Summarizing sensors data in vehicular ad hoc networks

International audienceThis article focuses on data aggregation in vehicular ad hoc networks. In such networks, sensor data are usually produced and exchanged between vehicles in order to warn or inform the drivers when an event is detected (e.g., accident, emergency braking, parking space released, vehicle with non-functioning brake lights, etc.). In the following, we present a solution to aggregate and store these data in order to have a history of past events. We therefore use Flajolet-Martin sketches. Our goal is to generate additional knowledge to assist drivers by providing them useful information even if no event is transmitted by vehicles in the vicinity

A scalable dynamic parking allocation framework

International audienceCities suffer from high traffic c ongestion of which one of the main causes is the unorganized pursuit for available parking. Apart from traffic congestion, the blind search for a parking slot causes financial and environmental losses. We consider a general parking allocation scenario in which the GPS data of a set of vehicles, such as the current locations and destinations of the vehicles, are available to a central agency which will guide the vehicles toward a designated parking lot, instead of the entered destination. In its natural form, the parking allocation problem is dynamic, i.e., its input is continuously updated. Therefore, standard static allocation and assignment rules do not apply in this case. In this paper, we propose a framework capable of tackling these real-time updates. From a methodological point of view, solving the dynamic version of the parking allocation problem represents a quantum leap compared with solving the static version. We achieve this goal by solving a sequence of 0-1 programming models over the planning horizon, and we develop several parking policies. The proposed policies are empirically compared on real data gathered from three European cities: Belgrade, Luxembourg, and Lyon. The results show that our framework is scalable and can improve the quality of the allocation, in particular when parking capacities are low

The parking allocation problem for connected vehicles

International audienceIn this paper, we propose a parking allocation model that takes into account the basic constraints and objectives of a problem where parking lots are assigned to vehicles. We assume vehicles are connected and can exchange information with a central intelligence. Vehicle arrival times can be provided by a GPS device, and the estimated number of available parking slots, at each future time moment and for each parking lot is used as an input. Our initial model is static and may be viewed as a variant of the generalized assignment problem. However, the model can be rerun, and the algorithm can handle dynamic changes by frequently solving the static model, each time producing an updated solution. In practice this approach is feasible only if reliable quality solutions of the static model are obtained within a few seconds since the GPS can continuously provide new input regarding the vehicle’s positioning and its destinations. We propose a 0–1 programming model to compute exact solutions, together with a variable neighborhood search-based heuristic to obtain approximate solutions for larger instances. Computational results on randomly generated instances are provided to evaluate the performance of the proposed approaches

Sharing with Caution: Managing Parking Spaces in Vehicular Networks

By exchanging events in a vehicular ad hoc network (VANET), drivers can receive interesting information while driving. For example, they can be informed of available parking spaces in their vicinity. A suitable protocol is needed to disseminate the events efficiently within the area where they are relevant. Moreover, in such a competitive context where each vehicle may be interested in a resource, it is crucial not to communicate that resource to each driver in the vicinity. Otherwise, those drivers would waste time trying to reach a parking space and only one of them would be fulfilled, which would lead to a poor satisfaction in the system. To solve this problem, we detail in this paper a reservation protocol that efficiently allocates parking spaces in vehicular ad hoc networks and avoids the competition among the vehicles. We have integrated our protocol within VESPA, a system that we have designed for vehicles to share information in VANETs. An experimental evaluation is provided, which proves the usefulness and benefits of our reservation protocol in both parking lots and urban scenarios. Besides, we present an in-depth study of the state of the art on this topic, that shows the interest and the originality of our approach

Opportunistic Data Services in Least Developed Countries: Benefits, Challenges and Feasibility Issues

International audiencefacilitator in establishing primary education, reducing mortality or supporting commercial initiatives in Least Developed Countries. The main barrier to the development of IT services in these regions is not only the lack of communication facilities, but also the lack of consistent information systems, security procedures, economic and legal support, as well as political commitment. In this paper, we propose the vision of an infrastructure-less data platform well suited for the development of innovative IT services in Least Developed Countries. We propose a participatory approach, called Folk-IS, where each individual implements a small subset of a complete information system thanks to highly secure, portable and low-cost personal devices as well as opportunistic networking, without the need for any form of infrastructure. In this paper, we focus on the exploitation and feasibility analysis of the Folk-IS vision. We also review the technical challenges that are specific to this approac

Accès aux données dans les systèmes d'information pervasifs

Le développement des réseaux sans fil et des dispositifs mobiles (ordinateurs portables, PDA communicants, capteurs, etc.) constaté ces dernières années entraine de profondes mutations des applications et des services proposés aux utilisateurs. Nous entrons aujourd'hui dans l'ère de l'informatique pervasive avec pour enjeu de proposer des services et de rendre les données disponibles n'importe où et n'importe quand. Le système d'information n'échappe pas à cette évolution et devient lui aussi pervasif. L'information y est stockée partout, dans différents formats et sur différents types de terminaux interconnectés. Notre travail se concentre sur les problèmes liés à l'accès aux données dans les systèmes d'information pervasifs. Ces systèmes, dits « ambiants », évoluent dans un contexte particulièrement dynamique du fait de la mobilité des utilisateurs et des sources de données qui peuvent apparaître et disparaître à tout moment. Les techniques traditionnellement utilisées pour accéder aux données, dans les bases de données réparties ou les systèmes pair-à-pair par exemple, sont ainsi totalement remises en cause. En effet, la mobilité des sources de données et les possibles déconnexions rendent impossibles la gestion et l'exploitation d'un schéma de placement décrivant la localisation des différentes sources de données accessibles. Dans ce contexte, nous proposons donc de nouvelles techniques d'accès dédiées aux systèmes d'information pervasifs. Plus précisément, nos contributions concernent : - Un modèle d'évaluation et d'optimisation de requêtes dans les environnements pair-à-pair hybrides, associant terminaux mobiles et serveurs fixes, adapté à la mobilité des terminaux et à leurs ressources restreintes (e.g., énergie) - Des techniques de partage d'informations dans les environnements pair-à-pair mobiles, où plus aucune infrastructure fixe n'est exploitable et où les échanges de données reposent sur des interactions directes entre les terminaux. Ces travaux ont été appliqués au contexte de la communication inter-véhicules. - Enfin, notre dernière contribution concerne la proposition de mécanismes d'auto-adaptation permettant à un évaluateur de requêtes de se reconfigurer dynamiquement en fonction des changements de contexte (e.g., connectivité, mobilité, autonomie, etc.), particulièrement fréquents dans les systèmes pervasifs. Nos travaux ont été réalisés dans le cadre de différents projets et ont conduit à la soutenance de plusieurs thèses de doctorat et masters recherche

Introduction : SoLoMo, de nouveaux enjeux pour la gestion des données

International audienc

Managing CORBA Objects with Dynamic Behaviour in a Directory

International audienceAbstract: At present, objects may be located on Corba (Common Object Request Broker Architecture [14]) platforms using either the naming service [15] or the trading service [17], both standardized by OMG (Object Management Group). By associating a name to a Corba object, the naming service helps users in retrieving a particular object managed by a remote server. The trading service allows, on its own, to localize objects according to the properties they have exported to the trader. Directory services, and particularly LDAP (Lightweight Directory Access Protocol [19]), the most famous directory in the world of the Internet, combine features provided by naming and trading services. Directory services provide advanced features to query directory entries on their names and/or their properties. This paper proposes a Directory Service relying on the LDAP naming model, adapted to the management of dynamic Corba objects, that is objects frequently updated. The directory service also proposes query facilities and a query evaluation model adapted to the management of distribution and possible failures induced by the integration of Corba objects in directories