Special Feature

Sensor-based Hardware Technology
Supporting Daily Activities
Shin’ichiro Mutoh†, Jun Terada, Fumiharu Morisawa,
Yasuhiro Sato, and Yuichi Kado
Abstract
Services that provide remote sensing and remote control of home appliances connected to a home network are expected to make our daily lives safer, healthier, more convenient, and more comfortable. Afterreviewing the current state of sensor-based services, this article introduces technology for expanding thepossibilities of home networks focusing on small adaptive sensors with communication functions (sensor nodes) that can respond flexibly to diversified and changing user needs.

1. Distributing people-centered information via
a home network
As broadband “always-on” access environments
such as ADSL (asymmetric digital subscriber line)
and FTTH (fiber to the home) become commonplace,there are growing expectations for services that con† NTT Microsystem Integration Laboratories
Atsugi-shi, 243-0198 Japan
E-mail: mutoh@aecl.ntt.co.jp

nect home sensors and electronic appliances into a
network and send information obtained from thathome network to an Internet site to enable home
appliances to be controlled from remote locations [1].
People are mainly involved with real-world events,and services for obtaining and distributing information about such events as well as providing services
related to that information are expected to increase
network traffic in a completely new way comparedwith conventional uses of the Internet such as Web
browsing and e-mail. Figure 1 illustrates the infor-Sensor and sensor-node technology for the naturalacquisition of data related to people: the source of value
IDs andsensing values

InternetStores, converts,
and otherwise
processes datafrom a homeand provides
users withvaluableinformation

Information flowfor home sensing/operations

Information(value)Sensor nodes

Home network

Technology that enables users to obtain and process
remote information through natural and intuitive operations

Fig. 1. Data generation and information flow in a home network.

Vol. 3 No. 1 Jan. 200537

Special Feature

mation-distribution cycle in the home network. It
requires sensor and sensor-node technology for
obtaining data related to people (the source of value)
and those sensors need to be given communication
functions. It is now becoming possible to supply lowcost sensors for detecting a wide variety of environmental data such as temperature, humidity, heat,light, pressure, sound, smell, and acceleration. Placing such sensors inside a house should lead to valueadded services for the home such as monitoring thehealth of occupants to prevent lifestyle-related diseases, managing the expiry dates of purchased products and foodstuffs, tracking the location of valuables
and important documents, and controlling the indoor
environment to reduce stress. One example of such avalue-added service that is already being provided isa weekly health check whereby familiar measurement devices such as weight scales, pedometers, andblood pressure gauges are given communication
functions and the data they obtain is sent to an Internet site via a personal computer. Another requirement
for maintaining this cycle of information is to enable
an ordinary home user to obtain remote information
through natural and intuitive operations. Specifically,
it must be easy for the user to access sensing information collected at his/her house from a remote location and to control household appliances connected tothe home network. Here, we introduce sensor-based
hardware technology as the key to expanding homenetwork services.

2. Home sensing services and associatedproblems
Home-network sensing services can be classified asshown in Fig. 2. In Type I, the simplest format, a sensor installed in a home sends sensing data to the network either periodically or at certain times in a unidirectional manner. Two examples in this category arehome security services that detect and report intruders using sensors that detect motion or human characteristics (infrared sensors) and health management
services that send data from medical and measuring
devices such as electrocardiographs, blood pressuregauges, and weight scales. Type II features bidirectional transmission. In contrast to Type I, this allows
devices connected to the home network to be controlled in some way from the network side. Two
examples are webcam services that allow the user tocontrol the camera’s field of view and appliance-control services based on sensing data that describes conditions within a home. Type-I and Type-II services
are both based on a one-to-one relationship between
sensors and services. In other words, the assumption
is that a sensor installed in the home will be used onlyfor a specific, predetermined service. But looking tothe future, sensors that can be used for multiple applications would enable diversified network services
based on home sensing data. At present, however,sensor nodes have fixed hardware specifications(such as measurement period, measurement precision, and signal amplification factor) established for

NetworkHome

Type I
Unidirectional

SensorSensorSensing data

Sensing data

Type II
Bidirectional
Appliance,etc.
SensorType III
Bidirectionalplus

Dynamic
sensing
control

Control signals

Sensing data
Control signals

Fig. 2. Types of sensing and remote control in a home network.

38

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Special Feature

specific applications, so it is not possible to obtain
optimal sensing results for different applications.

(switch) S1 and conversion precision adjusted bycontrolling feedback to satisfy the sensing needs ofdifferent users. A screenshot of an adaptive sensing
service using body monitoring as an example isshown in Fig. 4(a). This service obtains and displays
a remote user’s pulse, body temperature, and othervital signs as an application on the network side. Figure 4(b) shows a window for setting sensing conditions remotely. It allows the user and sensors to beselected and the analog/digital converter’s frequency
and precision and the amplifier’s amplification factor
to be set from a remote location.

3. New sensor nodes to promote the use of homesensing
Type-III sensing services (Fig. 2) aim to solve thisproblem through a configuration based on adaptive
sensing nodes [2]. The key feature of this type of service is the ability to control sensing operations bysending setting commands from the network side.
Sensing is accomplished by amplifying the extremely small analog signal output by the sensor, converting that analog signal to a digital signal at a certain
sampling frequency and number of bits, and sendingthat digital value to the network. A new circuit configuration is introduced so that sensing control commands can be sent from applications on the network
to the sensor-nodes and interpreted there to set theamplification factor, sampling period, conversion
precision, etc.
An adaptive cyclic analog/digital converter isshown in Fig. 3 as an example of such a circuit configuration. The sampling frequency can be adjusted
by changing the operating frequency of transistor

4. Integrating video for natural access to thehomeServices that connect the network with the homeare beginning to be proposed and offered to enable
users to control electronic devices connected to thenetwork and to check sensor output (such as the video
output of a security camera). These are advanced
examples of Type-II services. We believe, however,that two main issues must be addressed before these
services can achieve widespread penetration. First, aservice menu centered on user needs must be pro-×2Input analog signal
φ3Feedback loop

S2
Shift register

S1φ1φ2

Input analog signal

Fig. 3. Adaptive cyclic analog/digital converter.

Select user
User ID

Cardiac sound wave
Select type of sensor
Pulse waveform
Select settings

Pulse rate
Body
temperature

Set the sensing
operation
Body temperature(a) Screenshot of display of sensing results(b) Window for setting sensing operations

Fig. 4. Application to remote health monitoring (home-sensing operations are set from the network side).

Vol. 3 No. 1 Jan. 2005

39Special Feature(a) Conventional (text-based) type

Homenetwork-Schedule video
recorder-Turn on airconditioner-What is mydaughter’s bodytemperature?
(b) Video-based type

HomeAdjust
temperature of
air conditioner
Schedulevideo
recorder36.5°C,
normalFig. 5. Remote access to home network services (controlling home appliances and obtaining sensing data).

posed and initial deployment cost and monthly service cost must be decreased. Second, services must
be user friendly. Using them must be just as easy as
switching on a television set and changing channels.
As shown in Fig. 5(a), to switch on a home appliancefrom a remote location, for example, the current procedure is to use a personal computer or cell phone,enter the appliance ID from the keyboard, press theappropriate keys to enter information in the channelsetting box or on/off-control section, press the Enter
key, and wait for the transmission to complete.
To provide a better solution, NTT Microsystem
Integration Laboratories is studying technology for
integrating video images with remote control andsensing operations [3], [4]. The service concept basedon this technology is shown in Fig. 5(b). The display
adds a red mark near an object like a television set or
air conditioner. The user need only click on a redmark to control the device to schedule a video
recorder or adjust the temperature setting of the air
conditioner, for example. A user can also get a child’s
pulse rate and body temperature from a remote location by simply clicking on the mark near that child.
The idea here is to achieve remote sensing and device
control through natural and intuitive actions, that is,
by simply touching (clicking) an “object about which
I want information” or an “object that I want to control” displayed in a realtime video of the real world.
The concept is based on miniature tags (Fig. 6) thattransmit and receive infrared radiation so that thetwo-dimensional coordinates of each object in a camera’s field of view can be obtained with high preci40

Fig. 6. Infrared tag.

sion. First of all, an infrared camera is used to capture
the infrared radiation emitted by the miniature tag
having the current ID number of interest. Using lightinstead of radio waves enables greater precision inposition detection. The output signal from the camerais then used to determine the coordinates of the emission point from the intensity of that radiation. In thisway, the position of people and objects in the camera’s field of view can be extracted in real time. Thissystem can perform high-speed recognition of 50 real
objects per second including moving bodies and canidentify the positions of about 100 objects in the fieldof view. As a result, detailed information about
almost all objects in a room can be obtained, ranging
from their presence or absence to their movement history.
In this system, the processing to be executed whena displayed mark is clicked must be set up beforehand. The current prototype system supports four
clickable positions per mark, so up to four actions canbe performed for the device corresponding to a mark.
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Special Feature

However, the number of actions that will actually beneeded and whether or not hierarchical processing(e.g., by displaying a process menu with sub-menus
for item selection) will be required will depend on theservice in question. The chosen configuration may
also have to be modified in future and dynamic downloading of processes from the network may also beneeded. For these reasons, this system should bemanaged by software. Finally, to make it even easier
to use, the system should be linked with user interface
technology oriented to the real world so that users canspecify intended marks using hand or body gesturesinstead of using a mouse, for example, to select amark displayed on the screen [5].
5. Future developments
We introduced an adaptive-sensor-node configuration and infrared position-detection tag as key
devices for expanding the use of home networks.
These devices support diverse user needs above andbeyond network connections and make home-network operations intuitive and easy to use. To launchsuch home-network services, we will need to address
various issues associated with marketing such smallscale hardware including cost, shape, performance,Vol. 3 No. 1 Jan. 2005

and battery life. NTT Microsystem Integration Laboratories is working to overcome such issues throughthe research and development of low-voltage andlow-power analog and RF circuit techniques, highperformance and ultrasmall components fabricatedwith MEMS (microelectromechanical systems) technology, and small batteries.
References
[1]

[2]

[3]

[4]

[5]

R. Kakinuma and N. Fujii, “Next-generation Home Network Technology,” NTT Technical Journal, Vol. 14, No.11, pp. 51-54, Nov.
2002 (in Japanese).
J. Terada, Y. Sato, F. Morisawa, S. Mutoh, K. Fujii, and Y. Kado, “A
Wireless Sensor-Network System with a Dynamically Programmable
Sensor Interface,” IEEE Sensors, Abst., pp. 202-203, Oct. 2003.
F. Morisawa, J. Terada, Y. Sato, S. Mutoh, and Y. Kado, “Touching
Remote Objects,” Proceedings of Interaction 2003, pp. 223-224, Mar.
2003 (in Japanese).
S. Mutoh, F. Morisawa, J. Terada, Y. Sato, and Y. Kado, “Stick-onCommunicator and Its Broadband Applications—A Compact Wireless Device with a Built-in Sensor and Actuator Connecting the RealWorld and the Network,” NTT Technical Review, Vol. 2, No. 2, pp.
53-57, 2004.
E. Hosoya, M. Kitabata, H. Sato, I. Harada, H. Nojima, F. Morisawa,
S. Mutoh, and A. Onozawa, “A Mirror Metaphor Interaction System:
Touching Remote Real Objects in an Augmented Reality Environment,” The 2nd IEEE and ACM Int. Symp. On Mixed and Augmented Reality, pp. 350-351, 2003.

41

Special FeatureShin’ichiro Mutoh

Yasuhiro SatoGroup Leader, Low-voltage Circuits ResearchGroup, Smart Device Laboratory, NTTMicrosystem Integration Laboratories.
He received the B.E. and M.E. degrees in electronic engineering from Chiba University, Chiba
in 1986 and 1988, respectively. He joined NTT
in 1988. Since then he has been engaged in R&D
of 1-V operating logic and memory circuit technology. He moved to NTT Microsystem Integration Laboratories in 2001. His current interests
are small ubiquitous devices such as a low-power
sensor node and its network applications forsharing real-world information on networks. He
received the Young Engineer Award from theInstitute of Electronics, Information and Communication Engineers (IEICE) of Japan. He is amember of IEEE and IEICE.

Senior Research Engineer, Supervisor, Smart
Devices Laboratory, NTT Microsystem Integration Laboratories.
He received the B.S. and M.S. degrees in inorganic chemistry from the University of Tokyo,
Tokyo in 1987 and 1989, respectively. In 1989,
he joined NTT LSI Laboratories, Atsugi, Japan.
He has been engaged in R&D of LSI interconnection technology, ultrathin-film CMOS/SOI
process and device technology, and low-power
communication appliances. He is a member ofthe Japan Society of Applied Physics, IEICE, andIEEE.

Yuichi KadoJun Terada
Research Engineer, Smart Devices Laboratory,
NTT Microsystem Integration Laboratories.
He received the B.E. degree in electrical engineering and M.E. degree in computer sciencefrom Keio University, Yokohama, Kanagawa in
1993 and 1995, respectively. In 1995, he joined
NTT LSI Laboratories to study analog LSIs,
especially A/D and D/A converters. Since 1999,
he has been engaged in research on systems forachieving ubiquitous services in NTT Microsystem Integration Laboratories. He is a member ofIEEE and the Information Processing Society ofJapan (IPSJ).

Executive Manager, Smart Device Laboratory,
NTT Microsystem Integration Laboratories.
He received the M.E. and Ph.D. degrees inelectronics from Tohoku University, Sendai,
Miyagi in 1983 and 1998, respectively. In 1983,
he joined NTT Electrical Communications Laboratories, where he engaged in research on SOI
structure formation by hetero-epitaxial growth.
From 1989 to 1998, he worked on the development of fully-depleted CMOS/SIMOX LSI andultra-low-power CMOS circuits. From 1999, heengaged in R&D of compact network appliances
using ultra-low-power CMOS circuit technologies for ubiquitous communications. He hasserved as a program committee member ofISSCC since 1999 and a technical committee
member of IEEE Computer Elements since 2003.
He is a member of IEEE and IEICE.

Fumiharu Morisawa
Low-voltage Circuits Research Group, Smart
Devices Laboratory, NTT Microsystem Integration Laboratories.
He received the B.E. and M.E. degrees in computer science from Keio University, Yokohama,
Kanagawa in 1997 and 1999, respectively. In
1999, he joined NTT Telecommunications Energy Laboratories, Atsugi, Japan. He has been
engaged in R&D on StiC and its applications. His
current interest is very-low-power-consumption
active tag systems. He is a member of IPSJ,
IEICE, and IEEE.

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