Reusable Framework for
Location-Aware Mobile Applications
Salah Eldwaib
Ericsson, P.O.Box 5307,Tripoli,
LIBYAN ARAB JAMAHIRIYA
+218 91 3120339
r.j.pooley@hw.ac.uk
Rob Pooley
Heriot Watt University
Edinburgh EH14 4AS, UK
+44 131 451 3367
r.j.pooley@hw.ac.uk

ABSTRACT
A fundamental dilemma in location-aware mobile applications is
how to determine their physical location. Because pervasive
computing is still immature, and its ubiquitous infrastructure is
not set to serve location-aware applications, much research has
been conducted in the last few years to use available technologies
to determine physical location. This paper describes the definition
and implementation of a generic location identification
framework which is reusable by most location-aware mobile
applications. A review of technologies for location determination
leads to the design of a Location Abstract Framework (LAF) to
implement different location sensing techniques under a common
Application Programming Interface (API). A Java Micro-Edition
(J2ME) implementation of LAF using Radio Frequency
Identification (RFID) based location sensing methods is described
Categories and Subject Descriptors
D.2.13 [Software Engineering]: Reusable Software – reusable
libraries
General Terms
Design, Standardization.
Keywords
Location aware, object oriented framework, J2ME, RFID, GPS.
1. INTRODUCTION
Sensing the current physical location is the major hurdle in
developing the location-aware applications
“A central problem in location-aware computing is the
determination of physical location. Researchers in academia and
industry have created numerous location-sensing systems that
differ with respect to accuracy, coverage, frequency of location
updates, and cost of installation and maintenance” [1].
National Research Council of National Academies (USA) said:
“development of innovative applications that use location
sensing will foster location-aware computing. Key research
opportunities include the development of common standards for
location-sensing application programming interfaces (APIs);
techniques for reducing the costs of deploying and managing
location-sensing infrastructure… Such an effort would be similar
to the early research efforts that led to the Internet and the Web”
[2].
Currently, application developers cannot find one API that
encapsulates all the location-sensing methods; they must develop
their own code for a specific method. This paper defines a
Location Abstract Framework (LAF) that can be used to support
all location-sensing requirements and techniques. LAF represents
a core location-sensing API interface.
Mobile Information Devices (MID’s) such as PDA’s and mobile
phones are the targeted platform. It is a challenge to make LAF as
portable and platform independent as possible, especially as
MID’s have a wide range of operating systems and features.
Section 2 reviews location sensing and mobile platforms. Section
3 outlines the “CADIES” project as a user for LAF and defines
user requirements for any similar project. Section 4 explains the
development model. Section 5 outlines the LAF Design, while
section 6 covers the system implementation, testing, and
integration with location-based applications. Finally section 7
summarises the achievements, and suggests future work.
2. BACKGROUND
2.1 Positioning Technologies
There are a few of different ways of sensing location. in use.
RFID or Radio Frequency Identification uses wireless radio
signals to transmit or reflect a unique serial number that
represents the ID of an object. The process of labeling objects
using RFID is called object tagging RFID systems are divided
into two types, active and passive. [3]
Active RFID Systems: the tags include power source (battery or
other) and transmit data stored on their chip. They have a read
range of 20-100 meters, much longer than the Passive tags. [4].
Passive RFID Systems: the tags reflect the radio waves (energy)
received from the reader, and have no power source or
transmitter; their range is a few centimeters to a few meters [4].
Global Positioning System (GPS) uses 24 NAVSTAR satellites to
provide accurate estimates of position, time, and speed of a GPS
receiver. It reads signals from four satellites or more, and
calculates the distance to each using the difference between the
signal sending time and arrival time [11]. It is available
worldwide, 24 hours a day, and gives 3-D positions. However, it
requires “line-of-sight” between the receiver and the reference
satellites; also objects nearby may cause “multipart interference”
[6], making it less reliable in urban areas and indoors.
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Mobility 2009, Sep 2-4, Nice, France Copyright © 2009
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Bluetooth is a short-range wireless technology, globally available,
and connecting a significant range of devices. WiFi (Wireless
Fidelity) is a wireless LAN protocol, developed in 1990 by the
IEEE 802 committee, as IEEE 802..
Researchers have used the signal strength of the WiFi access
points in a building to estimate the physical location [7].
However, products are proprietary . Also the signal strength is not
static. Research such as [8] and [9] has tried to increase accuracy.
Cellular networks, such as mobile phone networks, can provide a
location service, but generally available systems lack accuracy
and the error can be more that 1km depending on the cell size.
This allows only limited use, but recent work may change this.
We concluded that none of these approaches would work in all
likely conditions. Thus we decided to build a technology
independent framework to provide a single interface for location
dependent applications.
2.2 Development platforms
We were also faced with a choice of platform on which to base
our implementation. The systems below were considered.
J2ME or Java 2 Micro Edition is a small-scale version of Java 2
Standard Edition to suit constrained devices that have less
capability than normal computers. It runs on a small footprint
version of the Java Virtual Machine, the KVM. This makes it
highly portable. It is free for most mobile phones and PDAs.
Palm OS was one of the earliest platforms for applications on
Personal Digital Assistants (PDAs). It suffers from a lack of
portability, since it is a proprietary system, owned originally by
Palm Inc. It uses C++, but is not particularly easy to program. It
runs almost exclusively on Palm devices, although it is moving
towards a Linux kernel, which may make it more widely used.
.NET Mobile Framework is Microsoft’s proprietary platform uses
the C# programming language and runs only on Windows
compatible devices. It is attractive because it fits in the .NET
world, interoperating with PCs and other Windows machines. It
suffers from relatively high costs of development tools.
The framework was implemented using J2ME because of its
portability, and the fact that it is designed for small, and limited
devices. However, much of what was learned could be applied in
one of the other development environments above.
3. TARGET USERS
The intention of this paper is to define Location Abstract
Framework (LAF) for the location identification, and describe an
instance of LAF using one location identification methods such as
RFID. This means that the project can be used by two types of
users:
User Type 1: is a developer of location-aware mobile application
that wants to use this work as an API for location sensing.
User Type 2: is a developer that wants to add an implementation
of another location identification technique using LAF structure
to enrich the LAF package for location sensing.
3.1 CADIES as a User of This Project
CADIES is a location-aware virtual tour guide project in the
Computer Science department of Heriot Watt University. “Cadie”
is a Scottish term used to describe the boys who used to exchange
news and stories on the Royal Mile of Edinburgh’s Old Town.
The CADIES project uses a location-aware virtual tour guide on a
PDA or a mobile phone to tell the user stories about his/her
current location. Users can also add a story, or listen to comments
and recordings of previous visitors. CADIES provided a real
example of “User Type 1” of LAF. CADIES can act as “User
Type 2” as well if other location methods are added using LAF.
3.2 User Requirements
Developers of “Type 1” want LAF to provide an API which is:
• suitable for use in all handheld devices.
• able to represent the location in unified format,
independent of the location sensing method used.
• portable and platform independent.
Other requirements of developers of “Type 2” include:
• LAF and its data structure should be designed to
abstract all the different means of location sensing, to
simplify adding another technique for location sensing.
4. DEVELOPMENT
Currently, location-aware mobile application (LAMA) developers
have no one framework that encapsulates all location-sensing
methods.

Figure 1: Current situation of Location-Aware Applications
In Figure 1, location-aware mobile application (LAMA)-1 uses
GPS to identify its location. To do this, it needs to interface the
GPS receiver and get involved in all its operations such as
connecting and disconnecting to the receiver, waiting, receiving,
and parsing GPS data, and updating location information, as well
as handling I/O exceptions. Using these complex operations may
affect the main business of the application. Also LAMA-1 cannot
reuse this location-sensing as an interface to another location-
sensing method such as RFID, and needs a lot of work to add this.
Additionally, the previous effort is not enough to make LAMA-1
able to work on another device with a different operating system.
LAMAs need a common interface to handle location sensing for
mobile. This paper describes an appropriate solution.
Mobile Phone J2ME
PDA with WindowsCE OS
LAMA 1
(GPS Handling is part
of its business)
GPS
Receiver
RFID
Reader
LAMA 2
(RFID Handling is
part of its business)