NTT Technical Review
January 2015 Vol. 13 No. 1
View from the Top
Hiromichi Shinohara, Senior Executive Vice President and Head of R&D
Strategy Department, NTT
Strengthening the Individual to Reinforce the Entire Group—Towards the
Next Stage 2.0

Feature Articles: R&D on Devices Using Life-assist
Technologies
Trends in ICT Involving Life-assist Technologies to Address Social Challenges
Development of Applications for a Wearable Electrode Embedded in Inner
Shirt
Blood Flow Observed with Smartphone―Ultracompact Wearable Blood
Flow Sensor
MicroTAS for Biosensors
Ultralow-power Sensor Node with Nanowatt Wireless Circuit Technology
Terahertz Device Technologies for Ultrafast Data Downburst Applications
Continuous Wave Terahertz Spectroscopy System Designed for Medical Field

Regular Articles
Color-temperature Correspondence: Its Nature and Its Impact on Object
Temperature Perception
DataBridge: Technology to Transfer Data Securely and Efficiently Between
Terminals Connected to Different Networks

Global Standardization Activities
Report of ITU-T TSAG Meeting and Activities of NTT R&D European
Representative Office

New NTT Colleagues
We welcome our newcomers to the NTT Group

External Awards/Papers Published in Technical Journals
and Conference Proceedings
External Awards/Papers Published in Technical Journals and Conference
Proceedings

View from the Top

Strengthening the Individual toReinforce the Entire Group—Towards the Next Stage 2.0
Hiromichi Shinohara
Senior Executive Vice President and Head of
R&D Strategy Department, NTT
Overview

Information and communication technology (ICT) has become an indispensable part of our lives supporting finance, education, medical care, andpublic administration. What kind of viewpoint or behavioral pattern must
experts and specialists have in order to develop innovative technologies forachieving a safe and secure society? We sat down with Representative
Director and Senior Executive Vice President Hiromichi Shinohara to findout how NTT deals with this question as a leading company.
Keywords: R&D, efficiency, competiveness

Making R&D more competitive and efficient—Mr. Shinohara, it’s been about half a year since you
took up your post as Senior Executive Vice President.
Please tell us about the conditions that surroundtechnology development today and its future direction.
Well, I see no difference in direction between myposition as Head of R&D Strategy Department and as
Senior Executive Vice President, but I do feel that myview of research and development (R&D) from amanagement perspective has intensified. Of course,
the importance I place on R&D to grow the NTT
Group has not changed, but I must now consider how
to make R&D more efficient and competitive acrossthe entire NTT Group.
At present, each of the Group companies is pursuing R&D based on its own policies, which means thatwork can sometimes be duplicated. To prevent thisfrom happening, I bring together the heads of tech

nology development at each Group company so thatthey can talk about how to pursue joint development
and how best to eliminate overlap in order to optimize
work in hot-topic areas such as big data, softwaredefined networking, and network functions virtualization.
It may be thought that this approach is taken on
behalf of the NTT laboratories by NTT as the holding
company, but it’s essential to enhance the competitiveness of the entire NTT Group. As one who is
promoting more efficient and competitive R&D, I
consider that one of my new duties is to make it absolutely clear that this approach that I advocate always
has the profits of the entire NTT Group in mind.
Changing gears! The ‘whole’ cannot be
reinforced without strengthening the individual.
—It seems that attempting to make R&D more efficient while trying to make it more competitive at thesame time is somewhat of a contradiction. How
NTT Technical Review

View from the Topshould researchers take on this challenge?
I consider both to be important and both to be amatter of priority! For example, it goes without saying that R&D is absolutely necessary for an enterprise like the NTT Group that seeks to grow its business by developing and commercializing new technologies and services. On the other hand, making
R&D more efficient is a necessity from the viewpointof corporate management. In addition, these twogoals of raising the efficiency and competiveness of
R&D are not contradictory; both can be achieved
together.
The NTT Group boasts about 2500 researchers
within the holding company alone as well as manyand diverse research fields appropriate to such a large
number of researchers.
Efficiency and innovation are necessary in all
research fields, but the specific means of achieving
them vary depending on the research theme anddevelopment phase. For example, even in the case of“open innovation” that we have recently been emphasizing, researchers need to be aware of what approachshould be taken in each research field within theentire NTT Group.
This is especially true when researchers are considering their respective roles in open innovation andcollaboration. It is not simply a matter of giving workthat one cannot do to others; one must be knowledgeable of one’s own strengths and those of other teammembers and combine those strengths. This assessment can be different depending on whether or not
the R&D in question is pursued with a strong sense of
purpose. It means the difference between having adesire to develop technology that people find attractive or having a desire to provide society with something really useful. If the latter, the most optimal
technology would naturally be selected, as opposed
to holding on tenaciously to one’s own technology.
I would also like to have our researchers “change
gears” according to the present stage of their work. At
the research stage, I would like the focus to be onachieving results that individuals are recognized for,such as published papers, but in the commercialization stage, I would like the focus to be on social contributions and product and service penetration.
This way of thinking should prevent individuals
from taking matters concerning open innovation attheir own pace and minimize lost opportunities tomake proposals to the market. It should also helptransform the cooperative system within the NTT
Group.
Vol. 13 No. 1 Jan. 2015

—I see: testing the waters and changing gears inresearch work based on many aspects such as theindividual’s attitude and market conditions areimportant. The direction to take can be clarified inthis way.
To begin with, I would ask a researcher to reassess
the project that he or she is working on. In the case ofbasic research, one cannot cut corners and do shoddy
work. At the same time, commercializing the resultsof research for practical use is important. I would likethe researcher to consider the state of progress of theresearch and current market trends and give serious
thought as to how that project is currently positioned
in the steps involved in moving from basic research tocommercialization. To the researcher, I would say:
“Try changing your point of view by putting yourself
in the mind of a person one or two levels higher thanyou.”
R&D is an aggregate of “individuals” having different values. If all employees exhibited the same behavioral pattern, we could not hope for any improvement
in values. I believe that it’s important that eachresearcher be aware of the type of behavioral patternthat he or she should adopt. It’s not a question of
simply receiving orders from above and doing what
one is told. It is more important to ask oneself whatrole one should play as a researcher and get moving
by looking upon that role as “work.”
By the way, it’s not my intention here to impose acertain way of doing things on anyone. I would likeall of our researchers as specialists to find on theirown the best techniques to achieve their R&D goals.
That is, I would like them to find the best way to reachthe summit of the mountain they are climbing. What’sView from the Top

important here is that the mountain that each of us
must climb is something common to all of us. For thisreason, I ask researchers to not get caught up in thewords uttered by their superiors and colleagues but tocontinuously refine their ability to grasp the real
meaning or intention behind those words. The wholecannot be reinforced without strengthening the individual!
Towards the Next Stage 2.0: Updating NTT’s
Medium-Term Management Strategy—What, then, is the mountain to climb in 2015?
NTT announced an update to its Medium-Term
Management Strategy as part of its first-half financial
results for the fiscal year ending March 31, 2015
released last November. This update, called “Towards
the Next Stage 2.0,” states that management willplace more importance this year on increasing profits.
This includes cost efficiency made possible by ourinnovative technologies. For corporate management,
cost efficiency is extremely important along withincreased profits.
However, employees say that they don’t feel a boost
in morale when hearing that their work is contributing to “cost efficiency.” Perhaps this is because of the
feelings evoked upon interpreting the words “increase”
and “efficiency.” At the risk of repeating myself,

though, there is value in cost efficiency.
Let me tell you about our undertakings this year in
the form of three main projects.
1. Strengthen the competitiveness (enhance theprofitability) of network services
Strengthening the competitiveness of our network
services can only be achieved through technology
development. In just these last few years, we havebeen introducing integrated-layer transport equipment (100G Policy Traffic Switch) to simplify the
network originally configured with multistage connections and a Packet Transport Multiplexer linksystem to achieve low-cost transmission by integrating the fixed telephone network and the Internet on
the packet network. These measures have beenachieving cost efficiency and contributing greatly tomeeting management objectives. So this year too, I
ask our researchers to work with conviction instrengthening the competitiveness of our network
services.
As for enhancing the profitability of our network
services, I will promote R&D on finding ways ofusing the network to increase revenues in addition toefforts at streamlining network operations and making them cost efficient. However, I would like to see
the NTT Group create new value together with ourpartners in a behind-the-scenes role, not as a main
player. Of importance here is that the results of collaboration in R&D have the power of making 1 + 1
equal not 2 but rather, 3 or 4! This is what I expect of
R&D. I would like to move forward by taking the
viewpoint of our partner and thinking always how
best to use the results of our research to increase ourpartner’s value.
2. Strengthen the cyber security field
This year, we will also work to strengthen the field ofcyber security. As you know, cyber attacks are increasing dramatically year-by-year and evolving rapidly.
In today’s society, all industrial fields including
power, transport, and distribution are interconnected
via the network. It is therefore imperative that we asan ICT enterprise increase our cyber security abilities, but at the same time, society on the whole must
deploy and strengthen cyber security systems. With
this in mind, we will first undertake the developmentof cyber security professionals within the NTT
Group. In a five-year plan running to 2020, the goal
is to train about 10,000 employees within Japan indevelopment, consultation, and other cyber securityrelated areas.

NTT Technical Review

View from the Top

Additionally, in the new fiscal year, we will contribute to cyber security training for Japan on the whole.
For example, we will provide a course titled “Cyberattack and Cyber-defense Technologies” at Waseda
University. This course will be given by NTT engineers active in the field and will cover the ever-changing conditions in cyber security. In the future, wewould like to expand such courses to many more universities in collaboration with other companies. We
are also endeavoring to provide a course titled“Information Security for Complete Novices” as partof gacco, a joint project of NTT DOCOMO and NTT
Knowledge Square providing MOOCs (massive open
online courses).
3. M ake social contributions through globally
advanced technologies
We will advance the preparation for the international sports event to be held in Japan in five years. Of
course, we can anticipate all kinds of attacks fromfame-seeking hackers as is typical of major events, soenhancing cyber security for this event is a must. For
this reason, we will mount a full response to thesethreats by establishing a close link between operations and technology development. We also expect
network traffic characteristics that we have not experienced before to occur in certain areas and duringcertain time periods as spectators congregate or move
about during this event. The challenge here is to comeup with novel means of dealing flexibly and economically with these traffic characteristics and raising reliability, including the use of Wi-Fi*. We havealready begun testing with a focus on detecting thesigns of such traffic characteristics. In addition, we
aim to leverage advanced technologies to present
information with a high sense of presence heretofore
not experienced and to provide a user-friendly network environment. Our target audience here will not
only be tourists from abroad but also those attending
events in various regions of Japan. I believe that theprovision of technologies and services that caninspire and surprise society can help foster the development of children—our future leaders—and provide
a great opportunity for Japan to display its fundamental strengths to the world.
—Mr. Shinohara, as we enter a new year, can you
leave us with a message for all NTT employees?
I would be happy to. First, to our young employees,*

please keep in mind that a wide variety of viewpoints
can be used in assessing whether something is rightor wrong, and what is right or wrong can even changewith the times. So please try to state your case to thepeople around you based first on your own logic.
Then, if opposing opinions are expressed, use that as
an opportunity to reevaluate and refine your ideas
instead of getting discouraged. What you should fear
is losing out on an opportunity to grow.
Next, to our medium- and long-term employees, thetime you have left to experience your work is, in reality, becoming shorter compared to your younger
days. So be aggressive in expressing your opinions
before it’s too late. Both autonomy and heteronomy
are important. Make an effort to create an environment in which you can listen to the opinions of thosearound you and revise your own opinions accordingly.

Interviewee profile
Career highlights
Hiromichi Shinohara joined Nippon Telegraphand Telephone Public Corporation (now NTT) in
April 1978. In June 2003, he became a Vice
President of Access Network Service Systems
Laboratories of the Information Sharing
Laboratory Group. He became a Senior Vice
President of the Information Sharing Laboratory
Group in June 2007. In June 2009, he became aMember of the Board of NTT and Head of R&D
Strategy Department. In June 2012, he became
Executive Vice President and Head of R&D
Strategy Department. In June 2014, he took up
his present position.

Wi-Fi is a registered trademark of Wi-Fi Alliance.

Vol. 13 No. 1 Jan. 2015



Feature Articles: R&D on Devices Using Life-assist Technologies

Trends in ICT Involving Life-assist
Technologies to Address Social
Challenges
Hiroki Morimura, Hiroshi Koizumi, and Akihiko Hirata
Abstract

Various social challenges exist, and some have become serious issues in recent years, for example, therising cost of medical care due to our aging society and the declining population, and also the increasing
infrastructure maintenance costs. Many solutions based on information and communication technology(ICT) are being advocated in various fields and domains. In this article, we review technical trends in
ICT directed towards such social challenges, and we introduce life-assist technology that has been developed based on device research and development at NTT laboratories as a new innovative approach tomeeting these challenges. The potential use of life-assist technology in gathering and analyzing data on
the conditions of people or infrastructure to predict abnormalities could play a major role in preventing
illnesses or accidents.
Keywords: healthcare device, low-power wireless sensor nodes, terahertz technology

1. Introduction
Wearable devices equipped with a sensing function
and wireless communication capability have become
a focus of attention in recent years. Although wirelesssensor networks (WSNs) have been advocated as away to advance the ubiquitous network society bytransmitting various sensing data to the Internet, there
is a lack of key applications for these networks due torestrictions on the size and battery life of the sensor
nodes. WSNs have therefore not become as widespread as ICT (information and communication technology), which has spread dramatically.
1.1 Advances in technology
However, this situation is rapidly changing with the
explosive popularity of smartphones. Smartphones
come pre-installed with the GPS (global positioning
system) function, Wi-Fi*1, Bluetooth*2, and accelerometers, which provide a basic platform for sensor
nodes. Moreover, they also function as a hub stationthat connects to various kinds of electrical equipment. For these reasons, smartphones are starting tobe utilized as a platform for connecting wearable
devices.
Before the widespread use of smartphones, all components of wearable devices such as the display, processor, wireless communication, and sensing unit,
had to be unified in one package. This situation has
abruptly changed, though. Now, they only have tohave a sensing function and short-range wirelesscommunication capability. Furthermore, there are
growing expectations for the development of small
sensor nodes that can be embedded in any object
without the need for node maintenance. These small
sensor nodes will be able to provide more efficient
services for infrastructure maintenance, building
maintenance, and logistics management. Concretely
speaking, these are self-powered wireless sensor
nodes that harvest minute amounts of energy from theenvironment.
Thus, we are seeing the start of huge data processing using cloud technology, which enables the*1	 Wi-Fi is a registered trademark of Wi-Fi Alliance.
*2 Bluetooth is a registered trademark of Bluetooth SIG Inc.

NTT Technical Review

Feature Articles

Healthcare applications

Infrastructure applications
Electronic medical
record server

Medical service

Infrastructure• Weather, disaster data
management server • Pedestrian traffic flow

Low-power sensor

Ultrafast wireless link
• Downburst of
medical data
Noninvasive inspection• Lipid, glucose• GTP etc.

Service provider• Content
Data

Healthcare server

Watching-overHealthcare/Sports/ management server
Health promotion

Monitoring/Maintenance/Disaster management
Ultrasmall sensor

Wearable sensor
Home care/Health check-up
GTP: Guanosine triphosphate

Fig. 1. Innovative approaches to social challenges through life-assist technology.

extraction of useful information and returns it to society or users. This information is commonly known as
big data. Another advance is that an infrastructure
connecting all devices and sensors to the Internet—
referred to as the Internet of things (IoT), M2M(machine to machine), or ambient intelligence—isbecoming a reality.
1.2 Industrial revolutions
This technological progress has led to many
approaches being explored in attempts to build a safe,
secure, and healthy society by connecting the realworld and cyberspace in a network. In recent history,
there have been three industrial revolutions due totechnological innovations. The primary industrial
revolution in the second half of the 18th century
occurred with the invention of the steam engine. The
second one was a result of the remarkable improvement in productivity in the second half of the 19th
century. The IT (information technology) revolution
in the second half of the 20th century is also called thetertiary industrial revolution. A fourth industrial revolution is expected to occur in around 2030, whencyberspace unites with the real world to create something called a cyber-physical system. It is said that
IoT will play an important role in the fourth indusVol. 13 No. 1 Jan. 2015

trial revolution. Therefore, data gathering is one of
the initial tasks for approaches aimed at meetingsocial challenges.
A very important issue in business strategy is determining how to obtain information about people andthings in the real world from the cyberspace of theInternet. Many technologies have been developed inattempts to meet this challenge. A device that contributes to resolving this issue is called a social device. Ifsuch social devices become widely used by people inhomes, offices, and infrastructure, it is expected thatthese devices will help to solve social challenges andcontribute to people living happy and fulfilling lives.
2. Life-assist technology based on social devices
NTT Device Technology Laboratories has beendeveloping social-device technology that includes
sensing and short-range communications to monitor
the conditions of people or infrastructure and to support data analyses and diagnoses, as shown in Fig. 1.
We believe that these social devices connected to the
network will lead to new business opportunities, andthat a safe, secure, and healthy society will become areality. Moreover, they will also contribute to efficiently reducing infrastructure maintenance costsFeature Articles

Lifelog

M2M
Environmental
information

CLOUD
Advanced information
processing

Vital signs andmental healthinformation“Concierge”• Life support• Recommendations
Wearable andnatural user interface“Big data”• Safety• Economy

User
experience

Real-world oriented interface
sensing & actuation
M2M

Textureinterface

CO2
CH4
Blood pressure

Glass-type device

Multi-sensor shirt

Environmental
sensingHome
healthcare

Respiration
Pulse

Blood flow
Lifelog
Blood coagulation

CO2: carbon dioxide
CH4: methaneFig. 2. User experience boosted by wearable devices.

(e.g., due to their labor-saving capabilities and the useof full automation). It is thought that wearable devices with sensing and transmitting functions andultrasmall, batteryless sensor nodes with an energy
harvester as a front-end for big data will pave the way
to such a propitious world.
Life-assist technology is based on social devices,
but it also includes ultrafast wireless links and ultrahigh-resolution sensing to create new possibilities inmedicine. Life-assist technology involves more thanjust devices, however; it also concerns technology forassisting us in our life directly or indirectly. Researchand development (R&D) is currently underway inthree areas of life-assist technology, as follows.
2.1 Healthcare devices
An image of the new user experience with healthcare devices consisting of wearable technologies is
illustrated in Fig. 2. Wearable devices can be worn invarious forms such as a watch, glasses, a necklace, ora shirt. The place where such healthcare devices areworn on the body and the implemented function areimportant. Everyday biomedical signals are simply
individual big data (on one’s physical and/or mental
condition, and current activity) that change continuously with the environment. Our technical aim is to
extract and provide this valuable information without
disrupting a person’s activities. Therefore, we aredeveloping wearable devices that connect to mobile

devices. Mobile computing devices such as smartphones are very convenient as platforms for carryingout data transfer to the cloud because they are
equipped with a high-performance processor, a highdefinition display, and large storage capacity. Highadded-value information processed in the cloud using
machine learning is fed back to the user. We are promoting the research of wearable healthcare devices inorder to provide an epoch-making user experiencethat supports a healthy and comfortable life.
2.2 Low-power wireless sensor nodes
Services using low-power wireless sensor nodes areillustrated in Fig. 3. We want to reduce the power
consumption of our wireless sensor nodes to the point
where one coin-type battery lasts for ten years, orthere is no need of a battery at all owing to energy
harvesting technology, such as with indoor light
power generation. This will eliminate the need fornode maintenance and make it possible to installlarge numbers of sensor nodes almost anywhere.
With such technology, monitoring and telecontrol ofappliances in homes will become possible by using
sensing information. Furthermore, the ability to analyze the gathered data will lead to the creation of new
businesses in areas such as childcare support, watching-over the elderly services, home medical care,infrastructure maintenance, and environmental monitoring.
NTT Technical Review

Feature Articles

Primary data
analysis

When going out • Infrastructure maintenance• Environment monitoring
Appliance control

Sensing information

Childcare support
Data gathering

Sensor/appliance control

Server system(Telecommunications carrier)High-value-added
information
Information
Data gatheringinterpretation

Server system(Service provider)

Sensing information• Analysis results• Merchandise info.
Information
notification

User’s home

Telecontrol

Watching-over service

Home care serviceHome
gateway

Photochemicalsmog alert

Ultralow-power
wireless sensor node

Environmental
information

Fig. 3. Various services based on ultralow-power wireless sensor nodes.

Inspection ofbuildings

Ultrafast
wireless link
CT image

Wireless devices

Toxic gasmonitoring

Medicine analysis

CO alarm!

Crack

System integration
THz light-wave source
Radar

Database

Ultrafast devices developed by NTT
Compoundsemiconductor

CT: computed tomography
IC: integrated circuit

High-speed ICs

PhotodiodeTHz: terahertz

Fig. 4. Millimeter-wave and terahertz-band ultrahigh-speed wireless communication and sensing systems.

2.3 T erahertz-band ultrahigh-speed wirelesscommunication and sensing system
Our ultrahigh-speed wireless communication andsensing technologies use millimeter waves and terahertz waves (Fig. 4). These waves are broadband
Vol. 13 No. 1 Jan. 2015

waves that strongly interact with molecules; however,these frequency bands have not been investigated forindustrial use because it is difficult for the state-of-the art
devices to generate and detect terahertz waves. NTT has
made it possible to construct millimeter-wave-bandFeature Articles

or terahertz-band wireless communications and sensing systems by developing ultrafast transistors andphotodiodes. These systems are expected to be used
for instantaneous download of large-capacity data at
medical sites, nondestructive inspection of buildings,
and remote monitoring of toxic gases at the scene offires.
3. Topics and structure of Feature Articles
The Feature Articles in this issue introduce six
areas we are working on at NTT laboratories.
The first three cover our healthcare devices. The
article entitled “Development of Applications for a
Wearable Electrode Embedded in Inner Shirt” presents application examples for a wearable heart-rateand electrocardiogram (ECG) monitoring system that
includes our wearable device for detecting and transmitting ECG signals. This system obtains a user’s
vital information when the user simply wears theshirt, without getting in the way of normal daily life
activities, and it extracts useful information such aschanges in both mental and physical condition.
Examples of applications for entertainment and lifelog recording are explained [1].
The article entitled “Blood Flow Observed with
Smartphone—Ultracompact Wearable Blood Flow
Sensor” explains the concept of a blood flow sensor
and discusses the design, performance, and application of a system developed at NTT. The unique system design concept was devised for functional use
with a smartphone and achieves drastic weight andpower savings [2].
A new blood test technology using integration of
surface plasmon resonance (SPR) and microfluidics
is introduced in “MicroTAS for Biosensors.” Thisbiosensor is expected to be applied in medical examinations in which the blood coagulation of patients isobserved in order to check for abnormal heart rhythm(atrial fibrillation), cerebral infarction, DVT (deepvein thrombosis, or so-called economy class syndrome), and other conditions. We demonstrate how
our new design combining SPR and microfluidics
solves issues in blood coagulation examinations [3].
The two subsequent articles describe sensing andmobile devices that use ultralow power and ultrahighspeed wireless technologies.
“Ultralow-power Sensor Node with Nanowatt
Wireless Circuit Technology” presents nanowattlevel wireless circuit techniques and an evaluation kit
that enables us to evaluate experiments by connecting
various sensors. These techniques make it possible tocreate small wireless sensor nodes without the needto replace batteries. The article describes the effectiveness of the sensor node in logistics management
and infrastructure maintenance and as a simple meansof transmitting vital data [4].
“Terahertz Device Technologies for Ultrafast Data
Downburst Applications” presents the recent progress in modulator IC (integrated circuit) and antenna
technologies for terahertz wireless communications,which is expected to achieve 100-Gbit/s data transmission. These technologies enable us to download
large-capacity data instantaneously. Therefore, one
promising application of these technologies is instantaneous transfer of large capacity data such as image
data between medical devices at medical sites [5].
The final article, “Continuous Wave Terahertz
Spectroscopy System Designed for Medical Field,”presents advanced approaches that contribute to predicting a medicine’s efficacy. This technology features the use of terahertz-band homodyne spectroscopy using continuous waves. We have shown that
our spectroscopy system enables quantitative analyses that can distinguish the pharmaceutical cocrystals
that affect the efficacy of medicine [6].
As demonstrated by these six Feature Articles, thecontinued R&D of life-assist technology based onsocial devices as a new innovative approach to social
challenges will contribute to our ability to live happier, healthier, and more fulfilling lives.
References
[1]

[2]

[3]

[4]

[5]

[6]

T. Ogasawara, K. Ono, N. Matsuura, M. Yamaguchi, J. Watanabe, and
S. Tsukada, “Development of Applications for a Wearable Electrode
Embedded in Inner Shirt,” NTT Technical Review, Vol. 13, No. 1,
2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
01fa2.html
K. Kuwabara, Y. Higuchi, H. Koizumi, and R. Kasahara, “Blood Flow
Observed with Smartphone—Ultracompact Wearable Blood Flow
Sensor,” NTT Technical Review, Vol. 13, No. 1, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
01fa3.html
Y. Iwasaki and M. Seyama, “MicroTAS for Biosensors,” NTT Technical Review, Vol. 13, No. 1, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
01fa4.html
S. Oshima, K. Matsunaga, T. Kondo, and H. Morimura “Ultralowpower Sensor Node with Nanowatt Wireless Circuit Technology,”
NTT Technical Review, Vol. 13, No. 1, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
01fa5.html
H.-J. Song, T. Tajima, and M. Yaita “Terahertz Device Technologies
for Ultrafast Data Downburst Applications,” NTT Technical Review,Vol. 13, No. 1, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
01fa6.html
K. Ajito, J.-Y. Kim, and H.-J. Song, “Continuous Wave Terahertz
Spectroscopy System Designed for Medical Field,” NTT Technical

NTT Technical Review

Feature Articles

Review, Vol. 13, No. 1, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
01fa7.html

Hiroki Morimura

Senior Research Engineer, Supervisor, Group
Leader of Ambient Device Research Group,
Social Device Technology Laboratory, NTT
Device Technology Laboratories.
He received the B.E. in physical electronics,
the M.E. in applied electronics, and the Dr.Eng.
in advanced applied electronics from the Tokyo
Institute of Technology in 1991, 1993, and 2004,
respectively. He joined NTT in 1993. He has
been engaged in R&D of low-voltage, low-power
SRAM (static random access memory) andcomplementary metal oxide semiconductor(CMOS) fingerprint sensors. His research interests include noise tolerant circuit design for
short-range wireless communications, ultralow
power circuit techniques for batteryless sensor
nodes, and integrated CMOS-MEMS (microelectromechanical system) technology.
Dr. Morimura served on the program committee of the Symposium on VLSI technology(2011–2014), and the program subcommittee on
Advanced Circuits and Systems of SSDM
(2011–2013). He also served as a special section
editorial committee member of the IEICE Transactions on Electronics in 2011–2012. He received
the 2004 CSS Best Paper Award, the 2006 IEICEBest Paper Award, the Best Paper Award of the
Symposium on Integrated MEMS Technology at
the 26th Sensor Symposium, and the Best Paper
Award of IEEE CPMT Symposium Japan 2012.
He is a member of the Institute of Electrical andElectronics Engineers (IEEE), the Institute ofElectronics, Information and Communication
Engineers (IEICE), and the Japan Society ofApplied Physics (JSAP).

Vol. 13 No. 1 Jan. 2015

Hiroshi Koizumi

Senior Research Engineer, Supervisor, Group
Leader of Biosensing Technology ResearchGroup, Social Device Technology Laboratory,
NTT Device Technology Laboratories.
He received the B.S. and M.S. in materials
engineering from Waseda University, Tokyo, in1990 and 1992, respectively. Since joining NTT
LSI Laboratories in 1992, he has been engaged in
R&D of high-speed LSIs for optical communications. His current research interests include optical-biosensing devices. He is a member of IEEE,
JSAP, and IEICE.

Akihiko Hirata

Senior Research Engineer, Supervisor, Group
Leader of Imaging and Sensing Technology
Research Group, Social Device Technology
Laboratory, NTT Device Technology Laboratories.
He received the B.S. and M.S. in chemistry andthe Dr. Eng. in electrical and electronics engineering from the University of Tokyo in 1992,
1994, and 2007, respectively. He received the2011 Commendation for Science and Technology by the Minister of Education, Culture, Sports,
Science and Technology.

Feature Articles: R&D on Devices Using Life-assist Technologies

Development of Applications for a
Wearable Electrode Embedded inInner Shirt
Takayuki Ogasawara, Kazuyoshi Ono,
Nobuaki Matsuura, Masumi Yamaguchi,
Junji Watanabe, and Shingo Tsukada
Abstract

NTT has developed a conductive fabric called hitoe that enables continuous measurement of the biological signals of the person wearing it. Heartbeat variations and electrocardiogram signals detected
through hitoe are transmitted wirelessly by a compact dedicated device to a smartphone or tablet, where
they can be readily checked using an application. Such technology is expected to lead to the creation of
new services in fields such as sports training, health enhancement, security and safety, medical care support, and entertainment. In this article, we introduce some examples of approaches to application development.
Keywords: wearable, electrocardiogram, smartphone

1. Introduction
NTT has collaborated with the textile manufacturer
Toray Industries, Inc., to develop a conductive fabriccalled hitoe that enables continuous measurement of
the biological signals of the person wearing it [1].
Hitoe is a woven fabric that was created by coatingfiber surfaces with an electrically conductive polymer
material (PEDOT-PSS: poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)) [2]. Integrating thisfabric with an inner shirt makes it possible to easily
record heartbeat variations and electrocardiogramsignals over the long term in a variety of daily life
scenarios (Fig. 1). These physiological signals aremeasured and then transmitted wirelessly by a compact dedicated device to a smartphone or tablet,where they can be readily checked by using theappropriate application.
Heartbeat variations are naturally of interest in thefield of healthcare, but they can also be used as healthindicators in sports or dietary activities [3]. It haspreviously been reported that hitoe can stably measure vital data during sports activities, for example, insports with intense movements such as badminton[4]. In addition, variations in heartbeat are thought tobe related to the sympathetic nervous system and are
known to act as indicators of emotional stress [5]. By
focusing on the development of both physical andemotional aspects, we can expect to see new services
created in the fields of sports training, health enhancement, sleep management, medical care support, security/safety, and entertainment. To cover such a variety
of services, it is essential to implement highly applicable systems in which smartphones and tablets arelinked to a cloud service. In this article, we introduce
three initiatives from the entertainment field and the
security/safety field as applications of hitoe.
2. Applications in the entertainment field
Hitoe was exhibited at the Niconico Super Conference 3, an event attracting 100,000 fans of the
NTT Technical Review

Feature Articles

Wearable devices

Smartphones or tablets

Hitoe integrated
in a shirt

Cloud
Vital data

Vital data
Electrocardiogram

Analyzed data

Medical assistance

Variety of services

TransmitterEntertainment

Data storage and analysis

SportsSafetyHealthcare

Fig. 1. Future applications of wearable system using hitoe fabric.

170
160

Ishida 4-dan
Ito 5-danHeart rate (bpm)150

7-2 rook (60)

140
130
120

Elevation from the middle game

110
100
90

Consistently within 70-80 bpm

80
70
60

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Shogi move number(b) Heart rates during final game(a) Appearance on screen

Fig. 2. Heartbeat Shogi.

Niconico website, on April 26–27, 2014, at Makuhari
Messe, Chiba, Japan [6]. We asked various guests towear hitoe shirts during the conference, and we held
five events including talk shows and games. We
describe two events here: the First hitoe Cup Heartbeat Shogi Tournament and the Analog Game Workshop at Heartbeat University.
2.1 First hitoe Cup Heartbeat Shogi Tournament
Heartbeat Shogi is a name we coined for this event.
It is a shogi (Japanese chess) TV program in which
the heart rates of the players wearing hitoe shirts were
measured and displayed to visitors on monitors and toan online audience over the Internet. We were looking
for a new form of entertainment in which viewers
could not only enjoy the battles taking place on thegame boards and the body language of the players but
Vol. 13 No. 1 Jan. 2015

could also understand the physiological changes theplayers were experiencing that we usually have nomeans of knowing about from their outside appearance. We set up a tournament and invited three professional players to take part in it (Fig. 2). The players
wore hitoe inner-shirts during the matches.
The heart rates of the players during the final gameare shown in Fig. 2(b). The heart rate is plotted along
the vertical axis and the shogi move number along thehorizontal axis. The heart rate of Shingo Ito, 5-dan(on the right in Fig. 2(a)), was within the 70- to 80bpm level throughout the entire game. The heart rateof Naohiro Ishida, 4-dan (on the left in Fig. 2(a)), on
the other hand, tended to rise from the middle gameand even reached the 160-bpm level in the endgame.
Such information was delivered to the audience inreal time by integrating the wearable technology with

Feature Articles

an Internet image relay.
If we focus on more subtle heartbeat variations, we
see that the heart rate of Ishida peaked at 7-2 rook in
the middle game (Fig. 2(b)). This occurred at a gameposition where he took Ito’s bishop. Ishida’s heart
rate continued to rise even in the endgame until Ito
resigned. We think that this gives a glimpse into thecorrespondence between heartbeat variations andgame position and can become a method of conveying a further sense of excitement to the audience.
Naohiro Ishida won the tournament and was given
the title of First hitoe Heartbeat Shogi Meijin by
Hiroo Unoura, President & CEO (Chief Executive
Officer) of NTT. A better understanding of the relationship between heartbeat variations and emotional
state was gained from the post-game discussion.
Ishida, 4-dan, thought back and said that “The endgame was so tense, I could feel my own heartbeat.
Even though I was playing aggressively and was in
the lead, one false move and I would have lost thegame.” We can infer from this that the anticipation of
making the most of his chances in the game caused
him inner tension. Ito, 5-dan, said that “By the endgame, I thought I had already lost, so I was completely relaxed.” This perspective might be one reason why his heartbeat variations were stable throughthe game. With shogi, decisive moments and relative
superiority according to the game position can beseen on the board. However, the players’ own evaluations of the board positions and their level of tension
can usually only be determined by their expressions
or actions. We expect that the display of heart rates as
an element that mirrors changes in the tension andemotional state of the players during games such as
shogi will add new interest for viewers.
2.2 Analog game workshop at Heartbeat University
Heartbeat University is an educational program led
by instructors with interests in particular areas. The
first instructor we invited to be part of this program
was Jun Kusaba, the originator of Game Market,
Japan’s largest analog game experience and sales
event and also the executive of the Gaming History
Society. He gave a lecture and led workshops in an
analog game. During the workshops, participants
who were acting as students played an analog gameunder the coaching of Mr. Kusaba. The students wore
hitoe shirts, and their heart rates were measured(Fig. 3(a)). We used the card game called Divinare in
the workshop sessions (Fig. 3(b)). There are cards infour colors (red, blue, yellow, and green), and thegame involves correctly predicting how many cardsof each color were dealt. In this game, the luck andhunches of the players feature highly, in contrast to
shogi, and even a beginner has a chance of winning.
It was therefore expected that the heartbeat variations
would be different from those of the shogi players.
Each student was given three points if the predicted
number of cards matched the correct number of cards,
one point if the number differed by one, and minus
one point otherwise.
They played four rounds and competed for the total
number of points. An example of a student’s heartbeat
variations is shown in Fig. 3(c). A rise in heart rate
can be seen near the end of each round. This was
assumed to be related to the way that the difference inhis predicted number of cards and the correct numberof cards was revealed at the end of each round; thepreviously unknown correct number of cards isgradually revealed as the game progresses. One student replied in a questionnaire given after the gamewas finished, that after the second round, “I was infine form so I thought I might win if I carried on” andafter the fourth round, “I thought that I would definitely hold on to my lead and receive a prize.” Thisshows that it is possible for such anticipation andagitation to be reflected in the heart rate.
However, variations in heart rate such as those ofthis student were not the only interesting example.
There was another student whose heart rate remained
about 30 bpm higher than usual from beginning toend, irrespective of developments during the game.
To integrate biosignal measurements effectively into
entertainment, it is important that repeatability
between large numbers of people is confirmed andalso that variations in the biosignals are presented incorrespondence with the event in a way that the audience can understand. It is essential to explore theconcept of creating events based on an understandingof the mechanisms of the body, then to search formethods of applying biological information fromvarious viewpoints.
3. Application to security/safety
It is now possible to buy and sell an enormous variety of goods over the Internet, and the demand for
distribution and delivery of goods is therefore veryhigh. This has increased the importance of understanding the physical condition and stresses of vehicle
drivers. Focusing on heartbeat variations and perspiration as stress markers during driving is thought tobe effective for this [7]. We had people wear hitoe
NTT Technical Review

Feature Articles

Blue
Red

Green
Yellow(a) Appearance on screen(b) Image of Divinare game
Explanationof the rules

LectureWorkshop
1st round

Closing

2nd round

3rd round Final

Heart rate (bpm)

160
150
140
130
120
110
100
90
80

0

10

20

30

40

50

60

Time (minute)(c) Heart rate of one player during Divinare lecture and workshop

Fig. 3. Heartbeat University.

shirts and then measured their heartbeat variations
while they participated in driving tests under real-life
conditions. An example of an electrocardiogram
waveform taken while a subject was driving is shownin Fig. 4(a). The subject’s R waves, which are features of the electrocardiogram waveform, can clearly
be seen. Photos taken when the driver was travelingalong a road through a pass in a mountain region andalong a suburban road with good visibility are shownin Figs. 4(b) and 4(c). The road through the mountainpass was a narrow one-lane road with a sequence of
curves such as that shown in the photo. In contrast,
the road with good visibility was a two-lane road thatwas fairly straight.
We can visualize heartbeat variations from an electrocardiogram waveform by representing them inPoincaré plots, as shown in Figs. 4(d) and 4(e). A
Poincaré plot is a graph in which the n-th RR interval(the interval between two consecutive R waves; see
Fig. 4(a)) from the start of measurement is plotted on
the horizontal axis, and the next (n+1)-th RR intervalis plotted on the vertical axis. When the driver is in a
stressful situation, the fluctuations in heartbeat variations are small, and the plotted points clump together[8]. Conversely, when the driver is relaxed, the plots
Vol. 13 No. 1 Jan. 2015

scatter. A comparison of the plots of Figs. 4(d) and4(e) shows that the plot for the mountain pass road isclumped closer together than that for the good-visibility road, suggesting the driver was under morestress on the mountain road. A questionnaire was later
given to the driver, who said that on the mountainpass road, “I was driving cautiously since I didn’tknow when an oncoming car would appear from ablind corner,” which verified that the driver had acertain sense of tension. This was a fundamental
evaluation, but in the future, we plan to estimate
driver fatigue, impaired physical condition, or drowsiness, which will contribute to improved security andsafety while driving and also effective employee
management support.
4. Future developments
In this article, we introduced three applications of
hitoe. The ways in which these applications are
implemented and combined with other technology
will differ with the intended use, but it is importantthat each application has a high level of usability. We
should provide a system that is easy to use, even forpeople who are not experienced with smartphones,Voltage (mV)Feature Articles

2.5
2
1.5
1
0.5
0
−0.5
−1
−1.5

R wave0

1

2

RR interval

345Time (s)

6

7

8

9

10

(a) Example of an electrocardiogram during driving(c) Road with good visibility

1000

1000

900

900

(n+1)-th RR interval (ms)(n+1)-th RR interval (ms)(b) Mountain pass

800
700
600
500
400
300
300 400 500 600 700 800 900 1000n-th RR interval (ms)

800
700
600
500
400
300
300 400 500 600 700 800 900 1000n-th RR interval (ms)(d) Poincaré plot for mountain pass (e) Poincaré plot for road with good visibility

Fig. 4. Heart rate of driver while driving.

and a full range of functions corresponding to individual needs. Apart from the methods described here,
we are also promoting links with the GPS (global
positioning system) functions of smartphones, various sensors, SNSs (social networking services), anddigital games with business partners.

[4]

[5]
[6]

References
[1]
[2]

[3]



NTT press release published on January 30, 2014 (in Japanese).
http://www.ntt.co.jp/news2014/1401/140130a.html
S. Tsukada, N. Kasai, R. Kawano, K. Takagahara, K. Fujii, and K.
Sumitomo, “Electrocardiogram Monitoring Simply by Wearing a
Shirt––For Medical, Healthcare, Sports, and Entertainment, ” NTT
Technical Review, Vol. 12, No. 4, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
04fa4.html“Heart Rate Training,” R. Benson, D. Connolly, Human Kinetics,
2011.

[7]
[8]

K. Takagahara, K. Ono, N. Oda, and T. Teshigawara, “‘hitoe’—A
Wearable Sensor Developed through Cross-industrial Collaboration,”
NTT Technical Review, Vol. 12, No. 9, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
09ra1.html
G. G. Berntson and J. T. Cacioppo, “Heart Rate Variability: Stress andPsychiatric Conditions,” In: M. Malik, A. J. Camm, editors. Dynamic
Electrocardiography. New York: Blackwell Futura, 2004. pp. 57–64.
S. Usui, U. Tamai, and S. Kinoshita, “Report on NTT Super Future
Laboratory Exibit at Niconico Super Conference 3,” NTT Technical
Journal, Vol. 26, No. 7, pp.59–62 (in Japanese).
http://www.ntt.co.jp/journal/1407/files/jn201407059.pdf
J. A. Healey and R. W. Picard, “Detecting Stress during Real-world
Driving Tasks Using Physiological Sensors,” IEEE Transactions onIntelligent Transportation Systems, Vol. 6, No. 2, pp. 156–166, 2005.
Y. Matsumoto, N. Mori, R. Mitajiri, and Z. Jiang, “Study of Mental
Stress Evaluation Based on Analysis of Heart Rate Variability - Considerations of Evaluation by Pattern Recognition,” Journal of Life
Support Engineering, Vol. 24, No. 2, pp. 62–69, 2012.

NTT Technical Review

Feature Articles

Takayuki Ogasawara

Masumi Yamaguchi

Research Engineer, Healthcare Device Development Project, NTT Device Innovation Center.
He received the B.E. and M.E. in applied physics from Hokkaido University in 2006 and 2009,
respectively. He also completed the Developmental Brain Science Master’s Program at the
Research and Education Center for Brain Science, Hokkaido University, in 2009. He joined
NTT Microsystem Integration Laboratories in2009. His current interests include biosensors
and wireless communications. He is a member ofIEEE (Institute of Electrical and Electronics
Engineers) and the Institute of Electronics, Information, and Communication Engineers (IEICE).

Manager, Research Planning Department,
NTT Science and Core Technology Laboratory
Group.
He received the B.S. in physics from Kanazawa
University in 1998, and the M.S. and Ph.D. inphysics from Kyoto University in 2000 and 2003.
He joined NTT Basic Research Laboratories in2003 as a research associate. He became a permanent researcher in 2005. His research has
included transport and optical properties of lowdimensional electron systems. He is a member of
the Physical Society of Japan, JSAP, and IEICE.

Kazuyoshi Ono

Junji Watanabe

Research Engineer, Healthcare Device Development Project, NTT Device Innovation Center.
He received the B.S. in physics from Tokyo
University of Science, Chiba, in 2004 and the
M.E. in advanced applied electronics from Tokyo
Institute of Technology, Kanagawa, in 2006. He
joined NTT in 2006. He is now with NTT Device
Innovation Center, where he is researching anddeveloping MEMS (microelectromechanicalsystems) devices. He is a member of the Japan
Society of Applied Physics (JSAP) and IEICE.

Nobuaki Matsuura

Senior Research Engineer, Healthcare Device
Development Project, NTT Device Innovation
Center.
He received the B.S. in applied physics andM.E. in energy science from Tokyo Institute ofTechnology in 1990 and 1992, respectively. He
joined NTT in 1992. Since then, he has been
conducting research on optical interconnection
technology. He is a member of IEICE.

Vol. 13 No. 1 Jan. 2015

Senior Research Scientist, NTT Communication Science Laboratories.
He received the B.E. and M.E. in mathematicalengineering and information physics from the
University of Tokyo in 2000 and 2002, respectively. He received the Ph.D. in information science and technology from the University ofTokyo in 2005. From 2005 to 2009, he was a
PRESTO researcher in the project called Foundation of Technology Supporting the Creation of
Digital Media Content at the Japan Science &Technology Agency (JST). From 2009 to 2011,
he was a Research Fellow at the Japan Society for
the Promotion of Science. He became a research
specialist at NTT Communication Science Laboratories in 2011, and a research scientist in 2013.
He studies cognitive science and communication
devices with applied human perception. His
fields of interests are visual and haptic perception
and communications.

Shingo Tsukada

Senior Distinguished Researcher, Supervisor,
Materials Science Laboratory, NTT Basic
Research Laboratories.
He received the M.D. Diploma and Licensefrom Toyama University in 1990, and the Ph.D.
in medicine from the University of Tsukuba,
Ibaraki, in 2003. He joined NTT Basic ResearchLaboratories as a research specialist in 2010 andhas been in his present position since 2013. He is
engaged in work on human-machine interfaces,
including wearable electrodes and their systems,
both in vivo and in vitro, especially in the neuroscience field. He is a member of the Japan Neuroscience Society, the Physiological Society ofJapan, the Japanese Circulation Society, and theSociety for Neuroscience.

Feature Articles: R&D on Devices Using Life-assist Technologies

Blood Flow Observed with
Smartphone— Ultracompact
Wearable Blood Flow Sensor
Kei Kuwabara, Yuichi Higuchi, Hiroshi Koizumi,
and Ryoichi Kasahara
Abstract

The flow of blood that circulates through the entire human body and supports life changes dynamically with our emotional and physical state and reveals a huge amount of information. If the flow ofblood could be easily visualized in our daily lives, we could expect to see a range of useful applications
in areas such as health, beauty, and sports. In this article, we introduce an ultracompact, wearable bloodflow sensor that is linked to a smartphone, making it possible to view the flow of blood anywhere and at
any time.
Keywords: blood, smartphone, wearable

1. Introduction
The adult human body is estimated to consist of
several dozen trillion cells [1]. The oxygen and nutrients necessary for the life of these cells are supplied
via the blood that circulates through the entire body.
In addition, carbon dioxide and other waste products
excreted from the cells are collected in the blood
flow. The red blood cells, the major component ofblood, account for a large proportion of the total cells
in the human body, so we can say that our lives aresupported by the flow of blood.
Various health problems can occur if this vital flow
is impeded. Heart disease and cerebrovascular disease, the second and third most common causes ofdeath among Japanese people, are prime examples ofthis. Other bodily disorders that routinely worry
many people, for example, chills, numbness, andbody stiffness, are also thought to be caused mainly
by obstructions in the flow of blood [2]. The importance of blood flow is also recognized in areas suchas the beauty industry and sports medicine.
Thus, the flow of blood is vital to human life, and if
we could better comprehend it, it might lead to peoplerethinking their lifestyles and undertaking activities
to improve blood circulation. However, it has notbeen possible for people to measure their blood flowroutinely. This is because commercially available
blood flow meters are large, impossible to carryaround, and expensive, so they can only be used in
hospitals and other such facilities. Consequently, we
are applying technology acquired through NTT’s pastcommunications-related research and development(R&D) to develop a portable, compact blood flow
sensor [3]. We have extended this technology evenfurther and linked this blood flow sensor to a smartphone, which will enable users to visualize the flowof blood in daily life over extended periods.
2. System configuration and operating principle
The configuration of our prototype blood flow sensor system is shown in Fig. 1. This system consists ofa sensor device and a dedicated application for asmartphone. The sensor device consists of a sensor
head and a main unit. A laser diode (LD) and a photo
diode (PD)—a light-sensitive element—are installedin the sensor head. Infrared light from the laser shines
NTT Technical Review

Feature Articles

Wirelesstransmission

Sensor device

Smartphone

Sensor head
Electrical cable

Blood flow
animation
Heartbeatanimation

Main unit

Blood flow
volume graph
PD
Skin

ω0+ ω

LD
ω0

ω0

Capillary vessel
DermisFig. 1. System configuration of blood flow sensor.

Vol. 13 No. 1 Jan. 2015

Commercially available
blood flow meter

10,000Previous prototype
Weight (kg)on the skin, and light that is scattered back is detectedby the PD. Light that strikes and is scattered by the
red blood cells moving within the blood vessels generates a frequency shift that is proportional to thevelocity of the moving red blood cells due to the Doppler effect of light, so it is possible to acquire information relating to the flow of blood by analyzing thefrequency spectrum of the detected signal [4]. With
this information, the smartphone provides visualizations such as a graph of the blood flow volume*1 oranimations of the flow of blood and the beatingheart.
The weight and power consumption of this bloodflow sensor are compared with those of a previous
NTT prototype model and a commercially available
blood flow meter in Fig. 2. The weight and power
consumption of the previous NTT prototype model
were far lower than those of the commercial bloodflow meter. The weight was approximately one-thirtieth lower, and the power consumption was approximately one-fortieth lower. Our current prototype
model reduces these values even further; the respective weight and power consumption are approximately one-quarter and one one-hundredth that of theprevious NTT prototype. This enables a new form of
use in that it can continuously monitor changes in the
blood-flow during the day, while being easily carriedaround in daily life. There are two reasons we wereable to achieve such huge reductions in weight andpower consumption. The first reason is that some of
the functions installed in the previous sensor device
are now provided by the smartphone because the1000
This device
100

10
100

10
1
0.1
0.01
Power consumption (W)

0.001

Fig. 2. Comparison of blood flow sensors.

overall system design is based on a link with a smartphone. The second reason is that we modified thecircuitry and signal processing so that the blood flow
sensor would operate intermittently at high speed inorder to achieve efficient operation. We explain thesetechnologies in more detail in the following sections.

*1	 Blood flow volume: A quantity equivalent to the sum of the products of the velocity of the blood cells and the number of blood
cells.

Feature Articles

Minimizing the amount oftransmitted data by
extracting feature values.

Opticalsensing

AnalogDigitalprocessing processing

Wirelesstransmission

Sensor device

Digitalprocessing

Display

Storage

Smartphone

Fig. 3. Sharing of functions between sensor device and smartphone.

3. System design technology linked tosmartphone
A blood flow sensor must have certain functions,for example, optical sensing, analog signal processing, digital signal processing, the capability to display
the analysis results, and storage. In the past, sensor
devices had to be equipped with all of these functions. However, this situation has changed greatly
with the recent spread of smartphones. Smartphones
come equipped with features such as a sophisticatedprocessor, a high-definition display, a large-capacity
memory, and communications functions, and therefore, we were able to install only the minimum necessary functions in the sensor device by actively applying other functions on the smartphone. A sensor thatfunctions in integration with a smartphone in this way
is called an appcessory (a portmanteau word combining application and accessory), and it has recently
become a new trend in sensor development.
To make the sensor device smaller and reduce its
power consumption, it is important to optimize thesharing of functions between the sensor device andthe smartphone. An image of the function-sharing ofour prototype blood flow sensor is shown in Fig. 3.
The sensor device implements the processing of raw
data acquired by optical sensing—from amplification, filtering, and sampling, to the extraction of feature values by digital signal processing. It relies on asmartphone for other functions such as advanced
digital signal processing and the display and storageof analysis results. Having the sensor device transmit
the measured raw data (without processing it) to thesmartphone would reduce the amount of data processing, but there is a trade-off in that the amount ofdata being transmitted would increase. Thus, wereduce the amount of communications data to lessthan one one-hundredth that of the case when the sensor device transmits the measured raw data to thesmartphone, by transmitting feature values after
extracting them from the raw data on the sensor
device side, as described previously. This minimizes
the power consumption of the sensor device.
4. Reduced power consumption by intermittent
operation
The operation and power consumption of the previous blood flow sensor and the blood flow sensor wehave newly prototyped are shown in Figs. 4(a) and
4(b). In the previous blood flow sensor, the laser fires
continuously during the measurement, the analog anddigital circuitry also operates continuously, and themeasurement results are transmitted frequently. In
contrast, our new blood flow sensor implements efficient measurement operations, which substantiallyreduces power consumption. More specifically, theamplification and filtering of signals is done within ashort time period by having the laser fire for only
short periods intermittently and having the analog
circuitry operate intermittently in tune with the laser.
The digital circuitry also goes into sleep mode assoon as it has sampled the signal and extracted feature
values in order to reduce power consumption.
NTT Technical Review

Feature Articles

Powerconsumption(a) Previous prototype
Wireless transmission

Laser
Analog circuitry
Digital circuitry

Time

Power
consumption(b) This device
Laser Analog circuitry Digital circuitry

Wireless transmission

Time

5. Examples of measuring blood flow volume
Here, we introduce examples of measuring bloodflow volume using this blood flow sensor. The resultsof measuring blood flow volume when the blood flow
sensor was attached to a fingertip and the arm wasraised and then lowered are plotted in Fig. 5(a). It isclear that the blood flow volume at the fingertip drops
when the arm is raised, due to the effect of gravity, but
it returns when the arm is lowered. Thus, the flow ofblood in a person changes dynamically with routine
actions.
Vol. 13 No. 1 Jan. 2015(a)

Arm israised.
05

Arm is lowered.
101520Time (sec.)

25

30

40

50

(b)
Blood flow (a.u.)

For wireless communications, we adopted theBluetooth*2 low energy (BLE) method, which canoperate with low power consumption by using intermittent communications. BLE is a new communication method that is installed in Android*3 operating
systems from version 4.3. This enables even lower
power consumption than in previous versions ofBluetooth by transmitting small amounts of data, at a
maximum of approximately 20 bytes per packet, only
when necessary. With our newly prototyped bloodflow sensor, we make the most of BLE communication capabilities and implement efficient communications by collecting the measured data in a buffer
without transmitting it immediately, and then transmitting the data in a batch once a packet is full. In thisway, we greatly reduce power consumption by running all the optical sensing, analog signal processing,digital signal processing, and wireless communication processing intermittently, making it possible tomonitor the flow of blood over long periods of timewith a small battery.

Blood flow (a.u.)

Fig. 4. Operation and power consumption of blood flow sensors.

0

10

20
30
Time (sec.)

Fig. 5. R esults of measuring blood flow at (a) fingertip,and (b) earlobe.

The results of measuring blood flow volume at an
earlobe are shown in Fig. 5(b). The blood flow volume at the earlobe has periodic fluctuations atapproximately 1-s and 10-s intervals. The fluctuations at approximately 1-s intervals correspond to theheartbeat, and those in the approximately 10-s cycle
represent the contraction motion of blood vessels,
which is referred to as vasomotion. These fluctuations vary with certain conditions such as the physical*2 Bluetooth is a registered trademark of Bluetooth SIG Inc.
*3 Android is a registered trademark of Google Inc.



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Drive

Blood flow (a.u.), Heart rate (bpm)140White: relax at home
eat

shop

eat

shop

study
study
sleep

eat

sleep

exercise120

Blood flow
Heart rate

100
80
60
40
20
0
9:00

11:00

13:00

15:00

17:00

19:00

21:00
23:00
Time

1:00

3:00

5:00

7:00

9:00

Fig. 6. Results of measuring blood flow continuously for 24 hours.

or emotional state, and therefore, various applicationsof this phenomenon are being investigated [5].
The results of measuring blood flow volume for 24hours continuously during daily life are shown in
Fig. 6. The figure also shows the simultaneously
measured heart rate when the subject was wearing ahitoe wearable electrode inner shirt [6]. The effects
on blood flow of daily actions such as driving, eating
meals, and sleeping can be perceived. By taking suchmeasurements, people who are concerned aboutbodily disorders caused by bad circulation can obtain
information on improving their circulation in daily
life. It used to be impossible to use a blood flow sensor to measure blood flow over long periods while
going about our daily lives, but the features of theblood flow sensor we have newly prototyped, namely
its small size and low power consumption, have madeit possible to achieve this for the first time.
6. Future development
The flow of blood changes dynamically in response
to our emotional and physical states, and it contains avast amount of information. The fields of applicationof a wearable blood flow sensor that can measure theflow of blood anywhere and at any time cover a wide
range including routine circulation monitoring, at-home medical care, beauty, and sports. We are actively promoting collaboration with businesses and universities that have strengths in these fields, and we areworking on creating services that support people inliving healthy and active lives.
References
[1]

[2]

[3]

[4]
[5]

[6]

E. Bianconi, A. Piovesan, F. Facchin, A. Beraudi, R. Casadei, F. Frabetti, L. Vitale, M.C. Pelleri, S. Tassani, F. Piva, S. Perez-Amodio, P.
Strippoli, and S. Canaider, “An Estimation of the Number of Cells in
the Human Body,” Annuals of Human Biology, Vol. 40, No. 6, pp.
463–471, 2013.
N. Ushiroyama, “Clinical Analysis and Correspondence with Pathological Condition of Chills—What Pathological Condition is
Observed by the Chills? Can it be Cured?”, Journal of Clinical andExperimental Medicine, Vol. 215, No. 11, pp. 925–929, 2005 (inJapanese).
T. Kiyokura, S. Mino, and J. Shimada, “Wearable Laser Blood Flowmeter,” NTT Technical Review, Vol. 4, No. 1, 2006.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2006
01038.pdf
R. Bonner and R. Nossal, “Model for Laser Doppler Measurements ofBlood Flow in Tissue,” Applied Optics, Vol. 20, No. 12, pp. 2097–
2107, 1981.
H. Mukae, M. Mochizuki, and Y. Taniguchi, “Physiological Analysisof Mood State Using Spontaneous Rhythmic Oscillation Measured
with Laser Doppler Flowmetry,” Japanese Journal of Physiological
Anthropology, Vol. 11, No. 2, pp. 81–86, 2006 (in Japanese).
K. Takagahara, K. Ono, N. Oda, and T. Teshigawara, “‘hitoe’—A
Wearable Sensor Developed through Cross-industrial Collaboration,”
NTT Technical Review, Vol. 12, No. 9, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
09ra1.html

NTT Technical Review

Feature Articles

Kei Kuwabara

Hiroshi Koizumi

Yuichi Higuchi

Ryoichi Kasahara

Research Engineer, NTT Device Innovation
Center.
He received the B.E. and M.E. in electronics
engineering from Keio University, Kanagawa, in2002 and 2004, respectively. In 2004, he joinedNTT. He is now with the NTT Device Innovation
Center, where he is engaged in the research anddevelopment of vital sensing devices. He is amember of the Institute of Electrical and Electronics Engineers (IEEE), the Japan Society ofApplied Physics (JSAP), and the Institute ofElectronics, Information and Communication
Engineers (IEICE).

Researcher, Social Device Technology Laboratory, NTT Device Technology Laboratories.
He received the B.E. and M.E. from Kyoto
University in 2006 and 2008, respectively. He
joined NTT Microsystem Integration Laboratories in 2008. He is currently studying free-space
optical devices for optical telecommunications
and biosensing. He is a member of IEICE and theJapan Society for Precision Engineering.

Vol. 13 No. 1 Jan. 2015

Senior Research Engineer, Supervisor, Group
Leader of Biosensing Technology ResearchGroup, Social Device Technology Laboratory,
NTT Device Technology Laboratories.
He received the B.S. and M.S. in materials
engineering from Waseda University, Tokyo, in1990 and 1992, respectively. Since joining NTT
LSI Laboratories in 1992, he has been engaged inresearch and development of high-speed LSIs for
optical communications. His current researchinterests include optical-biosensing devices. He
is a member of IEEE, JSAP, and IEICE.

Senior Research Engineer, Supervisor, NTT
Device Innovation Center.
He received the B.E. in engineering from the
University of Electro-Communications, Tokyo,
in 1995 and the M.E. in engineering from Tohoku
University, Miyagi, in 1997. In 1997, he joined
NTT Photonics Laboratories, where he researchedsilica-based planar light-wave circuits. Since
2014, he has been engaged in developing vitalsensing devices. He is a member of JSAP and
IEICE.

Feature Articles: R&D on Devices Using Life-assist Technologies

MicroTAS for Biosensors
Yuzuru Iwasaki and Michiko Seyama
Abstract

Micro-total analysis systems (microTAS) are expected to be useful in daily healthcare applications in
the near future because of their ability to measure biological information from molecules in the humanbody. This information is now assessed using sophisticated analytical systems at specialized institutes.
MicroTAS is based on microfluidics, a multidisciplinary field that involves precise control of fluids atthe sub-millimeter scale. A microfluidic device handles liquid just as an electronic device handles electricity. In this article, we introduce microTAS technology currently under development that makes measurement protocols as simple as possible through the use of microfluidics and enables end users tomeasure their health condition by themselves.
Keywords: microfluidics, microTAS, biosensor

1. Introduction

easily and deal with small volumes automatically.

1.1 Overview of microTAS
Analytical chemistry is the scientific field concerning measurement of chemical substances. Bloodanalysis carried out as part of a medical health checkup is based on analytical chemistry techniques. The
primary discipline in analytical chemistry is carryingout chemical experimental protocols in a predefinedway. These protocols include the handling of cuvettes,
flasks, and pipettes. The basic idea of micro-total
analysis systems (microTAS) is to replace those laboratory liquid management tasks with a liquid handling circuit device (microfluidics) and reduce anentire laboratory room down to one chip (Fig. 1) [1].
This is why microTAS is also frequently referred toas lab on a chip.
The typical liquid handling tasks in analyticalchemistry include: dispensing, mixing, initiating areaction, filtration, transfer, and measurement. Eachtask requires time and labor if the experiment is carried out using discrete tools and measurement instruments. The task will become more difficult as the
sample volume is reduced. The use of microfluidic
devices makes it possible to replace such liquid handling tasks with small channels, valves, and junctions. These liquid handling components are formed
on a thin flat substrate, and the size is drasticallyreduced, so we can handle the sample liquid more

1.2 Microfluidic devices
Microfluidic devices are fabricated using photolithography and microelectromechanical systems(MEMS) technology, the same technology as thatused to integrate electronic circuit elements (registers, transistors, wiring) on a silicon wafer. Therefore,
the microfluidic device and the internal volume canbe fabricated with a small size. The microfluidic
devices have a micrometer-scale trench structure inwhich liquid flows. Therefore, a very small volume ofliquid can be handled and used for chemical reactionsin these devices. These characteristics of microfluidic
devices make them best suited for analyzing biological and medical samples that are difficult to collect ina large volume for sample analysis.
Microfluidics technology has advanced to the level
where elementary liquid handling functionality isachieved with a certain pattern or circuit of liquid
flow. For example, mixing is achieved with a Y pattern, dispensing with a cross pattern, and filtration
with a pillar array. These patterns are also constructedin a trench structure. These functional units are piecesof patterns in a plane structure, so we can combine
and integrate the pieces as in a jigsaw puzzle to construct a chemical reaction device that carries out aspecific and total chemical reaction, synthesis, andanalysis instead of having to manually carry out these

NTT Technical Review

Feature Articles

Dispensing
Protocol of analytical chemistry

12:00

MixingReaction
Filtration
Transfer
Detection

Fig. 1. Device integration of analytical chemistry by microTAS.

Efficientcatalysis

Molded 3D pattern

10–100 µm

Substrate

Mixing bydiffusion

Fluidic
channel

Surface effect

3D: three-dimensional

Fig. 2. Microfluidics.

tasks with separate tools. For example, polymerase
chain reaction (PCR) is a common process in genetic
biochemistry that amplifies the specific sequence of
deoxyribonucleic acid (DNA) concentration, and it isnecessary in DNA analysis. A PCR protocol consisting of multiple complex chemical reactions was carried out automatically using microfluidic devices[2].
Because microfluidic devices are fabricated using
MEMS mass production techniques, they can bemade in arbitrary patterns and in large quantities withhigh dimensional precision. A transparent material isused for the liquid circuit structure (Fig. 2) to enable
the liquid inside the microfluidic device to beVol. 13 No. 1 Jan. 2015

observed in order to measure and check the liquid
flow. Mold casting is a common method to makethese structures, as it enables repeated fabrication of
the devices.
Typically, the trench in a microfluidic device has across-sectional length of 10–1000 μm. The shorterthe length is, the smaller the internal volume is. Thisis advantageous for small volume reactions. In general, the area is proportional to the square of thelength, but the volume is proportional to the cubicsquare of the length. Therefore, the ratio of volume tosurface area of the internal microfluidics increases as
the length gets shorter. This makes the effect of theinternal wall of microfluidic devices very strongFeature Articles

Sa

mp

le h

old
e

r

Ca

16

m

m

pill

Picture of actual device

ary

arr

ay

Fl
pa ow ctte ircrnu
she it
et
An
t
m ibo
su icro- dy abs c htra an rraynetelStructure of device

Fig. 3. On-chip sample liquid flow system.

compared to macro-scale liquid handling tools. Thisis the same phenomenon as that of a straw placed in a
glass of liquid; the narrower the straw is, the higher it
can draw up the meniscus (the curve in the surface) of
the liquid due to capillary force. With microfluidic
devices, the smaller they are, the greater the capillary
force governing the liquid behavior.
Chemical reactions are usually facilitated by mixing, and mixing is a fundamental procedure in chemical analysis. In a microfluidic device, mixing iscontrolled by flow and diffusion. The flow in mostmicrofluidic devices is very stable because liquid isheld between walls that are spaced closely together,and the mixing is controlled by the fluidic pattern.
When the internal wall is modified with a catalyst, thereaction efficiency is enhanced because the reactant
has only a short distance to travel to access the catalyst [1].
2. Biomolecule sensing
Current healthcare diagnosis involves collecting
biological samples (e.g., blood, urine) and analyzing
the components to determine the patient’s state ofhealth. In most local hospitals, the collected samples
are analyzed using specialized massive-scale measurement instruments installed in a specialized medical test center that is usually located away from thehospitals. These instruments measure a large numberof samples with high throughput; therefore the test
cost becomes low enough to be covered by medical
insurance. However, the patient or examinee cannot
find out the results on the day of sampling and alsocannot be tested more frequently than once a day toassess sudden changes.
However, frequent measurement of concentrationsof specific blood components is considered to beeffective for controlling or reducing the risk of lifestyle related adult illnesses such as diabetes andstroke. For these purposes, a way for examinees totest themselves at home instead of going to a hospitalis desired. This would also enable examinees tomonitor changes to their state of health that may
occur within a few days. This type of self-test shouldbe easy to do and low in cost, and microTAS has thepotential to help achieve this.
Conventional microTAS chips [1] have been successfully used in liquid handling tasks. However, thepumps that enable the liquid to flow through the circuits and the detectors used for the reaction monitoring are still too large to realize personal measurement
capabilities. To overcome this problem, we developed
a low cost microfluidic device that is integrated with
an autonomous liquid flow mechanism and a smallsized reaction detector; we describe it in the next section.
3. On-chip sample liquid flow system
We developed an on-chip sample liquid flow system using capillary force and surface tension [3]. This
device comprises a plastic substrate with antibody
array, a capillary array formed in a plastic plate, anda plastic sheet with a flow circuit pattern (Fig. 3).
These three parts are simply bonded by an adhesive
agent on both sides of the sheet. The liquid circuits
NTT Technical Review

Feature Articles

Antibody
array channel

Sample holder

Flow circuit
pattern sheet

Antibody

Capillary array

Test reagent

Plastic substrate(a) Application of test reagent

Test liquid(b) Application of test liquid

Fig. 4. Self-flow microfluidic device.

connect a sample holder, an antibody array microchannel substrate, and a capillary array to each other.
The internal surface of the fluidic device is hydrophilic. The device works as follows. An aqueous test
reagent is introduced in the sample holder. Capillary
force causes the test reagent to flow into the antibody
array channel as in the principle of the narrow straw.
The flow stops when the channel is filled if the volume of the reagent is set equal to the internal volumeof the channel. In this stage, the capillary force of thehead and tail of the liquid plug (i.e., a volume of liquid in air) is balanced (Fig. 4(a)). In this way, thisdevice can control the liquid flow in the channel byitself.
When the test liquid is added to the sample holder,
the capillary force of the tail of the liquid becomes
lower compared to the head. Then the head moves tothe capillary array. The test reagent and the test liquidthat follows it flow under the many capillaries. The
liquid is pumped up by the capillaries, and the test
liquid flows continuously through the antibody array
channel (Fig. 4(b)). This continuous flow enables theantibodies and molecules in the test liquid to react
efficiently. The test sample, which may be a biologically hazardous substance, flows into the capillaries
and stays in the device.
This device can be used with a small multi-point
SPR (surface plasmon resonance) instrument* [4] thatwas developed by NTT. This instrument can detect
subtle refractive index changes of the entire length ofVol. 13 No. 1 Jan. 2015

the channel at the same time. The refractive index
changes are generally caused by the reaction of amolecularly thin film of immobilized antibodies toantigens in the channel. The instrument is sensitive
enough to detect changes at the monomolecular-layer
level. Therefore, antibody reactions in the antibody
array channel can be easily detected.
The developed device had nine antibodies of different specificities in the channel. After the test reagent
was introduced, the refractive index recorded by SPR
showed a flat response because no reaction occurredin the channel, as shown in Fig. 5. Then, after the
addition of the test liquid, the refractive index
increased because of the refractive index difference
between the test reagent and the test liquid. This is anindication of the arrival of a sample. At this stage, theantigens in the test liquid started to react with antibodies in the channel. The reacted antibodies (yellow
and black curves) showed a further increase in therefractive index. This is because the complex formation by a specific binding of antigen and antibody
causes a high density region (high refractive index) in
the channel. In contrast, the other seven curves
showed a constant response, which is a result of nobinding occurring between antibodies and moleculesin the sample. In this way we can measure the pattern*

SPR instrument: A chemical reaction measurement system thatcan detect monomolecular-layer level refractive index changes.
Refractive index changes of antigens captured by antibodies canbe directly detected.

Feature Articles

Test liquid
application

Reaction of
responsive antibodies

Refractive index

High

Continuous flow oftest reagent

Reaction ofunresponsive antibodies

300 s
Low
Time

Fig. 5. Response of antibody array measured by SPR.

of response from nine antibodies in a simple operation. Because each antibody detects its specific biologically relevant molecule, we can evaluate themolecular components of the sample from theresponse pattern of antibodies. By changing the combination of antibodies, we can use this device for
specific applications.
Moreover, because the raw data of the SPR instrument consist of a sequence of image data, the device
can also detect sample introduction and flow conditions (e.g., whether the liquid is stuck, is leaking, orthere has been a liquid introduction error) automatically through the use of sophisticated image processing technology. This automatic recognition helps end
users to carry out correct measurements. We developed these technical elements using a simple sensor
system.

chemical analysis of biological samples that can be
carried out as easily as making a phone call using
microTAS. Data analysis of frequent measurements
and a large number of examinees will make it possible to detect abnormal health conditions before theyrequire costly treatment. We expect that the developed technology will be useful in providing new services to achieve improved health outcomes at a lower
cost, and will expand the choice of treatments foreach person.
References[1][2]

4. Future perspectives[3]

We developed our on-chip sample liquid flow system with the aim of using it in on-site measurementin the dairy industry as a first step, for example, toidentify the pathogens in milk samples on dairy
farms. There has long been a demand in this field fora means of instant chemical analysis. In the next step,
we are developing technologies enabling personal[4]

C. D. Chin, V. Linder, and S. K. Sia, “Commercialization of Microfluidic Point-of-care Diagnostic Devices,” Lab on a Chip, Vol. 12, No.
12, pp. 2118–2134, 2012.
E. T. Lagally, J. R. Scherer, R. G. Blazej, N. M. Toriello, B. A. Diep,
M. Ramchandani, G. F. Sensabaugh, L. W. Riley, and R. A. Mathies,“Integrated Portable Genetic Analysis Microsystem for Pathogen/
Infectious Disease Detection,” Analytical Chemistry, Vol. 76, No. 11,
pp. 3162–3170, 2004.
T. Horiuchi, T. Miura, Y. Iwasaki, M. Seyama, S. Inoue, J. Takahashi,
T. Haga, and E. Tamechika, “Passive Fluidic Chip Composed of Integrated Vertical Capillary Tubes Developed for On-site SPR Immunoassay Analysis Targeting Real Samples,” Sensors, Vol. 12, No. 6, pp.
7095–7108, 2012.
Y. Iwasaki, T. Tobita, T. Horiuchi, and M. Seyama, “Chemical Sensors
and Surface Plasmon Resonance Biosensors,” NTT Technical Review,Vol. 4, No. 1, pp. 21–29, 2006.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2006
01021.pdf

NTT Technical Review

Feature Articles

Yuzuru Iwasaki

Senior Research Engineer, Biosensing Technology Research Group, NTT Device Technology Laboratories.
He received the B.E. in 1986 and the M.E. in1989 from Tokyo Institute of Technology, and the
Ph.D. in chemical engineering from the University of Tokyo in 1992. He joined NTT Basic
Research Laboratories in 1992 and studied electrochemical microsensors, batteries, and surface
plasmon resonance biosensors. He is currently
studying microfluidics based biosensors for the
dairy industry and the human healthcare field bycombining biochemistry, electrochemistry, fluid
mechanics, and information processing technologies. He is a member of the Chemical Society ofJapan, the Electrochemical Society of Japan, andthe Society for Chemistry and Micro-Nano Systems.

Vol. 13 No. 1 Jan. 2015

Michiko Seyama

Senior Research Engineer, Supervisor, Healthcare & Environmental-Sensing Device Project,
NTT Device Innovation Center.
She received the B.E., M.E., and Ph.D. inapplied chemistry from Waseda University,
Tokyo, in 1995, 1997, and 2004, respectively.
She joined NTT in 1997 and studied odor sensors
and their application to environmental andhealthcare monitoring systems, and micro-TAS
based biosensors for animal and human healthcare. She is currently studying wearable sensors
and their application in the fields of healthcare
and sports training. She is a member of the Japan
Society of Applied Physics, and the American
Chemical Society.

Feature Articles: R&D on Devices Using Life-assist Technologies

Ultralow-power Sensor Node with
Nanowatt Wireless Circuit
Technology
Shoichi Oshima, Kenichi Matsunaga, Toshihiko Kondo,
and Hiroki Morimura
Abstract

Wireless sensor nodes (WSNs) can be mounted on many kinds of objects in order to gather information about them. This enables a range of applications in areas such as healthcare, security, and traceability. This article describes very tiny, ultralow-power WSNs in which nanowatt wireless circuit technology
achieves long-term driving without the need for maintenance.
Keywords: sensor node, sensor network, low-power wireless circuit

1. Introduction
The cabability of wireless sensor networks togather and analyze environmental information suchas vibration, temperature, angles, or positions will
enable the provision of new services. Such network
services, generally referred to as M2M (machine-tomachine) or the Internet of things (IoT), are attracting
a great deal of attention. For example, a current sensor attached to electrical appliances in a home can tell
us how much electricity is used or saved over time,and it will enable us to control appliances automatically. Sensing vibration patterns caused by wind can
indicate cracks in concrete structures of bridges orbuildings.
A wireless sensor network consists of wireless sensor nodes (WSNs) that can be mounted on anything
and can monitor environmental or physical conditions. An image of how cargo in transport is monitored is shown in Fig. 1. WSNs attached to the cargo
or to transport vehicles monitor temperature, location, or physical shocks. Then, master receivers connected to a network gather information from the
WSNs and send it to servers via public networks suchas Wi-Fi*1 or 3G/4G (third generation/fourth generation). The servers store and analyze the data to pro

duce real-time distribution schedules or to maintainquality assurance.
One proposed requirement for WSNs is that they bemuch smaller in size and lower in cost than whatever
they are attached to. Another is that they have batteries if the objects they are attached to do not. However,this last requirement is difficult to meet. Smaller batteries tend to die rather quickly, so we may need toreplace them often, which would raise maintenancecosts. To avoid this, WSNs should be able to operate
on one battery for as long as the item they are mounted on lasts, say about 10 years, without maintenance.
In some situations, it may be possible to use ambient
energy sources such as solar energy, temperature, orvibration, to charge batteries.
In this article, we introduce ultralow-power circuit
technology for WSNs as a way to achieve long-term
WSN operation with a small battery, and we compare
the power consumption of our WSNs to that of a conventional wireless system.
2. Ultralow-power wireless technology
Fabricated WSNs with ultralow-power wireless*1	 Wi-Fi is a registered trademark of Wi-Fi Alliance.

NTT Technical Review

Feature Articles

Network

Servers
3G/4G network

Location

Analyze

Traffic jam

Weather
Sensing

Danger

Hurryup!!

• Distribution route• Quality assurance• Delivery time

Fig. 1. Wireless sensor network to monitor cargo in transport.

Solar battery
5 mm
Vibration
sensorCapacitor

Wireless LSI
AntennaSolarbattery

Evaluation kit

Vibration
sensorCapacitor

1-MHzring oscillator

Pulse
counterID
generator

300-MHzring oscillator

Amp.

Acceleration
temperature
sensorU-FL
Sensorconnector
UART

UART
connector

Microcontroller
PSoC5LP
A/D
32-bitARM
processor

Antenna

Wireless
LSI

Wireless LSI(b) WSN evaluation kit(a) 5 mm × 5 mm × 5 mm WSN
A/D: analog to digital
ARM: Acorn RISC (reduced instruction set computing) machine
LSI: large scale integrated circuit
UART: universal asynchronous receiver-transmitter
U-FL: user function libraryFig. 2. Compact and ultralow-power WSNs.

technology are shown in Fig. 2. A 5 × 5 × 5-mm WSN
with a solar battery and vibration sensor is illustrated
in Fig. 2(a). It transmits identifications (IDs) whenthe vibration sensor detects a sufficient physicalVol. 13 No. 1 Jan. 2015

shock. We confirmed in a marketing demonstrationthat this type of WSN was effective for monitoring
which products in a store were most popular bycounting the number of times products were removed
Feature Articles

Power consumption (W)Conventional system

Start-up

Transmitting

End

Start-up
Transmitting

End

Time

Proposed technology

Fig. 3. Low-power technology.

from store shelves (for purchase or closer examination by customers) [1]. An evaluation kit of WSN
with vibration and temperature sensors and a connector for connection to other sensors is shown in
Fig. 2(b). WSNs of this type can transmit sensing dataat the timing of the sensor’s trigger and timer. We
demonstrated the ability of such sensors to monitor
indoor temperatures and human heartbeats [2].
Both types of WSNs feature the large-scale integration of nanowatt wireless circuits. The power consumption of the wireless transmitter from startup to
the end of data-block transmission [3] is shown in
Fig. 3. We use short impulse signals instead of a continuous sinosidal wave—the conventional method—
to transmit “1” and “0” binary data. The pulses are
generated by a ring oscillator, and when they stopcoming, the wireless circuits also stop. This intermittent-driving technology enables us to reduce the total
wireless circuit activation time and achieve ultralow
power.
In what follows, we explain the driving energy of
WSNs and compare our technology with that of
EnOcean*2, a widely known low-power wirelessproduct [4]. EnOcean uses a mechanical energy generator; when the button is pushed, energy is generated
and IDs are sent wirelessly into the air. It is popularin Europe, where it is used in buildings to control
light switches without electrical wiring.
3. Power consumption of WSNs
A block diagram of our WSN is shown in Fig. 4.
The WSN comprises a wireless transmitter, digitalsignal-processing (DSP) controller, sensor, and batSensorDSP
controller

Wirelesstransmitter

Battery (Regulator)

Fig. 4. Block diagram of WSN.

tery. Here we consider the use of a small lithium
battery. The lifetime, L, of the battery is expressed asfollows:
L [h] = C [mAh] ÷ I [mA] × SF,
where C is the energy capacity of the battery, I is theaverage current consumption, and SF is its safety factor, which corresponds to drops in battery quality due
to aging or contamination. For example, if we use acoin-type battery such as a CR2032 with an average
current of 1 mA, the battery lifetime is about six days;
with an average current of 10 µA, the lifetime is 1.7
years.
Next we look at the WSN’s power consumption.
The power consumption changes with the driving*2 EnOcean is a registered trademark of EnOcean GmbH.

NTT Technical Review

Feature Articles

State 1: Standby

SensorState 2: Startup

DSP
controller

Wirelesstransmitter

SensorDSP
controller

Wirelesstransmitter

Battery

Battery

Example of DSP wake-up (the same as
sensor and wireless transmitter)

State 3: Sensing

SensorState 4: Transmitting

DSP
controller

Wirelesstransmitter

SensorDSP
controller

Wirelesstransmitter

Battery

Battery

Fig. 5. Power consumption of each state.

condtions. The driving conditions can be said to comprise the following four states:
1.	Standby state: activation of minimum necessary elements of circuits in each block, almost
the same as sleeping
2.	Startup state: transition to activation of eachblock
3.	Sensing state: environmental sensing and data
analysis, including communication between
DSP and sensor
4. Transmitting state: wireless transmission
Now let us consider the periodic transmission ofsensing data. In state 1, most of the components ofeach block are inactive, and only the minimum necessary elements are activated, for example, the RTC(real-time clock), which counts the periods, and regulators that supply voltage. Some current leakage
occurs in this state. The WSN must wake up the DSP
controller in order to carry out sensing and transmitting. At this time, the WSN enters state 2 for a while
to stabilize the oscillator and to read data stored inmemory. Next, the DSP controller instructs the sensor
to start sensing to acquire data. This requires state 2Vol. 13 No. 1 Jan. 2015

in order to wake-up the sensor block. Then, the state
will change to state 3. After data have been acquired,
the system enters state 2 again to wake up wirelesscircuits, and the wireless transmission sequence
starts. After state 4, the driving condition returns tostate 1. The power consumption of each state isshown in Fig. 5.
We plot the average power consumption, taking allstates into consideration, for transmitting data versus
the transmission interval for EnOcean and ourultralow-power technology [5] in Fig. 6. In the
EnOcean system, 12-byte data are transmitted threetimes per cycle. The plot for EnOcean includes thepower of the standard sensor and the voltage. Whenthe interval is long, the static energy, corresponding
to state 1, is dominant in the total power consumption, and the power becomes constant. In contrast,
when the interval becomes shorter, the power consumption increases in proportion to the driving energy of each circuit. EnOcean products are specialized
for a button-type power generator, i.e., triggered driving. When they are used periodically, they are useful
in long intervals of over 100 seconds.
Feature Articles

Packet size: 12 bytes, 3-time repetition
EnOcean product10,000

Proposed technology, case 1(Micro-controller)
Proposed technology, case 2(Light DSP)

Average power consumption (µA)

Commercial power supply
1000

100
10

Conventional
fields1
New fields
0.1
0.01

0.1

1

10

100

1000

Transmitting interval (sec)Fig. 6. Average power consumption versus transmitting interval.

µA region

Wireless block

1/100

DSP and sensing block

10

1
nA region

Average power consumption (µA)

100

0.1

EnOceanCase 1Case 2

Fig. 7. Average power consumption of one-second transmitting interval.

The power consumption for our ultralow-power
technology is plotted for the same condition as thatfor EnOcean—12-byte data with three transmissions
per cycle. We consider two cases: using a commercially available micro-controller to transmit sensor
data (case 1) and using simple DSP to transmit only
IDs (case 2). The power consumption for a one-second interval is shown in Fig. 7. When the interval isshort, the differences between EnOcean and our technology become large because the power consumptionof our wireless circuits is 1/100 that of the EnOcean
product. In EnOcean, the wireless block accounts formost of the power consumption. In contrast, with ourtechnology, the dominant factor in the power consumption for transmitting sensing data is the power
used for sensing. Thus, our technology can reduce thetotal power of WSNs. Moreover, if the system needs
only ID information, we can take advantage of themuch smaller power consumption of DSP for futherpower saving. For shorter intervals, we have to further reduce the power consumption of every block.
When the average power consumption becomes
higher than 100 µA, we must use a large energy
source such as a commercial power supply instead ofa battery (Fig. 6). When the transmitting interval islonger than 100 seconds, the conventional approach,
NTT Technical Review

Feature Articles

such as that of EnOcean, becomes useful. When theinterval is 0.1 to 10 seconds, our technology has substantial advantages over the conventional technology.
In such short intervals, data related to human activities, the distribution of things, and production processes are sampled continuously. This will pave theway to new applications.

References
[1]
[2]

[3]

[4]
[5]

Shoichi Oshima

Research Engineer, Ambient Device ResearchGroup, Social Device Technology Laboratory,
NTT Device Technology Laboratories.
He received the B.S., M.S., and Ph.D. in electrical engineering from Tohoku University,
Miyagi, in 2002, 2004, and 2008, respectively.
He joined NTT Microsystem Integration Laboratories in September 2008. His research interests
include wireless transceivers and circuit designfor low-power communication systems. He
received the Best Paper Award of IEEE Components, Packaging, and Manufacturing Technology(CPMT) Symposium Japan 2012. He is a member of the Institute of Electronics, Information,
and Communication Engineers (IEICE).

Kenichi Matsunaga

Researcher, Ambient Device Research Group,
Social Device Technology Laboratory, NTT
Device Technology Laboratories.
He received the M.E. in physical electronics
from Tokyo Institute of Technology in 2010. He
joined NTT Microsystem Integration Laboratories in 2010 and studies low-power complementary metal-oxide-semiconductor (CMOS) circuitdesign for WSNs. His research interests include
RF (radio frequency) CMOS and mixed signal
circuits.

Vol. 13 No. 1 Jan. 2015

“Gather Events from Things Distributed over Surroundings,” Proc. of
NTT R&D Forum 2013, Exhibit S-50, Tokyo, Japan, February 2013.
http://labevent.ecl.ntt.co.jp/forum2013/elements/pdf_eng/S-50_e.pdf“Semipermanent Driving Wireless Terminal for Sensor Network,”
Proc. of NTT R&D Forum 2014, Exhibit V-23, Tokyo, Japan, February 2014.
http://www.ntt.co.jp/RD/e/active/201402/en/nw/lh4ung0000000
gmd-att/V-23_e.pdf
S. Oshima, K. Matsunaga, H. Morimura, and M. Harada, “Intermittent Transmitter Circuit with Novel Feedback Source Follower Amplifier for Solar Powered 5-mm-cubic Wireless Sensor Nodes with 1/20
λ Dipole Antenna,” Proc. of the 2013 Symposium on VLSI Circuits,
pp. C150–151, Kyoto, Japan, June 2013.
Website of EnOcean, http://www.enocean.com/en/home/
EnOcean, “User Manual, Scavenger Transceiver Module STM 300/
STM 300C/ STM 300U,” July 2013.

Toshihiko Kondo

Senior Research Engineer, Ambient Device
Research Group, Social Device Technology
Laboratory, NTT Device Technology Laboratories.
He received the B.E., M.E., and Ph.D. inapplied chemistry from Osaka University in
1994, 1996, and 2006, respectively. He joined
NTT Integrated Information and Energy Systems
Laboratories in 1996 and studied hydrogenenergy systems for telecommunications equipment power supplies. Since 2004, he has been
engaged in research and development of communications systems and terminals for sensor
network services. He has recently been studying
terminals to accommodate common sensors to
networks.

Hiroki Morimura

Senior Research Engineer, Supervisor, Group
Leader of Ambient Device Research Group,
Social Device Technology Laboratory, NTT
Device Technology Laboratories.
He received the B.E. in physical electronics,
the M.E. in applied electronics, and the Dr.Eng.
in advanced applied electronics from the Tokyo
Institute of Technology in 1991, 1993, and 2004,
respectively. He joined NTT in 1993. He has
been engaged in the research and development of
low-voltage, low-power SRAM (static random
access memory) and CMOS fingerprint sensors.
His research interests include noise tolerant
circuit design for short-range wireless communications, ultralow-power circuit techniques forbatteryless sensor nodes, and integrated CMOSmicroelectromechanical systems (MEMS) technology.
Dr. Morimura served on the program committee of the Symposium on VLSI Technology,
2011–2014, and on the program subcommittee
on Advanced Circuits and Systems of SSDM,
2011–2013. He also served on the special section
editorial committee of the IEICE Transactions on
Electronics in 2011 and 2012. He received the2004 CSS Best Paper Award, the 2006 IEICEBest Paper Award, the Best Paper Award of the
Symposium on Integrated MEMS Technology at
the 26th Sensor Symposium, and the Best Paper
Award of IEEE CPMT Symposium Japan 2012.
He is a member of IEEE (Institute of Electricaland Electronics Engineers), IEICE, and JSAP
(Japan Society of Applied Physics).

Feature Articles: R&D on Devices Using Life-assist Technologies

Terahertz Device Technologies for
Ultrafast Data Downburst
Applications
Ho-Jin Song, Takuro Tajima, and Makoto Yaita
Abstract

Advances in medical imaging technology such as computed tomography and magnetic resonanceimaging have made it possible to capture minute defects inside the human body. Correspondingly, thevolume of such imaging data has been dramatically increasing. There is also a demand to access such
medical data using mobile terminal devices. To accommodate this demand, a wireless system withextremely high throughput of 100 Gbit/s or more is essential to enable instant data downloading. In thisarticle, we give an overview of recent progress in terahertz communications, particularly in front-end
technologies, which hold high promise for realizing future ultrafast wireless link applications.
Keywords: ultrafast wireless communications, terahertz wave, terahertz communications

1. Introduction
Steady progress is continuously being made in ICT(information and communication technology), andthis has led to substantial changes in hospitals and in
the healthcare field in general. Medical records
including computed tomography (CT) and magnetic
resonance imaging (MRI) data, which were initiallyin the form of paper documents, are now translated
into electrical signals and recorded digitally in electronic medical records (EMRs). Doctors can lookthrough the medical data via a mobile terminal suchas a tablet computer or smartphone anywhere anddiagnose and treat their patients remotely. The use of
the EMR and telemedicine system will not only
improve medical services in quality but also lead tonew ones.
The quality of medical services is also being
improved with the advances in medical instruments
and equipment. For instance, state-of-the-art medical
imaging systems can detect tiny defects and abnormalities in the human body, which used to be difficult
to detect. These advances, especially in the resolutionof medical imaging instruments, have led to an explosive increase in the volume of medical data, which

has consequently created problems in managing,
maintaining, and storing the EMRs. When a CT
image is taken of the area from the chest to the abdomen with 0.5 mm resolution, approximately 2000
fragments of CT images are produced that require
about 1 GB of storage per patient. In view of the factthat CT is now widely and frequently used in hospitals, one can easily estimate that several hundreds ofgigabytes of medical data are generated by a CT
machine in a single day. The volume of a person’s
EMRs if he/she had a regular medical check in thelast ten years would be at least 10 GB, and probably
much more. Unfortunately, however, the existing
wireless data transmission systems are not fastenough to deal with the medical data commonly used
these days and may even cause degradation of service
quality.
We review in this article the recent progressachieved in an ultrafast wireless system we are developing called data downburst, which can transmit ahuge amount of medical data instantaneously by utilizing the huge bandwidth of terahertz waves.

NTT Technical Review

Feature Articles

2. Terahertz wireless

3. Terahertz ICs in 300-GHz band

To achieve ultrafast throughput of 100 Gbit/s ormore, we focused on the terahertz frequency band,
which is located between the microwave and farinfrared light-wave bands in the electromagnetic
spectrum [1]. In terms of frequency, it is defined as
100 GHz to 10 THz in general and is frequently
referred to as the terahertz gap or the forbidden
region because of the huge technical barriers in generating and detecting signals at these high frequencies. The conductivity of metals usually used forsignal wires or waveguides gradually degrades as thefrequency increases, resulting in large signal loss at
terahertz frequencies. Because of this, many terahertz
signal generators produce very weak signals or areusually operated at impractically low temperatures ataround −196°C or even below. Though high power of
1 W or more can be technically generated at terahertz
frequencies, it requires a generator so large it would
fill a room. Despite these technical difficulties, theinherently large bandwidth of terahertz waves isbelieved to be the only means to achieve the 100Gbit/s wireless system. The frequency is approximately 100 times higher than that of microwaves,which the current wireless system operates at, and theavailable bandwidth is also that much larger.
In 2009, we first proved the effectiveness of theterahertz wave for a large data rate wireless system byexperimentally demonstrating 8-Gbit/s data transmission at terahertz frequencies even with a weak powersignal emitter, poor sensitivity receiver, and no signal
processing. By improving the bandwidth of thedevices used in the feasibility test, we were able toincrease the maximum data rate up to 24 Gbit/s,
which is approximately five times higher than thenewest USB (universal serial bus) wire connection
technology. These demonstrations clearly showed
how the large bandwidth is important to obtain a highdata rate in wireless communications systems. Since
then, we have continued to investigate and developfunctional radio frequency (RF) front-end component
integrated circuits (ICs) based on semiconductor
devices that are necessary for practical systems interms of cost, size, and power consumption. The
results we have achieved have greatly influenced theglobal movement toward standardization in the Institute of Electrical and Electronics Engineers (IEEE)for 100-Gbit/s wireless communications systems.

The composition of the RF front end for terahertz
communications systems is basically similar to thatof conventional radio systems that consist of amplifiers, modulator/demodulators, local oscillators, andother components. However, the design considerations for the RF front end and component ICs operating at terahertz frequencies are quite different fromthose for the microwave frequency band because of
the large loss and large bandwidth. For example, forward microstrip lines exhibit lower conductive loss
but require an inductive inter-layer via between thetransistors and signal lines, which leads to inductive
signal loss. In contrast, the inverted microstrip lines,
in which the signal line is located in the bottom layer,
do not require the interlayer via, although the overall
conductive loss is quite high due to the thin signalline.
On the basis of these design considerations, wehave designed important front-end components suchas an amplifier, oscillator, and quadrature phase shift
keying (QPSK) modulator and demodulator at 300
GHz, where the first atmospheric window is located.
These were fabricated using state-of-the-art compound semiconductor transistor technologies ofwhich the cut-off frequency (fmax) is approximately
650 GHz.
A photo of a fabricated 300-GHz three-stage amplifier in cascode configuration is shown in Fig. 1 alongwith a schematic diagram for a single stage and themeasured gain and noise figure characteristics. The
measured small-signal gain and bandwidth areapproximately 28 dB at the center frequency and a
10% bandwidth at a single power supply of 3.3 V andtotal current of around 80 mA. The measured noise
figure in the operating bandwidth at around 300 GHz
is approximately 10–12 dB, which is the lowest everreported at these high frequencies. It is most likely
also due to the minimized signal loss in the circuitachieved by proper selection of the transmission
lines.
A voltage controlled oscillator (VCO) is anotherimportant RF block used to generate the terahertz
signals on which data will be carried. A photo of afabricated VCO is shown in Fig. 2, as well as themeasured spectrum and time-domain traces of outputs. For the design of the oscillator, we selected thecommon-collector Colpitts topology because of its
simple configuration, which helps to avoid signal loss
from the circuit complexity. In addition, for the
QPSK modulation scheme, the VCO was designed toVol. 13 No. 1 Jan. 2015



VBB VCC
D1 D2 D3 R1

Input

Output

TL8
TL9 TL12
C3

C1

Q2
C4

TL3

Input

1200 × 1000 mm2

TL11

TL1

TL13
TL4

TL6

Output

TL7
TL5
C5

Q1

20

10

15

0

10

–10

5

–20
0
220 240 260 280 300 320 340
Frequency (GHz)
(c)

TL2

C2

(a)

25

20

Gain (dB)

TL10

TL8

30
C6

Noise figure (dB)

Feature Articles

(b)

90°
Output0°
OutputIntensity (dB)0

Measurement span = 1 GHz

–10
–20
–30

Intensity (arb. units)

Fig. 1. Fabricated 300-GHz amplifier; (a) top-view photo, (b) schematic for single stage, and (c) measured gain and noise
figure.

0°
Output90°
Output–40(a)Frequency(b)Time (/period)(c)Fig. 2. Fabricated VCO; (a) top-view photo, (b) measured spectrum of output, and (c) measured time domain trace of 0°
and 90° outputs.

have four outputs of which the phase states are at 0°,90°, 180°, and 270°, which is generally called aquadrature VCO. We achieved this by cross-locking
two identical oscillators by forcing a node on thesymmetry line in the circuit in the in-phase at thesecond harmonic frequency. The two unit oscillators
should be as close as possible, so we employed theinverted microstrip lines, which are advantageous inloss for short distances. As a result, the single-mode
oscillation and quadrature signal generation is clearlyshown in Fig. 2. To the best of our knowledge, this is
the first successful demonstration of a quadrature
VCO in the 300-GHz frequency band in the world.
The phase noise, which is the figure of merit that
implies frequency stability of an oscillator, was measured to be approximately –90.4 dBc/Hz at a 10-MHz
offset frequency, which is sufficient for QPSK modulation.
To generate and detect QPSK signals, we selected a
direct conversion scheme rather than the heterodyne
configuration commonly used in many radio systems.
Terahertz communications utilize large bandwidth,

so a direct conversion scheme is advantageous forhandling a large bandwidth signal with no signal distortion. Photos of the fabricated QPSK modulator anddemodulator are shown in Fig. 3. As can be seen, twodifferent transmission lines—forward and inverted
microstrip lines—were simultaneously adopted in thedesign. Passive components for balanced signaling
are implemented with the forward microstrip lines
and can thus be seen clearly, while core parts implemented with the inverted microstrip lines are not seen
due to the topmost metal used as a ground plane.
To examine the maximum data rate which themodulator and demodulator can operate at, we prepared a test IC in which the modulator and demodulator were directly connected by the short forward
microstrip line and performed back-to-back tests at
up to 60 Gbit/s. The measured eye diagrams of thedemodulated signals at several data rates are shown in
Fig. 4. As can be seen, at up to 50 Gbit/s, the eye
diagrams are clear and open, and the bit error rate ison the order of 10−8 or lower. Although it is half thegoal we are aiming for, the 50 Gbit/s is more than ten
NTT Technical Review

Feature Articles

I-data input−
1120 × 880 µm2 +1120 × 880 µm2

LO
input

Output+−Q-data input(a)I-data input
+
−

LO
input

Input

−
+
Q-data input(b)Fig. 3. Fabricated QPSK; (a) modulator and (b) demodulator.

50 Gbit/s

50 Gbit/s

BER=8.1e−10

I-ch
56 Gbit/s

I-ch

Q-ch

BER=6.4e−8

60 Gbit/s

BER=4.5e−4

I-ch

BER=N/A

Fig. 4. Measured eye-diagrams and bit error rates (BER)
at up to 60 Gbit/s.

times faster than the fastest existing wireless system
and is as fast as it takes to completely download asingle DVD (digital versatile disc) movie in a second.
4. 300-GHz horn antenna integrated
in LTCC package
The terahertz package in a terahertz wireless frontend module must have an antenna to radiate or capture wireless signals and an interconnection to connect the antenna and RF frond-end ICs to be installed
Vol. 13 No. 1 Jan. 2015

in the package. In the terahertz band, as the wavelength gets shorter, it becomes possible to miniaturize
the antenna and package. A compact and low costterahertz package enables the development of a frontend module that can be embedded into tablet computers and smartphones.
However, conventional terahertz modules are metal
packages with a silicon lens antenna on which the IC
is directly attached with precise alignment. These
packages are expensive, and it is difficult to implement interconnection to the IC with them.
Therefore, we developed a 300-GHz package integrated with a horn antenna by utilizing the ceramicmaterial known as low temperature co-fired ceramics(LTCC), which is used in microwave and millimeterwave packages [2]. A cross-sectional view of the
proposed terahertz package is illustrated in Fig. 5.
Integrating the antenna into the package not only
makes it possible to integrate the terahertz IC, powersource, and high-density signal line but also to miniaturize the antenna and the interconnection. Furthermore, it resolves the issue of interconnection and low
cost for high-volume production.
A prototype of the antenna using LTCC multi-layered substrates is shown in Fig. 6. The horn antennais shaped by gradually widening the cavity surrounding the vias and metal layers. The antenna is around 5× 5 × 3 mm in size. Despite the antenna’s compactness, its gain is 15 dBi or more, and the bandwidth ismore than 60 GHz. An interconnection between theantenna and IC was also developed using LTCC
multi-layered substrates [3]. A probe was placed in
the waveguide formed in the LTCC to effectively
couple the electromagnetic wave propagating in the
waveguide and convert the propagation mode of the
waveguide into the propagation mode of the microstrip
Feature Articles

Horn antenna
Metal layer

Via
SignalMulti-layered
LTCC
MMIC
Lid
Interconnection
MMIC: monolithic microwave integrated circuit

Fig. 5. LTCC package integrated with 300-GHz antenna.

20
Metal layer

Horn
Multi-layered
LTCC

Gain (dBi)

15

10

5

0
270

3 mm

285

300

315

330

Frequency (GHz)
(a)

(b)

Fig. 6. LTCC horn antenna; (a) photo and (b) measured antenna gain.

line that connects to the IC. A prototype of the interconnection using LTCC multi-layered substrates isshown in Fig. 7. The size of the interconnection isaround 1 × 1 × 0.3 mm. The insertion loss is less than
3 dB, and the bandwidth is around 40 GHz. We aim
to develop a compact and low-cost terahertz front-end
module by integrating these components into a single
package with a terahertz IC.
5. Conclusion and future perspective
In the history of progress achieved in wireless communications technologies, the advances in terms ofdata rate in the last few years have been much greaterthan those during the first 100 years, but the speed ofprogress is not fast enough to accommodate thedemand from users, which is explosively increasing.
This is because the operating frequencies of wirelesssystems are still in the microwave frequencies, where
bandwidth is inherently limited. At this time, one may
think the use of terahertz waves, of which the frequency is 100 times higher than that of the microwave
band, for wireless communications is technicallynonsense. However, when we consider that theamount of digital information generated is exponentially increasing day by day, and recent new industries related to big data and cloud computing will
accelerate the increase further, it is not difficult toestimate that the large bandwidth in the terahertz
wave band will be necessary in the next ten years.
NTT Technical Review

Feature Articles

Metal layer

0
Probe

IC

Loss (dB)2
440 GHz

6
8
10
270

1 mm
(a)

290
310
Frequency (GHz)

330

(b)

Fig. 7. Interconnection integrated in LTCC; (a) photo of mode transition probe and (b) measured loss.

We have taken a future perspective and have developed several RF front-end components including anamplifier, oscillator, and modulator/demodulator for
future terahertz communications at 300 GHz. We
have also demonstrated the successful operation of
300-GHz QPSK ICs at data rates up to 50 Gbit/s,
which is ten times faster than current state-of-the-art
wireless systems. In addition, we investigated compact packaging technology for practical use. These
results indicate the great potential of terahertz waves
for use in future ultrafast data downburst systems
providing data rates of 100 Gbit/s or more.

development program on ‘Multi-tens gigabit wirelesscommunication technology at sub-terahertz frequencies’ of the Ministry of Internal Affairs and Communications, Japan.
References
[1]
[2]

[3]

Acknowledgement

H.-J. Song and T. Nagatsuma, “Present and Future of Terahertz Communications,” IEEE Transactions on Terahertz Science and Technology, Vol. 1, No. 1, pp. 256–263, 2011.
T. Tajima, H.-J. Song, K. Ajito, M. Yaita, and N. Kukutsu, “300-GHz
LTCC Horn Antennas Based on Antenna-in-package Technology,”
Proc. of the 43rd European Microwave Conference, pp. 231–234,
Nuremberg, Germany, October 2013.
T. Tajima, H.-J. Song, and M. Yaita, “Wideband Probe-type
Microstrip-to-waveguide Transition Integrated in LTCC,” Electronics
Letters, Vol. 50, No. 3, pp. 194–195, 2014.

This work was supported in part by the research andVol. 13 No. 1 Jan. 2015



Feature Articles

Ho-Jin Song

Senior Research Engineer, Social Device Technology Laboratory, NTT Device Technology
Laboratories.
He received the B.S. in electronics engineeringfrom Kyungpook National University, Korea, in1999 and the M.S. and Ph.D. in information andcommunications engineering from Gwangju
Institute of Science and Technology (GIST),
Korea, in 2001 and 2005, respectively. From2005 to 2006, he was a research professor at theCenter for Hybrid Optical Access Networks(CHOAN) at GIST, Korea. Since joining NTT
Microsystem Integration Laboratories in 2006,
he has been working on the development of millimeter-wave and sub-terahertz wave systems forcommunications, sensing, imaging, and measurement applications using photonic technologies and high-speed electronics. Dr. Song is amember of IEEE and the Institute of Electronics,
Information and Communication Engineers(IEICE).

Makoto Yaita

Senior Research Engineer, Supervisor, Social
Device Technology Laboratory, NTT Device
Technology Laboratories.
He received the B.S. and M.E. from Waseda
University, Tokyo, in 1988 and 1990, respectively. In 1990, he joined NTT LSI Laboratories,
where he was engaged in the research and development of measurement technologies for highspeed devices and ultrafast-optical signals. From1999 to 2008, he was engaged in the development of the digital television relay network in
NTT Communications. He is currently a SeniorResearch Engineer and Supervisor with NTT
Device Technology Laboratories. His current
research involves millimeter-wave and sub-terahertz-wave radio transmission.

Takuro Tajima

Senior Research Engineer, Social Device Technology Laboratory, NTT Device Technology
Laboratories.
He received the B.E. and M.E. in electronicengineering from the University of Tokyo in2000 and 2002, respectively. He joined NTT in
2002 and moved to NTT Device Technology
Laboratories in 2014. His research interests
include terahertz antennas and spectroscopic
systems. He is a member of IEICE and the Japan
Society of Applied Physics.

NTT Technical Review

Feature Articles: R&D on Devices Using Life-assist Technologies

Continuous Wave Terahertz
Spectroscopy System Designed for
Medical Field
Katsuhiro Ajito, Jae-Young Kim, and Ho-Jin Song
Abstract

We have constructed a continuous wave (CW) terahertz spectroscopy system using photonic integration-compatible technology. This system is intended for use in the medical field as a miniaturized terahertz spectroscopy system, in contrast to the conventional pulsed wave method. This system can simultaneously measure the absorption and phase (dielectric constant) responses of a sample, and it exhibits
a dynamic range of at least 75 dB at under 1 THz. In addition, we used the CW spectroscopy system toidentify a new type of complex molecule crystal (cocrystal) formed from a molecule of a pharmaceutical
drug and various coformers. Cocrystals have been developed for use in the pharmaceutical manufacturing field to improve the solubility and absorbability of medicines. By fixing the measurement frequency
at the absorption peak of intermolecular interactions of those crystals, we obtained a two-dimensional
distribution of cocrystals within a test tablet.
Keywords: homodyne, pharmaceutical products, cocrystal

1. Introduction
Terahertz (THz) spectroscopy has been used in thefield of astronomy for the past few decades as a formof passive spectroscopy for observing the rotationalmodes of gaseous molecules. However, as the use ofactive spectroscopy for analyzing molecules, crystals, and even biological samples has become morecommon, it has attracted a lot of attention as a newspectroscopic analysis technique. THz spectroscopy
involves the penetration of THz waves within a solid,
which makes it possible to discriminate the intermolecular interactions between molecules or crystals
inside the solid. It is anticipated that it will be appliedin areas where it is difficult to apply X-ray diffraction
methods such as with materials or ultrafine particles
having multiple components that are mixed together.
THz waves lie between light waves and microwaves
in the range from 0.1 to 10 THz (1011 to 1013 Hz), andtherefore, they easily penetrate materials that are notreadily transparent to visible light such as paper,
wood, and plastic, enabling nondestructive analysis.
In the region above 1 THz, there are many vibration
modes of molecules or crystals that occur due to theintermolecular interactions. Consequently, the spectral fingerprint, in which the vibration modes absorb
THz waves, allows us to identify the materials. The
molecular interaction is stronger as the frequency
increases. However, the penetration of THz waves
within solids tends to decrease because the shorter
wavelengths at higher frequencies are easily scatteredby particles. Therefore, there is a limited region
inside the frequency range from 0.3 to 5 THz where
the two advantages of deep penetration and spectral
fingerprint are both obtained. Even within the THz
spectrum in the low frequency region of 0.1–0.3 THz,
it is difficult to identify molecules or crystals eventhough penetration is easy, whereas in the higher frequency region of 5–10 THz, extremely high loss
limits the available sample thickness within thin films
or surfaces.

NTT Technical Review

Feature Articles

PIN modulator 1
PIN modulator 2

Homodyne phase control circuiton silicon photonics
Crystalidentification

LD 1 SOA
Emitter

LD 2 SOA
LD driver

I/O

DAC/ADC

Receiver<Table>On-chip THz spectrometer
Comp.: compound
DAC/ADC: digital-to-analog converter/analog-to-digitalconverter
LD: laser diodeI/O: input/output
PIN: positive/intrinsic/negative
SOA: semiconductor optical amplifier

TabletSafety and reassuranceof pharmaceuticals

Comp. A

50%

Comp. B

10%

Comp. C

3%

Fig. 1. Application of miniaturized CW THz spectroscopy system in medical field.

2. Miniaturization of devices and application
to medical field
Process analytical technology (PAT) is a system fordesigning, analyzing, and managing the manufacturing process, and for ultimately guaranteeing productquality. The United States Food and Drug Administration (FDA) has published guidelines for introducing PAT into pharmaceutical production. Consequently, there is an increasing need for the analysis of
medicines to reassure consumers and increase safety.
Accordingly, the application of THz spectroscopy inthe medical field requires not only high system performance in areas such as sensitivity, stability, andspeed, but also a miniaturized THz spectroscopy system such as an on-chip analyzer for convenient nondestructive inspection of pharmaceutical products. A
conceptual diagram of the miniaturized continuouswave (CW) THz spectroscopy system and its use in
the medical field is shown in Fig. 1. Current THz
spectroscopy systems generally employ a pulsed
wave method based on a femtosecond pulse laser,
although it is very difficult to miniaturize certain
components such as delay controllers. In contrast, theCW method is less challenging to reduce the size ofVol. 13 No. 1 Jan. 2015

components because all components from the laser
diodes to the THz emitter, receiver, and optical waveguides can be fabricated on chip by using common
photonic integration technologies. As a first demonstration, we previously used silicon photonics technology to fabricate a THz phase control circuit only afew square millimeters in size, and we verified theoperation of the circuit in the CW THz spectroscopy
system [1].
The phase-controlled CW THz homodyne spectroscopy system uses photomixing of light waves
from two laser sources, as shown in Fig. 2. The frequency of the THz waves is the same as the frequency
difference between the two laser sources. When theTHz waves generated from the photomixer arrive at
the receiver, a photoconductive antenna (PCA) mixes
the THz waves using a phase-controlled replica signal transmitted via an optical waveguide. The principle of homodyne detection enables the use of two
general-purpose free-running laser sources such as a
1.55-μm-band semiconductor diode laser, and therefore, THz waves can be simply generated and tuned
over a wide bandwidth by changing the wavelengthof the lasers. Also, the homodyne detection method
still supports the two important advantages ofFeature Articles

Laser 1(1.5 µm)
Laser 2
(1.5 µm)

fTHz = ν 1 − ν 2

ν1

Photomixer
ν2

PCA
receiver

Pr

Ppump

Phase controlν 1: Freq. of laser 1
ν 2: Freq. of laser 2
PCA: photoconductive antenna

Pr: Received power
Ppump: Pumping powerten
er ionh
Co tectdeDynamic range

Ende veltec optio encoherent detection methods—detection of both intensity and phase responses, and a high dynamic range.
A comparison of the dynamic ranges of the coherent
and envelope detection methods is shown in Fig. 3.
When Pr is receiving power and Ppump is higher
pumped power as noted in Fig. 2, the output fromenvelope detection (Pr2) is always lower than the output from coherent detection (Pr × Ppump).
A schematic diagram of a THz spectroscopy andimaging system using the CW homodyne method isshown in Fig. 4 [2]. LD 1 and LD 2 are variable-frequency and fixed-frequency laser diodes, respectively. The outputs of these two laser diodes are amplified
by an erbium-doped fiber amplifier (EDFA); then theTHz wave is generated by photomixing in a uni-traveling carrier photodiode (UTC-PD). The THz waves
from the UTC-PD transmitter passing through thesample on a two-dimensional (2D) scanning stage arethen injected into the PCA receiver. Two phase modulators, PM 1 and PM 2, positioned between the LDs
and the UTC-PD provide phase control operations forthe homodyne detection. The relationship between
the controlled phase of the CW THz wave and thereceived signal waveform is illustrated in Fig. 5.
When symmetrical sawtooth waveforms are applied
to PM 1 and PM 2, they linearly change the phaseshift between –2π and 2π. The received signal thenforms a sine wave at a fixed frequency even without asample. Thus, when a sample is inserted, the THz
amplitude (As) and phase (∠ΦS) responses of thesample directly change the received sine wave,
enabling the measurement of the THz absorption anddielectric constant of the sample. In this method, thetwo phase modulators are used to mitigate the limited
dynamic range caused by the nonlinearity of bothphase modulators. A high dynamic range of 100 dB at
0.3 THz and 75 dB at 1 THz were obtained from thehomodyne system, as shown in Fig. 6. Several sharp

Signal-to-noise ratio (log)Fig. 2. Operating principle of CW THz homodyne spectroscopy system.

0∝ Pr × Ppump ∝ (Pr)2
Pr = Ppump
Maximum received
power in experiments
Received power (log)Fig. 3. C omparison of dynamic ranges of coherent andenvelope detection methods.

Phase control
EDFA circuit

UTC-PDtransmitter

LD 1

AS ∠ φ S

Tunable laser
EDFA
LD 2

2D scanning
sample stage

PM 2

Fixed laser
PC

PM 1
PCA
receiverfC

Data

Received signal
Lock-inAS∠( fd ·t+φ S)

AS: absorption by sample
fC: control frequency
fd : detection frequency
t: time∠φ S: phase shift by sample
PC: personal computer
PM: phase modulator

Fig. 4. S chematic of CW THz homodyne spectroscopy
and imaging system.

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AS

Received signal(sine wave)

Dynamic range (dB)Without sample
With sampletfd(20 kHz)2π

PM 1

Phase control−2πPhase response (°C)

∠φ S

t

φ THz

PM 2
fC (5 kHz)

Fig. 5. Relationship of phase control and received
signals.

SampleTransmission
1

Signal(through 0.3-m
air path)
Noise
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Frequency (THz)
1.10
1.41
1.66
Absorption
THz
THz
THz
peaks ofwater vapor

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Frequency (THz)

40 s/image (60 × 40 points)

1.0

1.2

1.3

1.4

1.5

1.6

1.7

(THz)

0
330

2
1

0.8

270
180
90
0
−90
−180
−270

Dynamic range• 100 dB (0.3 THz)
• 75 dB (1 THz)

Fig. 6. Dynamic range and vapor absorption.

THz imaging

Test tablet ofpharmaceuticalcocrystals

100
90
80
70
60
50
40
30
20
10
0

3

−30
Phase

10 mm

10 mm

1 : 100% PE
2 : 20% Caf:Oxa + 80% PE
3 : 40% Caf:Oxa + 60% PE

THz spectrum
Relative permittivity

Caf:Oxa: caffeine-oxalic
cocrystal
PE: polyethylene

Absorbance

1.5

3

1.0
0.5

2

0.0

1

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Frequency (THz)

2.5
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5

15 s/spectrum(900 points, 2-GHz step)
3
2

1

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Frequency (THz)

Fig. 7. Identification of cocrystal components of pharmaceutical tablet.

peaks in the spectra caused by atmospheric moisture
were clearly detected with corresponding phasechanges.

Vol. 13 No. 1 Jan. 2015

3. Identification experiment
An example of the identification of cocrystal components of a pharmaceutical tablet is shown in Fig. 7[3]. A test sample containing cocrystals of caffeine
and oxalic acid, which has high absorption of THz
Feature Articles

waves, was used in the experiment. The test tablet
was 10 mm in diameter and approximately 1 mm inthickness and contained cocrystals mixed with polyethylene powder. The density of the cocrystals was
20% at the top left and 40% at the bottom right, asshown in the figure. The THz spectrum shown at thebottom of Fig. 7 was measured in 2-GHz steps, and it
took approximately 15 s to capture 900 points. We
can see that the broad cocrystal absorption peaks arelocated in the vicinity of 1.4 THz, and the intensity is
proportional to density. The dielectric constant alsochanges at the peak absorption frequency weighted
by the cocrystal density. As shown at the top of the
figure, the THz images were also measured with thesame experimental setup by using the 2D scan at a
fixed frequency. Each image consists of 60 × 40
points, and the measurement time was approximately
40 s. This is very fast in comparison with the THz
spectroscopy device using pulse waves and amechanical type of delay stage, where the imaging
usually takes several hours. The images at 1.4 THz
clearly show the cocrystal distribution because thatfrequency corresponds to the cocrystal absorption
peak. Although the current measurement speed islimited by the movement of the 2D scanning stage,
we expect that a faster stage and an advanced scanning method can further improve the speed.

4. Future plans
We introduced the CW THz homodyne spectroscopy and imaging system and demonstrated its usage
for a medical application. The CW method has huge
potential advantages because of its compactness andfast imaging speed. However, currently, the frequency
range possible with the CW spectroscopy system isonly in the range of 0.3–2 THz, and the pulse method
is superior in measurement sensitivity and bandwidth.
Therefore, we are first focusing on developing ahigher-power THz CW generator that operates at awider bandwidth and has higher sensitivity. In addition, it is necessary to improve the method of THz
spectrum analysis in order to overcome the difficultyof identifying multiple components in commerciallyavailable pharmaceutical products [4].
References
[1]

[2]

[3]
[4]



J.-Y. Kim, H. Nishi, H.-J. Song, H. Fukuda, M. Yaita, A. Hirata, andK. Ajito, “Compact and Stable THz Vector Spectroscopy Using Silicon Photonics Technology,” Optics Express, Vol. 22, No. 6, pp.
7178–7185, 2014.
J.-Y. Kim, H.-J. Song, K. Ajito, M. Yaita, and N. Kukutsu, “Continuous-wave THz Homodyne Spectroscopy and Imaging System With
Electro-optical Phase Modulation for High Dynamic Range,” IEEE
Transactions on Terahertz Science and Technology, Vol. 3, No. 2, pp.
158–164, 2013.
J.-Y. Kim, H.-J. Song, M. Yaita, A. Hirata, and K. Ajito, “CW-THz
Vector Spectroscopy and Imaging System based on 1.55-μm Fiberoptics,” Optics Express, Vol. 22, No. 2, pp. 1735–1741, 2014.
K. Ajito, J.-Y. Kim, Y. Ueno, H.-J. Song, K. Ueda, W. Limwikrant, K.
Yamamoto, and K. Moribe, “Nondestructive Multicomponent Terahertz Chemical Imaging of Medicine in Tablets,” Journal of The
Electrochemical Society, Vol. 161, No. 9, pp. B171–B175, 2014.

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Feature Articles

Katsuhiro Ajito

Senior Research Scientist, Distinguished Technical Member, Social Device Technology Laboratory, NTT Device Technology Laboratories.
He received the Ph.D. in applied chemistryfrom the University of Tokyo in 1995 and joined
NTT Basic Research Laboratories the same year.
From 1995 to 2007, he studied glutamate in single synapses using Raman spectroscopy andlaser tweezers. His current research interests
include the study of nano- and biochemistry
using THz spectroscopy and imaging techniques.
He received the Young Scientist Award for the
Presentation of an Excellent Paper from theJapan Society of Applied Physics (JSAP) in 1999
and the Tatsuo Itoh Award from IEEE (Instituteof Electrical and Electronics Engineers) Microwave Theory and Techniques Society in 2014. He
has been the Executive Director and the Chair of
the Terahertz Spectroscopy Division of the Spectroscopical Society of Japan (SPSJ) since 2005;
he was also the Secretary of the Terahertz Interest
Group in IEEE 802.15 Working Group for wireless personal area networks from 2011 to 2013
and the Chair of the Micro/Nano Electromechanical Systems and Bio/Medical Analyses
Area of the International Conference on Solid
State Devices and Materials in JSAP from 2012
to 2013. He is a member of JSAP, SPSJ, theChemical Society of Japan (CSJ), the American
Chemical Society, and IEEE.

Ho-Jin Song

Senior Research Engineer, Social Device Technology Laboratory, NTT Device Technology
Laboratories.
He received the B.S. in electronics engineeringfrom Kyungpook National University, Korea, in1999 and the M.S. and Ph.D. in information andcommunications engineering from Gwangju
Institute of Science and Technology (GIST),
Korea, in 2001 and 2005, respectively. From2005 to 2006, he was a research professor at theCenter for Hybrid Optical Access Networks(CHOAN) at GIST. Since joining NTT Microsystem Integration Laboratories in 2006, he has
been working on the development of millimeterwave and sub-terahertz wave systems for communications, sensing, imaging, and measurement
applications using photonic technologies andhigh-speed electronics. Dr. Song is a member ofIEEE and the Institute of Electronics, Information and Communication Engineers (IEICE).

Jae-Young Kim

Post-doctoral Researcher, Social Device Technology Laboratory, NTT Device Technology
Laboratories.
He received the B.S., M.S., and Ph.D. in electrical and electronic engineering from Yonsei
University, Seoul, Korea, in 2004, 2006, and2011, respectively. For his Ph.D. dissertation, heinvestigated integrated circuits and optoelectronics for millimeter-wave wireless communication.
In 2011, he joined NTT Microsystem Integration
Laboratories as a post-doctoral researcher. His
research interests are millimeter-wave and THz
systems for wireless communication, and sensing and imaging applications based on photonic
and high-speed electronic technologies. He is amember of IEEE.

Vol. 13 No. 1 Jan. 2015

Regular Articles

Color-temperature Correspondence:Its Nature and Its Impact on Object
Temperature Perception
Hsin-Ni Ho
Abstract

Color cues are often used to represent information concerning temperature, with red typically being
associated with warm/hot, and blue with cold. Recent research from NTT Communication Science
Laboratories demonstrated that such correspondences between color and temperature are not merely adesign practice derived from a common sense belief. Instead, they have an actual impact on our
information processing efficiency and object temperature perception. These findings are useful for thedevelopment of multimodal interfaces whose purpose is to provide a holistic experience intelecommunication and virtual environments.
Keywords: multisensory information processing, multimodal interface, temperature perception

1. Introduction
In developing multimodal interfaces aimed at providing a holistic experience in telecommunicationand virtual reality environments, it is important tounderstand how our brains process and integrate multisensory information in order to achieve optimal
performance. Color cues have been widely used toindicate information concerning temperature in thefields of industrial and interior design [1–4], andtherefore, our current research on multisensory information processing focuses on such correspondences
between color and temperature.
Correspondences between color and temperature
have been studied by asking people to rate coloredstimuli as being either warm or cold [2, 3, 5–7] or by
instructing people to report which color they were
reminded of when a thermal stimulus was presented
to them [6]. As expected, people reported the color
red being more often associated with warm, and blue
with cold. This kind of association has been shown toaffect people’s feelings of warmth and coldness, withreddish colors inducing warm feelings and bluishcolors inducing cold feelings [3, 7–12]. The effects ofcolor shown in those studies are presumably knowl

edge-based. That is, the effect may result from direct
employment of the knowledge of red-warm/blue-cold
association per se, since in those previous studies,
only subjective measures were used, and in most of
the experiments the warmth and coldness were only
thought of, rather than being physically presented.
In our research on color-temperature correspondences, we investigated whether such correspondences could have an actual impact on people’s information processing efficiency and object temperature
perception. The findings are expected to be useful indesigning multimodal interfaces that aim to represent
thermal information in virtual environments.
2. Impact of color-temperature correspondenceson efficiency of information processing
We utilized two objective behavioral measures: the
Implicit Association Test (IAT) and a priming task inorder to examine what impact color-temperature correspondences have on information processing [13].
Both paradigms use reaction time (RT) as an objective task performance measure.

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Regular Articles

(b)

(a)

Congruent

Incongruent

Congruent
800
Blue

Warm

Cold

Incongruent***

Thermal word

Color

600
RT (ms)

Red

400

200

Red

Blue

Cold

Warm

0
Response target

Fig. 1. (a) Stimulus-response key assignment. (b) Results of the IAT. Congruent key assignments are represented by whitebars and incongruent assignments by striped bars. The error bars show the standard errors of the means; thesymbols * and ** respectively indicate the statistical significance of p<0.05 and p<0.01.

2.1 Simplified IAT
IAT is widely used in social psychology to assess
the strength of an individual’s automatic associations
between different concepts [14]. Here, we adapted asimplified version of IAT introduced by Parise andSpence [15] to examine the correspondences between
color and temperature. In the experiment, a series ofcolor patches and thermal words were presented on adisplay, one at a time. The participants’ task was tocategorize thermal words (warm versus cold) or color
patches (red versus blue) with two response keys. We
manipulated the assignment of the color and temperature to each response key, as shown in Fig. 1(a). The
foundation of the IAT is that it is easier to map twoconcepts into the same response key when they areinternally associated (congruent) than when they areinternally unrelated (incongruent). The participantsconsisted of 11 people (6 women), between the agesof 19 and 37; all had normal color vision.
We found that people’s responses were faster withcongruent key assignments (red-warm, blue-cold)
than with the incongruent key assignments (red-cold,
blue-warm), regardless of whether the response target
was a thermal word or a color patch (see Fig. 1(b)).
Our results indicated that correspondences between
color and temperature affect the speed of response toa color or thermal stimulus. Incongruent combinations may lead to a prolonging processing time.

Vol. 13 No. 1 Jan. 2015

2.2 Priming task
We also used a priming task to investigate the interaction between color and temperature during information processing. In the experiment, color andthermal stimuli were presented sequentially in eachtrial, with the first stimulus acting as the task-irrelevant prime and the second stimulus as the target.
When the prime consisted of a color stimulus, thetarget was a thermal stimulus, and vice versa. We
manipulated the congruency of prime and target presented in each trial, so that half of the trials werecongruent (e.g., red and warm) while the others wereincongruent (e.g., red and cold). The color stimuli
used were color patches, and the thermal stimuli usedwere words such as warm or cold that indicate thermal conditions, or physical warmth or coldness
applied to the skin of the participant’s index finger.
The participants consisted of 31 people (23 women),between the ages of 19 and 61; all had normal color
vision. They were instructed to discriminate the color
target (i.e., red or blue) or the thermal target (i.e.,
warm or cold) as rapidly as possible. Our purpose
was to assess the influence of a prime stimulus on theperception of the target stimulus under different
color-temperature combinations.
We found that exposure to a thermal stimulus had
no effect on the RTs to discriminate the color of astimulus (Figs. 2(b) and 2(d)), regardless of whether
the thermal stimulus was semantic or physical, but
exposure to a color stimulus did affect the RTs requiredRegular Articles

Thermal stimulus as target

Color stimulus as target
(b)

2500

2500

2000

2000
RT (ms)Thermalword

RT (ms)

(a)

1500
1000

1000

500

500

0
Prime

0
Prime

TargetTarget“Cold”“Warm”**(c)“Warm” “Cold”

Physical Physicalcoldness warmth

Physical Physicalcoldness warmth

2500

2000

2000

1500

1500

RT (ms)RT (ms)“Cold” “Warm”

(d)
2500

Physicaltemperature

1500

1000

1000

500

500

0

0
Prime

Prime
TargetPhysicalcoldness

Physical
warmthTargetCongruent

Incongruent

Fig. 2. RTs for participants discriminating (a) thermal words and (b) color stimuli when the prime is a thermal word, and (c)physical temperature and (d) color stimuli when the prime is a physical temperature. Congruent and incongruent
combinations are shown in white and striped bars, respectively. Error bars indicate the standard errors of the means,
and * indicates statistical significance of p<0.05.

to discriminate a physical temperature (Fig. 2(c)).
This asymmetrical effect suggested that the colortemperature association might be stronger in the
direction of color to temperature than temperature tocolor. This is not unexpected given that colors areoften used to indicate temperature, but temperature isseldom used to indicate color. It was also found thatwhen the target was a thermal word, there was noeffect (Fig. 2(a)). However, when the target was aphysical temperature, the RTs were significantly
faster with a congruent prime (Fig. 2(c)).
While IAT indicated that the correspondences
between color and temperature have similar effects
on the speed of response to a color or a thermal
stimulus, a priming task showed that the correspondences are more effective in reducing the RTs forphysical thermal stimuli than for color stimuli. This

difference in the results presumably comes from thedifference between these two paradigms. In IAT, asingle stimulus is presented in each trial, and thisdesign ensures that the effects result from the difference in the color-temperature congruency between
the two stimulus-response key assignments (SeeFig. 1(a)), rather than the stimulus per se. Therefore,
similar effects were obtained for a color and a thermal
stimulus as long as the color and temperature wereassociated. In contrast, in the priming task, two
stimuli are presented in a single trial, and this design
allows for the possible interaction between the color
and thermal stimuli during information processing.
Thus, the effect of color-temperature correspondences would be more effective for a target stimulus that
requires a relatively long processing time such as aphysical temperature (RT of ~2000 ms, see Fig. 2(c)).
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Regular Articles

This is because a congruent color prime may facilitate people’s classifying/labeling a physical temperature to the response categories warm and cold andtherefore reduce the RTs. In the case of a color target,
the facilitation would be limited because its RTs
are already short in the first place (500–600 ms; see
Figs. 2(b) and 2(d)).
In summary, our findings from both tasks demonstrated that the correspondences between color andtemperature have an effect on information processing
efficiency. These findings are useful for the design ofmultimodal interfaces that intend to convey information with both visual (color) and thermal feedback.
3. Impact of color-temperature correspondenceson object temperature perception
While our research introduced in section 2 confirmed that correspondences between color and temperature have an actual impact on information processing efficiency, it remains unclear whether suchcorrespondences can influence temperature perception. Although previous studies have shown thatcolor-temperature correspondences can affect people’s feelings of warmth and coldness, in most ofthese studies the temperature information was presented to the participants in an indirect, non-contact
fashion [3, 7–12]. Because the most intuitive andnatural way for people to obtain temperature information is to directly touch the object of interest, ourpurpose was to understand whether colors can still
exert an influence under this circumstance. Although
an old study reported some effects of color on object
temperature judgments (e.g., green objects weremore likely to be judged as warm than purple objects)[16], it remains unclear whether and how the effect isassociated with the prevailing color-temperature correspondences.
When a hand touches an object, the feelings ofwarmth or coldness depend on not only the object
temperature but also the hand temperature [17].
Accordingly, we studied the effect of color on object
temperature perception by manipulating either theobject color or the hand color while participants
touched an object (Fig. 3(a)). We developed a novel
multimodal system that utilizes a thermal display andadvanced projection technology (Fig. 3(b)). This system can project colors onto the hand region selectively when the hand touches the object surface, andit can also control the temperature of the object surface. We varied the temperature of the object surface
and asked the participants to judge whether or not theVol. 13 No. 1 Jan. 2015

(b)

(a)

Object

Hand

Blue

Red

Fig. 3. ( a) We manipulated object colors by attaching blue
or red paper to the thermal display and hand colors
by projecting blue or red light onto the hand. (b) The
novel multimodal system developed for this study
can perform feedback control to the surface
temperature of the thermal display and selectively
project colors onto the hand that was in contact withthe thermal display.

object felt warm [18]. Our purpose was to see whether object and hand colors have an influence on thelowest temperature required for the object to feelwarm.
What we found is that colors can affect our perception of object temperature, but not in the way thatpeople would expect. Our data indicated that a red
object, relative to a blue object, raises the lowest temperature required for an object to feel warm by 0.5°C(see Fig. 4(a)). In other words, our results indicatedthat a blue object is more likely to be judged as warm
than a red object of the same physical temperature,
which goes against the general expectation from the
red-warm/blue-cold association. When the hand wascolored red or blue, a reverse effect was found. Thistime, the lowest warm temperature for a red hand was
lower than that for a blue hand by about 0.5°C (seeFig. 4(b)), indicating that red hands made objects feel
warmer. Although the effect of colors here mightseem small at first glance, our hands are able to detect
temperature changes as small as 0.2°C and to distinguish temperatures that differ by as little as 0.03–
0.09°C [19, 20]; thus, a change of 0.5°C is in fact
relatively large and clearly perceptible.
It is known that the brain integrates visual and tactile information when estimating the properties of an
object explored by the hand [21]. For properties suchas size or surface roughness, direct sensory inputs andRegular Articles(a)32

Object temperature
34
33

(b)
TObject (°C)

32

Object temperature
33
34

Object feels warm

Object feels warm

Object feels warm

Warm!

Not warm

TObject (°C)

Object feels warm

Warm!

Not warm

Fig. 4. (a) A red object, relative to a blue object, raises the lowest temperature required for an object to feel warm, so that a
blue object is more likely to be judged as warm than a red object of the same physical temperature. (b) The lowest
warm temperature for a red hand was lower than that for a blue hand, so that with a red hand, participants tended tojudge the touched object as being warmer than they did with a blue hand.

expectations based on the visual information are
averaged, so that the final perception is biased toward
the expectations [21, 22]. In the case of estimating thetemperature of an object, our data suggest that insteadof taking the average of the expected and direct temperature inputs, our brain focuses on the difference
between the two. As a result, the final perception is
opposite to the expectation. Other object properties
that have the same integration rule include weight, inwhich a larger object is tended to be judged as lighter
than a smaller object of the same mass [23–27], andforce, in which the perceived force from an impact on
the palm is tended to be judged as weaker when thecollision speed is fast compared to when the collision
speed is slow [28].
In summary, our findings demonstrate that bothobject and hand colors can directly modulate temperature perception of an object touched by the hand
and that the effect is opposite to the common redwarm/blue-cold expectation.
4. Applications to multimodal interface design
While current applications of color-temperaturecorrespondences mainly focus on modulating people’s thermal experiences in different environmental
conditions and providing information concerningtemperature with color cues, our new findings thatcolor-temperature correspondences have an impact
on not only the efficiency of information processing
but also object temperature perception provide newguidelines for multimodal interface design.
For applications involving visual and thermal feedback, as indicated in section 2, it is important to avoid
presenting incongruent visual and temperature information, such as presenting the color red and a lowtemperature together, especially in situations whereusers need to respond to physical temperature information. This is because with incongruent combinations of color and temperature, the time required forusers to process the information could be prolonged,
and the performance of the interface would degrade.
When the purpose of the interface is to create a holistic experience of interacting with an object in virtualenvironments or at a remote site, manipulating theobject and hand colors with visual feedback can infact modulate the perceived warmness or coldness
during hand-object interactions, as indicated in section 3. For example, coloring a user’s hand red would
make an object held in the hand feel warmer, andcoloring a user’s hand blue would make the object
feel cooler. It is important to note, however, that whenmanipulating the color of the object itself, the opposite effect is obtained. That is, when coloring an
object red, it would give a cooler feeling instead of a
warmer feeling. Because thermal feedback control isrelatively complicated and requires special hardware,
the effect of object and hand colors on temperature
perception would allow a more energy-saving andlower cost multimodal interface.

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5. Conclusion
Our findings on color-temperature correspondences
not only provide fresh insights on how our brains
process multisensory information, but they are also
expected to contribute to the development of interfaces for providing multimodal information andholistic experiences in telecommunication and virtualenvironments.
References[1]

M. Tinker, “Effect of Stimulus-texture upon Apparent Warmth andAffective Value of Colors,” The American Journal of Psychology, Vol.
51, pp. 532–535, 1938.
[2] B. Wright, “The Influence of Hue, Lightness, and Saturation on
Apparent Warmth and Weight,” The American Journal of Psychology,
Vol. 75, No. 2, pp. 232–241, 1962.
[3] P. C. Berry, “Effect of Colored Illumination upon Perceived
Temperature,” Journal of Applied Psychology, Vol. 45, No. 4, pp.
248–250, 1961.
[4] A. Fenko, H. N. J. Schifferstein, P. Hekkert, “Looking Hot or Feeling
Hot: What Determines the Product Experience of Warmth?”,Materials and Design, Vol. 31, No. 3, pp.1325–1331, 2010.
[5] C. L. Hardin, “Red and Yellow, Green and Blue, Warm and Cool:
Explaining Color Appearance,” Journal of Consciousness Studies,Vol. 7, No. 8–9, pp. 113–122, 2000.
[6] G. A. Morgan, F. E. Goodson, and T. Jones, “Age Differences in the
Associations Between Felt Temperatures and Color Choices,” The
American Journal of Psychology, Vol. 88, No. 1, pp. 125–130, 1975.
[7] G. A. Michael and P. Rolhion, “Cool Colors: Color-induced Nasal
Thermal Sensations,” Neuroscience Letters, Vol. 436, No. 2, pp.
141–144, 2008.
[8] N. Matsubara, A. Gassho, and Y. Kurazumi, “Facilitatory Effects ofEnvironmental Sounds on Hue-heat Phenomena,” Proc. of the 18th
International Congress on Acoustics, pp. II-1775–1778, Kyoto, Japan,
2004.
[9] J. Winzen, F. Albers, and C. Marggraf-Micheel, “The Influence ofColoured Light in the Aircraft Cabin on Passenger Thermal Comfort,”
Lighting Research and Technology, 2013.
[10] P. O. Fanger, N. O. Breum, and E. Jerking, “Can Colour and Noise
Influence Man’s Thermal Comfort,” Ergonomics, Vol. 20, No. 1, pp.
11–18, 1977.
[11] F. H. Durgin, L. Evans, N. Dunphy, S. Klostermann, and K. Simmons,“Rubber Hands Feel the Touch of Light,” Psychological Science, Vol.
18, No. 2, pp. 152–157, 2007.
[12] G. A. Michael, H. Galich, S. Relland, and S. Prud’hon, “Hot Colors:
The Nature and Specificity of Color-induced Nasal Thermal
Sensations,” Behavioural Brain Research, Vol. 207, No. 2, pp. 418–
428, 2010.
[13] H.-N. Ho, G. H. Van Doorn, T. Kawabe, J. Watanabe, and C. Spence,“Colour-Temperature Correspondences: When Reactions to Thermal
Stimuli Are Influenced by Colour,” PLoS ONE, Vol. 9, No. 3, 2014.
[14] A. G. Greenwald, D. E. McGhee, and J. L. Schwartz, “Measuring
Individual Differences in Implicit Cognition: The Implicit Association
Test,” Journal of Personality and Social Psychology, Vol. 74, No. 6,
pp. 1464–1480, 1998.
[15] C. V. Parise and C. Spence, “Audiovisual Crossmodal Correspondences
and Sound Symbolism: A Study Using the Implicit Association Test,”Experimental Brain Research,” Vol. 220, No. 3–4, pp. 319–333,
2012.
[16] M. F. Mogensen and H. B. English, “The Apparent Warmth ofColors,” The American Journal of Psychology, Vol. 37, pp. 427–428,
1926.
[17] H.-N. Ho and L. A. Jones, “Contribution of Thermal Cues to MaterialVol. 13 No. 1 Jan. 2015

Discrimination and Localization,” Perception & Psychophysics, Vol.
68, pp. 118–128, 2006.
[18] H.-N. Ho, D. Iwai, Y. Yoshikawa, J. Watanabe, and S. Nishida,“Combining Colour and Temperature: A Blue Object is More Likely
to Be Judged as Warm Than a Red Object,” Scientific Reports, Vol. 4,
2014.
[19] J. C. Stevens and K. K. Choo, “Temperature Sensitivity of the Body
Surface over the Life Span,” Somatosensory & Motor Research, Vol.
15, No. 1, pp. 13–28, 1998.
[20] K. O. Johnson, I. Darian-Smith, C. LaMotte, B. Johnson, and S.
Oldfield, “Coding of Incremental Changes in Skin Temperature by a
Population of Warm Fibers in the Monkey: Correlation with Intensity
Discrimination in Man,” Journal of Neurophysiology, Vol. 42, No. 4,
pp. 1332–1353, 1979.
[21] M. O. Ernst and M. S. Banks, “Humans Integrate Visual and Haptic
Information in a Statistically Optimal Fashion,” Nature, Vol. 415, pp.
429–433, 2002.
[22] S. J. Lederman, G. Thorne, and B. Jones, “Perception of Texture by
Vision and Touch: Multidimensionality and Intersensory Integration,”
Journal of Experimental Psychology: Human Perception and
Performance, Vol. 12, pp. 169–180, 1986.
[23] M. O. Ernst, “Perceptual Learning: Inverting the Size-weight
Illusion,” Current Biology, Vol. 19, No. 1, pp. 23–25, 2009.
[24] J. B. Brayanov and M. A. Smith, “Bayesian and ‘Anti-Bayesian’
Biases in Sensory Integration for Action and Perception in the Sizeweight Illusion,” Journal of Neurophysiology, Vol. 103, No. 3, pp.
1518–1531, 2010.
[25] L. A. Jones, “Perception of Force and Weight: Theory and Research,”
Psychological Bulletin, Vol. 100, No. 3, pp. 29–42, 1986.
[26] H. E. Ross, “When Is a Weight Not Illusory?”, Quarterly Journal of
Experimental Psychology, Vol. 21, No. 4, pp. 346–355, 1969.
[27] A. Charpentier, “Analyse Expérimentale de Quelques Éléments de laSensation de Poids [Experimental Study of Some Aspects of Weight
Perception],” Archives de Physiologie Normale et Pathologique, Vol.
3., pp. 122–135, 1891.
[28] K. Arai and K. Okajima, “Tactile Force Perception Depends on the
Visual Speed of the Collision Object,” Journal of Vision, Vol. 9, No.
11, pp. 1–9, 2009.

Hsin-Ni Ho

Research Scientist, Sensory Representation
Research Group, Human and Information Science Laboratory, NTT Communication Science
Laboratories.
She received the Ph.D. in mechanical engineering from the Massachusetts Institute of Technology, USA, in 2006. She joined NTT Communication Science Laboratories as a Research Associate in 2007 and became a Research Scientist in
2010. Her research interests include haptic perception, multisensory interactions, material perception, and development of haptic interfaces.
She is a member of the Haptics Committee in theSociety of Instrument and Control Engineers,
Japan, the Virtual Reality Society of Japan, theSociety for Neuroscience, the Japan Neuroscience Society, and the Japanese Psychonomic
Society.

Regular Articles

DataBridge: Technology to Transfer
Data Securely and Efficiently
Between Terminals Connected to
Different Networks
Hiroyuki Adachi, Nagatoshi Nawa, Fumihiro Yokose,
Kimio Tsuchikawa, and Akira Inoue
Abstract

NTT Access Network Service Systems Laboratories is working on enhancing operational efficiency
and reducing operational errors. In this article, we introduce our product called DataBridge, whichenables data to be transferred securely and efficiently between terminals connected to different
networks.
Keywords: data transfer, security, operational efficiency

1. Introduction

2. DataBridge outline

Companies use various operation systems (OpSs)
to improve operational efficiency and ultimately
reduce costs. For the most part, OpSs are applied totypical operations in which the volume of business islarge rather than to atypical operations in which thebusiness volume is comparatively small. Atypicaloperations occur less frequently, but their total business volume is not insignificant because there aremany types of such operations. To further improve
operational efficiency, we need more than ever toaddress the issue of improving the efficiency ofoperations that are difficult for OpSs to handle.
NTT Access Network Service Systems Laboratories is proposing client side cooperation as a solution
to this issue. This solution enables OpSs to cooperatewith each other through terminals rather than throughsystem servers or networks. It has a minimal impact
on OpSs and can be applied flexibly according tooperations because it is applied on the client side. We
have developed DataBridge as one of the elemental
technologies of client side cooperation.

It is often the case that networks used within a corporation cannot be interconnected mainly because of
security constraints. Networks for OpSs are designed
to transfer only necessary data, and mission-criticaltasks will not be affected even if OpSs are not connected to the Internet. However, in some atypicaloperations such as sending e-mail with attached files
that are stored only in OpSs, there is a need to
exchange data between different networks.
In such cases, data are currently transferred bymanual operations such as using universal serial bus(USB) flash drives, or by printing the information on
paper and manually inputting it. DataBridge allows
transfer of data between terminals that are not interconnected via a network, based on the concept ofclient side cooperation. It ensures that data will betransferred securely and efficiently, which is not thecase with the conventional approach of using USB
flash drives or manually inputting data printed on
paper, as shown in Fig. 1.
In general there is a trade-off relationship between

NTT Technical Review

Regular Articles

SystemA

Customer
information

Unable to connect
because of security rules

USB flash drives

Current
situation

SystemB

Printing on paper• Risk of information leakage• Added manual workload
DataBridge
Secure

RESET

USB
A2

A1

USB
B2

Efficient

POWER

B1

Fig. 1. Schematic of DataBridge.

Receive the file froma read-only disk drive

Send a file using one of two ways:• Print (Send after conversion to PDF)
• Drag & drop (Send file directly)

RESET USB

Sending PC

A2

USB

A1 B2

POWER

B1

Receiving PC

DataBridge
PDF: Portable Document Format

Fig. 2. Utilization of DataBridge.

security and convenience. However, using the various
functions of DataBridge enables users to obtain themost suitable balance with respect to security criteria
and business content.
3. DataBridge mechanism
DataBridge is software for general purpose personal computers (PCs). It enables PCs to be used as adata bridge after the software has been installed inthem. (Hereinafter, a PC installed with DataBridge
software is referred to as “DataBridge”). DataBridge
has two USB client ports, one for sending and one forreceiving. It also has a function that filters the data
input to the sending port so that the user gets only
appropriate data from the receiving port (Fig. 2).
Vol. 13 No. 1 Jan. 2015

A user only needs to connect two USB cables inorder to utilize DataBridge—one from DataBridge tothe sending PC and one from DataBridge to thereceiving PC. DataBridge ensures the two networks
are never connected to each other because it transfers
data without an IP (Internet protocol) connection.
The sending PC recognizes DataBridge as a virtual
printer, and the receiving PC recognizes it as a readonly removable drive. Users who specify DataBridge
as a printer when printing applications (e.g., Excel or
OpS) can then get portable document format (PDF)
files on the receiving PC.
With this feature, DataBridge provides the following advantages to users.
(i)	It transfers only data that are permissible toextract from the system on paper.
Regular Articles

Table 1. Examples of setting items.
Setting item

Explanation

Data transfer restrictions

Per-day data volume and number of transfers can be limited to prevent unduly large
data transfers. Unrestricted volume and number of transfers can also be set.

Availability period

Available time and days can be set to prevent off-hours usage.

Automatic deletion time frame Time frame for automatic deletion of DataBridge-stored data can be set.
Policy expiration date

Policy expiration date can be set to enable periodic policy reviews. Data cannot betransferred after policy expires. Unlimited-duration policy can also be set.

Available terminals

Available sending PCs and receiving PCs can be registered.

Authorized users

Authorized users can be registered.

Unit recognition information

Identification names can be set for identifying which DataBridge unit was used
when using multiple units in parallel.

File filters

File name filters

Keywords can be set as file name filters. File names containing keywords enable
DataBridge to allow or disallow data transfers.

Application filters

Applications available for transfer can be set.

(ii)	It can remove viruses from files.
(iii)	It can transfer data in a single direction.
These advantages enable users to transfer data
securely. When users convert files to the PDF format,
it becomes difficult to reuse the data. Therefore,
DataBridge has a function that allows users to transfer files directly without converting them to PDF, aslong as the abovementioned items (i) and (ii) areunnecessary. (The administrator can freely configure
enable/disable settings.)
4. DataBridge features
4.1 S
 ecurity features to ensure safe andappropriate data transfer
DataBridge provides functions for transferring
appropriate data; the meaning of appropriate is determined based on the conditions listed in Table 1.
DataBridge can filter files by checking file names
and types; thus, it functions as a file type filter bychecking whether file extensions coincide with thefile contents. DataBridge can even extract and checkarchived files in formats such as zip and lha.
It also has functions to ensure that usage is limited
to authorized users and connected PCs. The administrator registers the MAC (media access control)
address of PCs so that only registered PCs can use thesystem. Its user recognition function displays a dialog
box in which the user name and password are entered.
It can also recognize users by using Windows login
information.
By combining these functions, the administrator
can set different rules for different people, dependingon the positions they hold within their company ororganization.
Some examples of usage and restrictions are:∙	Managers can use DataBridge at any time via allconnected PCs.
∙	Rank-and-file users can use it only from 9 a.m. to
5 p.m. and only via their own PCs.
∙	Dispatched employees can transfer only Excel
files for which the file name includes the word
application.
Because data stored in DataBridge may not betaken from the office, DataBridge encrypts the stored
data and automatically erases the data if it detects a
disconnection or power-off of the USB cable being
used. The erased data can never be restored.
4.2 Automatic usage history record for audits
It is important to ensure that the administrator isable to check whether data have been transferredappropriately. If this check is done using a manual
operation, it imposes a heavy burden on both the person recording the usage history and the person checking it. To prevent this, DataBridge automaticallyrecords the usage history showing who used the system and when, as well as what files were used andfrom which PC and to which PC data were transferred. This usage history is basically stored inside
DataBridge but can be transferred outside of it, which
is useful when multiple DataBridge units are used inparallel.
4.3 Comparison with USB flash drives
USB flash drives are used for transferring data
between terminals that are not interconnected over a
network, and they present risks of unauthorized use
NTT Technical Review

Regular Articles

Operation for order processing

Operation for facility management

NW for customer service

NW for facility
management

4 Dataautomaticallyentered toequipment
management
system

DataBridge
1 Transfer data

generated
automaticallyfrom ordermanagement
systemUMS

Sending PC

Receiving PC
RESET

USB
A2

A1

USB
B2

POWER

B1

3 Data received

2 Data sent

UMS

NW: network

Fig. 3. Automated operation by combining DataBridge and UMS.

and information leakage. DataBridge prevents theserisks by limiting the ways data are transferred and byrecording the usage history.
4.4 Cooperation with UMS
The Unified Management Support System (UMS)
is a software program that automates a variety ofoperations being executed on a single terminal. Like
DataBridge, it is an example of client side cooperation technology [1, 2]. Combining DataBridge andthe UMS makes it possible to automate operations
that span across terminals that are not interconnected
via a network, as shown in Fig. 3.
5. Summary and future plans
We have developed DataBridge, which enables
users to transfer data easily and securely between

Vol. 13 No. 1 Jan. 2015

terminals connected to different networks without
any need to modify existing networks or systems.
DataBridge is currently being used in the NTT Group.
The DataBridge technology was transferred to NTT
Software Corporation, where the plan is to further
develop and commercialize it.
References
[1]

[2]

F. Yokose and A. Inoue, “UMS: Software to Automate Operators’
Actions,” NTT Technical Review, Vol. 9, No. 8, 2011.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2011
08ra4.html
H. Adachi, K. Hotta, F. Yokose, T. Toyoda, and A. Inoue, “UMS:
Software for Automating Operators’ Actions to Rapidly Improve
Operational Efficiency at Low Cost,” NTT Technical Review, Vol. 12,
No. 2, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
02fa1.html

Regular Articles

Hiroyuki Adachi

Kimio Tsuchikawa

Engineer, Access Network Operation Project,
NTT Access Network Service Systems Laboratories.
He received the M.E. in physics from Osaka
City University in 2011. He joined NTT WEST
in 2011 and worked in the Nagoya Branch until
2013, after which he moved to NTT Access Network Service Systems Laboratories. He is currently engaged in research and development ofoperation support systems of access networks.

Senior Research Engineer, Access Network
Operation Project, NTT Access Network Service
Systems Laboratories.
He received the M.E. in applied physics from
Nagoya University in 2002. He joined NTT in
2002 and is currently engaged in developing
operation support systems for access networks.

Nagatoshi Nawa

Akira Inoue

Senior Research Engineer, Access Network
Operation Project, NTT Access Network Service
Systems Laboratories.
He received the M.E. in information engineering from the University of Tokyo in 1994. He
joined NTT in 1994 and is currently engaged indeveloping operation support systems for accessnetworks.

Senior Research Engineer, Supervisor, AccessNetwork Operation Project, NTT Access Network Service Systems Laboratories.
He received the M.E. in mechanical engineering from Osaka University in 1994. He joined
NTT in 1994 and is currently engaged inresearching navigation technologies for future
networks. He received the Academic Encouragement Award from the Institute of Electronics,
Information and Communication Engineers(IEICE) in 2002. He is a senior member of
IEICE.

Fumihiro Yokose

Network Business Headquarters, Strategic
Network Management Department, NTT EAST.
He received the M.E. in electrical engineeringfrom the University of Electro-Communications,Tokyo, in 2007. He joined NTT Access Network
Service Systems Laboratories from 2007 to
2014. He moved to NTT EAST in July 2014.



NTT Technical Review

Global Standardization Activities

Report of ITU-T TSAG Meeting and
Activities of NTT R&D European
Representative Office
Masakatsu Fujiwara
Abstract

The ITU-T TSAG (International Telecommunication Union, Telecommunication Standardization Sector, Telecommunication Standardization Advisory Group) and Review Committee conducted meetings
June 16–20, 2014. This document reports the results of deliberations on major issues in this TSAG meeting: revision of patent policy and the creation of two new Focus Groups. It also covers the activities ofNTT’s R&D (Research and Development) European Representative Office based in Frankfurt, Germany
with respect to major standards conferences in Europe.
Keywords: ITU-T TSAG, patent policy, R&D

1. Summary of TSAG and Review
Committee meeting
The International Telecommunication Union, Telecommunication Standardization Sector (ITU-T)’s
Telecommunication Standardization Advisory Group(TSAG) meeting differs from that of standard Study
Groups (SGs), the objective of which is to create recommendations. Instead, it is intended as an event todebate ITU-T’s standardization activities, work plans,
and methodologies. Topics covered include approaches to the way future standardization will be deliberated, how standardization is to be maintained acrossmultiple SGs, the creation of Focus Groups (FGs) for
the intensive investigation of new issues, and otherthemes.
The Review Committee is a group created for the
purposes of debating the organizational structure of
ITU-T beyond 2016 with an eye to efficient deliberation on standards issues, and for considering partnerships with other standards organizations. Mr. Yoichi
Maeda, formerly with NTT and now the chief executive officer and senior vice president of TTC (Telecommunication Technology Committee), serves as
its chair.
Focusing on trends in TSAG and the Review Com

mittee enables members to gain an early understanding of the major thrust of ITU-T’s activities as awhole. The following section describes the core
issues discussed at the June 2014 TSAG and Review
Committee meetings.
2. Core issues discussed at June 2014 meeting
The meetings in June were held at ITU headquarters in Geneva, Switzerland, and they focused on twocore issues—the revisions to patent policy and thecreation of two new FGs.
2.1 Revision of patent policy
For a year and a half prior to the meeting, ITU’s
patent policy had been debated by the ITU-T Telecommunication Standardization Bureau (TSB)
Director’s Ad Hoc Group on IPR (intellectual property rights). Reaching a consensus was difficult, with
one side in favor of licensers and the other in favor oflicensees. An emergency proposal to revise patent
policy on injunctive relief was presented at the meeting by representatives from the US government.
The Ad-Hoc Group had been deliberating on 1)
assignment and transfer of patent rights, 2) the definition of reasonable and non-discriminatory, and 3) the
NTT Technical Review

Global Standardization Activities

limits on the right to demand an injunction. While aconsensus was reached at this TSAG meeting concerning point 1, there was no sign of reaching a resolution or compromise on points 2 and 3.
The US has been looking for ways to alleviate themajor outlays of costs and manpower borne fromlawsuits over standard-essential patents, and the UScontingent expressed a desire to communicate a government-level policy that promotes their swift resolution.
However, the proposal came amidst a lack of sufficient advance coordination between the teams fromthe US and other countries, and there was little in theway of indication that an inquiry of said nature isunderway. As a result, the majority of non-US countries attended without IPR specialists (whereas the
US had close to 20). Participants came to the meetingwith the assumption that progress on the above front
would be difficult and that deliberations would haveto be ongoing, so the US did not garner support for its
proposal. At NTT, the NTT Intellectual Property
Center has been dealing with this case, and we werein accordance with other countries in postponing
deliberations on this matter until the next ITU-T IPR
Ad Hoc Group meeting.
As a result, a resolution on the issue was deferred,
and the Ad Hoc Group decided to reexamine the subject, with TSAG requesting the Ad Hoc Group to
release an agreement at the TSAG meeting to be heldin June 2015.
2.2 Creation of new FGs
2.2.1 FG Aviation
In response to the March 2014 incident of Malaysia
Airlines Flight 370 going missing, the Malaysian
government proposed the creation of an FG to explore
the use of cloud computing technologies as a meansof collecting real-time aircraft flight data. Attendees,
Japan included, agreed to this proposal, which will
establish the Aviation Application of Cloud Computing for Flight Data Monitoring FG.
The International Civil Aviation Organization(ICAO) also plans to cooperate on issues of real-time
aircraft flight data collection. The organization isaware that this project will require coordination notjust with ITU, but with ICAO, ISO/IEC JTC 1 (Joint
Technical Committee 1 of the International Organization for Standardization and the International Electrotechnical Commission), ISO Technical Committee(TC) 20, and other units. The standardization issue at
ITU-T is expected to focus on the use of big data andcloud technologies, as well as data searching andVol. 13 No. 1 Jan. 2015

security. Plans are for Malaysia to present a candidate
for FG Chair and for China and ICAO to present acandidate for Vice Chair. NTT plans to explore ways
to contribute to this FG from the vector of cloud services, big data, and security.
2.2.2 Digital Finance Services
The US-based Bill and Melinda Gates Foundation(B&MGF) proposed the creation of a Digital Financial Services FG at ITU-T. B&MGF was founded byBill Gates, the former chairman of Microsoft, and hiswife Melinda, and is the world’s largest charitablefoundation.
Digital Financial Services refers to digital methods
for the safe remittance and receipt of money for people primarily in developing countries who lackphysical bank accounts. A study on these systems asa whole, including telecommunications, will proceedfrom ITU-T. It was made clear that the funds for thisstudy would come from the aforementioned foundation, with the FG Director coming from the same.
ITU-T SG2, SG3, SG13, SG16, and SG17 expressed
their readiness to collaborate with the FG. Collaboration with ITU-T and other organizations, such as ISO
TC 68, ISO/IEC JTC 1, GSMA (Groupe Spéciale
Mobile Association), and SWIFT (Society for Worldwide Interbank Financial Telecommunication), wasalso highlighted. NTT must carefully follow where
the investigation leads in order to ensure the outcome
does not conflict in a technical manner with our existing mobile payment services.
3. Future ITU-T trends
The new FG issues agreed upon at this year’s TSAG
meeting involve proactively utilizing information andcommunication technology (ICT) and standardization to address social needs. A key point to thisattempt is that it will be consistent with e-health,smart grid, and ITS (intelligent transport system)
approaches and will not involve the orthodox horizontal approach to classifying issues by layer, butinstead will employ a vertical, integrated approach tothese layers and consider how standardization must
be deployed in the aid of existing social concerns.
Japan must actively contribute to these efforts, andthrough our activities at ITU-T, aid the developmentof global business by understanding vertical (industry-wide) needs.

Global Standardization Activities

4. Activities of Frankfurt R&D European
Representative Office
The R&D (Research and Development) European
Representative Office was established in 2010 as anoverseas branch of the NTT Research and Development Planning Department for the promotion of our
network operator partnerships, joint research, andstandardization activities in Europe.
Based in Frankfurt, Germany, the organization is
the sole representative office in Europe under the
NTT holding company. The staff currently consists ofthis author alone.
The goal in establishing this office is to further
expand NTT’s R&D activities in Europe. Thus,
efforts are underway to communicate with eachcountry’s carrier and vendor research organizations
to build trust and create wide-ranging partnerships.
In terms of standardization, in addition to participating in discussions on standardization strategy suchas the TSAG described herein, and also taking part ina timely fashion in new technical endeavors, thisoffice is simultaneously supporting the globalizationof R&D as a whole and launching investigation into
the use and joint research of ICT in Europe. The
European office is also working to build partnerships
with carriers and has contributed to the smooth collaboration in research activities with major European
carriers such as BT and Orange; in addition, the business side of the firm has promoted communicationand collaboration with carriers.
Europe has begun taking steps to deliberate on aframework for the future, with Horizon 2020, the successor to FP7 (7th Framework Programme), itself aprogram designed to foster R&D, being launched asa new seven-year plan. The European Commission(EC) is also supporting a multitude of research programs. In particular, deliberation on 5G, the fifth
generation mobile telecommunications system, israpidly moving into motion through industry-government-academia partnerships in Europe. In December
2013, 5GPPP (5G Public-Private Partnership Association), an agreement on public-private research,
was officially inaugurated as part of the EU’s movetowards establishment of 5G services. Horizon 2020
is moving forward with cutting-edge approaches inhealthcare systems, smart cities and communities,
and transportation, areas of core importance to NTT,so the progress of the program merits careful attention.
NTT’s R&D European Representative Office plans
to focus closely on R&D trends in the above areas and

how they concern telecommunications networks, aswell as movements within vertically oriented industries.
Going forward, we plan to further strengthen our
R&D partnerships with overseas Group companies
and to enhance the communication of information onthese topics to contribute to the global activities of the
NTT Group.

Masakatsu Fujiwara

General Manager, NTT R&D European Representative Office, NTT Research and Development Planning Department.
He received the B.E. in electrical engineeringand the M.E. in applied systems science from
Kyoto University in 1994 and 1996, respectively,
and the M.B.A. from Cornell University, USA, in
2005. After joining NTT Network Service Systems Laboratories in 1996, he was engaged in
R&D of key technologies for network management systems during 1996–2007 and 2010–2013.
He was engaged in R&D strategy planning at
NTT Research and Development Planning
Department during 2007–2010. He has been withNTT R&D European Representative Office inFrankfurt, Germany, since 2013.

NTT Technical Review

New NTT Colleagues––We welcome our newcomers to the NTT Group
This is a corner of the NTT Technical Review where we introduce our new affiliate companies.

InfoTrust AG
IT security service provider; established in 2002, headquartered in Switzerland
Founded in 2002 and based in Zurich, InfoTrust AG is one of the most successful information technology (IT)security companies in Switzerland. Their team of experienced IT security specialists with proven industry knowhow advises companies on all IT security issues and has successfully positioned itself over the years in the Swiss
market. In November 2014, InfoTrust AG was fully acquired by NTT Com Security AG, a global information
security and risk management organization and a member of the NTT Communications Group. For further
information about InfoTrust AG, please visit http://www.infotrust.ch/Contacts:
NTT Com Security AG
http://www.nttcomsecurity.com/en/news-and-events/press-releases/nid-00365/ntt-com-security-ag-acquiresinfotrust-ag-in-switzerland-and-extends-market-leadership-in-europe/
OaktonTechnology and consulting service provider; established in 1988, headquartered in Australia
Founded in 1988, Oakton is a consulting and technology firm based in Melbourne, Australia. For over 25 years,
Oakton has worked with corporate and government clients across a range of industries. The company brings
together a deep experience-based understanding of the issues and trends of key industry sectors, with an intimate
knowledge of business processes, operational processes, and management systems. In November 2014, Oakton
was acquired by Dimension Data Holdings plc, an ICT (information and communication technology) services
and solutions provider and a member of the NTT Group. For further information about Oakton, please visit
http://www.oakton.com.au/
Contacts:
Dimension Data Holdings plc
http://www.dimensiondata.com/Global/Downloadable%20Documents/Dimension%20Data%20Australia%20
Announces%20Successful%20Acquisition%20of%20Oakton.pdf

NTT Technical Review

New NTT Colleagues

Electronic Environments Corporation
Mission-critical lifecycle services provider; established in 1986, headquartered in USA
For nearly three decades, Electronic Environments Corporation (EEC) has successfully helped thousands oftelecom and datacenter clients maximize the productivity of their mission-critical infrastructure. EEC provides
design, construction, maintenance and 24/7 support services throughout all phases of the mission-critical lifecycle. EEC’s proven practices enable IT and facilities managers to optimize the reliability, performance, andvalue of their datacenter and telecom sites. In December 2014, NTT FACILITIES, INC., the leader in designingand constructing state-of-the-art information facilities that support communications and Internet infrastructure
and a member of the NTT Group, acquired a majority stake in EEC. For further information about Electronic
Environments Corporation, please visit http://www.eecnet.com/Home/
Contacts:
Public Relations Office, General Affairs and Personnel Division,
NTT FACILITIES, INC.
http://www.ntt-f.co.jp/english/news/heisei26/h26-1117.html

Vol. 13 No. 1 Jan. 2015



External Awards
Outstanding Paper Award
Winner: Ryo Ishii, Kazuhiro Otsuka, Shiro Kumano, and Junji
Yamato, NTT Communication Science Research Laboratories
Date: November 14, 2014
Organization: 16th ACM International Conference on MultimodalInteraction
For “Analysis of Respiration for Prediction of “Who Will Be Next
Speaker and When” in Multi-Party Meetings.”
To build a model for predicting the next speaker and the start timeof the next utterance in multi-party meetings, we performed a fundamental study of how respiration could be effective for the prediction
model. The results of the analysis reveal that a speaker inhales more
rapidly and quickly right after the end of a unit of utterance in turnkeeping. The next speaker takes a bigger breath toward speaking inturn-changing than listeners who will not become the next speaker.
The results of the evaluation of our prediction model suggest that the
speaker’s inhalation right after a unit of utterance is effective forpredicting whether turn-keeping or turn-changing will occur about
350 ms before the start time of the next utterance, and that the listener’s inhalation before the next utterance is effective for predicting thenext speaker in turn-changing about 900 ms before the start time of
the next utterance.
Published as: R. Ishii, K. Otsuka, S. Kumano, and J. Yamato,“Analysis of Respiration for Prediction of “Who Will Be Next
Speaker and When” in Multi-Party Meetings,” Proc. of the 16th ACM
International Conference on Multimodal Interaction, pp. 18–25,
Istanbul, Turkey, November 2014.
APMC 2014 Prize
Winner: Kazuki Maruta, NTT Access Network Service Systems
Laboratories; Jun Mashino, Takatoshi Sugiyama, NTT Network
Innovation Laboratories
Date: November 6, 2014
Organization: Institute of Electronics, Information and Communication Engineers (IEICE)
For “Blind Adaptive Arrays with Subcarrier Transmission Power
Assignment for Spectrum Superposing.”
Published as: K. Maruta, J. Mashino, and T. Sugiyama, “Blind
Adaptive Arrays with Subcarrier Transmission Power Assignment forSpectrum Superposing,” Proc. of the 2014 Asia-Pacific Microwave
Conference (APMC 2014), Sendai, Japan, November 2014.

Hornarable Mention Poster Award
Winner: Takahiro Matsumoto, Shunichi Seko, Ryosuke Aoki, Akihiro Miyata, Tomoki Watanabe, and Tomohiro Yamada, NTT Service
Evolution Laboratories
Date: October 30, 2014
Organization: The Second International Conference on HumanAgent Interaction (HAI 2014) organizing committee
For “Affective Agents for Enhancing Emotional Experience.”
We propose shared emotional experience agents that enhance theuser’s emotional experience through emotional contagion. Our
experiment had 12 participants, who watched videos together with arobot that expressed an emotional state using its body and voice. The
results suggest that the affective robot makes the user more excitedand relaxed, and less depressed and afraid than if they viewed it
alone.
Published as: T. Matsumoto, S. Seko, R. Aoki, A. Miyata, T. Watanabe, and T. Yamada, “Affective Agents for Enhancing Emotional
Experience,” Proc. of HAI 2014, pp. 169–172, Ibaraki, Japan, October 2014.
Best Technical Exhibition Award
Winner: Takayuki Yamada, Doohwan Lee, Hiroyuki Shiba, Yo
Yamaguchi, Takana Kaho, Tadao Nakagawa, and Kazuhiro Uehara,
NTT Network Innovation Laboratories
Date: October 31, 2014
Organization: SmartCom2014 (Singapore - Japan International
Workshop on Smart Wireless Communications) organizing committee
For “Broadband Spectrum Sensing Platform based on Received
Waveform Cross-correlation Using Distributed Sensors.”
ETSI NFV Excellence Award
Winner: Tetsuya Nakamura, Research Laboratories, NTT DOCOMO
Date: November 21, 2014
Organization: European Telecommunications Standards Institute(ETSI)For outstanding leadership and support for network functions virtualization (NFV) in Phase 1.

NTT Technical Review

Papers Published in Technical Journals andConference Proceedings
Evaluation of Window Interface in Remote Cooperative
Work Involving Pointing Gestures
R. Ishii, S. Ozawa, H. Kawamura, A. Kojima, Y. Nakano, and K.
OtsukaProc. of the Seventh International Conference on Advances in
Computer-Human Interactions (ACHI 2014), pp. 242–251, Barcelona, Spain, March 2014.
We previously proposed a “MoPaCo” window interface systemthat can reproduce a communication partner’s space within a display
as if the display were a glass window to achieve geometrical consistency between remote spaces. Experiment results demonstrated it
enables users to feel that the distance between themselves and theirconversational partners on video is about the same as in a face-to-facesituation and the partner is actually present. We consider MoPaCo
can generate video images that smoothly transmit gazes and pointing
gestures; this paper describes experimental tests of the system’s
effectiveness in doing so. Results suggest MoPaCo allows users toaccurately identify target objects as they would under face-to-faceconditions through an actual glass window. Results of experiments on
conversation quality show MoPaCo facilitates smooth conversationand communication among users and strengthens their memories of
the conversations, suggesting the users actively engage in conversation, and the system makes a strong impression on them.

Nine Years of Memory of Personal Things: Accuracy andDistortions
N. Shingaki, M. Kitabata, H. Matsuoka, T. Takada, A. Orino, Y.
Kato, Y. Tsuzuki, and T. Owada
Cognitive Studies, Vol. 21, No. 1, pp. 15–28, March 2014.
How should we save our memories? Many people keep diaries andtake pictures for that purpose. In this study, we kept things of personal significance in a time capsule for nine years and examined
whether personal memories could be saved in a time capsule and how
they might possibly change over time. We held a workshop in 2003
when participants put something that they had possessed which had
personal significance at that time of their life. They were interviewed
to explain what kinds of significance these possessions had for them,and these interview sessions were recorded. Nine years after the initial workshop, the participants came together again. Before the time
capsule was opened, they were asked to recall what they had put inthe time capsule and to describe in what ways their item in the time
capsule had been significant to them. By comparing the contents ofthe participants’ responses between 2003 and 2012, we found that agreat deal of the contents had changed.

Analysis and Modeling of Next Speaking Start Timing in
Multi-party Meetings
R. Ishii, K. Otsuka, S. Kumano, and J. Yamato
Proc. of IEEE International Conference on Acoustics, Speech, andSignal Processing (ICASSP 2014), pp. 694–698, Florence, Italy, May
2014.
To realize a conversational interface where an agent system cansmoothly communicate with multiple persons, it is imperative toknow how the start timing of speaking is decided. We demonstrate aVol. 13 No. 1 Jan. 2015

relationship between gaze transition patterns and the start timing of
the next spoken utterance against the end of the last spoken utterance
in multi-party meetings. Then, we construct a prediction model forthe start timing using gaze transition patterns near the end of an utterance. An analysis of data collected from natural multi-party meetings
reveals a strong relationship between gaze transition patterns of thecurrent speaker, next speaker, and listener and the start timing of thenext speaker. On the basis of the results, we used gaze transition patterns of the speaker, next speaker, and listener, and mutual gaze as
variables, and devised several prediction models. A model using all
features performed the best and was able to predict the start timing
well.

Quantum Algorithms for Finding Constant-sized Subhypergraphs over 3-uniform Hypergraphs
F. Le Gall, H. Nishimura, and S. Tani
Proc. of the 20th International Computing and Combinatorics
Conference (COCOON 2014), pp. 429–440, Atlanta, GA, USA,
August 2014.
We develop a general framework to construct quantum algorithms
that detect whether a 3-uniform hypergraph given as input contains a
sub-hypergraph isomorphic to a pre-specified constant-sized hypergraph. This framework is based on the concept of nested quantum
walks recently proposed by Jeffery, Kothari, and Magniez[SODA’13], and extends the methodology designed by Lee, Magniez, and Santha [SODA’13] for similar problems over graphs. As
applications, we obtain a quantum algorithm for finding a 4-clique ina 3-uniform hypergraph on n vertices with query complexity
O(n1.883), and a quantum algorithm for determining if a ternary
operator over a set of size n is associative with query complexity
O(n2.113).

An In-Operation IP-over-Optical Network Planning Methodthat Supports Unpredictable IP Traffic Transitions
T. Tanaka and A. Hirano
Proc. of the 40th European Conference on Optical Communications (ECOC 2014), Cannes, France, September 2014.
We propose a first-time in-operation IP (Internet protocol)-overoptical network planning method that offers optical path provisioning
criteria under temporal and geographical IP traffic changes. Simulations show the proposed method can support traffic transitions withless additional optical path provisioning.

Proposal and Evaluation of Web Framework for Ubiquitous
Sensor Network
T. Nakamura, K. Mori, Y. Higashijima, M. Nakamura, H. Matsumura, and M. Matsuo
IEICE Transactions on Communications (Japanese Edition), Vol.
J97-B, No. 9, pp. 793–807, September 2014.
This paper proposes a web framework for a ubiquitous sensor
network (u-framework), which supports development of server-side
applications used for M2M services on wireless sensor networks, andPapers Published in Technical Journals and Conference Proceedings

evaluates the proposed method by applying it to development of
actual systems. We first analyzed some examples of vertical-domain
services using wireless sensor networks, and found that server-sidefunctions in each of the services share some degree of similarity. The
proposed u-framework is built on a web framework and extends it on
supporting sensor networks. Our method can save a great deal ofeffort in the development of such common functions. This paper also
proposes the real-world development studio, which supports development and debugging of sensor network services including serverside applications and sensor terminals. Evaluations of the proposed
methods applied to practical system developments for two independent field trials are also explained in this paper.

Distinct Pseudo-attraction Force Sensation by a Thumbsized Vibrator that Oscillates Asymmetrically
T. Amemiya and H. Gomi
Proc. of Eurohaptics 2014, pp. 88–95, Versailles, France, June
2014.
This paper describes the development of a thumb-sized force display for experiencing a kinesthetic illusory sensation of being continuously pushed or pulled. We previously succeeded in creating asensation of being pulled with a prototype based on a crank-slider
mechanism, but recently we did so with a thumb-sized actuator that
oscillates asymmetrically.
With this tiny and light force display, the directed force sensationis perceived just as strongly as with the previous larger prototypes.
We conducted a user study using the method of paired comparisons.
The results show that a specific vibrator with a 7-ms pulse at 40 Hz
induces the sensation most clearly and effectively.

Influence of Dolly Shape on Adhesive Property and Correlation Between Adhesion and Cross-cut Test Results
T. Miwa, Y. Takeshita, S. Sakata, and T. Sawada
Rust Prevention and Control Japan, Vol. 58, No. 10, pp. 368–372,
October 2014.
Coated steel structures need to be checked regularly for deterioration in the coatings and subsequently repainted at an appropriate
time. An adhesion test is the standard method for evaluating coating
adhesion, and a cross-cut test is usually used to evaluate peel resistance. In this study, adhesion was measured on the same sample using
two kinds of dollies with different shapes. One dolly had a hand-holdwith a spherical shape. In the adhesion test with this dolly, it was
found that the relative standard deviation in multiple adhesion measurements on the same sample was reduced to one fourth of that using
a standard dolly. Additionally, a new method of classifying cross-cut
test results for a coating on hot dip galvanized steel was developed,
and it was confirmed that there was consistency between the classification and the adhesion of the coatings.

Violation of Equipartition of Energy in Thermal Noise of a
Small DRAM
K. Nishiguchi and A. Fujiwara
Proc. of the 27th International Microprocesses and Nanotechnology Conference (MNC 2014), 6B-4-3, Fukuoka, Japan, November
2014.
We introduce a transition between the valid and invalid law ofequipartition of energy in thermal noise in a small DRAM (dynamic
random access memory). We analyzed Brownian motion, i.e., ther-

mal noise, of single electrons entering and exiting a small capacitor
whose Ec is comparable to kBT. When Ec>kBT, the electron motion
is suppressed due to the violation of the law of equipartition ofenergy.

Zero Dimensional Ion-sensitive Field-effect Transistors
R. Sivakumarasamy, K. Nishiguchi, A. Fujiwara, D. Vuillaume,and N. Clément
Proc. of MNC 2014, 6P-7-61, Fukuoka, Japan, November 2014.
We propose to fabricate and characterize a tiny pH electrode sosmall that the number of charged sites can be statistically null. We
also show a rupture in the universal pH response of such sensors andpropose a dedicated model.

Tunnel Diode Composed of MoS2/SiO2/Si Heterojunction
K. Nishiguchi, A. Castellanos-Gomez, H. Yamaguchi, A. Fujiwara,
H. S. J. van der Zant, and G. A. Steele
Proc. of MNC 2014, 5D-3-2, Fukuoka, Japan, November 2014.
We introduce a tunnel diode based on a combination of MoS2 witha Si MOSFET. An n-type-MoS2/SiO2/p-type-Si heterostructure provides current characteristics with negative differential resistance(NDR) reflecting the number of the MoS2 layers.

Analysis of Timing Structure of Eye Contact in Turn-changing
R. Ishii, K. Otsuka, S. Kumano, and J. Yamato
Proc. of the 16th ACM International Conference on MultimodalInteraction (ICMI 2014), the 7th Workshop on Eye Gaze in Intelligent Human Machine Interaction, pp. 15–20, Istanbul, Turkey,
November 2014.
With the aim of constructing a model for predicting the next
speaker and the start of the next utterance in multi-party meetings, we
focus on the timing structure of the eye contact between the speaker,
the listener, and the next speaker. The results of analysis show that thelisteners in turn-keeping tend to look at the speaker first more often,
before the speaker looks at the listeners than the next speaker in turnchanging looks at the speaker first before the speaker looks at the next
speaker when the eye contact with the speaker happens. The listeners
in turn-keeping also tend to look away from the speaker later more
often, after the speaker looks away from the listener than the listeners
and the next speaker in turn-changing look away from the speakerlater when the eye contact with the speaker happens.

OpenStack Upgrade Without Down Time
T. Natsume and Y. Liu
Proc. of OpenStack Summit November 2014 Paris, Paris, France,
November 2014.
Many public cloud service providers utilize OpenStack software tobuild IaaS (Infrastructure as a Service) systems. OpenStack is open
source software that is developed by a community that many organizations and individuals participate in. New versions of OpenStack arereleased at intervals of six months, and only the two latest versions
are maintained. Therefore, system update methods without service
interruption are necessary for public cloud service providers whowant to keep the systems up to date. This document proposes system
update methods without service interruption in public cloud services

NTT Technical Review

Papers Published in Technical Journals and Conference Proceedings

and explains an evaluation of the proposed update methods. Furthermore, we describe some problematic issues which were found in theevaluation. On the basis of these issues, items to be improved aresuggested to the OpenStack community.

Impact of Pulse Poling on Static and Dynamic Ferroelastic-domain Contributions in Tetragonal Pb(Ti, Zr)O3 Films
Determined by In-situ x–ray Diffraction Analysis
M. Nakajima, A. Wada, T. Yamada, Y. Ehara, T. Kobayashi, and H.
Funakubo
Journal of Applied Physics, Vol. 116, No. 19, pp. 194102–1941027, November 2014.
The effects of bipolar pulse poling on the ferroelastic domain
structure and their contribution to the electrical and piezoelectric
properties of Pb(Ti0.7Zr0.3)O3 films are investigated. Micro x-ray diffraction measurements clearly show that the volume fraction of the
c-domain increases irreversibly as the poling field is increased, leading to changes in the remanent polarization, dielectric constant, andpiezoelectric coefficient. Theoretical estimations well explain thechanges of remanent polarization and dielectric constant, but theincrease in piezoelectric coefficient is much larger than the theoretical estimation. In-situ x-ray diffraction analysis under an electricfield reveals that this disagreement is due to the unexpected activationof the ferroelastic domain wall motion. Our results provide new
insight into the poling effect on the electric and piezoelectric properties of ferroelectric films.

Electric Tuning of Direct-indirect Optical Transitions in
SiliconJ. Noborisaka, K. Nishiguchi, and A. Fujiwara
Scientific Reports, Vol. 4, No. 6950, pp. 1–6, November 2014.
Electronic band structures in semiconductors are uniquely determined by the constituent elements of the lattice. For example, bulk
silicon has an indirect bandgap, and it prohibits efficient light emission. Here, we report the electrical tuning of the direct/indirect band
optical transition in an ultrathin silicon-on-insulator (SOI) gatedmetal-oxide-semiconductor (MOS) light-emitting diode. A special
Si/SiO2 interface formed by high-temperature annealing that shows
stronger valley coupling enables us to observe phononless direct optical transition. Furthermore, by controlling the gate field, its strength

Vol. 13 No. 1 Jan. 2015

can be electrically tuned to 16 times that of the indirect transition,
which is nearly 800 times larger than the weak direct transition inbulk silicon. These results will therefore assist the development ofboth complementary MOS (CMOS)-compatible silicon photonics
and the emerging “valleytronics” based on the control of the valley
degree of freedom.

Auto Bias Control and Bias Hold Circuit for IQ-modulator
in Flexible Optical QAM Transmitter with Nyquist Filtering
H. Kawakami, T. Kobayashi, M. Yoshida, T. Kataoka, and Y. Miyamoto
Optical Express, Vol. 22, No. 23, pp. 28163–28168, November
2014.
An auto bias control (ABC) technique for the IQ (in-phase andquadrature)-modulator of a flexible optical QAM (quadrature amplitude modulation) transmitter is described. This technique can support
various optical QAM signal formats with Nyquist filtering and electronic dispersion pre-compensation. 16-, 32-, and 64-QAM signals(21 Gbaud) are successfully generated, and all bias voltages are held
to their optimum value even when signal format is changed.

Improving Method of Disaster Response Manual Based on
the Guidelines of the Cabinet Office by ICT
F. Ichinose, H. Hayashi, Y. Takeguchi, T. Yamamoto, M. Zusho,
and Y. Maeda
Journal of Institute of Social Safety Science, No. 24, pp. 201–210,
November 2014.
The guidelines for earthquakes occurring in a local city were
exhibited in August 2013 by the Cabinet Office. These guidelines area checklist of response actions to implement in the event of an earthquake. It is expected that a municipality can prepare a very effective
emergency response manual if the municipality bases the manual onthese guidelines and clarifies the Emergency Support Functions in
the manual. In this paper, we describe the efficient method used in
Kashihara-shi. We have improved the Disaster Response Manual andclarified the Emergency Support Functions in Kashihara-shi based on
the guidelines and by utilizing information and communications
technology.

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