Letters

RFID-based Automatic Area Detection
System
Masamitsu Nakura†, Junichi Iwatani, Hiroki Shibayama,and Hideaki Kimata
Abstract
NTT Access Network Service Systems Laboratories is developing automatic area detection systems
and wireless local area network (WLAN) middleware that improve the usability of WLAN systems topromote WLAN services. This article describes a recently developed automatic area detection system
based on radio frequency identification (RFID).

1. Introduction
RFID tagPublic wireless local area network(WLAN) services have rapidly become
WLAN access point
popular because many users use WLAN
PDA issystems at home and in the office.
powered on
Though the hot spots for WLAN serPublic WLAN
vices have increased, the areas are limitContent is
network
ed because they are spot-based, unlike
downloaded
cellular phone services which are available almost everywhere. Therefore,
PDA iswhen using WLAN services, a user
powered off
WLAN service area
must go through the following steps:
make sure that he/she is within the service area, power on the terminal, actiFig. 1. Outline of RFID-based area detection system.
vate the application software, download
WLAN technology (Fig. 1). It consists of RFID tags,
content, and then power off the terminal. All of these
RFID readers, and WLAN middleware installed in aprocedures should be done step by step by hand. To
personal digital assistant (PDA). It is targeted at thesimplify this complicated process, we have developed
users of public WLAN services. RFID tags, which
an automatic area detection system based on radiotransmit ID signals intermittently, are installed at thefrequency identification (RFID). Users need not recboundary of each WLAN spot area. An RFID reader
ognize the service areas, and all steps are done autois connected to a PDA that has WLAN middleware
matically by the system.
installed. When a user enters a WLAN spot area, theRFID reader detects the signal from the RFID tag and
2. System outline
powers on the PDA. When the WLAN middleware
detects that the PDA is active, it establishes a conThe system uses a combination of RFID andnection to the network via the WLAN, activatesapplications, and finally powers off the PDA. Thus,† NTT Access Network Service Systems Laboratories
the user only needs to carry the PDA with its power
Yokosuka-shi, 239-0847 Japan
E-mail: Nakura.Masamitsu@ansl.ntt.co.jp
off. When the user enters the spot area, everything isVol. 3 No. 11 Nov. 2005

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done automatically. This improves convenience andreduces power consumption.

This section describes the specifications and functions of the RFID tag, RFID reader, and WLAN middleware (Tables 1 and 2; Figs. 2 and 3).
The RFID tag is a license-exempt radio device thattransmits weak signals in the 315-MHz band. The
transmission range is about 10 m. The ID length for
RFID is up to 128 bits. The administrator can change
the ID to support different public WLAN services.
We have also developed various types of power supply for RFID tags because they may be used at various places. They support AC power, primary batteries, and solar batteries.
The RFID reader should be designed with careful
regard to its robustness and shape because it should
be attached to a PDA. The RFID reader we havedeveloped is designed for the Pocket PC e830 series
from Toshiba Corporation. The power supply for the
RFID reader is a secondary battery, which enables
both the RFID reader and the PDA to be recharged at
the same time. The ID information of RFID tags isregistered in the RFID readers in advance. When it
receives a signal from the RFID tag, the RFID reader
compares the received ID with the registered one.
Only if these IDs coincide does the RFID reader
power on the PDA. This reduces the PDA’s battery
consumption because the PDA is powered on only
when necessary.
To extend the life of the primary battery of the
RFID tags and the secondary battery of the RFID
reader more efficiently, we made it possible to change
the transmission intervals of the RFID tags and thereception intervals of the RFID readers. Assumingthat the system is used in railway stations and that theusers carry PDAs and walk within the stations, thebattery life of the primary battery is about threemonths and that of the secondary battery is about one
week. If AC power or solar power is used instead of
the primary battery, the transmission intervals of the
RFID tags can be shorten. This allows the reception
interval of the RFID reader to be longer and the lifeof the secondary battery should be up to one month.
The WLAN middleware, which supports Pocket
PC 2003 and Pocket PC 2003 Second Edition, has
three functions: WLAN control, application control,and PDA power control.

Table 1. Specifications of RFID tag.

Table 2. Specifications of RFID reader.

3. System specifications

Radio I/F

Extremely lower power radio

PDA

e830(W) by ToshibaBand

315 MHz

Size

W80, D52, H23 (mm)Modulation

FSK

Weight40 g (including battery)Rate

9.6 kbit/s

Reception

Intermittent

Transmission

Intermittent

LED

ID length

Max 128 bits

• Low battery warning• Recharging indicator• AC adapter• Primary battery• Solar battery

Power supply

Power supply

Secondary battery(rechargeable with PDA)(a) RFID tag.

(b) RFID reader.

Fig. 2. RFID tag and RFID reader.

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Application
Application control

WLAN middleware

Data flow

1) WLAN control function:• Parameters and priority settings for multiple profiles• Automatic login for public WLAN providers• Display of connection status and signal power• Security configuration
2) Application control function:• Executes applications automatically• Application setting and priority control for each profile
3) PDA power control function:• Powers off the PDA automatically after all applications
have been completed

PDA power
control

WLAN control

Operating system (Pocket PC2003 or Pocket PC2003 2nd edition), driver, hardware

Fig. 3. Functions of WLAN middleware.

The WLAN control function is as follows. The user
sets one or more WLAN profiles and their priorities.
Basic WLAN utility functions include connection
control, automatic authentication for public WLAN
service providers, status indication, and security configuration. In addition, the WLAN middleware supports roaming between different WLAN service
providers. For this function, two or more different
sets of security information can be assigned to thesame WLAN service provider. They are registeredand used as different WLAN profiles.
The application control function works in the following way. For each WLAN profile, one or more
applications are registered to be executed automatically. The priority and execution interval of eachapplication is variable. This makes it possible for theuser to receive e-mail and news continuously. In addition, if there are two or more access points near theuser, the PDA tries to connect to an access point, execute applications, and change the connection to theother access point.
The PDA power control function powers off the
PDA after all of the applications have been completed or the WLAN connection has been disconnectedby the user leaving the area. This function conserves
the PDA’s battery.
The WLAN middleware is available even when it isused without the RFID tags and readers. In this case,Vol. 3 No. 11 Nov. 2005

the user should manually power on the PDA and thenoperate the WLAN middleware to establish wirelessconnections and execute applications. The details of
this operation mode depend on the user’s circumstances.
4. Examples
Some examples of system usage are shown in Fig.
4. We assumed that three WLAN profiles were registered in the WLAN middleware: one for a home network and two for public WLAN service providers (Aand B). Their priorities are set in this order. The network information, authentication information, andapplications are also registered.
When using the PDA at home, the user should
power on the PDA by hand because no RFID tag isused at home. The WLAN middleware detects theaccess point at home and then connects to the WLAN
network, executes applications, downloads content,
and powers off the PDA automatically. If the PDA isalready powered on, this automatic process is initiated by operating the WLAN middleware. After the
automatic process, the user can browse the received
content.
Next, when the user goes to work, he keeps his PDA
in his bag with its power off. When he passes a ticket
gate in a railway station that is within the service area
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Three WLAN profiles and their applications are registered as follows:(1) Home access point: e-mail(2) WLAN service provider A: e-mail and news
(3) WLAN service provider B (roaming to A): e-mail and news

Home

Train station #1 (provider A)

FLET’S(1)

RFID tag(2)
Powered off
automatically

Carries PDA(powered off)

Powers on the PDA; accesses (1)and receives e-mail.

Poweredon by RFID

Connects to (2); receives e-mailand news

Train
Reads e-mail and news

Reads e-mail and news
Train

Train station #2 (provider B, roaming to provider A)(3)

RFID tag
Carries PDA
powered off

Powered off
automaticallyConnects to (3); receives
e-mail and news

OfficePoweredon by RFID

Fig. 4. Examples of RFID-based automatic area detection.

of the public WLAN service provider A, the RFID
reader receives the signal from the RFID tag mounted near the ticket gate and powers on the PDA. When
the WLAN middleware detects the PDA’s activation,
it automatically detects a WLAN access point of service provider A, establishes a connection to the
WLAN network, executes applications, receives con68

tent, and powers off the PDA. The user can browse
the content anytime on the train or at the office.
Next, when the user goes home and enters the service area of public WLAN service provider B, theRFID reader powers on the PDA in the same way as
for service provider A. It detects an access point ofservice provider B and moves on to the automatic
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execution part. In this case, the PDA can connect tothe network of provider A via a roaming service
while in the service area of provider B. To support
this function, authentication information for roaming
access to provider A is registered as a different
WLAN profile than that for service provider B. In thisway, the PDA can connect to the network of provider
A via the roaming service within the service area ofprovider B and execute the applications for roaming
access to provider A.
As described above, users can control WLAN connections and applications more flexibly for various
environments and use WLAN services more easily
than in existing services.
5. Future plans
To promote public WLAN services, we plan tocarry out field trials on our system and evaluate its
usability.

Masamitsu Nakura
Senior Research Engineer, Third Promotion
Project, NTT Access Network Service Systems
Laboratories, NTT Corporation.
He received the B.E. degree in electronic engineering from Tokyo Denki University in 1985.
Since joining the NTT Electrical Communication
Laboratories, Tokyo in 1985, he has been
engaged in R&D of a network control scheme forsatellite communication systems. Since 1995, hehas been engaged in R&D of wireless access systems. He is a member of the Institute of Electronics, Information and Communication Engineers (IEICE) of Japan.

Junichi Iwatani
Engineer, Third Promotion Project, NTT
Access Network Service Systems Laboratories.
He received the B.E. and M.E. degrees in electronics engineering from the University of Tokyoin 1994 and 1996. He joined NTT Wireless Systems Laboratories in 1996. He has been engaged
in R&D of high-speed WLAN systems, especially in the development of software for accesspoints and network interfaces for HiperLAN2based WLAN systems. He has also been engaged
in a WLAN joint experiment in Scotland. Hispresent research interests are in nomadic broadband wireless access systems. He is a member of
IEICE.

Hiroki Shibayama
Engineer, Wireless Access Systems Project,
NTT Access Network Service Systems Laboratories.
He received the B.E. and M.E. degrees in electrical engineering from the Science University ofTokyo in 1996 and 1998. In 1998, he joined NTT
Wireless Systems Laboratories. He has been
engaged in R&D of broadband wireless accesssystems. He received the Young Engineers
Award from IEICE in 2005. He is a member of
IEICE.

Hideaki Kimata
Senior Research Engineer, Third Promotion
Project, NTT Access Network Service Systems
Laboratories.
He received the B.E. degree in electronic engineering from Kitami Institute of Technology in
1987. He joined NTT Network Systems Development Center, Tokyo in 1988. Since then, he
has been engaged in the development of satellite
communication system and wireless access systems. Since 2001, he has focused on R&D ofwireless access systems. He is a member of
IEICE.

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