Abstract: In a vehicular ad hoc network (VANET), cars can exchange infor-
mation by using short-range wireless communications. Along with the
opportunities oered by vehicular networks, a number of challenges also
arise. In particular, most works so far have focused on a push model,
where potentially useful data are pushed towards vehicles. The use of
pull models, that would allow users to send queries to a set of cars in
order to nd the desired information, has not been studied in depth.
The main challenge for pull models is the diculty to route the dif-
ferent results towards the query originator in a highly dynamic network
where the nodes move very quickly. To solve this issue, we propose Geo-
Vanet, an anonymous and non-intrusive geographic routing protocol which
ensures that the sender of a query can get a consistent answer. Our goal
is to ensure that the user will be able to retrieve the query results within
a bounded time. To prove the eectiveness of GeoVanet, an extensive
experimental evaluation has been performed, that proves the interest of
the proposal for both rural and urban areas. It shows that up to 80% of
the available query results are delivered to the user.
Abstract: In the last decade, a number of wireless and
small-sized devices (e.g., PDAs, smartphones, sensors,
laptops, etc.) with increasing computing capabilities
have appeared in the market at very aordable costs.
These devices have started to be embedded in modern cars in the form of on-board computers, GPS navigators, or even multimedia centers. Thus, the vehicles
can carry useful information, acting as data sources for
other vehicles. Recently, some works have addressed
the problem of processing queries in such highly dynamic vehicular networks in order to share information
between drivers. The proposed query processing techniques usually rely on a push model. Hence, each vehicle
receives data from its neighbors and decides whether
they are relevant enough to be stored in a local data
cache. Then, the data may be used by a query processor to retrieve relevant data for the driver.
In this paper, we look at the problem from a broader
perspective and discuss the interest of multi-scale query
processing techniques in such context. The goal of such
techniques is to exploit, at the mobile device's level, different access modes (e.g., push, pull) and various data
sources (e.g., data cached locally, data stored by vehicles nearby, remote Web services, etc.) to provide the
users with results for their queries. We highlight the
most important challenges and outline some possible
approaches. We also present a prototype of a rst query
evaluator developed using the Microsoft LINQ API.
Abstract: This article focuses on intelligent transportation
systems and more precisely on inter-vehicle ad hoc networks.
A vehicular ad hoc network (VANET) is a highly dynamic
network, as the vehicles communicate using short range wireless
communications and can move very quickly. Thus, for example,
we can only rely on short interactions between the vehicles to
exchange information about relevant events.
In this article, we propose a dissemination protocol that
vehicles can use to share information by using vehicle-to-vehicle
communications. The dissemination approach considers the relevance
of the data, represented by what we call the encounter
probability, to decide when a rediffusion is needed. The protocol
is able to disseminate data about any type of event in the network
(e.g., available parking spaces, accidents or obstacles in the road,
information about moving objects such as emergency vehicles
that should get the right of way, etc.) by setting appropriate
weights for the different factors that affect the computation of
the encounter probability. An extensive experimental evaluation
shows the interest of the proposal: the vehicles receive the relevant
messages in time and the network overload is limited.
Abstract: The recent emergence of handheld devices
and wireless networks has provoked an exponential
increase in the number of mobile users. These users are
potential consumers of new applications, such as the
Location-Dependent Applications (LDA) examined in this
article. As their name implies, these applications depend
on location information, which is used to adapt and
customize the application for each user. In this article,
we focus on the problem of information localization,
particularly the evaluation of Location-Dependent Queries
(LDQ). Such queries allow, for example, a mobile user
who is in an airport to locate the closest bus stop to go to
the university. To evaluate these queries, the client
position must be retrieved. Often, positioning systems
such as GPS are used for this purpose; however, not all
mobile clients are equipped with such systems and these
systems are not well suited in every environments. To
remedy this lack, we propose a positioning solution based
on environment metadata, that can provide an
approximate client position, sufficient for evaluating LDQs.
This paper presents both the positioning system, and its
optimization with regard to minimizing response time and
economizing mobile device resources.
Abstract: The recent emergence of handheld devices and wireless networks has implied an exponential increase of terminals users. So, today, service providers have to propose new applications adapted to mobile environments. In this article, we describe a new class of distributed M-services called proximity applications. In such applications, two or more handheld devices, physically close to each other, can communicate and exchange data in a same communication area. These applications need a high degree of flexibility, for an easy and rapid application development. Based on the Hybrid Peer-To-Peer (P2P) software architecture, different problems such as scalability, deployment, security, reliability and information retrieval in M-services, can be more easily resolved. In this article, we focus on the information localization problematic in proximity applications. Existing localization solutions (naming services, trading services, etc.) are not well adapted to the dynamicity and the heterogeneity imposed in this environment. So, we propose a decentralized localization service relying on the directory service model and adapted to the management of numerous distributed resources. This service allows users to locate and discover information, particularly location based services retrieved in function of users location.
Abstract: The transportation domain brings particular needs dealing with the specificities of the environment (highly mobile, distributed, unstable network connection, ...). In this paper, we propose a first step in providing a dynamic adaptable framework responding to the non-functional needs of transportationâs applicative services. Among the most important services we can name positioning, time or communication capabilities. To achieve both this flexibility and automate context adaptation, we rely on a Service Oriented architecture and experiment our proposition on the inter-vehicular communication system, VESPA.
Abstract: This paper focuses on intelligent transportation
systems and more precisely on inter-vehicle ad hoc networks.
Such networks are highly dynamic due to the movements of the
vehicles and the short range of the wireless communications.
Thus, for example, we can only rely on short interactions
between the vehicles to exchange data about relevant events.
We propose a new dissemination technique for vehicles to
share information using V2V communications. Our goal is to
make possible the exchange of information between vehicles
when they encounter each other, taking into account the relevance
of the data to the drivers. The originality of our proposal
is that it relies on an encounter probability to disseminate data
about any type of event (e.g., available parking spaces, obstacles
in the road, information relative to the coordination of vehicles
in emergency situations, etc.) in the network.
Abstract: This paper focuses on intelligent transportation systems.
Specifically, we look at data management issues in intervehicle
ad hoc networks. Such networks are highly dynamic
due to the movements of the vehicles and the short range
of the wireless communications. Thus, for example, we can
only rely on short interactions between the vehicles. Consequently,
new data management techniques adapted to this
context are needed.
More precisely, we propose a new technique to estimate
the relevance of data to the drivers. The originality of our
proposal is that we identify and classify the different types
of information that may be shared on the roads (e.g., available
parking spaces, obstacles in the road, information relative
to the coordination of vehicles in emergency situations,
etc.). We then propose a unified solution to support
all those types of information. Our experimental evaluation
shows the feasibility and interest of our approach.
Abstract: The query service is the key element enabling users to identify
and access data or services. If the growth of mobility
in recent years makes it necessary to support different types
of queries (continuous, location dependent, spatio-temporal,
etc..), it has also resulted in the emergence of new and dedicated
evaluation and optimization techniques. These different
types of queries or techniques are useful and efficient depending
on the usage conditions in which the user is located.
Today, it is necessary to have, in pervasive environments, a
query service that adapts to context changes (application
constraints, user preferences, connectivity profile mobility,
etc.). In this paper we propose an architecture of a query
service dynamically adaptable to the context. This adaptability
is managed and controlled by an adaptation manager
by use of rules. Our solution not only allows the addition
and removal of new features dynamically, it also allows the
change of used evaluation techniques in order to use the
adapted one to the environment.
Abstract: VESPA (Vehicular Event Sharing with a mobile P2P Architecture)
is a system for enabling vehicles to share information
in vehicular ad-hoc networks (VANETs). The originality
of VESPA is to process and disseminate any type of
event (e.g., available parking spaces, accidents, emergency
braking, information relative to the coordination of vehicles
in emergency situations, etc.). The basic functions of
VESPA are both disseminating events to potentially interested
vehicles and evaluating their relevance once received in
order to determine, for instance, whether the driver should
be warned or not.
This paper concentrates on knowledge extraction in VESPA.
In particular, it focusses on how to exploit data exchanged
among vehicles to produce knowledge to be used later on
by drivers. Existing systems only use exchanged data to
produce warnings for drivers when needed. Then, data is
considered obsolete and is deleted. In contrast, we propose
to aggregate data once it becomes âobsoleteâ. Our objective
is to produce additional knowledge to be used by drivers
when no relevant data has been communicated by neighboring
vehicles. For example, by aggregating events it is
possible to dynamically detect potentially dangerous road
segments or to determine the areas where the probability to
find an available parking space is high.
Abstract: These last years, the evolution of nomadic terminals and mobile
networks has yield to the development of the ubiquitous
computing. In this context, actual query evaluation and optimization
techniques in distributed databases based on the
use of a global schema and a cost model are no more relevant.
Furthermore, a query processor deployed in this type
of environment must face a significant heterogeneity, in particular
mobile terminals, communication networks and different
data sources. In order to cope with this heterogeneity,
such service should have the capability to adapt itself dynamically.
In this paper, we describe the problems related
to query processing in mobile environment and the needs for
adaptability.
Abstract: Nowadays, execution environments of applications are more and more heterogeneous: from powerful servers to smart cards. In order to assume the heterogeneity and the portability of applications, the componentâbased model has emerged as a model to develop new distributed applications. Thus, these applications are built as an assembly of interchangeable software blocks. Nevertheless, the gain of adaptability that comes from the use of component does not stretch to non-functional services (such as transaction management, security, etc). So, we suggest complementing the existing solution by facilitating the adaptability of non-functional services to their environment. Therefore, we propose to design a non-functional service as composition of small components. Besides, it is possible to supply the most appropriate version of a non-functional service to an application. So, in our approach, the application is composed by assembling both business components and non-functional components.
Abstract: The recent emergence of handheld devices and wireless networks has implied an exponential increase of terminals users. So, today, service providers have to propose new applications adapted to mobile environments. In this paper, we propose and describe a new class of distributed applications called the proximity applications. In such applications, two or more handheld devices, physically close to each other, can communicate and exchange data in a secure way. Proximity applications rely on the use of both different mobile devices and heterogeneous wireless networks. Thus, these applications need a high degree of flexibility, for an easy and rapid application development. In this context, our purpose is to study the interest of the Hybrid Peer-To-Peer (P2P) architecture model use specially for the extensibility, the fault-tolerance management and the scalability of proximity applications. Moreover, thanks to this model, proximity applications can easily face to the heterogeneity of devices and networks.
