1,721,022 research outputs found
Extended Erlang-B law for performance evaluation of radio resources sharing in GSM/(E)GPRS networks
No full textSensors networks : Application to the tracking of moving targets
No full textL’objet de cette thèse est l’étude et la mise en place de solutions pour des problèmes de poursuite de cibles mobiles en exploitant les réseaux sans fil. L’objectilf principal est le développement de solutions pour l’exploitation des petits drones dans des applications civiles. La sécurité de vol est un élément primordial. A l’instar des avions pilotés et en outre des capacités d'évitement de collision, l’identification, la localisation et le tracking des petits drones, sont des conditions sine qua non pour l'intégration de cette technologie dans l’espace aérien. Il faut donc pouvoir planifier des trajectoires pour les drones qui assurent d’une part une meilleur localisation, un meilleur tracking, et qui garantissent l'évitement d’obstacles et les collisions. Les pistes étudiées dans cette thèse sont des sujets d’actualités. Elles couvrent deux catégories principales de contributions : premièrement, la planification des trajectoires et le suivi des drones avec des missions de livraison de colis et de collecte de données, et deuxièmement, la détection d’intrusion dans une zone sensible par l’utilisation d’une flotte de drones. Les résultats montrent que l’intégration du segment drone aux réseaux terrestres sans fil présente une valeur ajoutée et pertinente et ouvre de nouvelles perspectives à l’utilisation de cette technologie dans le domaine civil.For decades Unmanned Aerial Vehicles (UAVs) are widely used in modern warfare for surveillance, reconnaissance, sensing, battle damage assessment and attacking. The benefits of UAVs include reduced cost and no warfighter risk. In fact UAVs use is increased by time,especially under the concept of the network centric operation environment and under the concept of revolution in military affairs. On the other hand, the UAVs technology which originates from military applications, arouse the interest of the civilian, and yet, the domestic use began with limited aerial patrols of the nation’s borders, disaster and law enforcement situation. Recently, these products have also been destined to the commercial market and have gained much attention. Although UAVs use is expanding, their level of automation, cooperation and integration in civil application is far from being efficient and the design principles of such cooperation, coordination and self-organization under an Ad-hoc networkof a multi-UAV still need intensive studies and remain an open research problem. In this thesis, the investigated tracks were drawn both from the literature review and from the news topics. Thus, they covered two main classes of contributions, first, path planning and tracking of drones with package delivery and data gathering missions, and second, intrusion detection in a sensitive area through the use of networked drones.The results show that the integration of the drone segment to the terrestrial wireless network presents a relevant added value and opens new perspectives to the use of this technology in the civilian realm
Increasing vehicles cooperative perception through enhanced CAM service
No full textDans la première partie de cette thèse, nous avons exploré les avantages de l’exploitation des capteurs embarqués pour élargir la prise de conscience du véhicule dans le contexte des communications coopératives. Par la suite, nous avons examiné la sensibilité des balises (CAM et ECAM) aux différentes topologies de mobilité des véhicules des scénarios urbains et autoroutiers pour différentes densités de trafic. De même, nous avons démontré l’importance de la portée de détection du capteur ainsi que différents modèles de perte de propagation sur la communication coopérative de CAM et ECAM grâce à des résultats de simulation étendus. Dans la deuxième partie de la thèse, nous avons proposé un mécanisme de relais de données, nommé (IRB), sur le module de transmission pour rediffuser les informations. Avant d’émettre sa balise, un véhicule intègre les informations, préalablement reçues via sa source de communication, à condition que le véhicule concerné soit disponible dans sa portée de communication. Les performances de ce schéma ont été vérifiées à l’aide de nombreux résultats de simulation. Enfin, dans cette thèse, nous avons introduit notre autre algorithme de prérogative, (DCPB), pour choisir efficacement le véhicule le plus approprié pour la transmission de la balise parmi les véhicules voisins. Cette méthode exploite la capacité du capteur à détecter plus d’objets comme source de son algorithme dynamique pour minimiser la contention sur le canal d’accès. Plus tard, nous illustrons l’efficacité de cet algorithme dynamique basé sur les priorités (DCPB) dans divers scénarios de véhicules grâce à des simulations pervasives.In the first part of this thesis, we explored the benefits of exploiting embedded sensors in enlarging the vehicle's awareness in context of cooperative communications. Subsequently, we examined the beacons (CAM and ECAM) sensitivity to the different vehicle mobility topologies of Urban and highway scenarios for various traffic densities. Likewise we demonstrated the significance of sensor detection range as well as different propagation loss models on the cooperative communication ofCAM and ECAM through extensive simulation results.The second part of thesis, we proposed a data relaying mechanism, named (IRB), on the transmission module to re-broadcast the information. Before transmitting its beacon, a vehicle incorporates the information, previously received via its communication source, provided that the related vehicle should be available in its communication range. The performance of this schemehas been verified with the help of extensive simulation results.Finally, in this thesis, we introduced our an other prerogative algorithm, (DCPB), to efficiently choose the most suitable vehicle for beacon transmission among the neighboring vehicles. This method exploits the sensor's ability of detecting more objects as a source of its dynamic algorithm to minimize the contention on access channel. Later we illustrate the efficacy of this priority-based dynamic algorithm (DCPB) in various vehicle scenarios through pervasive simulations
Algorithms for Tasks Offloading on Multiple Mobile Edge Servers
No full textLe déchargement de calculs est l’une des solutions les plus prometteuses pour surmonter le manque d e ressources au niveau des terminaux mobiles. Elle permet l’exécution d’une partie ou de la totalité d’une application mobile dans le cloud. L’objectif est d’améliorer les temps d’exécution et de réduire la consommation énergétique. Malheureusement, le cloud est généralement éloignés des équipements terminaux. Ce qui rend cette approche souffrir de délais importants et fluctuants. Cela est particulièrement problématique pour certaines applications pour lesquelles un temps de réponse réduit est nécessaire. Pour réduire ce délai d’accès, l’une des approches émergentes est de pousser le Cloud vers la bordure du réseau. Cette proximité permet aux applications mobiles de décharger leurs tâches et données vers un Cloud “local” ou “Edge Cloud”.Dans cette thèse, nous nous concentrons sur le déchargement de calculs dans une architecture de type mobiles (Mobile Edge Computing – MEC), composée de plusieurs serveurs de périphérie. Notre objectif est d’explorer de nouvelles stratégies de déchargement efficaces afin d’améliorer les performances des applications tant du point de vue délais de calcul que consommation énergétique, tout en garantissant les contraintes de temps d’exécution des applications. Notre première contribution est une nouvelle stratégie de déchargement sur plusieurs serveurs de périphérie. Nous proposons par la suite une extension de cette stratégie en incluant également le Cloud. Nous évaluons ces stratégies tant du point de vue théorique que pratique avec l’implémentation d’un middleware de déchargement. Finalement, nous proposons une nouvelle approche élastique dans le cas d’applications multitâches caractérisées par un graphe de dépendances entre les tâches.Computation offloading is one of the most promising paradigm to overcome the lack of computational resources in mobile devices. Basically, it allows the execution of part orall of a mobile application in the cloud. The main objective is to reduce both execution time and energy consumption for the mobile terminals. Unfortunately, even if clouds have rich computing and storage resources, they are usually geographically far from mobile applications and may suffer from large delays, which is particularly problematic for mobile applications with small response time requirements. To reduce this long delay, one of the emerging approach is to push the cloud to the network edge. This proximity gives the opportunity to mobile users to offload their tasks to “local” cloud for processing. An Edge Cloud can be seen as small data center acting as a shadow image of larger data centers. This geographical proximity between mobile applications and edge cloud means that the access delay can be greatly reduced, but affects also higher throughput, improved responsiveness and better scalability. In this thesis, we focus on computation offloading in mobile environment (Mobile Edge Computing - MEC), composed of several edge servers. Our goal is to explore new and effective offloading strategies to improve applications performances in both execution time and energy consumption, while ensuring application requirements. Our first contribution is a new offloading strategy in the case of multiple edge servers. Thenwe extend this strategy to include the Cloud. Both strategies have been evaluated theoretically and experimentally by the implementation of an offloading middleware. Finally, we propose a new elastic approach in the case of multitasking applications characterized by a graph of dependencies between tasks
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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