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

DOI： 10.1109/wcnc61545.2025.10978468

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

DOI： 10.3390/s25061935

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

DOI： 10.1109/icaiic64266.2025.10920754

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

DOI： 10.1109/iscit63075.2024.10793703

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

DOI： 10.20944/preprints202408.0998.v1

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

DOI： 10.1109/apwcs61586.2024.10679283

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

DOI： 10.1109/icufn61752.2024.10625638

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

DOI： 10.3390/s24062006

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

DOI： 10.1109/icaiic60209.2024.10463216

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

DOI： 10.1109/icoin59985.2024.10572031

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

DOI： 10.1109/ccnc51664.2024.10454793

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

DOI： 10.1109/ccnc51664.2024.10454797

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

DOI： 10.3390/fi16010005

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

DOI： 10.1109/vtc2023-fall60731.2023.10333477

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

DOI： 10.1109/pimrc56721.2023.10293860

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

DOI： 10.1587/comex.2023TCL0015

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

DOI： 10.3390/network3030016

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

DOI： 10.1109/icufn57995.2023.10200815

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

DOI： 10.3390/s23031402

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

DOI： 10.3390/network2040029

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

To deal with recent increasing mobile traffic, ultra-broadband communication with millimeter-wave (mmWave) has been regarded as a key technology for 5G cellular networks. In a previous study, a mmWave heterogeneous network was composed of several mmWave small cells overlaid on the coverage of a macro cell. However, as seen from the optical fiber penetration rate worldwide, it is difficult to say that backhaul with Gbps order is available everywhere. In the case of using mmWave access under a limited backhaul capacity, it becomes a bottleneck at the backhaul; thus, mmWave access cannot fully demonstrate its potential. On the other hand, the concept of multi-access edge computing (MEC) has been proposed to decrease the response latency compared to cloud computing by deploying storage and computation resources to the user side of mobile networks. This paper introduces MEC into mmWave heterogeneous networks and proposes a content prefetching algorithm to resolve such backhaul issues. Context information, such as the destination, mobility, and traffic tendency, is shared through the macro cell to the prefetch application and data that the users request. Prefetched data is stored in the MEC and then transmitted via mmWave without a backhaul bottleneck. The effectiveness is verified through computer simulations where we implement realistic user mobility as well as traffic and backhauling models. The results show that the proposed framework achieved 95% system capacity even under the constraint of a 1 Gbps backhaul link.

DOI： 10.3390/s22186983

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

DOI： 10.3390/s22145145

Web of Science

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

DOI： 10.1016/j.comnet.2021.108750

Scopus

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Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ICUFN49451.2021.9528693

Scopus

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Publishing type：Research paper (scientific journal)  

DOI： 10.3390/s21237855

Scopus

PubMed

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Publishing type：Research paper (scientific journal)  

DOI： 10.1109/ACCESS.2021.3068839

Scopus

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

DOI： 10.1109/APWCS50173.2021.9548763

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/apwcs2/apwcs2021.html#OzasaTS21

Publishing type：Research paper (scientific journal)  

DOI： 10.1109/OJVT.2021.3049783

Scopus

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Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2020NVP0002

Scopus

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Other Link： https://dblp.uni-trier.de/db/journals/ieicetb/ieicetb104.html#NakamuraNNKDSTS21

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

DOI： 10.1109/ICCWorkshops49005.2020.9145269

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/icc/icc2020w.html#NakazatoNYLTS20

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

DOI： 10.1109/VTC2020-Fall49728.2020.9348602

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2020f.html#OzasaNHTS20

Publishing type：Research paper (international conference proceedings)  

DOI： 10.23919/URSIAP-RASC.2019.8738198

Scopus

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Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ICREST.2019.8644474

Scopus

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

DOI： 10.1109/VTCFall.2019.8891130

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2019f.html#NakamuraNKD0TS19

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

DOI： 10.1109/WCNCW.2019.8902699

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/wcnc/wcncw2019.html#TranNNSSK19

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

DOI： 10.1109/GLOBECOM38437.2019.9013346

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/globecom/globecom2019.html#NakazatoNTTS19

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

DOI： 10.1109/ICUFN.2019.8805914

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/icufn/icufn2019.html#NakazatoTTS19

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

DOI： 10.1109/CCNC.2019.8651725

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Other Link： https://dblp.uni-trier.de/db/conf/ccnc/ccnc2019.html#NakamuraTS19

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

DOI： 10.1109/GLOBECOM38437.2019.9014261

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Other Link： https://dblp.uni-trier.de/db/conf/globecom/globecom2019.html#LiYFTS19

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2017NEI0004

Scopus

arXiv

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet101b.html#YuHSIKKTTS18

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

DOI： 10.1109/VTCSpring.2018.8417625

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2018s.html#NishiuchiTS18

Publishing type：Research paper (scientific journal)  

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Other Link： https://dblp.uni-trier.de/db/journals/corr/corr1804.html#abs-1804-02124

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

DOI： 10.1109/ICCW.2018.8403583

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/icc/icc2018w.html#TranNFTDSHSBBY18

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2017NEP0002

Scopus

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet101b.html#TranSS18

Publishing type：Research paper (scientific journal)  

DOI： 10.3390/jsan7040043

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Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/APMC.2017.8251586

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Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TVT.2017.2696049

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

DOI： 10.1109/CSCN.2017.8088598

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Other Link： https://dblp.uni-trier.de/db/conf/cscn/cscn2017.html#FrascollaMTTDSK17

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

DOI： 10.1109/SPAWC.2017.8227745

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Other Link： https://dblp.uni-trier.de/db/conf/spawc/spawc2017.html#SakaguchiTO17

Wireless engineers and business planners commonly raise the question on
where, when, and how millimeter-wave (mmWave) will be used in 5G and beyond.
Since the next generation network is not just a new radio access standard, but
instead an integration of networks for vertical markets with diverse
applications, answers to the question depend on scenarios and use cases to be
deployed. This paper gives four 5G mmWave deployment examples and describes in
chronological order the scenarios and use cases of their probable deployment,
including expected system architectures and hardware prototypes. The paper
starts with 28 GHz outdoor backhauling for fixed wireless access and moving
hotspots, which will be demonstrated at the PyeongChang winter Olympic games in
2018. The second deployment example is a 60 GHz unlicensed indoor access system
at the Tokyo-Narita airport, which is combined with Mobile Edge Computing (MEC)
to enable ultra-high speed content download with low latency. The third example
is mmWave mesh network to be used as a micro Radio Access Network ({\mu}-RAN),
for cost-effective backhauling of small-cell Base Stations (BSs) in dense urban
scenarios. The last example is mmWave based Vehicular-to-Vehicular (V2V) and
Vehicular-to-Everything (V2X) communications system, which enables automated
driving by exchanging High Definition (HD) dynamic map information between cars
and Roadside Units (RSUs). For 5G and beyond, mmWave and MEC will play
important roles for a diverse set of applications that require both ultra-high
data rate and low latency communications.

arXiv

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Other Link： https://dblp.uni-trier.de/db/journals/corr/corr1704.html#SakaguchiHBSCDP17

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

DOI： 10.1109/GLOCOMW.2017.8269214

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Other Link： https://dblp.uni-trier.de/db/conf/globecom/globecom2017w.html#SantosOTSK17

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

DOI： 10.1109/ICCW.2017.7962655

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Other Link： https://dblp.uni-trier.de/db/conf/icc/icc2017w.html#OgawaTSH17

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transele.E100.C.790

Scopus

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet100c.html#SakaguchiHBSCDP17

Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/IEEE-IWS.2016.7585457

Scopus

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Language：Japanese  

CiNii Books

CiNii Research

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

Although 60 GHz millimeter wave (mm-Wave) systems employing OFDM can provide multi-Gbps data rate, the high level of phase noise (PN) of the mm-Wave transceivers induces inter-carrier interference (ICI) that degrades the performance of the OFDM systems. In the conventional method, the effects of PN can be well compensated by the iterative receiver processing; however, it has high complexity. In the previous work, we proposed a simple frequency domain ICI compensation, that linearly combines the channel equalized receive signals; however, it needs PN-robust channel estimation methods. In this paper we evaluate the proposed scheme with considering the channel estimation, and propose a PN-robust channel estimation method.

DOI： 10.1587/comex.2016XBL0070

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

DOI： 10.1109/WCNCW.2016.7552698

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Other Link： https://dblp.uni-trier.de/db/conf/wcnc/wcncw2016.html#TranSRSA16

Publishing type：Research paper (international conference proceedings)  

Scopus

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

DOI： 10.1587/transcom.2015EBP3224

Scopus

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Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2015EBP3448

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet99b.html#KamataTSA16a

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

DOI： 10.1109/WCNC.2016.7564669

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Other Link： https://dblp.uni-trier.de/db/conf/wcnc/wcnc2016.html#TranSRSA16a

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

DOI： 10.1587/transcom.2015EBP3318

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arXiv

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

DOI： 10.1587/transcom.2015EBP3265

Scopus

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Recently,60 GHz millimeter wave(mm-Wave)systems have been extensively studied. In standards,like IEEE 208.11ad, there are 4 channels with total 9 GHz bandwidth in 60 GHz band,and each channel can provide maximally over than 6 Gbps data rate. For compensating the high propagation loss of mm-Wave,analogue beamforming(BF)in RF band is also proposed.Here, we are aiming at the further improvement of mm-Wave channels with multi-user multiple-input and multiple-output (MU-MIMO) spatial multiplexing. In this report, we evaluate user scheduling algorithms with the analogue BF using a small conference room channel model and 3-sector access point. And a proportionally fair MU-MIMO user scheduling method is proposed.

DOI： 10.11485/itetr.40.23.0_43

CiNii Books

CiNii Research

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Language：Japanese  

CiNii Books

CiNii Research

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

DOI： 10.1109/MILCOM.2015.7357444

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Other Link： https://dblp.uni-trier.de/db/conf/milcom/milcom2015.html#HanizTSTHYA15

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

DOI： 10.1109/CSCN.2015.7390433

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/cscn/cscn2015.html#MaltsevBPMDTS15

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

DOI： 10.1109/CSCN.2015.7390434

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/cscn/cscn2015.html#RezagahSTSN15

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.E98.B.388

Scopus

arXiv

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Other Link： https://www.wikidata.org/entity/Q58827417

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.E98.B.2508

Scopus

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet98b.html#HanizTISTHYA15

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transele.E98.C.242

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet98c.html#AndoTAYKYN15

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

DOI： 10.1109/PIMRC.2015.7343694

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/pimrc/pimrc2015.html#TranSRSA15

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

DOI： 10.1109/CSCN.2015.7390435

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/cscn/cscn2015.html#ShimodairaTSA15

Publishing type：Research paper (international conference proceedings)  

Scopus

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Publishing type：Research paper (international conference proceedings)  

Scopus

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Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.E97.B.1928

Scopus

arXiv

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet97b.html#MaeharaTSAF14

Publishing type：Research paper (scientific journal)  

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Other Link： https://dblp.uni-trier.de/db/journals/corr/corr1408.html#MaeharaTSAF14

Publishing type：Research paper (scientific journal)  

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Other Link： https://dblp.uni-trier.de/db/journals/corr/corr1412.html#SakaguchiTSNSTSSCKAH14

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

DOI： 10.1109/PIMRC.2014.7136536

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/pimrc/pimrc2014.html#WeilerPKSTS14

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

DOI： 10.1109/PIMRC.2014.7136540

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Other Link： https://dblp.uni-trier.de/db/conf/pimrc/pimrc2014.html#ShimodairaTANHS14

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.E97.B.2512

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet97b.html#RezagahTSAK14

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

DOI： 10.1109/ICCS.2014.7024857

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Other Link： https://dblp.uni-trier.de/db/conf/iccoms/iccoms2014.html#IshiharaSST14

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transele.E97.C.1005

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet97c.html#JeongTA14

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

DOI： 10.1587/transcom.E96.B.1338

Scopus

CiNii Books

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

DOI： 10.1587/transcom.E96.B.1176

Scopus

CiNii Books

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

DOI： 10.1587/transfun.E96.A.896

Scopus

CiNii Books

arXiv

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Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transele.E96.C.1254

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet96c.html#AndoTAYKYU13

Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/APMC.2013.6695221

Scopus

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Publishing type：Research paper (international conference proceedings)  

Scopus

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

DOI： 10.1109/ISPACS.2013.6704656

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Other Link： https://dblp.uni-trier.de/db/conf/ispacs/ispacs2013.html#SakaguchiSSRTA13

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

DOI： 10.1109/PIMRC.2013.6666535

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/pimrc/pimrc2013.html#MaeharaATSSAI13

Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TWC.2013.040413.121423

Scopus

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

DOI： 10.1109/GLOCOMW.2013.6824959

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Other Link： https://dblp.uni-trier.de/db/conf/globecom/globecom2013w.html#RezagahMTSAK13

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

DOI： 10.1587/transcom.E95.B.3498

Scopus

CiNii Books

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

DOI： 10.1587/transele.E95.C.1620

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CiNii Books

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

DOI： 10.1109/GLOCOMW.2012.6477740

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/globecom/globecom2012w.html#MatsuoRTSAKMKK12

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

DOI： 10.1109/VETECS.2012.6240286

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2012s.html#KidaMTMSA12

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

DOI： 10.1109/VETECS.2012.6240268

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2012s.html#LertwiramTSA12

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

DOI： 10.1109/ICCS.2012.6406119

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Other Link： https://dblp.uni-trier.de/db/conf/iccoms/iccoms2012.html#TranOHA12

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

DOI： 10.1109/ISSSE.2012.6374350

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

DOI： 10.1109/VETECS.2012.6240290

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2012s.html#RamamonjisonTSA12

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

DOI： 10.1109/PIMRC.2012.6362538

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Other Link： https://dblp.uni-trier.de/db/conf/pimrc/pimrc2012.html#ShimodairaTTSAMKKK12

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

DOI： 10.1109/ICCS.2012.6406113

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Other Link： https://dblp.uni-trier.de/db/conf/iccoms/iccoms2012.html#SanoTWSAHYA12

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

DOI： 10.1587/transcom.E95.B.1345

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet95b.html#LertwiramTMSA12

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

DOI： 10.1587/transcom.E95.B.1198

Scopus

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Publishing type：Research paper (international conference proceedings)   Publisher：ICST / IEEE  

DOI： 10.4108/icst.crowncom.2011.245939

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Other Link： https://dblp.uni-trier.de/rec/conf/crowncom/2011

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

DOI： 10.1109/VETECS.2011.5956705

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2011s.html#WicaksonoTSA11

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

DOI： 10.1109/VETECS.2010.5494064

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2010s.html#TranSA10

Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.E93.B.3362

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet93b.html#LeeTSA10

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

DOI： 10.1109/VETECS.2010.5493698

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Other Link： https://dblp.uni-trier.de/db/conf/vtc/vtc2010s.html#LertwiramTMSA10

Publishing type：Research paper (scientific journal)  

DOI： 10.1155/2010/476732

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DOI： 10.1587/transfun.E93.A.814

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DOI： 10.1109/ICICS.2009.5397596

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DOI： 10.1587/transcom.E92.B.3665

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DOI： 10.1109/ICICS.2009.5397526

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

DOI： 10.1109/PIMRC.2009.5449969

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

DOI： 10.1109/VETECS.2006.1683392

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Due to the popularization of smart phones and tablets in recent years, the traffic load on conventional cellular networks is predicted to be increased by 1000 times in the next 10 years. On the other hand, energy consumption of information processing has recently become an economic issue for operators as well as a big challenge for sustainable development. The design of 5G (the next generation of cellular networks) to be both spectral/energy efficient is now a hot discussion topic among researchers and industrial partners. In this paper, we consider the future cloud cooperated HetNet which enables global resource optimization among small cells. Exploiting this architecture, this paper investigates a joint optimization problem on both user association and dynamic ON/OFF of smallcell BSs to maximizing the spectral/energy efficiency of the network. Our numerical simulations show that without sacrificing the system's power resource, our proposed approach can effectively deactivate unnecessary BSs and attain the target 1000x system rate gain.

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The mobile traffic explosion has become a remarkable issue due to the proliferation of smart devices such as smart phones or tablets. The design of 5G (the next generation of cellular networks) to be both spectral/energy efficient is now a hot discussion topic among researchers and industrial partners. In this paper, we consider the future cloud cooperated HetNet which enables global resource optimization among small cells. The architecture allows dynamic ON/OFF of small cell BSs in adaptation to daily data traffic. This paper investigates a joint optimization problem on both user association and dynamic ON/OFF scheme of BSs to maximizing the spectral/energy efficiency of the network. Numerical simulations using developed system level simulator are conducted to validate the effectiveness of the proposed optimization scheme.

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Cellular network will fall into a crisis because of the mobile traffic explosion and proliferation of smart devices. In order to defeat this situation, 5G cellular networks which utilize the ultra wide band millimeter wave smallcell BSs has been investigated. Moreover, spectral efficiency can be improved by introducing MU-MIMO in the smallcell BSs. This paper proposes the novel cell association method for multiband heterogeneous cellular networks which considers traffic demands of users and user selection for MU-MIMO.

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Mobile traffic is increasing exponentially year by year and it will be over 1000 times higher than that of today in the near future. In order to tackle this matter, millimeter wave mobile access networks which can provide several GHz bandwidth attract international attention. This paper investigates the candidates of millimeter wave spectrum for 5G according to the international spectrum usage and propagation characteristic. Moreover, we compare the performance of the conventional system with new spectrum and evaluate the merit of each candidates.

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OFDM has been employed in many micro-wave communication systems for its high spectral efficiency and its robustness against the multi-path channel. In millimeter-wave communication systems, however, the phase noise that stems from the local oscillator at transmitter and receiver severely degrades the performance of OFDM system. In this paper, a novel low-complexity phase noise compensation method utilizing frequency domain signal processing is presented. It is revealed that complexity of the proposed method is reduced into 1/30 compared to one of the conventional methods.

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Recently due to the increasing data traffic, the unlicensed 60 GHz band has become attracted because of its larger bandwidth than conventional systems. The standardization has been done in the IEEE802.11ad. According to the standard, there are four channels and about 9 GHz bandwidth in total. Each channel is used by each user and all antennas adopted beamforming in RF. We examine for realizing 4 users spatially multiplexed at each channel by multiuser MIMO (Multiple-Input Multiple-Output) signal processing. We consider two problems. First one is how to modeling the channel. Channel information is important for RF beamforming and multiuser MIMO signal processing. Second one is how to choose RF beam pattern and users. Combination of RF beam pattern and selected users affects system performance.

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This paper presents a method to interpolate propagation channel statistics stored as fingerprints in a database for localization. The proposed interpolation method consists of interpolation in the bandwidth, frequency and spatial domains. The interpolated fingerprint database may be employed to identify illegal radio emitters in generally non-line-of-sight urban environments by introducing a multi-sensor system. A simple localization algorithm is also introduced in this paper, and the proposed method is evaluated through Monte Carlo simulations using location fingerprints obtained from ray-tracing simulations. Results show that using an interpolated fingerprint database may improve localization accuracy.

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Research on the combination of heterogeneous networks (HetNets) and splitting the control and user planes (C/U splitting) has gained momentum in both the mobile communication industry and the research community. In a C/U-splitting HetNet, both high mobility and large capacity can be achieved by separately manipulating the control plane in macro-cells and the user plane in small cells. To prove the concept of a C/U-splitting HetNet, we implemented such a system in our prototype hardware and evaluated its performance. In this report, the overview of C/U-splitting architecture and design of our C/U-splitting prototype are presented.

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In recent years, location estimation techniques have been attracting much attention because of rapidly growing location based services. This paper proposes a high-performance indoor localization system by combining Wi-Fi access points (AP) with fingerprint-based localization algorithm suitable for indoor environment in terms of estimation accuracy. Although many localization systems utilizing Wi-Fi have been proposed in the previous works, its localization accuracy is not so good because only Received Signal Strength (RSS) is available from off-the-shelf Wi-Fi modules. To utilize other parameters than RSS in localization system, we firstly propose a novel system which can collect and manage various RF parameters. Then, we also describe a novel localization algorithm utilizing Channel Impulse Response (CIR), which is enabled to be collect by using our proposed system. Simulation results validates the effectiveness of our proposed system in terms of localization accuracy.

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The unrelenting user traffic demand triggered by data-centric standards place a premium on area spectral and energy efficiency over already crowded wireless spectrum. A promising approach to solving this problem, which is being considered in 3GPP and Greentouch, is through a novel cellular architecture of cloud cooperated HetNet with heterogeneous deployment of base stations connected to C-RAN for enabling cooperated transmission. Especially, this architecture of low-power (ultra) wideband base stations (small cells) overlaid within the coverage of macro base station allows a C/U splitting mechanism where high-traffic data plane is shifted to the small cells and the whole network can be controlled and optimized by the macro base station in a centralized manner. As a first step to investigate the effectiveness of this novel architecture, this paper constructs an optimization problem on power allocation of base stations to maximize the system's rate-energy efficiency under a presumed user traffic model. Based on the optimization results, a corresponding control procedure at the C-plane is also proposed.

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To realize User-Centric Wireless Networks which integrates various wireless systems on a unified hardware platform toward easy and flexible network connections for users, we examine a multi-band power amplifier (PA) and digital predistortion (DPD) to compensate for nonlinear distortion. In general, output levels of the signals amplified simultaneously by the PA are different due to the nature of different wireless systems and especially when power control technique is employed. The nonlinear distortion generated on each band has different characteristics when the relationship for frequency bands of the amplified signals is harmonics. In this paper, we propose a dual-band DPD technique for simultaneous dual-band amplification with harmonic relationship. Moreover, we consider the characteristic of the distortion generated by the dual-band amplification with different output levels, and evaluate the performance of the proposed technique by computer simulation.

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To design spatial diversity of antennas in V2V communications, it is essential to understand the model of angular profile. In conventional mobile communications where communication is established among base station and mobile station, it is known that the spatial profile of base station is well approximated by a Laplace distribution while that of mobile station is approximated by uniform distribution. This paper reveals that conventional model of angular profile is not suitable for V2V communications where communication is established among mobile stations by investigating the propagation characteristics of V2V communication using raytracing simulator. It is concluded that angular profile of received signal can be modeled by the sum of two Laplace distributions. Moreover, it is found that diversity gain can be sufficiently achieved even when the antenna spacing is small.

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To realize User-Centric Wireless Networks which integrates various wireless systems on a unified hardware platform toward easy and flexible network connections for users, we examine a multi-band power amplifier (PA) and digital predistortion (DPD) to compensate for nonlinear distortion. DPD is needed to track nonlinear time-varying characteristic of PA due to a change over time or a change in temperature. To compensate for this time-varying characteristic, adaptive predistorter which updates and optimizes coefficients of a polynomial expression is often used. However, each feedback path for each band is needed to compensate for PA noninearity on concurrent amplification of multi-band signals. It results in the increase of the number of RF circuits and the degradation of the system's flexibility. In this paper, we propose a single feedback system employing multi-band mixer which can concurrently convert multi-band signal centered at separated RF frequencies into intermediate frequencies (IF). Our experimental results demonstrate the validity of this feedback system for multi-band digital predistortion technique.

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Recently, data traffic has increased with the spread of smart phone. To deal with this increasing data traffic, new bands for wireless communication are needed. Unlicensed 60-GHz frequency band has been attracted and the standardization is made in the IEEE802.11ad and the IEEE802.15.3c. According to the IEEE 802.11ad standard, four 2.16-GHz bandwidth channels are defined around the 60-GHz. We examine and will realize that 4 users are simultaneously served for each channel by exploiting space division multiple access (SDMA) and 16 users can be simultaneously served to maintain 6 Gbps throughput for each user. To achieve this throughput, modulation level needs more than 16 QAM. Therefore, Error Vector Magnitude (EVM) should be less than -17 dB. In this paper, we evaluate the relationship between EVM and RF impairments such as IQ imbalance, phase noise and PA nonlinearity. Numerical analysis and theoretical analysis shows the performance of each RF circuits to meet the target EVM.

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To realize "User-Centric Wireless Networks" which integrates various wireless systems on a unified hardware platform toward equipment miniaturization, we examine a multi-band power amplifier (PA) and digital predistortion (DPD) to compensate for nonlinear distortion. DPD is needed to track nonlinear time-varying characteristic of PA due to a change over time or a change in temperature. To compensate for this time-varying characteristic, adaptive predistorter which updates and optimizes coefficients of a polynomial expression is often used. In this adaptive predistorter, coefficients are updated to minimize adjacent channel power ratio (ACPR) or error vector magnitude (EVM) but convergence speed is slow if non-orthogonal polynomial model is applied for DPD design. Therefore, orthogonal polynomial model based on the probability distribution of input signal to PA is applied to improve the convergence speed. In this paper, we propose adaptive predistorter based on orthogonal polynomial model for dual-band single carrier signal.

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This paper proposes a relay placement optimization methodology for multi-hop relay networks in practical environments. By this method, we can estimate the minimum number of relay nodes to cover all sensor nodes in which locations of sensor and sink nodes are pre-assigned and packet loss rate can be minimized. In this method, we simply verify the candidate locations of relay nodes based on three dimensional data of environment geometry and locations of sink and sensor nodes, and then select the relay locations where all sensor nodes are connected to the network. For relay communication schemes, we utilize simple TDD relaying scheme and MIMO two-way relay employing network coding scheme. Consequently, the numerical results show that the proposed method can effectively minimize packet loss rate and delay, especially when two-way relaying scheme is applied.

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This paper proposes an innovative cell structure and clustering scheme for large scale cooperation which manifolds the capacity compared to conventional systems. Especially when there is some congeries of users m the network area the conventional uniform clustering wastes the network resources in sparse areas. Quite the contrary, in our proposed scheme, network resources are concentrated to the dense area through growing a cluster around the area of interest by adding base stations tier by tier and performing large scale coordinated multipoint (CoMP) transmission. Simulation results using 3GPP parameters and models confirm the significant superirity of our proposed method.

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Coordinated multipoint (CoMP) transmission has been proposed to solve the "cell edge problem" in cellular network. Even though there is still "cluster edge problem" if only the static clustering of CoMP is considered. Although this problem can be overcome by the introduction of the dynamic clustering method, which switches clustering patterns dynamically, it needs a complicated backhaul network. Without increasing the number of cluster patterns like dynamic clustering, this paper proposes a new concept of heterogeneous cellular network which deploys pico base stations at the cluster edges to reduce the backhaul complexity. Moreover, the effectiveness of the proposed network is validated by numerical results in which resource allocation optimization is considered.

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Coordinated multipoint (CoMP) transmission has been proposed to solve the "cell edge problem" in cellular network. Even though there is still "cluster edge problem" if only the static clustering of CoMP is considered. Although this problem can be overcome by the introduction of the dynamic clustering method, which switches clustering patterns dynamically, it needs a complicated backhaul network. Without increasing the number of cluster patterns like dynamic clustering, this paper proposes a new concept of heterogeneous cellular network which deploys pico base stations at the cluster edges to reduce the backhaul complexity. Moreover, the effectiveness of the proposed network is validated by numerical results in which resource allocation optimization is considered.

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In wireless communication complying with the regulation, very high frequency called millimeter wave band is assigned for TV network in indoor environment As millimeter wave circuits nowadays can be manufactured by CMOS technology, communication using millimeter wave is attracted and standardized in IEEE802 15 3c However mass production of the circuits becomes difficult as the characteristics of the local oscillator(LO) at millimeter wave band are no more as good as that of the conventional ones Therefore, LO with large phase noise must be used Phase noise causes ICI because of the destruction of orthogonality in OFDM system We show the resulted error floor analytically, and confirm this performance by numerical simulation This paper aims to improve this performance by digital signal processing, assuming a LO output spectrum following Lorentz model Then, we propose a new algorithm which can alleviate the degradation due to phase noise but overcome the problem of halving the spectral efficiency in conventional self cancellation method Finally, we confirm its effectiveness in parallel SISO system

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To realize "Flexible Wireless System" which integrates various wireless systems on a unified hardware platform, we examine a multi-band power amplifier (PA) toward equipment miniaturization. To compensate for this nonlinear distor- tion, we need to design a digital predistortion after analyzing the output characteristic of a wideband PA with a multi-band simultaneous amplifying. In this paper, we evaluate the error vector magnitude (EVM) and the adjacent channel power ratio (ACPR) using simultaneously amplifying multi-band OFDM signals and design its digital predistortion. Numerical analysis shows our proposed predistortion can improve both EVM and ACPR.

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The significance of relay deployment has gained much attention in implementing wireless application in given environment such as wireless sensor networks. Recent works showed that MIMO Two-way Multi-hop Networks (M2WMN) is a technique which is able to enhance relaying performance owing to its high spectral efficiency. This paper investigates the open problem of optimizing relay node placement for M2WMN in real environment to maximally exploit the capability of M2WMN. 3D ray tracing simulation in a U-shaped corridor environment is employed to attain practical propagation channels for evaluating the effectiveness and optimal relay placement of M2WMN. The analysis results show that by applying power control and finding the optimum node placement, M2WMN can improve the network capacity superior to other relaying schemes.

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Recently, heterogeneous network (HetNet), which is a network with pico base stations installed inside the cell range of conventional macro cells to accommodate rapidly increasing traffic, has become a hot research topic. Although pico BS location is a critical issue, most of conventional researches empirically decide pico BS locations and only discuss design parameters such as cell range, resource allocation, and power control. This paper considers the optimal pico BS locations in heterogeneous network with hotspots and also optimizes other design parameters. The effectiveness of the proposed method is validated by numerical results.

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This paper introduces a multi-band multi-signal transmission technology of Flexible Wireless System (FWS) for User-Centric Wireless Networks (UCWN). UCWN will allow users to make network connections easily at all times without being conscious of upgrades or differences in wireless systems. FWS is a unified wireless platform which simultaneously deals with various types of wireless signals. When FWS transmits signals of different systems simultaneously, the wideband power amplifier (PA) of FWS's transmitter amplifies the multi-band signals simultaneously. However, when multi-band transmitted signals are input to the PA, some distortion are generated due to the PA's nonlinearity. It requires a corresponding multi-band digital predistorter (PD) to compensate for the nonlinear characteristics. To realize the digital PD, in this paper, the wideband PA's nonlinear characteristics were showed using Volterra series analysis and experiments, when the wideband PA amplifies harmonically-related 2-band signals on 300MHz and 900MHz simultaneously.

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For guaranteeing future energy supply, researches on reforming conventional power systems have been done widely. As the next-generation power system utilizes the advance of ICT technologies toward a huge evolution, Smart grid has been becoming an attractive research topic recently. By real-time control of peak power consumption and effective power allocation, which can be supported by ICT functions of Smart grid, the power system is expected to become reliable and be able to avoid black-out in large area. In this paper, we report a developed demonstration of small-scale power control system functionally suppressing the power consumption with high reliability. Furthermore, toward the application to large-scale power control systems, a distributed control algorithm between small-scale systems is proposed and its effectiveness is shown through simulation results.

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Recently, multiuser MIMO communication system has attracted much attention because of their potential for increasing radio resource efficiency. Moreover, the system can provide high performance by selecting users based on their information such as channel state information(CSI) and average signal to noise power ratio called user scheduling. However, most of conventional works assume perfect CSI at the base station. In this paper, we focus on a more practical scenario where base station knows only imperfect CSI by using quantization codebook. We modify the conventional user scheduling algorithm for block diagonalization(BD) such that the modified algorithm selects users by considering the imperfect CSI, the average SINR, and the quantization error of users. In addition, we modify the conventional codebook to a new codebook which considers antenna correlation to decrease interference among users. Numerical analysis shows system capacity is improved by using the proposed user scheduling method and codebook.

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This paper proposes a method for location estimation of a cellular phone with illegal use using multiple sensors in an indoor environment with experimental validation. The proposal method is a location fingerprint scheme is which the statistical characteristics of the signal cross correlation among multiple sensors is employed. As the cross correlation between a pair of antenna fully stores the information of their complex channel responses, the proposed method can be considered as generalized scheme of all conventional location fingerprint ones including Received Signal Strength Indicator (RSSI), Time Difference of Arrival (TDOA), and Direction of Arrival (DOA). Besides, different from the conventional methods, in which the locality of spatial correlation is utilized, thus require fine-grid location measurements. The proposal one invokes statistical learning technique and estimates location based on the correlation of received samples with the statistical learning database. Therefore, the proposal methods superior than conventional ones in terms of location estimation accuracy and installation simplicity. An experiment conducted in this paper validates its superiority of the proposal method.

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We investigate the joint optimization of power allocation and transceiver weights in multiple-input multiple-output (MIMO) two-way multihop networks. The objective is to maximize the minimum weighted signal-to-interference-plus noise power ratio (SINR) of the multihop links while satisfying general linear power constraints at the transmit nodes. First, we derive a distributed power allocation algorithm by extending the notion of link SINR metric. Using that result, we propose an alternating optimization algorithm for solving the more complex MIMO transceiver weights optimization. We compare its performance against those of centralized and conventional schemes through numerical simulations. Our results show that the proposed algorithm provides considerable improvement to the end-to-end rate of multihop networks. In fact, it achieves, with low complexity and low coordination overhead, a rate performance close to an upper-bound that was obtained from a centralized optimization with a relaxed power constraint.

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We investigate the joint optimization of power allocation and transceiver weights in multiple-input multiple-output (MIMO) two-way multihop networks. The objective is to maximize the minimum weighted signal-to-interference-plus noise power ratio (SINR) of the multihop links while satisfying general linear power constraints at the transmit nodes. First, we derive a distributed power allocation algorithm by extending the notion of link SINR metric. Using that result, we propose an alternating optimization algorithm for solving the more complex MIMO transceiver weights optimization. We compare its performance against those of centralized and conventional schemes through numerical simulations. Our results show that the proposed algorithm provides considerable improvement to the end-to-end rate of multihop networks. In fact, it achieves, with low complexity and low coordination overhead, a rate performance close to an upper-bound that was obtained from a centralized optimization with a relaxed power constraint.

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Recently, there is demand to constract wireless communication systems which can adapt to tremendous incerase of network traffic. Heterogeneous Network (HetNet) consisting of small and low-power nodes deployed inside the conventional macro cell areas is considerd as solution. By using HetNet, the network poformance is improved owing to interference control by resource allocation and Cell Range Expanssion. In this paper, we formulate the HetNet resource allocation model and derive the optimal network paramters by solving the corresponding optimiation problem.

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Recently, location estimation of unidentified radio emitter by using multi sensors has been attracting attention. Conventionally, most location estimation methods employ received signal strength indicator (RSSI), time difference of arrival (TDOA) or direction of arrival (DOA). However, the accuracy of these estimation methods are degraded due to multipath fading especially in urban areas. So that, we propose a new location estimation which combines RSSI, TDOA and DOA. Using proposed location estimation scheme, a spectrum map can be created scheme based on the estimated locations of radio em...

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ユビキタスセンサーネットワークの実現に向けてセンサーノートの電池寿命問題が大きな課題となっている.筆者らは,屋内環境において無線センサーネットワークと無線電力伝送を融合させることにより,電池寿命問題を解決したワイヤレスグリッドの概念を提案してきた.本稿では,電力伝送とデータ伝送の双方を加味したワイヤレスグリッドのための回線設計を行い,スループット特性などを従来法と比較する.提案システムの無線電力伝送では室内環境に面的に分布する各センサーノードの駆動電力100μWを所要電力と設計とし、無線充電効率を向上させる送受信ダイバシチ技術や定在波による長時間的な信号電力劣化を回避するための搬送波シフトダイバシチ技術等の様々な工夫が行われている.またデータ伝送ではネットワークトポロジに適応したマルチユーザMIMO技術に基づくマルチプルアクセス方式を提案し,ネットワーク全体の周波数利用効率の向上を図る.数値解析により提案システムのネットワーク周波数利用効率が従来法に比べて10倍以上の改善効果があることを示す.提案する無線グリッドシステムにより自律的で高信頼高効率なユビキタスセンサーネットワークを実現できる.
Sensor node life-time limitation in wireless sensor networks has long become an issue, preventing the realization of a reliable ubiquitous network. By fusing wireless sensor network and wireless power transmission, the authors have proposed the concept of wireless grid to solve the battery life problem in indoor environment. In this paper, we perform the link design for wireless grid including both the power transmission and the data transmission transfer and compare the performance to conventional sensor networks. The wireless power transmission of the proposed system is designed to support spatially distributed indoor sensors with driving power of 100μW by introducing techniques e.g. transceiver diversity and carrier shifted multipoint transmission to improve power charging efficiency and avoid long-term signal power degradation due to standing wave problem. In addition, in data transmission link, multiple access scheme based on multi-user MIMO technologies is adapted to the network topology to improve the spectral efficiency of the entire network. Simulation results show an improvement of more than 10 times in terms of network spectral efficiency compared to conventional network. It can be said that the proposed technique can realize an autonomous and highly efficient ubiquitous sensor networks.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Recently, location estimation of unidentified radio emitter by using multi sensors has been attracting attention. Conventionally, most location estimation methods employ received signal strength indicator (RSSI), time difference of arrival (TDOA) or direction of arrival (DOA). However, the accuracy of these estimation methods are degraded due to multipath fading especially in urban areas. So that, we propose a new location estimation which combines RSSI, TDOA and DOA. Using proposed location estimation scheme, a spectrum map can be created scheme based on the estimated locations of radio emitters. We evaluate the performance of the proposed method by comparing with that of conventional methods employing RSSI and TDOA. In this paper, we call spectrum map observation system using multiple sensors as distributed spectrum monitor (DSM).

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

Sensor node life-time limitation in wireless sensor networks has long become an issue, preventing the realization of a reliable ubiquitous network. By fusing wireless sensor network and wireless power transmission, the authors have proposed the concept of wireless grid to solve the battery life problem in indoor environment. In this paper, we perform the link design for wireless grid including both the power transmission and the data transmission transfer and compare the performance to conventional sensor networks. The wireless power transmission of the proposed system is designed to suppor...

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Recently, location estimation of unidentified radio emitter by using multi sensors has been attracting attention. Conventionally, most location estimation methods employ received signal strength indicator (RSSI), time difference of arrival (TDOA) or direction of arrival (DOA). However, the accuracy of these estimation methods are degraded due to multipath fading especially in urban areas. So that, we propose a new location estimation which combines RSSI, TDOA and DOA. Using proposed location estimation scheme, a spectrum map can be created scheme based on the estimated locations of radio em...

CiNii Books

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

Sensor node life-time limitation in wireless sensor networks has long become an issue, preventing the realization of a reliable ubiquitous network. By fusing wireless sensor network and wireless power transmission, the authors have proposed the concept of wireless grid to solve the battery life problem in indoor environment. In this paper, we perform the link design for wireless grid including both the power transmission and the data transmission transfer and compare the performance to conventional sensor networks. The wireless power transmission of the proposed system is designed to suppor...

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Books

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Books

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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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.

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Language：Japanese   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.

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Language：Japanese   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.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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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.

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Language：Japanese   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.

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Language：Japanese   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.

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Language：English   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.

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Backbone wireless mesh network has been attracted much of attention due to a wide range of its application such as smart utility network, sensor network, etc. In recent publication, a cross-layer design employing multiple antenna techniques and network coding called 2D MIMO network coding has been proposed for two dimensional (2D) mesh network. Owing to interference cancellation ability of MIMO and bi-directional flow multiplexing capability of network coding in combination with an efficient channel access scheme of TDMA/TDD, 2D MIMO network coding provides significantly high end-to-end capacity. In this paper, a network simulator employing 2D MIMO network coding is developed and more details on packet relaying mechanism of the algorithm are presented. Besides, an efficient retransmission scheme is proposed for 2D MIMO network coding considering QoS guarantee. Simulation results show that 2D MIMO network coding achieves an extremely large improvement in network throughput, and packet delay reduction in comparison with CSMA/CA mesh networks. Moreover, end-to-end packet delivery ratio is improved by using the proposed retransmission scheme.

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In this report, a simulator of the cognitive MIMO mesh network (CMN), which can share the spectrum with a primary system such as wireless local area network (WLAN), is introduced. We have investigated the CMN to achieve a high effective and reliable distributed wireless networks. CMN equips cooperative sensing and estimation of channel occupancy rate to recognize the environment and dynamic MAC protocol and dynamic routing for effective spectrum sharing. In addition, to achieve more effective spectrum usage in the spectrum opportunity, we adapt MIMO twoway relay and network coding. In this report, the environment recognition techniques and the effective spectrum sharing techniques are mainly focused on. We also establish the simulator to evaluate the CMN and based on the evaluation by the simulator, the CMN can achieve high throughput performance while primary user's required throughput is satisfied.

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DOI： 10.1109/ICSPCS.2008.4813662

Scopus

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Infrastructure wireless mesh network has been attracted much of attention due to a wide range of its application such as public wireless access, sensor network, etc. The application of current MAC protocols to mesh network to support transmission of multiple unicast flows reveals inefficiency in resource (time and frequency) usage. In recent years, researchers show that significant network throughput gain can be achieved by employing network coding in a wireless environment. Also, for further improvement of network throughput in one dimensional (1-D) mesh topology, it is proposed to use multiple antenna technique combined with network coding. Being inspired by MIMO network coding in 1-D topology, in this paper, the authors establish a Y-typed MIMO network coding algorithm for a tree topology consisting of two branches. In this algorithm, network coded flows of branches are spatially multiplexed. Owing to the efficient sharing of frequency of network coding and co-channel interference cancellation ability of MIMO, the proposed algorithm shows an 8-fold gain in network capacity compared to conventional methods. Furthermore, by employing freedom of antenna used at each mesh node, the authors also propose a cooperative null beamforming algorithm suppressing interference when inter-route interference is taken into account. Finally, power control is combined with the proposed algorithms for best improvement of network capacity.

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Infrastructure wireless mesh network (WMN) has been attracted much of attention due to a wide range of its application: public wireless access, sensor network, etc. A combination of MIMO and network coding for one dimensional (1-D) topology for higher network capacity has been proposed in recent literature. In this paper, the authors extend MIMO network coding to two dimensional (2-D) topology. Two algorithms are proposed for two practical 2-D mesh topologies. Owing to the efficient sharing of frequency of network coding and co-channel interference cancellation ability of MIMO, both two proposed algorithms provide a significant gain to end-to-end network capacity. Furthermore, when long distanced co-channel interference is taken into account, the authors propose a cooperative null beamforming algorithm which can reduce the interference, thus increase overall network capacity performance. Simulation results show the good performance of the proposed methods.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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CiNii Books

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Books

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Language：Japanese   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.

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DOI： 10.1109/ICICS.2007.4449793

Web of Science

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In this paper, we conducted simulation using indoor wideband MIMO channel measurement data to show the effectiveness of several transceiver algorithms for multi-user MIMO system in real life environment. Extended from algorithms for single user MIMO system, ZF and VBLAST algorithms for downlink and uplink multi-user MIMO channel were proposed and researched. Algorithms for the case when both the base station and the mobile terminal are supported with multiple antennas are also proposed in recent years, namely ZF-DPC, Iterative Joint Optimization and Eigenmode-DPC. Performance of the above algorithms will be compared and discussed by simulation in IID channel, spatial correlation channel and MIMO channel measured in real life environment.

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In this paper, throughput performance of MIMO-OFDM system in real residential home environment was evaluated by using wideband MIMO channel measurement data. Computer simulations were carried out to compare the performance of MIMO-OFDM system with various detection schemes, i.e. MMSE, VBLAST, QRM-MLD and SVD-MIMO, to that of the conventional SISO-OFDM system. The results showed that, the SVD-MIMO transmission can provide the highest average and outage throughput under the assumption of perfect CSI feedback. On the other hand, QRM-MLD yields the best performance without CSI available at the transmitter. It was also found that the outage throughput performance of MMSE and VBLAST degrades severely due to the existence of spatial correlation in the real home environment.

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