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Takeuchi, Keigo

Affiliation Department of Electrical and Electronic Information Engineering
Title Associate Professor
Fields of Research Wireless communications / Information theory / Signal processing
Degree Doctor of Informatics (Kyoto University)
Academic Societies IEEE / IEICE / Physical Society of Japan
E-mail takeuchi@ee
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Laboratory website URL
Researcher information URL(researchmap) Researcher information


In future wireless communications, groundbreaking schemes are needed to satisfy high performance requirement. In order to realize such a paradigm shift in the field of communications, an interdisciplinary point of view is important in our researches. One sometimes recognizes that a problem is essentially the same as a problem that has been already solved in another research field, while there is no superficial relationship between the two problems. Our goal is to realize novel communication schemes by applying such achievements on the other fields to the field of communcations. Also, we are aiming to deliver our achievements on communications to different research fields in order to contribute to academic and industrial progress in wide fields including communications.

Theme1:Massive MIMO


Multiple-input multiple-output (MIMO) systems are a wireless communication system that uses multiple transmit and receive antennas for information transmission. In massive MIMO systems, base stations equip a large number of antennas to support many users simultaneously. Conventional receivers cannot be used to process all user signals jointly and efficiently. In our laboratory, we are aiming to construct efficient reception schemes for massive MIMO on the basis of an iterative method called expectation propagation and of its modification proposed in the field of compressed sensing.

Selected publications and works

[4] K. Takeuchi et al., “Performance Improvement of Iterative Multiuser Detection for Large Sparsely Spread CDMA Systems by Spatial Coupling,” IEEE Trans. Inf. Theory, vol. 61, no. 4, pp. 1768-1794, Apr. 2015.
[3] K. Takeuchi et al., “On an Achievable Rate of Large Rayleigh Block-Fading MIMO Channels With No CSI,” IEEE Trans. Inf. Theory, vol. 59, no. 10, pp. 6517-6541, Oct. 2013.
[2] K. Takeuchi et al., “Large-System Analysis of Joint Channel and Data Estimation for MIMO DS-CDMA Systems,” IEEE Trans. Inf. Theory, vol. 58, no. 3, pp. 1385-1412, Mar. 2012.
[1] K. Takeuchi et al., “Asymptotic Analysis of General Multiuser Detectors in MIMO DS-CDMA Channels,” IEEE J. Sel. Areas Commun., vol. 26, no. 3, pp. 486-496, Apr. 2008.


Massive MIMO, compressed sensing, expectation propagation

Theme2:Spatial Modulation


The signals 1, -1, or 0 (no transmission) is transmitted in spatial modulation, while 1 or -1 is sent in conventional modulation. Since information is conveyed by signal 0 (no transmittion), spatial modulation is an energy-efficient transmission scheme. A problem is an efficient blind estimation of the positions at which signals 0 have been sent. In our laboratory, we utilize a similarity between the problem and that considered in the field of compressed sensing to construct efficient reception schemes.

Selected publications and works

[2] K. Takeuchi, “Second-Order Optimality of Generalized Spatial Modulation for MIMO Channels with No CSI,” IEEE Wireless Commun. Lett., vol. 4, no. 6, pp. 613-616, Dec. 2015.
[1] K. Takeuchi, “Spatial Modulation Achieves Information-Theoretically Optimal Energy Efficiency,” IEEE Commun. Lett., vol. 19, no. 7, pp. 1133-1136, Jul. 2015.


Spatial modulation, energy efficiency, compressed sensing

Theme3:Multiuser Decoding


Decoding and multiuser detection have been separately developed in coding theory and communication theory, respectively. In multiuser decoding, on the basis of a combination of the two fields, joint detection and decoding are performed to realize a significant improvement in decoding performance. In our laboratory, we are aiming to improve the performance of multiuser decoding by applying spatial coupling, which was an idea to improve the performance of belief-propagation-based decoding up to the optimal performance.

Selected publications and works

[3] K. Takeuchi and S. Horio, “Iterative Multiuser Detection and Decoding with Spatially Coupled Interleaving,” IEEE Wireless Commun. Lett., vol. 2, no. 6, pp. 619-622, Dec. 2013.
[2] K. Takeuchi et al., “Iterative LMMSE Channel Estimation and Decoding Based on Probabilistic Bias,” IEEE Trans. Commun., vol. 61, no. 7, pp. 2853-2863, Jul. 2013.
[1] K. Takeuchi, “Accelerating Iterative Detection for Spatially Coupled Systems by Collaborative Training,” IEEE Commun. Lett., vol. 17, no. 3, pp. 451-454, Mar. 2013.


Multiuser decoding, belief propagation, spatial coupling

Title of class

Probability and Statistics / Numeric Analysis / Information and Communication Systems

Others (Awards, Committees, Board members)

Dec. 2017 IEEE Nagoya Section Young Researcher Award
Feb. 2016 2016 Exemplary Reviewers of IEEE Trans. Commun.
Feb. 2009 IEEE Kansai Section Student Paper Award

2018 15th IEEE Annual Cons. Commun. Netw. Conf. TPC member
2015 IEICE Trans. Fundamentals. Guest Associate Editor
2013-2017 IEICE Trans. Fundamentals. Associate Editor

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