10～2014.03. - multi-user detection and spin glass

keyword : spin glass, statistical phisics, random matrix, neural networks, associative memory

2005.04～2014.03. - Timing and frequency synchronization using two dimensional spreading code signal.

keyword : Ambiguity function, Wigner distribution, spread spectrum system

2001.04.

**Current and Past Project**

- The purpose of the Project entitled "the Mathematical Theory for Modelling Complex Systems and Its Transdisciplinary Applications in Science and Technology" is to develop a mathematical theory that will facilitate the modelling of complex systems and the creation of transdisciplinary applications of this theory in science and technology. This will be done through exploiting advances in mathematical engineering (a discipline originally developed in Japan) and chaos engineering (a field aimed at creating various applications based on deterministic chaos, fractals and complex networks).

**Academic Activities**

**Papers**

1. | Y. Jitsumatsu, U. Michiwaki, and Y. Oohama, Conditional Information Leakage Given Eavesdropper's Received Signals in Wiretap Channels, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences , 10.1587/transfun.2020EAP1017, 104, 1, 295-304, 2021.01, [URL], Information leakage in Wyner's wiretap channel model is usually defined as the mutual information between the secret message and the eavesdropper's received signal. We define a new quantity called “conditional information leakage given the eavesdropper's received signals,” which expresses the amount of information that an eavesdropper gains from his/her received signal. A benefit of introducing this quantity is that we can develop a fast algorithm for computing the conditional information leakage, which has linear complexity in the code length n, while the complexity for computing the usual information leakage is exponential in n. Validity of such a conditional information leakage as a security criterion is confirmed by studying the cases of binary symmetric channels and binary erasure channels.. |

2. | Yutaka Jitsumatsu, Invariant Set of Two-Dimensional Dynamics of Golden Ratio Encoders, Nonlinear Theory and Its Applications, IEICE, 10.1587/nolta.12.75, E12-N, 1, 75-87, 2021.01, [URL], A discrete-time two-dimensional dynamical system appears in a Golden Ratio Encoder (GRE), a type of analog-to-digital converter. One of the essential elements in analyzing a given dynamical system is identifying the invariant set of that system. The invariant set of dynamics of GREs is not known, except in special cases. We herein determine the invariant set of the dynamics of GREs with an amplification factor α and a threshold θ for a wide range of parameters (α, θ). The invariant set is separated into six sub-regions and the transition probabilities between the sub-regions are defined. We show that the uniform distribution on the invariant set is an invariant density for this dynamical system.. |

3. | Yutaka Jitsumatsu and Yasutada Oohama, A New Iterative Algorithm for Computing the Correct Decoding Probability Exponent of Discrete Memoryless Channels, IEEE Transactions on Information Theory, 10.1109/TIT.2019.2950678, 66, 3, 1585-1606, 2019.10, [URL], Dueck and Körner’s reliability function for discrete memoryless channels for rates above the capacity coincides with Arimoto’s exponent of correct decoding probability. The two exponent functions are described by seemingly different optimization problems over the space of probability distributions. Arimoto gave an iterative algorithm for solving the optimization problem that appears in his exponent function. However, no algorithm to solve the optimization problem that appears in Dueck and Körner’s exponent has been proposed. This paper proposes a new iterative algorithm for solving the minimization problem in Dueck and Körner’s exponent. In the proposed algorithm, a double minimization form with respect to two joint distributions on input and output symbols is introduced. This double minimization is connected to another double minimization that appears in Arimoto’s algorithm. Such a connection leads to a quadruple minimization problem, by which the match of Arimoto and Dueck-Köorner exponents is easily proved.. |

4. | Dongshin Yang, Yutaka Jitsumatsu, Super resolution channel estimation by using spread spectrum signal and atomic norm minimization, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, 10.1587/transfun.E101.A.2141, E101A, 12, 2141-2148, 2018.12, [URL], Compressed Sensing (CS) is known to provide better channel estimation performance than the Least Square (LS) method for channel estimation. However, multipath delays may not be resolved if they span between the grids. This grid problem of CS is an obstacle to super resolution channel estimation. An Atomic Norm (AN) minimization is one of the methods for estimating continuous parameters. The AN minimization can successfully recover a spectrally sparse signal from a few time-domain samples even though the dictionary is continuous. There are studies showing that the AN minimization method has better resolution than conventional CS methods. In this paper, we propose a channel estimation method based on the AN minimization for Spread Spectrum (SS) systems. The accuracy of the proposed channel estimation is compared with the conventional LS method and Dantzig Selector (DS) of the CS. In addition to the application of channel estimation in wireless communication, we also show that the AN minimization can be applied to Global Positioning System (GPS) using Gold sequence.. |

5. | Dongshin Yang and Yutaka Jitsumatsu, Dividing the grids of compressed sensing for channel estimation and investigating Markov codes, Nonlinear Theory and Its Applications, IEICE, https://doi.org/10.1587/nolta.9.259, 9, 2, 259-267, 2018.04, [URL]. |

6. | YUTAKA JITSUMATSU, Kazuya Matsumura, A β-ary to binary conversion for random number generation using a β encoder, Nonlinear Theory and Its Applications, IEICE, http://doi.org/10.1587/nolta.7.38, 7, 1, 38-55, 2016.01, [URL], A β encoder is an analog-to-digital (A/D) converter, proposed by Daubechies et al. in 2002, that outputs a truncated sequence of β expansion of an input value x. It is known that the conventional pulse code modulation (PCM) that outputs the binary expansion of x is sensitive to the offset of the threshold voltage, while a β encoder is robust to such an offset. We propose an algorithm that calculates the binary expansion of an interval that is identified by an output sequence from a β encoder. Such a method is referred to as a β-ary to binary converter. We generate sequences of random numbers, using a hardware β encoder followed by the β-ary to binary converter. The randomness of the generated binary random numbers is verified by the National Institute of Standards and Technology (NIST) statistical test suite.. |

7. | YUTAKA JITSUMATSU, Tohru Kohda, Digital Phase Updating Loop and Delay-Doppler Space Division Multiplexing for Higher Order MPSK, 7th Int. Workshop Multiple Access Communications, 10.1007/978-3-319-10262-7_1, 8715, 1-15, 2014.12, [URL], An alternative to the use of higher order Quadrature Amplitude Modulation (QAM) that shows strong variations of output amplitude is the use of higher order Phase Shift Keying (PSK). The bit error probability of higher order PSK is sensitive to phase distortion that is caused by propagation delay and Doppler frequency estimation errors. Phase Updating Loop (PUL) is a generalization of a Phase Locked Loop (PLL) that can estimate the delay and the Doppler accurately. In order to realize a higher order PSK, we recently proposed a delay-Doppler Space Division Multiplexing (dD-SDM) method in which a parameter space consisting of delay and Doppler is partitioned into several sub-spaces and each subspace has its assigned signature codes. In this paper, digital PUL is defined. Simulation results show that by the use of the dD-SDM method together with digital PUL we can successfully demodulate 256PSK data.. |

8. | YUTAKA JITSUMATSU, Tatsuro Higuchi, Masahiro Hashiguchi, Optimal Sign Patterns for a Generalized Schmidl-Cox Method, Sequences and Their Applications 2014, 10.1007/978-3-319-12325-7_23, 8865, 269-279, 2014.11, [URL], The timing synchronization method proposed by Schmidl and Cox for orthogonal frequency division multiplexing (OFDM) systems uses a reference block consisting of two identical parts, while the one proposed by Shi and Serpedin uses a reference block consisting of four parts with a sign pattern (+1,+1,−1,+1). The accuracy of estimated delays of the latter method is higher than the former. In this paper, the number of partitions is generalized as an integer number M. Two criteria for optimization are proposed. Optimal codes with code length 5≤M≤30 are investigated.. |

9. | YUTAKA JITSUMATSU, Tohru Kohda, Kazuyuki Aihara, Delay-Doppler Space Division-based Multiple-Access Solves Multiple-Target Detection, Lecture Notes in Computer Science, 10.1007/978-3-319-03871-1_5, 8310, 39-53, 2013.12, [URL]. |

10. | YUTAKA JITSUMATSU, Welch Bound for Bandlimited and Timelimited Signals, Lecture Notes in Computer Science, 7280, 269-278, 2012.09, Synchronisation must be established in any communication systems. In multicarrier communications, time and frequency offsets are taken into account. We use cross-ambiguity function to evaluate synchronisation performance and the interference in a CDMA system with such two-dimensional offsets. Welch bound for one dimensional and discrete time cross correlation function is extended to the one for two dimensional and continuous time cross ambiguity functions. This bound is compared with an ambiguity function for continuous time signal generated from discrete time signal with rectangular chip waveforms.. |

11. | Y. Jitsumatsu and T. Kohda, Asynchrony, Markov, interference, RIMS Kokyuroku, 1742, 165-179, 2011.05, [URL]. |

12. | Yutaka Jitsumatsu and Tohru Kohda, Chip-Asynchronous Version of Welch Bound: Gaussian Pulse Improves BER Performance,, Sequences and Their Applications - SETA 2006, vol.4086, pp.351-363, 2006.09. |

13. | Yutaka Jitsumatsu, Tahir Abbas Khan and Tohru Kohda, Reduction of MAI in Asynchronous DS/CDMA Systems Using Post-Filter, IEICE Tranactions on Fundamentals, E87A, 9, 2301-2307, Vol. E87-A, No.9, pp. 2301-2307, 2004.09. |

14. | Jitsumatsu, Y.; Kohda, T., Bit error rate of incompletely synchronised correlator in asynchronous DS/CDMA system using SS Markovian codes, Electronics Letters, 10.1049/el:20020276, 38, 9, 415-416, Volume: 38 Issue: 9, Page(s): 415 -416, 2002.04. |

**Presentations**

1. | Dongshin Yang and Yutaka Jitsumatsu, Super Resolution Channel Estimation with Spread Spectrum Signal and Atomic Norm Minimization, 2018 International Symposium on Information Theory and Its Applications (ISITA), 2018.10, [URL], One of the important tasks in wireless communications is propagation delay estimation. It has been found that the channel estimation accuracy of compressed sensing is superior to the existing method based on signal parameter estimation through MUltiple SIgnal Classification (MUSIC) and Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT). However, there is a problem in the method that multipath delays may not be resolved if they span between the grids. This problem leads to inaccurate channel estimation. In this paper, we describe the Atomic Norm Minimization (ANM) that enables super resolution channel estimation. In additions, we propose ANM by using Spread Spectrum (SS) signal. In this study, we show new experiments using Gold code for Global Positioning System (GPS). We have also added a new experiment to check the performance of the ANM with SS signal.. |

2. | Koji Itaya, YUTAKA JITSUMATSU, Mean Square Quantization Error of Golden Ratio Encoders, Int. Symp. Nonliner Theory and its Application (NOLTA2017), 2017.12, [URL]. |

3. | On computation of secrecy exponent functions, [URL]. |

4. | On computation of secrecy exponent functions, [URL]. |

5. | Dongshin Yang, YUTAKA JITSUMATSU, Compressive Sensing of Up-Sampled Model and Atomic Norm for SuperResolution Radar, 2017 Int. Radar Sympo. (IRS2017), 2017.06, [URL]. |

6. | YUTAKA JITSUMATSU, Computation of the Random Coding Secrecy Exponent for a Constant Composition Ensemble, Proc. Int. Sympo. Inform. Theory, 2017.06, [URL]. |

7. | Yeelai Chew, YUTAKA JITSUMATSU, Estimation of Beta-Value for Pipelined Beta Encoders, Int. Symp. Nonliner Theory and its Application (NOLTA2016), 2016.11, [URL]. |

8. | Koji Itaya, YUTAKA JITSUMATSU, Random Number Generation Using Outputs from Multiple Beta Encoders, Int. Symp. Nonliner Theory and its Application (NOLTA2016), 2016.11, [URL]. |

9. | Dongshin Yang, YUTAKA JITSUMATSU, Discretization in Channel Estimation Using Compressed Sensing and Its Performance Improvement, 13th IEEE VTS Asia Pacific Wireless Communications Symposium (APWCS 2016), 2016.08, [URL]. |

10. | YUTAKA JITSUMATSU, Yasutada Oohama, Computing the Optimal Exponent of Correct Decoding for Discrete Memoryless Sources, Proc. Int. Sympo. Inform. Theory, 2016.07, [URL], The form of Dueck and K\"orner's exponent function for correct decoding probability for discrete memoryless channels at rates above the capacity is similar to the form of Csisz\'ar and K\"orner's exponent function for correct decoding probability i. |

11. | Shuntaro Ito, Dongshin Yang, YUTAKA JITSUMATSU, Estimation of Multi-path Channels by Using the Annihilating Filter Method, 2015 IEEE 82nd Vehicular Technology Conference, 2015.09, [URL], Estimation of the channel distortion {characteristics} is of crucial importance for realizing a reliable communication. In order to estimate the channel, a received signal is sampled at some rate. The Nyquist rate is widely used notion to determine the sampling rate of the received signal. On the other hand, Vetterli introduce{d} the concept of rate of innovation that is the degree of freedom of the signal space and proposed annihilating filter method, which solves a nonlinear simultaneous equation by means of finding roots of the characteristic polynomial of the equation. By using this technique, the number of samples can be reduced from the Nyquist rate. In this paper, we employ the annihilating filter method to perform the estimation of a multi-path channel. A spread spectrum signal with a wide bandwidth is transmitted, while the received signal is sampled at a very low sampling rate that is determined according to the rate of innovation.. |

12. | Yasutada Oohama, YUTAKA JITSUMATSU, A New Iterative Algorithm for Computing the Optimal Exponent of Correct Decoding for Discrete Memoryless Channels, Int. Sympo. Inform. Theory 2015, 2015.06, [URL], For a discrete memoryless channel, a lower bound for the correct decoding probability exponent was derived by Arimoto. He also gave an iterative algorithm for computing the exponent. Subsequently, Dueck and K\"orner determined the optimal exponent function of the correct decoding probability. In this paper, a new iterative algorithm that computes Dueck and K\"orner's exponent is presented. . |

13. | YUTAKA JITSUMATSU, Masahiro Hashiguchi, Tatsuro Higuchi, Optimal Sign Patterns for a Generalized Schmidl-Cox Method, Sequences and Their Applications 2014, 2014.11, [URL]. |

14. | Tatsuro Higuchi, YUTAKA JITSUMATSU, Performance Analysis of a Time Synchronization Method for Multipath Fading Channels with Doppler Shift, 17th Int. Symp. on Wireless Personal Multimedia Commun. (WPMC2014), 2014.09, [URL]. |

15. | YUTAKA JITSUMATSU, Tohru Kohda, Kazuyuki Aihara, Phase-tuned layers with multiple 2D SS codes realize 16PSK communication, 2014 IEEE Wireless Communications and Networking Conference , 2014.04. |

16. | Yutaka Jitsumatsu, Tohru Kohda, Kazuyuki Aihara, Delay-Doppler Space Division- based Multiple-Access Solves Multiple-Target Detection , 6th International Workshop on Multiple Access Communications(MACOM2013), 2013.12, [URL]. |

17. | Yutaka Jitsumatsu, Tohru Kohda, Kazuyuki Aihara, Recovering noncoherent MPSK signal with unknown delay and Doppler using its ambiguity function, 4th International Workshop on Recent Advances in Broadband Access Networks(RABAN2013), 2013.11, [URL]. |

18. | Yutaka Jitsumatsu, Tohru Kohda, Kazuyuki Aihara, PLL-free Receiver for Gabor Division/Spread Spectrum System, The 9th IEEE International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob2013), 2013.10, [URL]. |

19. | Yutaka Jitsumatsu, Tohru Kohda, Kazuyuki Aihara, Signals that can be easily time-frequency synchronized from their ambiguity function , IEEE Information Theory Workshop 2013(ITW2013), 2013.09, [URL]. |

20. | Yutaka Jitsumatsu, Tohru Kohda, Kazuyuki Aihara, Gabor Division/Spread Spectrum System is Separable in Time and Frequency Synchronization , 2013 IEEE 78th Vehicular Technology Conference: VTC2013-Fall, 2013.09, [URL]. |

21. | Yutaka Jitsumatsu, Tohru Kohda, Kazuyuki Aihara, Spread Spectrum-Based Cooperative and individual time-frequency synchronization , The Tenth International Symposium on Wireless Communication Systems(ISWCS2013) , 2013.08, [URL]. |

22. | Yutaka Jitsumatsu, Tohru Kohda, Kazuyuki Aihara, Separability of Time-Frequency Synchronization , International Radar Symposium 2013 (IRS2013) , 2013.06, [URL]. |

23. | YUTAKA JITSUMATSU, Tohru Kohda, Kazuyuki Aihara, Frequency-division spread-spectrum makes frequency synchronisation easy, IEEE Globecom 2012, 2012.12. |

**Membership in Academic Society**

- IEICE
- IEEE
- Society of Information Theory and Its Applications (SITA)

**Awards**

- Engineering Science Society Contribution Award (Editorial)
- Engineering Science Society Contribution Award (Society Operation)
- Best Paper Award
- Contribution as an associate editor for English journal

Your contribution to Engineering Science Society (ESS) in IEICE is highly appreciated. - The Best Paper award at the 6th International Workshop on Multiple Access Communications(MACOM-2013)

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