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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Reusability and hierarchical simulation modeling of communication systems for performance evaluation

Mrabet, Radouane 12 June 1995 (has links)
<p align="justify">The main contribution of this thesis is the emphasis made on the reusability concept, on one side, for designing a simulation environment, and on the other side, for defining two different levels of granularity for reusable network component libraries.</p> <p align="justify">The design of our simulation environment, called AMS for Atelier for Modeling and Simulation, was based on existing pieces of software, which proved their usefulness in their respective fields. In order to carry out this integration efficiently, a modular structure of the atelier was proposed. The structure has been divided into four phases. Each phase is responsible of a part of the performance evaluation cycle. The main novelty of this structure is the usage of a dedicated language as a means to define a clear border between the editing and simulation phases and to allow the portability of the atelier upon different platforms. A prototype of the atelier has been developed on a SUN machine running the SunOs operating system. It is developed in C language.</p> <p align="justify">The kernel of the AMS is its library of Detailed Basic Models (DBMs). Each DBM was designed in order to comply with the most important criterion which is reusability. Indeed, each DBM can be used in aeveral network architectures and can be a component of generic and composite models. Before the effective usage of a DBM, it is verified and validated in order to increase the model credibility. The most important contribution of this research is the definition of a methodology for modeling protocol entities as DBMs. We then tried to partly bridge the gap between specification and modeling. This methodology is based on the concept of function. Simple functions are modeled as reusable modules and stored into a library. The Function Based Methodology was designed to help the modeler to build efficiently and rapidly new protocols designed for the new generation of networks where several services can be provided. These new protocols can be dynamically tailored to the user' s requirements.</p>
2

A modular approach to the automatic design of control software for robot swarms: From a novel perspective on the reality gap to AutoMoDe

Francesca, Gianpiero 21 April 2017 (has links)
The main issue in swarm robotics is to design the behavior of the individual robots so that a desired collective behavior is achieved. A promising alternative to the classical trial-and-error design approach is to rely on automatic design methods. In an automatic design method, the problem of designing the control software for a robot swarm is cast into an optimization problem: the different design choices define a search space that is explored using an optimization algorithm. Most of the automatic design methods proposed so far belong to the framework of evolutionary robotics. Traditionally, in evolutionary robotics the control software is based on artificial neural networks and is optimized automatically via an evolutionary algorithm, following a process inspired by natural evolution. Evolutionary robotics has been successfully adopted to design robot swarms that perform various tasks. The results achieved show that automatic design is a viable and promising approach to designing the control software of robot swarms. Despite these successes, a widely recognized problem of evolutionary robotics is the difficulty to overcome the reality gap, that is, having a seamless transition from simulation to the real world. In this thesis, we aim at conceiving an effective automatic design approach that is able to deliver robot swarms that have high performance once deployed in the real world. To this, we consider the major problem in the automatic design of robot swarms: the reality gap problem. We analyze the reality gap problem from a machine learning perspective. We show that the reality gap problem bears a strong resemblance to the generalization problem encountered in supervised learning. By casting the reality gap problem into the bias-variance tradeoff, we show that the inability to overcome the reality gap experienced in evolutionary robotics could be explained by the excessive representational power of the control architecture adopted. Consequently, we propose AutoMoDe, a novel automatic design approach that adopts a control architecture with low representational power. AutoMoDe designs software in the form of a probabilistic finite state machine that is composed automatically starting from a number of pre-existing parametric modules. In the experimental analysis presented in this thesis, we show that adopting a control architecture that features a low representational power is beneficial: AutoMoDe performs better than an evolutionary approach. Moreover, AutoMoDe is able to design robot swarms that perform better that the ones designed by human designers. AutoMoDe is the first automatic design approach that it is shown to outperform human designers in a controlled experiment. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished
3

Approche méthodologique de la mise en place d'un réseau multiservice

François, Denis 13 September 1994 (has links) (PDF)
L'intégration des fonctions techniques urbaines permet d'envisager à la fois un développement qualitatif et quantitatif des prestations de services aux citadins, et une meilleure efficacité globale de l'organisation technique locale. Elle repose sur l'échange d'informations entre les services techniques grâce à un réseau de télécommunications partagé. Divers projets de mis en place de réseaux partagés ont existé en France à partir de 1987. Constatant d'une part l'intérêt présenté par l'intégration pour les politiques urbaines locales actuelles, et d'autre part le manque de réussite de ces initiatives, notre objectif dans ce travail est d'apporter une réponse globale au problème de la mise en place d'un réseau partagé pour l'intégration des fonctions techniques urbaines. Cela consiste à identifier les causes des problèmes et déterminer leurs remèdes. Nous avons recensés six collectivités locales (Besançon, Gardanne, Nîmes, Montpellier, Nancy et Paris) qui ont été le siège de tels projets. Grâce à la connaissance du contexte général dans lequel doit naître tout projet de ce type (Partie A), il est plus aisé d'expliquer les écueils mis en évidence comme s'étant opposés à la réussite des divers projets (Partie B). D'une part ces écueils tiennent au manque de référence, tant réelle que conceptuelle, relative au réseau partagé et à l'intégration, ils tiennent d'autre part à la difficile conduite d'un projet multi-acteur et innovant Proposé comme pouvant servir de référence conceptuelle à des projets futurs, un modèle générique de réseau pour l'intégration des fonctions est présenté. Le réseau multiservice - RMS - est une plate-forme télé-informatique intégrant des modules autonomes. Proposé comme pouvant servir de guide aux partenaires engagés dans la définition des caractéristiques d'un RMS spécifiquement local, (répondant au projet local d'intégration), une méthode de conception est présentée. Elle conduit à l'élaboration du Schéma Directeur du RMS.
4

Heterogeneous Networks: from integration to mobility

Qachri, Naïm 16 September 2015 (has links)
Français:La notion de réseaux hétérogènes correspond à l’intégration de plusieurs technologies de transmission de données sans-fil dans le but d’accroitre la qualité de service des communications dans les réseaux mobiles.Historiquement, les mécanismes de sécurité des réseaux mobiles et sans-fil ont été largement focalisés sur la protection d’équipement utilisateur au niveau du dernier saut de communication et sur base d’une connectivité simple et unique. Cette connectivité, réduite à sa plus simple expression, a restraint le développement des protocoles de sécurité à des protocoles bi-parties, qui couvrent l’authentification des équipements utilisateurs et le chiffrement sur des communicationsLes mécanismes de sécurité et de cryptographie ne sont donc pas suffisants pour protéger correctement et efficacement des connections parallèles ou leur mobilité au sein de réseaux hétérogènes. Le but de cette thèse de doctorat, à travers quatre contributions personnelles, est d’apporter de nouveaux mécanismes et protocoles de sécurité afin de protéger au mieux les réseaux hétérogènes:• La première contribution se focalise sur le développement d’une nouvelle primitive cryptographique pour la protection des transmissions sans-fil. La propriété principale de celle-ci est de protéger les trames en cas de capture. Cette primitive introduit, notamment, la notion de force brute probabiliste (ce qui veut dire qu’un attaquant ne peut pas choisir parmi différentes clés équiprobables laquelle est effectivement utilisée).• La seconde contribution propose un nouveau protocole pour gérer d’une manière sure et efficace la mobilité des équipements utilisateurs entre différentes technologies au sein de réseaux hétérogènes.• La troisième contribution couvre la gestion des clés maîtres des utilisateurs, embarqués au sein des cartes SIM, utilisées au sein des réseaux d’opérateurs mobiles. Nos protocoles et mécanismes automa- tisent des changements réguliers et sûrs de la clé maître, et ajoutent de la diversité dans la gestion des clés de sessions pour minimiser l’impact en cas de révélation de ces dernières (par le biais d’un vol de base de donnée, par exemple)• La quatrième contribution introduit un nouveau paradigme de connectivité pour les réseaux mo- biles basé sur des communications 1−à−n. Le paradigme redéfinit les frontières de sécurité et place l’équipement utilisateur au centre d’un groupe authentifié mobile. Par conséquent, le changement de paradigme mène à la création de nouveaux protocoles pour l’authentification, la gestion de la mo- bilité et la négociation protégées de clés afin de fournir une protection de bout en bout entre deux équipements utilisateurs ou plus. / English:Heterogeneous Networks (HetNets) is the integration of multiple wireless technologies to increase the quality of service of the communications in mobile networks. This evolution is the next generation of Public Land Mobile Networks (PLMNs).Mobile and wireless network security mechanisms have largely focused on the protection of the User Equipment (UE) within the last mile (the last hop of the communication in the chain of connected devices) and on single connections. The single connectivity has reduced the development of the security to two party protocols, and they cover the authentication of the UE to the mobile network and the encryption on a single channel based on homogeneous communications through a unique technology.The current security and cryptographic mechanisms are not sufficient to protect correctly, and efficiently, parallel connections or their mobility in HetNets. The purpose of the PhD Thesis is to bring new security protocols and mechanisms to protect HetNets.The contributions, that are brought by the thesis, follow the evolution of HetNets through 4 contributions by starting from the wireless transmissions to the largest frame of HetNets architecture:• The first contribution focuses on the development of an new cryptographic primitives for wireless transmissions. The main property is to protect the frame from eavesdropping. The primitive introduces the notion of probabilistic brute force (meaning that an attacker cannot decide among different keys which the used one).• The second contribution proposes a new protocol to manage efficiently and securely the mobility of the UEs between different technologies inside HetNets.• The third contribution covers the management of the master secrets, embedded within the Universal Subscriber Identity Module (USIM), in large PLMNs. Our mechanisms and protocols automate regular and secure changes of the master secret, and they add diversity in the management of session keys to minimize the impact of key leakages (in case of credential database theft, for instance).• The fourth contribution introduces a new connectivity paradigm for mobile networks based on one-to- many communications. The paradigm redesigns the security borders and puts the UE in the center of a mobile authenticated group. Therefore, the paradigm shift leads to new security protocols for authentication, mobility management, and secure negotiation to provide end-to-end encryption between two or more UEs. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
5

Reusability and hierarchical simulation modeling of communication systems for performance evaluation: Simulation environment, basic and generic models, transfer protocols

Mrabet, Radouane 12 June 1995 (has links)
<p align="justify">The main contribution of this thesis is the emphasis made on the reusability concept, on one side, for designing a simulation environment, and on the other side, for defining two different levels of granularity for reusable network component libraries.</p><p><p align="justify">The design of our simulation environment, called AMS for Atelier for Modeling and Simulation, was based on existing pieces of software, which proved their usefulness in their respective fields. In order to carry out this integration efficiently, a modular structure of the atelier was proposed. The structure has been divided into four phases. Each phase is responsible of a part of the performance evaluation cycle. The main novelty of this structure is the usage of a dedicated language as a means to define a clear border between the editing and simulation phases and to allow the portability of the atelier upon different platforms. A prototype of the atelier has been developed on a SUN machine running the SunOs operating system. It is developed in C language.</p><p><p align="justify">The kernel of the AMS is its library of Detailed Basic Models (DBMs). Each DBM was designed in order to comply with the most important criterion which is reusability. Indeed, each DBM can be used in aeveral network architectures and can be a component of generic and composite models. Before the effective usage of a DBM, it is verified and validated in order to increase the model credibility. The most important contribution of this research is the definition of a methodology for modeling protocol entities as DBMs. We then tried to partly bridge the gap between specification and modeling. This methodology is based on the concept of function. Simple functions are modeled as reusable modules and stored into a library. The Function Based Methodology was designed to help the modeler to build efficiently and rapidly new protocols designed for the new generation of networks where several services can be provided. These new protocols can be dynamically tailored to the user' s requirements.</p><p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

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