Country：Japan

Country：Japan

Country：Japan

Country：Japan

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/jiot.2023.3311736

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/OJVT.2023.3311544

Open Access

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/OJVT.2023.3300448

Open Access

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/ojvt.2023.3307674

Open Access

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/OJVT.2023.3288041

Open Access

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/OJVT.2023.3281723

Open Access

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/JIOT.2023.3244627

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/OJVT.2023.3237390

Open Access

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/OJVT.2022.3226192

Open Access

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/OJVT.2022.3215662

Open Access

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/twc.2022.3151662

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/jiot.2021.3138055

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/ojvt.2022.3164461

Open Access

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2021cep0011

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2020ebp3155

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2020dsp0008

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2021.3117252

Open Access

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2020ebp3142

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2020ebp3095

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/jsen.2021.3053158

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2019ebp3044

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TCCN.2019.2930594

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2018EBP3242

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2017EBP3448

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2017NEP0005

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>Smart metering systems with Wireless Smart Utility Network (Wi-SUN) have been introducing in gas and water infrastructures for optimal management of energy and resources. These wireless systems require low-power consumption to operate long period, e.g., 10 years by battery operation. One of the solutions is development of Media Access Control (MAC) protocol for low-power operation. The Feathery Receiver Initiated Transmission (F-RIT) protocol is one of the implementable low-power consumption MAC protocol complied with IEEE 802.15.4g global standard for the MAC layer of the Wi-SUN systems. In this paper, the feasibility and effectiveness of the F-RIT protocol are experimentally investigated in terms of communication link establishment success rate performance and power consumption performance by implementing the F-RIT protocol on commercial Wi-SUN modules equipped with IEEE 802.15.4g complied RF module.</p>

DOI： 10.1541/ieejeiss.137.1461

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2016SCI0002

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1541/ieejeiss.136.1555

Web of Science

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Image Information and Television Engineers  

DOI： 10.3169/itej.68.J502

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.E97.B.886

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.E97.13.875

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DOI： 10.1143/JJAP.51.07GG04

Web of Science

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DOI： 10.1587/transcom.E95.B.1345

Web of Science

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DOI： 10.1143/JJAP.48.07GB07

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DOI： 10.1143/JJAP.48.07GB06

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DOI： 10.1143/JJAP.47.6526

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1143/JJAP.46.4541

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/CCNC54725.2025.10976038

Language：English   Publishing type：Research paper (international conference proceedings)  

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DOI： 10.1109/CCNC54725.2025.10976054

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Language：English   Publishing type：Research paper (international conference proceedings)  

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DOI： 10.1109/VCC60689.2023.10475043

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/vtc2023-spring57618.2023.10201148

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DOI： 10.1109/CSCN57023.2022.10050970

Language：English  

DOI： 10.1109/CSCN57023.2022.10051012

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DOI： 10.1109/WPMC55625.2022.10014958

Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/VTC2022-Fall57202.2022.10012901

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/vtc2022-spring54318.2022.9860692

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/wpmc52694.2021.9700410

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/wpmc52694.2021.9700433

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/vtc2021-fall52928.2021.9625172

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/vtc2021-fall52928.2021.9625571

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/wf-iot51360.2021.9595050

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/vtc2021-spring51267.2021.9449069

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ccnc49032.2021.9369584

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ccnc49032.2021.9369627

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DOI： 10.1109/vtc2020-fall49728.2020.9348472

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/vtc2020-fall49728.2020.9348572

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/WPMC50192.2020.9309485

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/wf-iot48130.2020.9221467

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DOI： 10.1109/vtc2020-spring48590.2020.9128591

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/vtc2020-spring48590.2020.9129109

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ccnc46108.2020.9045557

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ccnc46108.2020.9045549

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ccnc46108.2020.9045471

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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DOI： 10.1109/DySPAN.2019.8935871

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DOI： 10.1109/VTCFall.2019.8891086

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DOI： 10.1109/PIMRC.2019.8904172

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DOI： 10.1109/WPMC.2018.8713129

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DOI： 10.1109/WPMC.2018.8713020

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DOI： 10.1109/WPMC.2018.8712894

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DOI： 10.1109/WPMC.2017.8301789

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DOI： 10.1109/VTCSpring.2017.8108398

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DOI： 10.1109/icc.2016.7510981

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DOI： 10.1109/vtcspring.2015.7146093

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/wpmc.2014.7014864

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DOI： 10.1109/wcnc.2014.6951977

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

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DOI： 10.1109/wcnc.2013.6554657

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DOI： 10.1109/vetecs.2012.6240286

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.4108/icst.crowncom.2011.245903

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/pimrcw.2010.5671368

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DOI： 10.1109/vetecs.2010.5493698

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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DOI： 10.1109/icics.2007.4449855

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CiNii Research

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CiNii Research

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CiNii Research

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CiNii Research

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CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Authorship：Lead author   Language：English   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (bulletin of university, research institution)   Publisher：京都大学電気関係教室・洛友会  

DOI： 10.14989/201397

CiNii Research

Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Authorship：Last author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper discusses key enabling technologies to realize wide area and mobile communication systems based on IEEE 802.15.4g wireless smart utility network (Wi-SUN) that is mainly used for advanced metering infrastructure. Firstly, three applications of the wide area and mobile communication systems are proposed. Then, transmission performance is evaluated by using propagation characteristic models for the three applications. Service area of the communication systems is finally estimated. Secondary, the service area calculation is validated by using actual Wi-SUN certified IEEE 802.15.4g modules. Thirdly adoption of maximum ratio combining diversity technique is proposed for the IEEE 802.15.4g based wide area and mobile communication systems. Then extension of the coverage area by the technique is evaluated by computer simulation.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Broadband communication systems using VHF band are studied to secure wider coverage area than conventional cellular phone network area using UHF band. The systems have been studied on fixed wireless access non multi-level modulation scheme. Though ARIB STD-T103 was standardized, no studies focused on mobile wireless communication environments with multi-level modulation. This paper proposes several receivers configuration for mobile communication systems using VHF band based on ARIB STD-T103 and shows the bit error rate performance by computer simulation under highly multipath fading environments.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper describes significance of VHF band broadband mobile communication systems in 5th generation mobile communication systems. Then, this paper introduces a developed broadband mobile communication prototype in VHF band that is compliant with ARIB STD-T103 and shows the bit error rate (BER) performance under multipath fading and non-fading environments.

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)   Publisher：THE INSTITUTE OF SYSTEMS, CONTROL AND INFORMATION ENGINEERS  

DOI： 10.11509/isciesci.59.10_381

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

In 5th generation mobile communication systems, shot range communication through higher frequency band is key technology. However, dense installing base station for covering the service are is necessary, because the coverage size through the high frequency band is small. In addition, installing base stations individually by each operator leads congestion installing. Congestion installing is not efficient in terms of mutual interferences, spatial restriction and CAPEX/OPEX. In this paper, inter-operator spectrum and infrastructure sharing in heterogeneous network is proposed. For efficient operation of network sharing in multi-band heterogeneous network, important factor is not only resource allocation but also cell association. This paper proposes resource allocation and cell association algorithms by using the sum of logarithm of user rate as utility function. Performances of proposed two proposed algorithms are demonstrated through computation simulation.

CiNii Research

Language：English   Publishing type：Research paper, summary (international conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Field experiments in the TV White Space (TVWS) were conducted under the White Space pilot program organized by U.K. Ofcom in July 2014, using IEEE 802.11af and TVWS LTE system both of which were developed by NICT, Japan. In the pilot program, it is mandatory for a White Space Device (WSD) to obtain available channels for transmission and maximum permitted transmission power from White Space Database (WSDB) according to its location, antenna height, device class and so on. The WSDB is required to be qualified by the Ofcom after a long test procedure to start the operation. Also, the WSDs are required to satisfy a very hard spectrum mask specified by the Ofcom. NICT has successfully passed the WSDB qualification process and developed WSDs with the spectrum mask requirements satisfied based on IEEE 802.11af and TVWS LTE. Using the developed WSDB and WSDs, the IEEE 802.11af system achieved 2 Mbps downlink throughput over 3.7 km with transmission power of 36dBm EIRP using one TV channel. Meanwhile, the TVWS LTE system achieved downlink throughput of 45.5 Mbps with 20 MHz (contiguous three TV channels) for each of uplink and downlink. It is the first achievement of the TVWS field experiments to measure the throughput of long-distance and broadband wireless link in the center of metropolitan urban area as in London, U.K..

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

For the coexistence management between primary and secondary users in TV white space, a simple propagation model for short range transmission and low antenna height is needed to define the interference risk area to primary user from secondary user. To estimate the area, measurements of building penetration loss have been conducted at UHF band, and a propagation model development and verification were performed by using a large-sized light-gauge steel building. Furthermore, same measurements have been conducted for a small-size light-gauge steel house and a wooden house, and extracted attenuation coefficients are compared.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this study, we investigate a propagation loss model for usage of TV White Space (TVWS) by secondary users (SU). Conventional propagation models in UHF band were usually created under assumptions of high base station antenna height and long distance. Therefore, those models do not match the conditions when a SU operating in TVWS has low antenna height and short propagation distance. We then conducted outdoor channel measurements based on near field communication using low height antenna in TVWS and found that a modified two-path model was effective for estimating interference area of SU.

CiNii Research

Authorship：Lead author   Language：English   Publishing type：Rapid communication, short report, research note, etc. (bulletin of university, research institution)  

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Demand for wireless communication has increased significantly, on the other hand, the frequency band available for wireless communication is scarce. Use of wireless communication in the TV White Spaces is expected as one of the effective solutions. This report shows the challenges and approach to implement IEEE 802.11af based Wireless Local Area Networks (WLAN) operating in TV White Spaces. Particularly, a study of out-of-band emission reduction schemes to meet a very strict transmission spectrum mask and the overview of the developed IEEE 802.11af prototype hardware are shown.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

White space LTE (WS-LTE) is studied as a candidate technique for improving the shortage situation of the spectrum especially in the cellular bands. In the indoor environment, more channels can be usable for white space communication by the loss of the walls. Therefore we propose a method to deploy multiple WS-LTE base stations with different settings using available WS channels. It provides more capacity than the case deploying multiple WS-LTE base stations with a unified setting. This report introduces the formulation and evaluation function of this method, and showing the feasibility of the method by simulation results.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

TV white space (WS) is expecting for effective use of frequency resources. Since TV broadcast which is primary service must not be affected from TVWS systems, the propagation characteristic to estimate the interference area is important. The propagation model of the Ministry of Posts and Telecommunications notification No. 640 is conventionally applied to estimate the primary service area, however, it is not supported to set the low antenna height and the short transmission distance less than 1km. For above reasons, a propagation experiment has been conducted to develop a propagation model for TVWS systems. From the measurement result of the received power versus distance, it is found that the two-path model with a reflection wave from ground will be applied. From this result, the propagation model to estimate the interference area of TVWS system is examined. Moreover, when transmission distance becomes long, it becomes impossible to disregard the vertical interval above sea level of TX and RX positions. Thus it becomes important to consider the land profile for calculation of the break point position in two-path model.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

There has been no report on field experiments for long-distance broadband communications over 10km using wireless communication systems based on TV white space standardized specifications. We have conducted experiments in Tono city, Iwate in December 2013 and confirmed that IEEE 802.22 system achieved throughput of 4.5Mbps for uplink and 5.2Mbps for downlink over 12.7km, respectively. Also, with the IEEE 802.22 system as backbone link, its access area was extended by multi-hop networking using an IEEE 802.11af system. It was demonstrated that the system provided a broadband Internet access in the area where neither wired nor wireless Internet access was available and that some applications such as web browsing, video phone and streaming were practically used.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper summarizes enabling technologies toward 5^<th> generation mobile communication systems: Cognitive Radio Dynamic spectrum access (DSA)/sharing (DSS) network, Cloud based radio with radio over fiber (RoF), millimeter wave mobile communication systems, and VHF and UHF band wireless communication systems.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper summarizes current developments activities of white space communication systems based on, cognitive radio technologies expected as an enabling technology toward next generation mobile communication systems. We also introduce the standardization activities on this area.

CiNii Research

Language：Japanese   Publisher：CQ出版  

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Frequency resources for wireless communications would be depleted by explosively grown wireless data traffic in the near future. Meanwhile, there are temporarily or spatially unused frequency resources which are called White Spaces in the frequency bands assigned for specific uses. In particular the White Spaces in the band for television broadcasting service are named TV White Spaces (TVWS). To approve the TVWS use of secondary systems, improvement of legal systems has been discussed in the USA, UK, Singapore, Japan, etc. In accordance with these circumstances, several task groups have standardized wireless communication systems operating in TVWS spectrums. Particularly, IEEE 802.11 Task Group (TG) af for the Wireless Local Area Network (WLAN) operating in TV White Spaces published the latest draft IEEE 802.11af/Draft 5.0 in July 2013. This report shows the world's first prototype hardware for IEEE 802.11af/Draft 5.0 based WLAN systems operating in TV White Spaces. The developed prototype hardware can meet the FCC's transmit spectrum mask for portable device.

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Demand for wireless communication has increased significantly, on the other hand, the frequency band available for wireless communication is scarce. Use of wireless communication in the TV white spaces has been promoted in various countries, and primary user protection is mandatory. Particularly, very strict transmit spectrum mask is configured by FCC in USA. In order to effective use of TV white spaces, this report proposes a transmit power control method based on adaptive time-domain windowing processing for orthogonal frequency division multiplexing (OFDM) based wireless communication systems operating on TV white spaces.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

White space communications where radio systems are operated as secondary use of the TV band avoiding radi interference to the TV broadcasting services are discussed in the world. Meanwhile, specifications of various radio systems fi local area and long distance wireless communications are being standardized as IEEE 802.11 of and IEEE 802.22. Furth essential specifications in order to realize the white space communications are also being discussed for standardization such white space database to protect the primary users from the secondary users and coexistence of secondary users, as in IEEE 802.19.1, to avoid interference between them. This paper introduces an evaluation system that integrates technologies mentioned above based on assumed usage scenarios to study feasibility of the white space communications.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Internal/External technical report, pre-print, etc.   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Demand for wireless communication has increased significantly, on the other hand, the frequency band available for wireless communication is scarce. Use of wireless communication in the TV white space has been promoted in various countries, and primary user protection is mandatory. Particularly, very strict transmit spec-trum mask is configured by FCC in USA. To satisfy this transmit spectrum mask, a transmit circuit requires a large number of digital low-pass filter taps. As a result, complexity of the transmit circuit increases significantly, which compromises the feasibility of its implementation. On the other hand, time-domain windowing scheme to suppress the out-of-band emission is used in IEEE 802.11a/g/n. In this report, the effectiveness of the time-domain windowing method in the TV white space is evaluated.

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Demand for wireless communication has increased significantly, on the other hand, the frequency band available for wireless communication has been very tight. Use of wireless communication in TV white space has been promoted in various countries. Currently, development of standards for wireless LAN in TV white space has been carried out in the Task Group af (TGaf) of the IEEE802.11 Working Group, aiming at the completion of work in 2013. In this report, we describe the trends in the physical layer in the stage of letter ballot in the standardization work of TGaf. Additionally, we propose a multi-channel operation system in order to make effective use of TV white space even in the plesence of other TV white space stations such as Area-1-seg stations.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

MIMO 2-way relay network is known as a solution to realize high data rate relay networks. 2-way relaying is possible provided that some interference cancellation techniques such as MIMO beamforming or network coding is properly preformed. To perform beamforming CSIT is needed. Here we employ relative calibration, so that channel reciprocity holds and CSIT is obtained without feedback from the receiver. In this paper, a demonstra- tion system for MIMO 2-way relay network using MIMO beamforming is implemented on our developed prototype hardware.

CiNii Research

Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.32.0_569

CiNii Research

Language：Japanese   Publisher：日本工業出版  

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

In recent years, researches of multi-hop relay networks have been becoming an attractive research topic owing to their demands in future wireless network systems such as sensor networks and smart utility networks. To achieve a high data rate and high reliability multi-hop relay network, synchronized MIMO two-way relay network which employs multiple antenna technique (MIMO) and high spectral efficiency modulation scheme OFDM has been proposed. To realize such synchronized network, the requirement for transmit and receive timing synchronization among nodes in the network is very strict to achieve high efficiency. This paper proposes a network synchronization scheme which enables simultaneous transmission of data packets and timing synchronization control packets, thus allows dynamic participation of node joining the network and realizes network topology flexibility. Furthermore, the proposed scheme is implemented in our developed hardware at 950MHz band to validate its effectiveness.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：一般社団法人電子情報通信学会  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

In recent years, wireless mesh network working as backhaul for several sensor network applications has been attracting much of attention. For realization of a high data rate and reliable mesh network, a synchronized mesh network technology employing OFDM as modulation scheme has been proposed. However, the conventional scheme requires many time slots for establishment of synchronization among nodes of the network, after which data transmission is performed. This paper proposes a novel network synchronization scheme where data transmission and synchronization establishment can be done simultaneously. The proposed algorithm is implemented in the developed 950MHz TDD MIMO two-way network prototype hardware, and its performance is verified.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Two-way MIMO relay is known as a key technology to achieve high efficiency multi-hop networks. In the two-way MIMO relay, a multi-hop network is treated as a BMAC channel that is a combination of broadcast and multiple access channels. Multiple forward and backward flows are spatially multiplexed as long as the number of flows do not exceed degree of freedom of the BMAC channel. Further performance improvement or complexity reduction can be achieved by using transmit power control and MIMO network coding. This paper firstly gives theory of the two-way MIMO relay and secondly shows measurement results of the two-way MIMO relay in a real environment by using a prototype hardware.

CiNii Research

Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.31.0_403

CiNii Research

Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

In recent years, owing to its benefit of improving network connectivity and flexibility, wireless multi-hop relay network has been attracting much attention with many promising applications in sensor networks and utility networks. When wireless multi-hop relay network is in operation as a secondary system, however, a spectrum sharing mechanism with the primary system should be employed. To achieve high spectral efficiency, it is required to recognize spectrum usage condition of the primary system by spectrum sensing and to assign available spectrum to the secondary system. In this paper, a spectrum sensing mechanism for 950MHz low power active radio system using FFT is proposed, and a hardware prototype employing the proposed mechanism is implemented.

CiNii Research

Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Relaying technique is one of potential technique to solve the shadow fading problem. In this paper, MIMO propagation measurements at 5 GHz band are conducted in a L-shaped corridor environment with various relay positions. The results show benefits of relay technique in the shadow fading environment and the optimum position for relay node can be determined. Performance of various relaying schemes including decode-and-forward, two-way relay employing network coding, and cooperative relay schemes are evaluated. As a result, two-way relay employing network coding achieves superior performance, while cooperative relaying scheme is not effective in the shadowing environment.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

A new concept of wireless grid to realize indoor wireless energy supply and ubiquitous network is proposed in this paper. Electrical power, for example generated by solar panels, are supplied to electronic and communication devices in indoor environments via the wireless grid as electro magnetic wave illuminations. The remaining energy, that are not consumed at the devices, are harvested by energy recycle walls. The devices powered by wireless grid create wireless links with small power under the limitation of wireless energy transmission. On the other hand, the wireless grid plays a role of wireless access network by cooperation among the grid nodes as well as wireless energy supply. Furthermore, the wireless grid unifies with backbone networks to realize heterogeneous ubiquitous networks.

CiNii Research

Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：Institute for Ultrasonic Elecronics  

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

Web of Science

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Wireless multi-hop relay networks have advantages such as robustness and flexibility over conventional fixed networks. Particularly, smart two-way multi-hop relay networks such as MIMO two-way multi-hop relay networks and network coding based two-way multi-hop relay networks, have large network capacity and have been receiving much attention. In this paper, a hardware prototype of a network coding based multi-channel two-way multi-hop relay network over the 950MHz band is developed. In the network, the nodes transmit and receive using time division duplex (TDD). The receiver receives orthogonal frequency division multiplexing (OFDM) signals from two neighboring transmitters simultaneously using multi-channel. Furthermore, to synchronize the receive timing, an extended ranging scheme for orthogonal frequency division multiple access (OFDMA) is implemented.

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

MIMO two-way multihop network (MIMO TMN) has been attracted as a multihop network which overcomes a problem of co-channel interference. In the MIMO TMN, each node has multiple antennas, forward stream (FS) and backward stream (BS) are multiplexed at same timeslot and channel, and interference are cancelled by transmit and receive weights at each node. MIMO TMN is generally operates in multipath fading environment. Orthogonal Frequency Division Multiplexing (OFDM) is known as a modulation scheme which takes advantages of multipath fading. In this paper, we propose MIMO-OFDM two-way multihop network (MIMO-OFDM TMN) and novel network synchronization scheme for proposed MIMO-OFDM TMN. In the proposed synchronization scheme, each transmit node transmits forward OFDM signal (FSG) and backward OFDM signal (BSG) at the same time. At each receive node, arrival time mismatch of FSG and BSG is not greater than guard interval (GI), and inter symbol interference (ISI) and inter carrier intereference (ICI) in demodulated signals is not occured.

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

Authorship：Lead author   Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.29.0_337

CiNii Research

Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.29.0_335

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this report, a performance comparison between feedback method and feedback-less method to obtain channel state information (CSI) is carried out in multi-user MIMO precoding system. In many MIMO precoding techniques, it is necessary to obtain the CSI in transmitter ahead of time. Two CSI obtaining techniques have been proposed. In feedback method, the estimated CSI at the receiver is fed back to the transmitter. On the other hand, feedback-less method has been proposed. In order to use the feedback-less method, channel reciprocity is required. However, the transmitter and receiver RF circuits must be calibrated to achieve channel reciprocity. In the feedback method, throughput performance deterioration is caused by the inaccuracy of the fed back CSI. It is expected that this deterioration of the throuhput performance is more severe in the case of multi-user MIMO than the case of single-user MIMO. This report shows the effectiveness of the feedback-less method to obtain the CSI in multi-user MIMO precoding system.

CiNii Research

Authorship：Lead author   Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：Institute for Ultrasonic Elecronics  

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, Propagation measurement system for MIMO relay network was fabricated, and measurement experiment was conducted. Although MIMO relay is known to increase channel capacity and enlarge area coverage of wireless network, there are rarely experiment results to show its superiority. In this paper, measurement system composed of three MIMO tranceivers and mobile positioners was fabricated, by which the channel reponses corresponding to the relative position of the three node (transmit, relay and receive node) cans be measured. The Initial experiment was conducted in the indoor environment of L-shaped corridor, where shadowing effect on the direct link between the transmitter and receiver is dominant, to validate the performance of MIMO relay system.

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Research

Authorship：Lead author   Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

This report proposes a peak-to-average power ratio (PAPR) reduction method for OFDM signals. Hop-field type neural network (NN) is applied to PAPR reduction with tone injection (TI) method. This proposed method is suitable for global search and PAPR is sufficiently reduced, and side information to transmit parameters for PAPR reduction to a receiver is not required. Furthermore, the proposed NN, in which several IFFTs are pruned for neuron state updating, has less computational complexity than that of the conventional NNs.

CiNii Research

Authorship：Lead author   Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.27.0_379

CiNii Research

Authorship：Lead author   Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)