Adolfo Aumaitre, Vicente Carrillo and F. Javier Ortega
Escuela Técnica Superior de Ingeniería Informática, Avda. Reina Mercedes s/n, 41012, Seville, Spain
Keywords: Location-based services, radio, geo-referenced, algorithm.
Abstract: This article presents a geo-referenced and personalized radio system for mobile terminals that works over
wireless broadband networks. The architecture of the system allows the combination of thematic contents
that are chosen by the user and contents with local information that depends in the first instance on GPS
coordinates, velocity and direction of travel of the user and in the second instance on the preferences of the
user, who can configure its terminal according to its interests. The requesting, downloading and playing of
local information is managed by a predictive algorithm that takes into account not only the position of the
terminal or the preferences of the user but also other features as the area where the information must be
played and the loading time.
Positioning is used to find out the spatial location of
a person in terms of longitude, latitude and altitude.
There are some technologies for positioning, but the
most well-known is GPS (Global Positioning
System) that consists of 24 satellites that are in
medium Earth orbit transmitting signals. GPS
receivers take this information and use triangulation
to calculate the user’s exact location. The European
system, GALILEO, will be operative in 2011-12 and
will provide a higher precision.
Positioning is the key concept to develop
location-based services, which provide information
taking into consideration the position of the users.
There are many possible applications for location-
based services such as health care, navigation,
The first generation of located-based services
was not successful, but the apparition of low-cost
GPS receivers and new geographic content changed
dramatically the situation. Nowadays there are
highly successful devices such as GPS navigators.
In the other hand, the radio is the most
widespread communication mean. Another
important feature of radio is that users do not need a
high degree of attention, so they can develop other
activities while they are listening to radio. This
feature allowed the evolution of use cases from
static (a person listening to radio at home) to
dynamic (a driver listening to radio).
The combination of the location-based services
and the radio establishes the basis for a new service
of information and entertainment of general purpose.
A new generation of digital, geo-referenced and
personalized radio that overcomes the limitations of
the current standards of digital broadcasting (DAB),
taking advantage of the features of the bidirectional
transmission of data by packets (UMTS, HSDPA,
At present there are many works about location-
based services, but few of them deal with the
application of these services to a radio system.
I. Takei et al. proposed a position-adaptive
broadcasting system for mobile terminals. The
approach is similar to the one proposed in this
article, but their solution consists of broadcasting
summaries of local information to all the terminals.
Then every terminal selects which summaries are
going to be extended and downloads the complete
contents from the corresponding server. This
solution is not feasible in this problem because the
contents of the thematic channel are played
asynchronously in every terminal and broadcasting
all the summaries of advertising may overload the
This article presents a new radio system for
mobile terminals. It allows the combination of
thematic contents that are chosen by the user (in a
Aumaitre A., Carrillo V. and Javier Ortega F. (2007).
In Proceedings of the Second International Conference on e-Business, pages 157-161
DOI: 10.5220/0002109301570161
similar way to a radio channel) and contents with
local information that depends on the location,
velocity and direction of travel of the user. The
second section is an introduction to the system
architecture. The third section concentrates in the
algorithm used by the terminals to select the
contents that are played. The proposed algorithm is
an adaptation of Takei’s algorithm that fulfils the
requirements of the problem exposed in this paper.
The fourth section illustrates the functioning of the
algorithm by means of a simulation.
In this section there is a brief resume of the business
model that involves the providers, the customers and
the technological means that allow their
interactuation. To illustrate this, there will be
expounded some habitual use cases that the system
The profile of the customer consists of a person
or group of persons that carry a terminal that is
playing auditive information. There may be portable
terminals that can be carried by a person, for
example a small radio receiver, but the most usual
profile consists of a person that is travelling by car
(or some vehicle of that kind) and is listening to the
terminal that is installed in its car. The choice of this
profile as predominant is based on the high
percentage of drivers that listen to radio, due to their
capability for developing activities (in this case
driving a car) while are consuming auditive
information. Other means that integrate sound and
images are not so suitable for drivers because can
cause distractions that jeopardize the safety.
The system allows to the customers consuming
two kinds of contents: one of them is a thematic
channel. The information is sent from the server to
all the terminals that select the channel (in a similar
way to a radio channel), but the innovative aspect is
that the content is asynchronous. Every terminal can
play different parts of the content at the same time.
This feature is necessary because the second kind of
content, the advertising, is asynchronous too because
is dependent on the position of the terminal. If the
thematic channel was synchronous, there may be
lost of information produced when the thematic
channel was replaced by the ads. So the terminals
request the data from the server when they need to
play some information of the thematic channel. If
some ad is inserted, the terminal continues playing
the thematic channel at the point it was interrupted.
Related to the kinds of contents there are two
kinds of providers. One of them is the contents
provider, that provides data for the thematic channel.
The other is the ad provider, that provides the geo-
referenced advertising.
There must be some technological resources that
support all the system. First of all there must be a
server that stores the thematic content and the geo-
referenced advertising, must receive the requests
from the terminals and must send the corresponding
data to every terminal. Another component of the
system is the terminal. The main use case consists of
a personal radio that has capability of playing the
data sent from the server and requesting the
necessary data to the server, This terminal can be
configured with the preferences of the customer. For
example, the user may not be interested in listening
information relative to hotels. The secondary case of
use consists of the web interaction. The terminal
may access to internet and apply information
extraction techniques to look for specific
information. The data found is converted to auditive
information with a voice synthesizer. Finally, the
terminal must have the capability to extend the
information about one specific ad. This is necessary
because one geo-reference ad must be a resume of
the information to avoid overloading the network
with information that may not be interesting for the
customer. If the customer was interested in some ad,
by pressing a button he can obtain a more detailed
The communication between the terminal and the
server must be through a wireless wide band
network. Nowadays this technology is supported by
UMTS but there are incoming standards as HDSPA
and WiMAX that improve the speed of transmission
and support more users.
To illustrate the functioning of the system some
possible use cases will be explained.
The first case of use consists of a family that is
travelling by car through Guadarrama Mountains.
They choose the thematic channel “Discover
Madrid” and activate the traffic warnings. While the
presenter talks about the mountains, the local
festivals and monuments, there are inserted some
warnings about the traffic in the area and some ads
about services that can be found through the route.
The second case consists of the owner of a new
restaurant located near an office building. He wants
to attract more clients, so hires the service to insert
an ad during the hour previous to habitual lunch
time. The ad is played in a ratio of 500 metres
ICE-B 2007 - International Conference on e-Business
around the restaurant. If a customer is interested,
presses the button “action” of the terminal, and the
information is extended. The owner of the restaurant
pays a fee for the emission of the ad and another fee
for every person that pressed the button “action”.
The third case consists of a local radio station
that broadcasts programmes about the history and
curiosities of Madrid. This programmes are geo-
referenced and integrated in the system explained
above, inserting placements for advertising. The
benefits of the emission of advertising in those
programmes is shared with the local radio station.
This way, the local radio station increases its
benefits reusing contents that already owns.
Figure 1: Architecture of the system.
Bellow is a description of the algorithm that
manages the contents that are played by the terminal.
This algorithm is the responsible for switching the
thematic and the local information channels and for
requesting, downloading and playing the data that is
related to the coordinates of the portable terminal.
The map is divided into rectangular pieces called
quadrants. At the beginning, the algorithm loads
into memory the quadrant related to the GPS
coordinates where the terminal is. But from then on,
it is necessary to predict which quadrants will be the
next ones to be crossed by the trajectory of the
terminal to avoid the delay caused by loading into
memory one quadrant when the terminal is already
into it.
Every quadrant is crossed by four lines that are
parallel to its sides. The distance between the sides
of the quadrant and these lines depend on the speed
of the vehicle. The higher the speed of the terminal,
the longer will be the distance. If the trajectory of
the terminal crosses one of this imaginary lines, the
terminal loads into memory all the quadrants that are
adjacent to the sub-quadrant where the terminal
enters. For example, in figure 2, the terminal will
probably enter into the sub-quadrant Q
. If it
happens, the quadrant Q
is loaded into memory. If
the vehicle enters into the sub-quadrant Q
, then the
quadrants Q
, Q
and Q
will be loaded into
Figure 2: Division of the map into quadrants.
Every quadrant contains the data relative to the
position of the points of interest and their influence
ratios. If the vehicle enters into the area delimited by
one influence ratio, the information related to that
point of interest must be played by the terminal.
Depending on the direction of the vehicle the
algorithm calculates the intersection of the trajectory
of the terminal and the influence areas. If one
influence area is intersected, the loading ratio is
added to the influence ratio. The loading ratio
represents the time necessary for requesting and
loading into memory the information relative to one
point of interest. It is directly proportional to the
speed of the vehicle and depends on the volume of
the information and the loading of the network too.
When the vehicle reaches one loading area, the
terminal begins to download from the server the data
relative to the point of interest. When the vehicle
reaches the influence area, the terminal plays the
information that was downloaded.
Figure 3: Influence and loading areas.
If the vehicle changes its trajectory when is
outside of any loading area, the new intersections
must be recalculated and the new loading ratios
reconsidered. If the vehicle is inside a loading area
but outside the influence area and its new trajectory
does not intersect the influence area, the information
is downloaded from the server and stores it in a
buffer, but it does not play it.
There are some problems related to the overlapping
of influence and loading areas. The simplest
solution consists of storing the information in a
playing buffer. This way all the information relative
to the points of interest is played, but if there are
some overlapped areas the information relative to
one point may be played when the terminal is
outside its influence area. Another solution consists
of assigning priorities to the points of interest. The
information pills are stored in the buffer sorted by
priority but when they have to be played, if the
terminal is outside the influence area, the
information is not played and deleted from the
The algorithm for selection of contents has been
programmed in Java. A graphic interface has been
developed to show the results of the simulations.
The interface draws one quadrant with the position
of the vehicle, its trajectory, the position of the
points of interest and their influence and loading
Figure 4: Screensave from simulation.
To illustrate the functioning of the algorithm
some screensaves from one simulation are shown
bellow. The quadrant of the simulation contains
seven points of interest with their corresponding
influence ratios.
The vehicle begins at Avda. Reina Mercedes
street. Its trajectory intersects three influences areas,
so the loading ratio is added to the influence ratio of
the areas intersected, as shown in figure 4.
The vehicle follows the predicted trajectory, so
enters inside the loading area of the first point of
interest. At that moment the data relative to the point
is downloaded from the server and stored in the
playing buffer. In the figure 5, the vehicle is just
entering inside the influence area of that point. The
information stored in the buffer is played then.
Figure 5: Screensave from simulation.
The simulation continues and the vehicle enters
inside the influence area of a second point and the
data relative to that point is played too. But before
entering the influence area of the third point, the
vehicle turns to the left, as shown in figure 6. The
new intersections of the trajectory with the influence
area are calculated, and the corresponding loading
ratios added. Along this trajectory the vehicle
brakes, so the loading ratios decrease.
Figure 6: Screensave from simulation.
ICE-B 2007 - International Conference on e-Business
Finally the vehicle continues the predicted
trajectory through the street and crosses the
influence area of two points of interest more, so their
contents are played too.
Figure 7: Screensave from simulation.
The problem of contents selection in location-based
services is well-known and studied in the case of
mobile phones, but there are few works about the
same problem in radio systems. The dissemination
services for advertising or news services in mobile
phones scenes do not have to manage a big amount
of data. In the case of radio systems the quantity of
information that has to be sent is much higher, so the
architecture of the system has to be considerably
Even the existing works about radio systems
can not be applied to solve the problem exposed in
this article due to the asynchronous nature of the
data that should be played by the terminals. The
solution proposed in this paper for contents selection
is a modification of Takei’s algorithm that takes
into account the requirements exposed before.
This project is currently in progress and there
are many aspects that require further research,
specially the ones related with the architecture of the
This work has been partially funded by the projects
TIN–2004–07246–C03–03 and OG–136/06 P–
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