BOOK MANAGEMENT SYSTEM USING VARIOUS SENSOR NETWORKYuuki Uranishi, Muneyuki Sakata, Ismail Arai,
Yoshitsugu Manabe, Hideki Sunahara and Kunihiro Chihara
Graduate School of Information ScienceNara Institute of Science and Technology
8916-5 Takayama, Ikoma, Nara, 630-0192 Japan
E-mail: yuuki-u@is.naist.jp
ABSTRACTThis paper proposes a system for managing users and books
in a room using various sensors. The proposed system consists of an RFID (Radio Frequency Identification) sensor,a non-contact IC card sensor and camera sensors. When auser enters a room, he/she is identified using IC card, and a
tracking process by camera sensors starts at the same timeof the identification. Users in the room are tracked by multiple camera sensors. Each book has an RFID tag, and an
RFID sensor is attached to a bookshelf. An existence ofthe books is observed by the RFID sensor. In addition, auser who takes out or returns the book can be recognizedby the camera sensors. A prototype was implemented, andthe system has demonstrated that the users and books wereobserved without cumbersome procedures.
Keywords: Book management, Sensor network, RFID, ICcard, Camera sensors
1. INTRODUCTION
Books in existing libraries are managed manually by librarians when the books are taken out or returned. The works
are expensive labor for the librarians, and the collections are
missing easily. It is highly desirable to manage the collections without increasing the works of the librarians.
To manage the books certainly, several book management systems have been proposed. A Radio Frequency Identification (RFID) technology is one common technology for
managing books automatically [1][2]. Each book has a unique RFID tag and an RFID tag reader is installed at acounter or gates. The book is checked at the counter or thegates. Such RFID systems have been introduced in many
libraries [3]. However, the conventional systems check only
the books. And the books are checked only when they havebeen taken out or brought into the library at the counter or
the gates. To check the books more certainly, it is desirable
that people in a room is observed at the same time in addition to the books, and the books are observed continuously
while the books are in the room.
We propose a novel book management system without
any procedures for checking out books. The proposed sysThis research is partly supported by 21st Century Center Of Excellence (COE) Program “Ubiquitous Networked Media Computing” of Nara
Institute of Science and Technology (NAIST).

tem consists of non-contact IC card sensors and camera sensors in addition to the RFID sensor (Figure 1). A user has an
IC card corresponding to the unique ID. The user is identified using the IC card when the user enters a room. AnRFID sensor is attached to each bookshelf. When a displacement of the books is detected by the RFID sensor, theRFID node refers who is in front of the bookshelf to thecamera sensor. The books are observed continuously in theproposed system. Therefore, books are managed more certainly. A framework of the proposed system is describedin this paper. In addition, a prototype is implemented anddemonstrated in multiple situations.

2. BOOK MANAGEMENT SYSTEM USING RFID
Several methods have been proposed for managing books
automatically and certainly. RFID is one of the commontechnologies for managing books in libraries [1][2][4]. Eachbook has a unique RFID tag, and an RFID sensor is placed
at a checkout counter or gates. The books are checked automatically when a user goes through the counter or the gates.
Because the conventional systems only check the books, auser who takes out and returns books should be checked using other technologies. In addition, the books are checked
only when they have been taken out or brought into the library. It implies that the books are checked manually by thelibrarians, therefore the conventional methods would not reduce the labor for the librarians completely. And it is difficult that the books are managed strictly using the conventional methods. To manage the books more certainly in libraries, we propose a book management system to fulfill
following requirements using an IC card sensor and camera
sensors in addition to the RFID sensor:• Users are identified automatically and only one; theidentified information are used in the other actions.
• Books are checked continuously while in a room, notonly checked at gates,• Displacements of the books are observed without any
procedures for users and librarians.

(a)Fig. 1. An overview of the proposed system. The proposedsystem consists of an IC node, an RFID node and camera
nodes. Each user has an IC card to identification, and eachbook has an RFID tag. Users are tracked and books are managed automatically, and user can take out or return books
without procedures.

3. PROPOSED SYSTEM
Figure 1 shows an overview of the proposed system. The
system consists of three kinds of nodes: an IC node, a camera node and an RFID node. Each node contains a sensor
and a computer basically, and they form a sensor network.
Processing on each node of the system is described below.
3.1. User Identification Using IC Card Sensors
Nowadays, non-contact IC card is widely used for electronic
identification, such as an admittance control system. In the
proposed system, the non-contact IC card sensor is used toidentify users when the users enter a room. Figure 2 shows
an example of the IC node. The IC node consists of a display in addition to an IC card sensor and a computer asshown in Fig. 2 (a). The user is identified by touching theuser’s IC card to the sensor (Fig. 2 (b)).
3.2. User Tracking Using Camera Sensors
Users in the room are tracked using camera nodes. A background subtraction method is used to track the users in combination with an inter-frame subtraction.

(b)

Fig. 2. A configuration example of an IC card sensor node.
The sensor is placed nearby the entrance for controlling admittance. (a) The IC node consists of an IC card sensor, acomputer and a display to show information. (b) When theuser touches the IC card to the sensor, the system identifies
and admits the user.

3.2.2. Update a background image
To adapt the tracking method to variable environment, abackground image is updated dynamically. The captured
image is divided into two regions: a region including a moving object, or not. The region including a moving object is
extracted using inter-frame subtraction (Fig. 3 (a)). It is assumed that the region not including the moving object is abackground region, and the background image is partly updated every frame (Fig. 3 (b)).
3.2.3. Estimate a geometric location of the user
A geometric location of a head of the user in the room isestimated from the extracted region as shown in Fig. 3 (c)and (d). For the estimation of the location, it is assumed thatthe pixel which has the smallest value of v (e.g. The marked
pixel in Fig. 3 (d)) is the top of the head, and the users’height is assumed as a fixed height. Reference points in theroom are given at the fixed height point in advance (Fig. 3(c)). The reference points are projected onto the captured
image. The geometric location of the user is estimated byinterpolation using the nearest three points on the captured
image as shown in Fig. 3 (d).
3.3. Book Observation Using RFID Sensors

3.2.1. Extract and track user regions
The users are tracked using camera nodes, and trajectoriesof the users are recorded. Figure 3 shows an example oftracking and estimating the position of the users. The node
starts tracking when the user is identified by the IC card
sensor. A background subtraction method is employed to
extract user regions in combination with an inter-frame subtraction. A region of a user is extracted using backgroundsubtraction and labeled. And a gravity of the user region istracked using a nearest neighbor method.

RFID nodes are placed to each bookshelf. Figure 4 shows
an example of implementation. An RFID sensor is attachedto the bookshelf as shown in Fig. 4 (a). Each book has aunique RFID tag (Fig. 4 (b)) and the books are observed
automatically by checking a reply from RFID tag.
The RFID node queries the tags on the books once forevery time interval. In case that a book does not reply andthe book has replied the previous query, it is assumed thatthe book is taken out at that time. Meanwhile, if it replies
newly then the book is returned to the bookshelf.

(a)

(b)

(c)

(d)

Fig. 3. An algorithm for tracking users in a room. (a) Moving objects are extracted using inter-frame subtraction method.
(b) A background image which is made dynamically. The captured image is divided into two regions: a region including
moving objects or not. The region not including any moving objects is assumed as a background. The background image ispartly updated every frame. The background image is used for extracting user regions. (c) The room is calibrated in advance,and reference points are given at fixed height (170 centimeters in this case). The reference points are used to estimate theusers’ geometric location. (d) An example of the user tracking. The reference points are imposed onto the camera image.
The geometric location of the user is estimated using the nearest three points from the user region.

3.4. Cooperation of Sensors
Figure 5 is a data-flow of the system. A procedure of book
management is explained based on Fig. 5.
At first, a tracking process is started by camera whena user touches to IC card sensor (1). And a camera node
refers the user ID of the user who has touched to the IC card
sensor to associate the user ID with the captured image ofthe user (2), the camera node keeps tracking the user using
multiple camera images. When books are taken out froma bookshelf or returned to the bookshelf, the RFID sensor
detects a displacement of the books. Then, the RFID noderequests the user ID of the user who is in front of the bookshelf to the camera node (3). At last, a series of events isadded to a history database (4) and the managing procedure
is completed automatically.
We implement the communication part of this system
by utilizing PIAX (P2P Interactive Agent extensions) [5]which is a framework to develop P2P applications. It integrates mobile agent based messaging and P2P discovery
mechanisms transparently. The mobile agents are written
in a Java library based on Aglets [6]. And, developers canchoose any kind of P2P network to construct systems. We
implement IC nodes, RFID nodes and camera nodes as mobile agents on PIAX. When they start communicating, acallAgent function in Java codes is called with some arguments as transmission data as shown in Fig.5. If the called
node has a reply, the sender can get the reply from the return value of the function. So, developers can construct a
distributed system with less difficulty to implement a communication part of a system. Since it is difficult to implement all parts of this book management system in Java, weonly write Java codes for a communication part. Communications between a node reading application and a mobileagent deal with socket protocols through a loopback device
IP address.

(a)(b)Fig. 4. An example of RFID-installed bookshelf and tagattached book. (a) In this case, an RFID sensor is set toa side wall of the bookshelf. Appropriate location of thesensor depends on a characteristic of the sensor. (b) Eachbook has a unique RFID tag, and the books are observed
automatically.

Despite increasing nodes, PIAX has P2P network architecture to enable scalability and search nodes rapidly. Anode on PIAX can search other nodes by given name orsome range of location. Even if some nodes have changed
their own IP addresses, a node can search other nodes. Unlike that, in conventional distributed systems, all nodes constantly had to know their IP addresses each other. So, developer can construct distributed system with less cost because they do not have to concern some network managements. Now, PIAX has mainly two types of P2P networkthat are DHT (Distributed Hash Tables) [7] and LL-Net [8].
P2P nodes can search other nodes by exactly matching withgiven name. So, if all nodes have a common rule for naming nodes, they can search other nodes rapidly. LL-net set
nodes on the P2P network based on their locations. It’s useful if sensors are mainly named by location (Ex. IC node“at the entrance”, or Camera node “on the wall”). So, wechoose LL-net.

Fig. 5. Data-flow of the proposed system. A tracking process starts when a user is identified by his/her IC card. Anda camera node refers a user ID to an IC node to associate
the user ID with the user captured by the camera sensor.
The next event is triggered when some books are taken outor returned. an RFID node refers a user ID to the camera
sensor node, because the people who is in front of the bookshelf is tracked by the camera sensors. And then the event
is added to a history database.

Table 1. Devices for the prototype.
DeviceModel Number
RFID Reader Unit
OMRON V720-HS04
RFID Sensor
OMRON V720S-BC5D4A
RFID TagOMRON V720S-D13P01
IC Card Format
SONY FeliCa [9]IC Card Sensor
SONY PaSoRi RC-S320

4. DEMONSTRATION AND DISCUSSION
A prototype was implemented to demonstrate the proposedsystem. Table 1 shows devices which are employed for theprototype.

4.1. Demonstration Environments
The prototype consists of a single bookshelf, a single RFID
tag sensor, an IC card sensor, two camera sensors and a history database. In addition, the prototype has a terminal toshow a status of books. Figure 6 (a) shows an overview ofthe prototype. The history database has a table as shown in
Table 2. The time interval of a query by the RFID sensor is
1 second, and the size and the framerate are 720×480 pixels
and 10 frames per second, respectively. The prototype wasdemonstrated in three environments: in our laboratory, in aconvention hall and a lobby of an office. Each space for thedemonstration is approximately 7 × 2 meters. Figure 6 (b)shows an example of a result in the laboratory. In addition,
another configuration of the prototype is shown in Figure 7.

Table 2. A table structure on the history database.
NameSupplement
rfid
A unique ID of the bookidm
A unique ID of the user who transport
the book
starttime A time when the user is started to track
endtimeA time when the book is taken out
or returned
state
The book is in the bookshelf (true)or not (false)
trajectory A tracked path of the user
snapshot An image taken when the book is moved

4.2. Discussion
A limitation and problems of the proposed system are discussed below.
4.2.1. Problems of Camera Sensors(a)First, our prototype could not estimate the accurate positionof users because of our two assumptions. In the practicalscene, each user’s height is variable and the head point cannot be fixed at a point which has the smallest value of v
in the extracted region of the image. Second, the present
tracking method fails to track if a user is occluded by otherusers or objects. Such occlusions are unavoidable problems
in a real library. Improved methods, such as usage of stereo
cameras, a model-based tracking method [10], a method using body parts [11] and color statistics-based method [12]are highly desirable.
4.2.2. Flicker of the RFID Sensor
Using the prototype, some displacements of books were
not detected correctly due to flickering of the RFID sensor. There are at least two factors to flicker: a position
and a sidelobe characteristic of the RFID antenna. It wasdifficult to check the tags when the RFID antenna was set
vertically from the RFID tags. Furthermore, the RFID antenna had a flicker when the book passed through a sidelobeof the antenna. The flicker leads to false detection of thedisplacement of the books. Therefore, a flicker reduction
mechanism must be implemented.

(b)Fig. 6. A prototype system. (a) An overview of the prototype. the prototype consists of a single bookshelf, a single RFID tag reader, an IC card reader, two cameras andservers. Five tag-including books were prepared for thedemonstration. (b) A screenshot of the viewer terminal. Theviewer shows the user who has taken or returned a book, atrajectory of the user, and the book which has taken or returned. And a snapshot of the user is captured and shown.

5. CONCLUSION
In this paper, a novel book management system has beenproposed. In the proposed system, an IC card sensor camera
sensor is employed in addition to the RFID sensors. Thesesensors are in a sensor network and they work jointly. A
prototype demonstrated that the proposed system managed
book without cumbersome procedures for users and librarians, and the books were observed continuously unlike conventional management systems.
Future work will aim at implementing user-tracking methodwith higher accuracy and flicker reduction method. And weare planning to replace IC sensor by a gate-type sensor to
identify users. In addition, it is desirable that the proposedsystem is demonstrated and evaluated in larger spaces andpractical libraries.
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Fig. 7. Another configuration of the prototype. The prototype was demonstrated in a convention hall. Captured images were not stable due to illumination changes.

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