MOVILTOOTH: CONTEXT-AWARE SYSTEM FOR MOBILE

PHONES BASED ON BLUETOOTH TECHNOLOGY

Juan P. Pece, Carlos Fern

andez, Carlos J. Escudero

Facultad de Informatica, University of A Coru

Campus de Elvi

na s/n, A Coru

na Spain

Keywords:

Bluetooth, context-aware, position, location, mobility.

Abstract:

Nowadays the amount of accessible information across Internet is enormous. Context-aware systems try to

ﬁlter and to adapt that information to the environment of the user who requests it. This paper introduces a

context-aware system that uses the physical location of the request origin. The system is designed for mobile

devices using Bluetooth radio-frequency technology for data transfer and location system. The main feature

of the system is its low cost and simplicity.

1 INTRODUCTION

Fast development and penetration of mobile terminals

(phones and PDAs) are providing the necessary re-

sources to the user for retrieving information anytime

anywhere. Due to the inherent characteristics of mo-

bility of those systems, a line of research arises in a

natural way: context-aware systems (Chen and Kotz,

2000). From the ﬁrst systems, as Cyberguide (Long,

1996), to Bluepulse project (Bluepulse, 2004), tech-

nologies have been changing, but the objectives are

still the same: to provide local information based on

the surrounding neighbourhood.

Before mobile technologies, information was ex-

tracted from ﬁxed clients based on some limited para-

meters: date, time, kind of terminal, ip address, user

proﬁle, · · · However, when considering mobile termi-

nals, a new dynamic parameter appears: geographic

location. The introduction of location information

opens a huge variety of new features services. Users

at a speciﬁc place primarily use services based on in-

formation of their direct neighbourhood.

Location information is obtained from a system

that estimates a mobile terminal position by using dif-

ferent physical phenomena and technologies (High-

tower and Borriello, 2001). If we use the geometric

properties of the received signal paths, we can make

some triangulation to provide location. This tech-

nique is one of the most popular between location sys-

tems (Bahl and Padmanabhan, 2000),(Priyantha et al.,

2000). However, triangulation techniques need com-

plicated algorithms to estimate the position of a user.

There exist simpliﬁed techniques to provide this loca-

tion. For example, by using previously observed fea-

tures of the environment and/or the presence/absence

of some signal in a short range, can be enough to

provide support for a context aware service. On the

other hand, any of the mentioned techniques can be

used with different technologies: radio-frequency, ul-

trasound, optical, proximity sensors, ...

Moviltooth, the system introduced in this paper, is

based on a technology that allows the communica-

tion and, simultaneously, acts as a positioning system:

Bluetooth (SIG, 2001c). This technology is widely

extended and adapts itself very well to the context-

aware problems (Ferrandez, 2003). Bluetooth is a

low-cost radio-frequency solution that provides links

between mobile terminals and a network. Coverage

range of Bluetooth devices is between 10 to 100 me-

ters (10 meters in mobile terminals). That makes

Bluetooth a good and simple mechanism to be used

as positioning system, based on the proximity to an

access point whose position is previously determined.

Moreover, Bluetooth gives us independence from the

phone carriers, providing a free access network.

This paper is structured as follows: section 2 de-

scribes the features of the developed system, the re-

sulting architecture and some implementation details;

section 3 introduces a test scenario, illustrating the

way Moviltooth works, and, ﬁnally, section 4 is de-

voted to the conclusions.

2 SYSTEM FEATURES

Moviltooth was developed with the following features

in mind:

144

Pece J., Fernández C. and Escudero C. (2005).

MOVILTOOTH: CONTEXT-AWARE SYSTEM FOR MOBILE PHONES BASED ON BLUETOOTH TECHNOLOGY.

In Proceedings of the Second International Conference on e-Business and Telecommunication Networks, pages 146-149

DOI: 10.5220/0001415901460149

 SciTePress

• Simplicity and low cost. It is not necessary to

consider complicated algorithms to make triangu-

lation. Bluetooth network devices (network cards,

access points, · · · ) are low cost. Moreover, Blue-

tooth communication is free for the ﬁnal user.

• Common transport and location technology. Blue-

tooth technology allows us to use it for recovering

information and to estimate positions.

• User transparency. Users ask for information by

using a standard protocol (HTTP), without intro-

ducing any context information. Location system

does not require any user interaction.

In order to provide these features it is necessary to

solve three basic problems:

• Communication: The communication of the mo-

bile with the system is made through Bluetooth.

The system has several Bluetooth access points

(AP) distributed in the neighbourhood of places of

interest. This way, when a user, with its phone

and the Moviltooth application started, arrives to

a place of interest, it is connected to the closest

access point and sends a generic request of infor-

mation (i.e. a speciﬁc URL). The AP forwards the

request to the central server to which it is connected

by Internet or Intranet.

• Location: The user always gets connected to the

system across an AP, whose position is known. The

server will identify the AP originating the request

and, therefore, it will obtain its location (neighbor-

hood). To let server know which AP is the origin

of the request, a parameter associated to it is sent

to the server. In our case, it is transmitted the phys-

ical address of the AP. The server has a database

mapping the APs physical addresses to their loca-

tions. Speciﬁc information, adapted to the context

of location, is return as a response. Bluetooth is

used, therefore, to solve the location with a simple

system based on the proximity to an access point.

• Navigability: HTML language is very suitable to

send information to the phone. This language al-

lows to incorporate links that allow navigation be-

tween information. Information is generated by

a content management system implemented as a

Web application. The phone uses a Browser that

allows to display the HTML pages and to use

the links. For the development of the prototype,

cHTML (compact HTML) (Kamada, 1998) was

used. cHTML is a subset of HTML contemplated

by the W3C (World Wide Web Consortium), very

suitable to small devices as mobile phones.

2.1 Architecture

The proposed system consists of three hardware com-

ponents. The global architecture scheme achieved is

shown in ﬁgure 1

Figure 1: System’s architecture

2.1.1 Components

Next we explain the three hardware components and

their corresponding applications.

• Mobile phone: The main component of the mo-

bile phone application is a small web browser. This

browser uses Bluetooth to send and to receive the

information. It is written en J2ME (Java 2 Micro

Edition) and uses the standard Sun’s JABWT API

as Bluetooth protocol stack, (Klingsheim, 2004),

(Qusay, 2003), (Hui, 2004).

It looks for system access points and requests in-

formation when a connection is ready. Once it

has got connected to an AP, the user can navigate

trough the information using the links of the re-

ceived pages. It is not allowed to the user to in-

troduce URLs by himself, that means, it is only al-

lowed to go to the main page URL, that have infor-

mation depending on the location of that AP, then,

navigate across the links. It is not a question of de-

veloping a web browser but a context-aware system

with web interface, that makes use of a part of the

already existing technologies in the Internet envi-

ronment.

• Access Point: For the development of the proto-

type the AP was a PC with a bridge application. Its

objective is to act as a connector between the appli-

cation of the mobile, and the Web application.

It is always waiting for connections and, when it

receives one, it redirects the requests to the server

adding its physical address as a parameter.

Bridge application was written in C language and,

to access to the Bluetooth adapter, it uses blueZ

(Holtmann, 2003), the ofﬁcial Linux Bluetooth

protocol stack.

The design of the bridge application can be divided

in three parts:

– tohttp library: It contains the necessary functions

for exchange information with the Web applica-

tions server, using the HTTP protocol.

MOVILTOOTH: CONTEXT-AWARE SYSTEM FOR MOBILE PHONES BASED ON BLUETOOTH TECHNOLOGY

145

– tobt library: It contains the functions necessary

for the exchange of information with the browser

through Bluetooth, using the RFCOMM proto-

col.

– sicd daemon: It is the main function. It uses the

two previous libraries to act as a bridge between

mobile and server. Also, the ﬁrst time that is exe-

cuted, it has to be registered in the Bluetooth ser-

vices database of the device, to be visible from

other devices.

• Server: Server subsystem is a Web application that

provides the HTML content, according to the re-

quest and to the physical address, received from the

bridge (as a URL parameter).

It contains the information corresponding to the

different neighborhoods. The sub-set of HTML,

cHTML (compact HTML) was used to transmit the

information.

A XML ﬁle represents the map that relates the

Bluetooth address of every AP to its physical lo-

cation. The default URL of the Moviltooth appli-

cation corresponds with a JSP code that uses JSTL

tags read the content of the map described previ-

ously. Then, using the ”source” parameter that the

URL should include, it chooses the correct point in

the map and it conﬁgures the response. When AP

address does not correspond with any point of the

map, ”PAGE NOT FOUND” message is returned.

There are other parameters that can be used to gen-

erate the response. One possibility is to adapt the

information to the kind of target device, according

to its characteristics (screen size, multimedia capa-

bilities). Another possibility is to have a users data-

base and to adapt the information to the proﬁle of

each user.

2.1.2 Communication between subsystems

Once a connection has been established between the

mobile and the AP, the communication process begins

and it has the following steps:

1. When the user fetches a link in a page of the sys-

tem, the mobile sends the URL requested to the AP

using the Bluetooth connection. The ﬁrst time that

the user requests information, the application uses

a ﬁxed URL deﬁned by default.

2. When the AP receives a URL from the mobile, it

adds its physical address as parameter. Then, it

opens a socket against the server and it sends to the

server a HTTP request, with the above mentioned

URL.

3. The server receives the HTTP request, and

processes it. Then, it sends the adapted response

to the AP.

4. Finally, the AP receives the HTTP response (head

and content) and sends it to the mobile using the

Bluetooth connection.

Therefore, we have two communication process:

Bluetooth communication and HTTP communica-

tion.

• Bluetooth Communication: A Bluetooth connec-

tion is established between the mobile device and

the access point. This connection keeps opened

while the mobile is inside the radio of Bluetooth

coverage of the AP.

There are two kinds of information exchanged be-

tween the mobile and the AP: requests of pages

from the mobile to the AP (by using URLs) and

server responses (that includes HTTP head and

HTML content of the requested page) from the AP

to the mobile. Two protocols can be used for estab-

lishing the connection between the bridge applica-

tion and the browser of the mobile phone: L2CAP

(SIG, 2001a) and RFCOMM (SIG, 2001b). RF-

COMM was the selected protocol to be used in

Moviltooth. This protocol was developed to trans-

mit information as a stream, not by packets. Con-

sidering a stream between the two ending-points

of the connection, information is transmitted any

time from one side, and it is received on the other

side asynchronously. Moreover, it is guaranteed

the same order for reading and writing information.

Thus, the mobile sends a URL for the stream and

reads the response in the same stream, once the AP

has written it.

• HTTP Communication: A HTTP connection is

opened between the AP and the web server. The

Web application is installed in a Web application

server. HTTP connection is independent of the

Bluetooth communication, so it is not necessary to

develop anything special, just the web application.

2.2 Limitations

Since Moviltooth is in its ﬁrst realese, it presents two

main limitations:

First, the coverage range of Bluetooth mobile

phones is 10 meters. Although it is a good feature that

we use for the positioning system, it can be a problem

if we want to give Bluetooth coverage in a wide range.

The solution is quite simple: to place several APs in

each interesting place. Moreover, bluetooth APs are

not expensive.

Second the maximum number of active devices that

can be connected to an Ap at the same time is 7, due

to Bluetooth speciﬁcation (the maximum number of

devices in a piconet is 8). Again, if we place several

access points in each place of interest, we can provide

access to more users.

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146

3 TEST SCENARIO

In order to test our prototype system, we designed the

following test scenario. Two PCs, working as access

points, were installed in two laboratories. Bridge ap-

plication was running in both PCs. There was another

PC working as a server. We started the mobile appli-

cation near PC 1 in laboratory 1, and then we moved

to PC 2 in laboratory 2.

Figure 2: Screenshot

Figure 2 shows the phone screen when we are near

PC 1. Once connected, we can follow the ”View in-

formation” link and go to the location page. Access

point 1 is supposed to be in the tower of Hercules (a

Roman lighthouse of La Coru

na, Spain). We can see

the information about the tower by following the link

”More information”.

While reading, we move from position 1 to position

2. At this moment the system automatically detects

that the connection is disabled there. We have to press

”search AP” option. In about 10 seconds another AP

is detected. Once connected to this AP the system

will show us the page of the state house, as AP 2 is

supposed to be near the state house.

4 CONCLUSION

This paper introduced a context-aware system based

on Bluetooth technology for mobile phones, called:

Moviltooth.

Moviltooth was developed to provide a simply low-

cost context aware information system suitable for

mobile devices (cellular phones, in particular). Blue-

tooth was selected as the medium access technology,

since it provides at the same time transport and lo-

cation mechanisms. Moreover, its low cost, indepen-

dence of comercial networks and support in many mo-

bile devices, give a promising future of Moviltooth.

A Moviltooth user only needs a mobile device run-

ning a J2ME application. When it arrives close to a

place of interest, the device will connect with the sys-

tems, providing information adapted to that location.

ACKNOWLEDGMENTS

This work has been supported by the Xunta de Gali-

cia, grant number PGIDITSIN105002PR.

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