Introduction

We are conducting research on new signal processing based on deep learning to achieve high-quality and flexible wireless communication. Additionally, we are studying new sensors that can detect biological signals such as heartbeats and breathing, as well as human behavior using radar and other technologies. Furthermore, we are researching detection technologies for mental disorders such as dementia and techniques for analyzing social media.

■Secure Information Sharing and Security
・Research Objective: To devise an adaptive data mapping mechanism using deep reinforcement learning for efficient digital twin data mapping in the Internet of Energy.
- Title: Deep Reinforcement Learning Based Data-Driven Mapping Mechanism of Digital Twin for Internet of Energy, Xu Siyu, Guan Xin, Peng Yu, Liu Yang, Cui Chen, Chen Hongyang, Ohtsuki Tomoaki, Han Zhu （IEEE Transactions on Network Science and Engineering） 11 （ 4 ） 3876-3890 Jul. 2024
・Research Objective: To introduce a new method for measuring explainability in machine learning models by referencing an approximated human model and comparing it with local explanations from common XAI tools.
- Title: Toward Building Trust in Machine Learning Models: Quantifying the Explainability by SHAP and References to Human Strategy, Li Zhaopeng, Bouazizi Mondher, Ohtsuki Tomoaki, Ishii Masakuni, Nakahara Eri （IEEE Access） 12 11010-11023
・Research Objective: To develop a method using multiple 2D Lidars for effective activity detection in indoor environments, particularly for monitoring potentially hazardous events for the elderly.
- Title: Activity Detection in Indoor Environments Using Multiple 2D Lidars, Bouazizi Mondher, Mora Alejandro Lorite, Feghoul Kevin, Ohtsuki Tomoaki （Sensors） 24 （ 2 ） 626 Jan. 2024
■Wireless Communication
・Research Objective: To develop a low-complexity and high-accuracy channel prediction method for interference alignment using an auto regressive model.
- Title: A Low-Complexity High-Accuracy AR Based Channel Prediction Method for Interference Alignment, Ozawa Masayoshi, Ohtsuki Tomoaki, Panahi Fereidoun H., Jiang Wenjie, Takatori Yasushi, Nakagawa Tadao （2018 IEEE Global Communications Conference (GLOBECOM)） 1-7 Dec. 2018
・Research Objective: To propose an energy-efficient channel hopping protocol for cognitive radio networks that addresses the issues of energy waste and unrealistic assumptions in existing multi-radio protocols.
- Title: Energy-Efficient Channel Hopping Protocol for Cognitive Radio Networks, Li Aohan, Han Guangjie, Ohtsuki Tomoaki （GLOBECOM 2017 - 2017 IEEE Global Communications Conference） 1-6 Dec. 2017
・Research Objective: To construct the optimal impersonation of CSI by a linear programming problem for maximizing leaked information to an untrusted relay in PLNC.
- Title: Optimal impersonation of CSI for maximizing leaked information to untrusted relay in PLNC, Takyu Osamu, Matsumoto Kengo, Ohtsuki Tomoaki, Fujii Takeo, Sasamori Fumihito, Handa Shiro （2016 IEEE Wireless Communications and Networking Conference） 1-5 Apr. 2016
■Algorithm Development
・Research Objective: To propose a decentralized automatic modulation classification method using lightweight network and model aggregation for improved training efficiency in wireless communications.
- Title: Lightweight Network and Model Aggregation for Automatic Modulation Classification in Wireless Communications, Fu Xue, Gui Guan, Wang Yu, Ohtsuki Tomoaki, Adebisi Bamidele, Gacanin Haris, Adachi Fumiyuki （2021 IEEE Wireless Communications and Networking Conference (WCNC)） 1-6 Mar. 2021
・Research Objective: To propose an effective radar signal recognition method using neural architecture search to automatically design convolutional neural networks.
- Title: An Effective Radar Signal Recognition Method Using Neural Architecture Search, Zhang Min, Luo Wang, Wang Yu, Sun Jinlong, Yang Jie, Ohtsuki Tomoaki （2021 IEEE 94th Vehicular Technology Conference (VTC2021-Fall)） 1-5 Sep. 2021
・Research Objective: Development of a lightweight residual neural network for automatic modulation classification in wireless communications.
- Title: Lightweight Network Design Based on ResNet Structure for Modulation Recognition, Lu Xiao, Tao Mengyuan, Fu Xue, Gui Guan, Ohtsuki Tomoaki, Sari Hikmet （2021 IEEE 94th Vehicular Technology Conference (VTC2021-Fall)） 1-5 Sep. 2021
■Signal Processing Design Based on Quantized Information
・Research Objective: To propose a novel Doppler sensor-based method for estimating blink duration by analyzing eyelids closing and opening behavior on a spectrogram.
- Title: Doppler Sensor-Based Blink Duration Estimation by Analysis of Eyelids Closing and Opening Behavior on Spectrogram, Yamamoto Kohei, Toyoda Kentaroh, Ohtsuki Tomoaki （IEEE Access） 7 42726-42734
・Research Objective: To develop a new direction-of-arrival estimation method for wideband signals that achieves high resolution and accuracy with low computational complexity.
- Title: Low Computational Complexity Direction-of-Arrival Estimation of Wideband Signal Sources Based on Squared TOPS, HAYASHI Hirotaka, OHTSUKI Tomoaki （IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences） E100.A （ 1 ） 219-226
・Research Objective: To develop a soft-decision-aided, joint MAP estimation method for channel coefficients and interference power in superposed OFDM transmission with minimal pilot overhead.
- Title: Joint SDA-MAP Estimation of Channel and Interference Power in Superposed OFDM Transmission, Kakizki Yuto, Ohtsuki Tomoaki, Kam Pooi-Yuen, Suzaki Kouhei, Sasaki Hirofumi, So Hideya （GLOBECOM 2017 - 2017 IEEE Global Communications Conference） 1-6 Dec. 2017
■User Preference and Behavior Analysis
・Research Objective: Identification of Bitcoin addresses related to High Yield Investment Programs through transactions pattern analysis.
- Title: Identification of High Yielding Investment Programs in Bitcoin via Transactions Pattern Analysis, Toyoda Kentaroh, Ohtsuki Tomoaki, Mathiopoulos P. Takis （GLOBECOM 2017 - 2017 IEEE Global Communications Conference） 1-6 Dec. 2017
・Research Objective: Development of a microwave-identification method for mobile-phone indoor localization using web-access time.
- Title: Mobile-phone indoor localization based on microwave identification using web-access time, Yamamoto Masaaki, Ohtsuki Tomoaki, Utsumi Hironori, Furukawa Naohiro （2014 IEEE Topical Conference on Wireless Sensors and Sensor Networks (WiSNet)） 28-30 Jan. 2014
・Research Objective: To develop an indoor monitoring system using wireless signals and antenna arrays to classify states and activities.
- Title: Array sensor: Monitoring using wireless signals, Hong Jihoon, Ohtsuki Tomoaki （2013 International Conference on ICT Convergence (ICTC)） 757-758 Oct. 2013
■Communication Resource Allocation Based on Integrated Environmental Cognition Estimation
・Research Objective: To propose a fast blind rendezvous scheme with full rendezvous diversity for secondary users in distributed heterogeneous cognitive radio networks.
- Title: A Fast Blind Scheme With Full Rendezvous Diversity for Heterogeneous Cognitive Radio Networks, Li Aohan, Han Guangjie, Ohtsuki Tomoaki （IEEE Transactions on Cognitive Communications and Networking） 5 （ 3 ） 805-818 Sep. 2019
・Research Objective: To propose a dynamic ABS assignment method to improve the resource utilisation of base stations and the convergence time of subframe assignment.
- Title: Improvements of femto‐base station resource utilisation and ABS assignment convergence for dynamic ABS assignment, Ozawa Masayoshi, Ohtsuki Tomoaki （IET Communications） 11 （ 3 ） 370-376 Feb. 2017
・Research Objective: To propose a design method of relative magnitude coefficients using Brent's method to improve system capacity in K-User MIMO interference channels.
- Title: Algorithm Design of Relative Magnitude Coefficients Using Brent's Method on the K-User MIMO-IFC, MATSUMURA Kunitaka, OHTSUKI Tomoaki （IEICE Transactions on Communications） E99.B （ 8 ） 1902-1909
■User Experience Enhancement
・Research Objective: To propose a QoE-aware optimization method for joint bit rate and playout threshold control in LTE networks to improve video streaming quality.
- Title: QoE-Aware Video Streaming Transmission Optimization Method for Playout Threshold Adjustment in LTE, Qi Yan, Ohtsuki Tomoaki （2018 IEEE 87th Vehicular Technology Conference (VTC Spring)） 1-5 Jun. 2018
・Research Objective: To develop a service-aware user-centric scheme that achieves multi-point fairness in resource allocation for C-RAN downlink CoMP transmission.
- Title: Multi-point fairness in resource allocation for C-RAN downlink CoMP transmission, Beylerian Anthony, Ohtsuki Tomoaki （EURASIP Journal on Wireless Communications and Networking） 2016 （ 1 ） Dec. 2016
・Research Objective: To evaluate the effects of audio and video communication from mothers on the sense of security and communicative actions of children staying at home alone.
- Title: Evaluation of effects of audio and video of mother on sense of security and communicative action of children staying at home, Suzuki Madoka, Ohtsuki Tomoaki （2015 Science and Information Conference (SAI)） 1424-1426 Jul. 2015
■Elderly Care Monitoring
・Research Objective: Developing an infrared array sensor-based method for localizing and counting people for health care and monitoring.
- Title: An Infrared Array Sensor-Based Method for Localizing and Counting People for Health Care and Monitoring, Bouazizi Mondher, Ohtsuki Tomoaki （2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)） 4151-4155 Jul. 2020
・Research Objective: To develop an anomaly detection method in toilets using FMCW radar and supervised machine learning to identify fainting incidents among the elderly.
- Title: FMCW Radar-Based Anomaly Detection in Toilet by Supervised Machine Learning Classifier, Takabatake Wataru, Yamamoto Kohei, Toyoda Kentaroh, Ohtsuki Tomoaki, Shibata Yohei, Nagate Atsushi （2019 IEEE Global Communications Conference (GLOBECOM)） 1-6 Dec. 2019
・Research Objective: To propose a detection algorithm for unexpected falls using array antenna to improve fall detection accuracy.
- Title: Detecting unexpected fall using array antenna, Hino Yusuke, Hong Jihoon, Ohtsuki Tomoaki （2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC)） 2104-2108 Sep. 2014
■New Sensor Technology
・Research Objective: To propose and evaluate a novel device-free passive localization system using an array sensor based on signal eigenvector to improve localization accuracy.
- Title: Signal Eigenvector-Based Device-Free Passive Localization Using Array Sensor, Hong Jihoon, Ohtsuki Tomoaki （IEEE Transactions on Vehicular Technology） 64 （ 4 ） 1354-1363 Apr. 2015
・Research Objective: To propose an activity recognition method using a low resolution infrared array sensor for monitoring fundamental activities of elderly people.
- Title: Activity recognition using low resolution infrared array sensor, Mashiyama Shota, Hong Jihoon, Ohtsuki Tomoaki （2015 IEEE International Conference on Communications (ICC)） Jun. 2015
・Research Objective: To develop a fall detection system using a low resolution infrared array sensor that ensures privacy, low cost, and convenience.
- Title: A fall detection system using low resolution infrared array sensor, Mashiyama Shota, Hong Jihoon, Ohtsuki Tomoaki （2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC)） 2109-2113 Sep. 2014
■New Category: Power Absorption Modeling
・Research Objective: To develop a method for power compensation in WLAN positioning using a smartphone to improve positioning accuracy.
- Title: Power compensation in WLAN positioning using a smartphone, Yamamoto Masaaki, Ohtsuki Tomoaki （2014 IEEE Ninth International Conference on Intelligent Sensors, Sensor Networks and Information Processing (ISSNIP)） 1-6 Apr. 2014
■Power Absorption Modeling
・Research Objective: To propose a scheme to suppress multiple wideband interferences based on the superposition probability for improved BER performance.
- Title: Suppression of multiple wideband interferences based on superposition probability, Kakizaki Yuto, Shibata Yohei, Ohtsuki Tomoaki, Mashino Jun （EURASIP Journal on Wireless Communications and Networking） 2016 （ 1 ） Dec. 2016
・Research Objective: To develop a power-absorption-based model for power compensation in WLAN positioning using smartphones.
- Title: Power-Absorption-Based Model for Power Compensation in WLAN Positioning Using Smartphone, YAMAMOTO Masaaki, OHTSUKI Tomoaki （IEICE Transactions on Communications） E98.B （ 6 ） 1125-1132
・Research Objective: To maximize global SNR and optimize power allocation for distributed estimation and data collection capacity in wireless sensor networks under individual power constraints.
- Title: Global SNR maximization for distributed estimation and capacity of data collection in wireless sensor networks using individual power constraint, Arifin Ajib Setyo, Ohtsuki Tomoaki （Signal and Information Processing Association Annual Summit and Conference (APSIPA), 2014 Asia-Pacific） 1-5 Dec. 2014
■New Category: Vehicular Device Applications
・Research Objective: To propose a decentralized learning-based scenario identification method for intelligent vehicular communications that improves training efficiency and reduces model complexity.
- Title: Decentralized Learning-based Scenario Identification Method for Intelligent Vehicular Communications, Zhou Yaru, Wangt Yu, Liu Pengfei, Yang Jie, Ohtsuki Tomoaki, Sari Hikmet （2021 IEEE 94th Vehicular Technology Conference (VTC2021-Fall)） 1-5 Sep. 2021
■New Category: Performance Comparison
・Research Objective: To develop a new DOA estimation method for MIMO radar systems using a temporal-spatial virtual array and adaptive PRI control technique for accurate estimation in the presence of multiple targets.
- Title: DOA estimation in MIMO radar using temporal spatial virtual array with MUSIC algorithm, Hayashi Hirotaka, Ohtsuki Tomoaki （2015 9th International Conference on Signal Processing and Communication Systems (ICSPCS)） 1-6 Dec. 2015
■Performance Comparison
・Research Objective: To study the influence of pedestrian blockage on mmWave cellular networks and propose reinforcement learning-based user association algorithms to mitigate its effects.
- Title: Influence and Mitigation of Pedestrian Blockage at mmWave Cellular Networks, Kumar S Yuva, Ohtsuki Tomoaki （IEEE Transactions on Vehicular Technology） 69 （ 12 ） 15442-15457 Dec. 2020
・Research Objective: To propose a novel dynamic grouping method for improving the recovery performance of block-structured sparse signals using block-sparse adaptive algorithms.
- Title: Recovery of Block-Structured Sparse Signal Using Block-Sparse Adaptive Algorithms via Dynamic Grouping, Ye Chen, Gui Guan, Xu Li, Ohtsuki Tomoaki （IEEE Access） 6 56069-56083
・Research Objective: Designing a co-location system using IGMM to accurately identify groups of co-located mobile users in real-time based on their radio signal similarities.
- Title: IGMM-Based Approach for Discovering Co-Located Mobile Users, Varela Pedro M., Hong Jihoon, Ohtsuki Tomoaki （2016 IEEE Global Communications Conference (GLOBECOM)） 1-6 Dec. 2016
■New Category: Smart City Concepts and Definitions
・Research Objective: To introduce the concept and definition of a smart city and explain the ambient intelligence that supports it.
- Title: A Smart City Based on Ambient Intelligence, OHTSUKI Tomoaki （IEICE Transactions on Communications） E100.B （ 9 ） 1547-1553
■New Category: Propagation Delay Analysis
・Research Objective: Development and performance evaluation of an MMSE macrodiversity reception system with delay difference correction for live broadcasts of road races.
- Title: Development and Performance Evaluation of MMSE MacroDiversity Reception System With Delay Difference Correction, Mitsuyama Kazuhiko, Ikeda Tetsuomi, Ohtsuki Tomoaki （IEEE Transactions on Vehicular Technology） 62 （ 9 ） 4288-4298 Nov. 2013
■Propagation Delay Analysis
・Research Objective: To propose a hybrid radios rendezvous (HRR) algorithm to improve rendezvous efficiency in heterogeneous cognitive radio networks.
- Title: Multiple Radios for Fast Rendezvous in Heterogeneous Cognitive Radio Networks, Li Aohan, Han Guangjie, Ohtsuki Tomoaki （IEEE Access） 7 37342-37359
■Signal Interference Management
・Research Objective: To propose a blind source separation approach using non-negative matrix factorization algorithms for high-resolution heartbeat detection in non-contact heart rate monitoring via Doppler radar.
- Title: Blind Source Separation on Non-Contact Heartbeat Detection by Non-Negative Matrix Factorization Algorithms, Ye Chen, Toyoda Kentaroh, Ohtsuki Tomoaki （IEEE Transactions on Biomedical Engineering） 67 （ 2 ） 482-494 Feb. 2020
・Research Objective: To propose a low-complexity subspace MMSE estimation method for improving channel estimation accuracy in massive MU-MIMO systems.
- Title: Low-Complexity Subspace MMSE Channel Estimation in Massive MU-MIMO System, Deng Yunfeng, Ohtsuki Tomoaki （IEEE Access） 8 124371-124381
・Research Objective: To develop a wireless MIMO switching system that enhances secure communication by mitigating the risk of information exploitation by untrusted relays through overloaded access and shared information signals.
- Title: Overloaded Wireless MIMO Switching for Secure Wireless Communication Exchanging to Untrusted Relay, Takahashi Arata, Sasamori Fumihito, Handa Shiro, Takyu Osamu, Fujii Takeo, Ohtsuki Tomoaki （2019 Eleventh International Conference on Ubiquitous and Future Networks (ICUFN)） 121-125 Jul. 2019

Areas of Research

・Secure Information Sharing and Security
・Wireless Communication
・Algorithm Development
・Signal Processing Design Based on Quantized Information
・User Preference and Behavior Analysis
・Traffic Prediction Based on Database
・Communication Resource Allocation Based on Integrated Environmental Cognition Estimation
・User Experience Enhancement
・Elderly Care Monitoring
・New Sensor Technology
・Vehicular Device Applications
・Smart City
・Propagation Analysis
・Signal Interference Management

Social Contributions

・Enhancing Communication and User Experience: This research optimizes communication resource allocation by analyzing user preferences and environmental data, improving user experience quality and ensuring safety.
・Improving Safety and Security through Technology: The development of a radio wave monitoring sensor that accurately identifies states and estimates positions enhances safety and security across various environments.