Actuellement, nous constatons une augmentation de demande de services vidéo sur les réseaux P2P. Ces réseaux jouent un rôle primordial dans la transmission de contenus multimédia à grande échelle pour des clients hétérogènes. Cependant, le déploiement de services vidéo temps réel sur les réseaux P2P a suscité un grand nombre de défis dû à l’hétérogénéité des terminaux et des réseaux d’accès, aux caractéristiques dynamiques des pairs, et aux autres problèmes hérités des protocoles TCP/IP, à savoir les pertes de paquets, les délais de transfert et la variation de la bande passante de bout-en-bout. Dans ce contexte, l’objectif de cette thèse est d’analyser les différents problèmes et de proposer un mécanisme de transport vidéo temps réel avec le provisionnement de la qualité de Service (QoS). Ainsi, nous proposons trois contributions majeures. Premièrement, il s’agit d’un mécanisme de streaming vidéo adaptatif permettant de sélectionner les meilleurs pair émetteurs. Ce mécanisme permet de structurer les pairs dans des réseaux overlay hybrides avec une prise en charge des caractéristiques sémantiques du contenu et des caractéristiques physiques du lien de transport. Nous présentons ensuite un mécanisme d’ordonnancement de paquets vidéo combiné à une commutation de pairs et/ou de flux pour assurer un transport lisse. Finalement, une architecture de collaboration entre les applications P2P et les fournisseurs de services / réseaux est proposée pour supporter un contrôle d’admission de flux. / There is an increasing demand for scalable deployment of real-time multimedia streaming applications over Internet. In this context, Peer-to-Peer (P2P) networks are playing an important role for supporting robust and large-scale transmission of multimedia content to heterogeneous clients. However, the deployment of real-time video streaming applications over P2P networks arises lot of challenges due to heterogeneity of terminals and access networks, dynamicity of peers, and other problems inherited from IP network. Real-time streaming applications are very sensitive to packet loss, jitter / transmission delay, and available end-to-end bandwidth. These elements have key importance in QoS provisioning and need extra consideration for smooth delivery of video streaming applications over P2P networks. Beside the abovementioned issues, P2P applications lack of awareness in constructing their overlay topologies and do not have any explicit interaction with service and network providers. This situation leads to inefficient utilization of network resources and may cause potential violation of peering agreements between providers. The aim of this thesis is to analyze these issues and to propose an adaptive real-time transport mechanism for QoS provisioning of Scalable Video Coding (SVC) applications over P2P networks. Our contributions in this dissertation are threefold. First, we propose a hybrid overlay organization mechanism allowing intelligent organization of sender peers based on network-awareness, media- awareness, and quality-awareness. This overlay organization is further used for an appropriate selection of best sender peers, and the efficient switching of peers to ensure a smooth video delivery when any of the sender peers is no more reliable. Second, we propose a packet video scheduling mechanism to assign different parts of the video content to specific peers. Third, we present a service provider driven P2P network framework that enables effective interaction between service / network providers and P2P applications to perform QoS provisioning mechanism for the video streaming.

L’un des défis majeurs dans la convergence des réseaux et des services vers la technologie IP est le maintien de la qualité de service (QoS) des flux audio/vidéo transmis sur des réseaux sans fil pour des utilisateurs mobiles et hétérogènes. Dans cet environnement, les services multimédia doivent faire face à plusieurs inconvénients engendrés par le manque de fiabilité d’un canal sans fil et son partage par plusieurs utilisateurs. Ces inconvénients sont accentués par l’hétérogénéité des terminaux de réception (capacité de décodage, espace de stockage, résolution d’affichage, etc.) qui doivent recevoir, décoder et afficher les flux multimédia. Afin d’assurer un accès universel aux services n’ importe où, n’importe quand et en utilisant n’importe quel terminal d’accès, les applications multimédia de nouvelle génération doivent interagir avec leur environnement pour, d’une part, informer les réseaux sous-jacents de leur besoins en QoS, et d’autre part, adapter dynamiquement leurs services en fonction des terminaux de réception et des variations intempestives des conditions de transmission. Dans ce contexte, nous proposons un nouveau système pour la transmission des flux audio/vidéo sur les réseaux 802.11 basé sur l’approche Cross-layer. Ce nouveau système, appelé XLAVS (Cross Layer Adaptive Video Streaming), communique activement avec l’ensemble des couches réseaux ainsi que le récepteur final pour déterminer l’adaptation optimale qui permet d’optimiser la QoS des flux audio/vidéo. Nos contributions se focalisent principalement sur les adaptations Cross-layer mises en œuvre par le XLAVS. Ces contributions sont organisées en deux grandes catégories : les adaptations ascendantes exécutées au niveau applicatif et les adaptations descendantes exécutées au niveau MAC 802.11. Dans la première catégorie, notre apport s’articule au tour de : (1) l’adaptation dynamique du débit vidéo en fonction du débit physique disponible dans le réseau 802.11 et (2) l’adaptation conjointe du taux de redondance FEC et du débit vidéo contrôlée par la puissance du signal et les taux de perte. Dans la deuxième catégorie, nous proposons deux mécanismes Cross-layer au niveau MAC 802.11 : (1) une fragmentation 802.11 adaptative pour trouver un compromis entre les pertes de paquets et l’overhead introduit par les couches 802.11 et (2) un groupage des images vidéo au niveau MAC pour permettre au flux vidéo d’avoir un accès au canal 802.11 proportionnel à son débit. / One of the big challenges in the convergence of networks and services to the IP technology is to maintain the Quality of service (QoS) for audio/video streams transmitted over wireless networks to heterogeneous mobiles users. In this environment, the multimedia services should face many shortcomings caused mainly by the wireless channel unreliability and its sharing among many users. These shortcomings are increased by the terminals heterogeneity (i.e. decoding capability, memory storage, display resolution, etc.) which should receive, decode and display the multimedia streams. In order to allow universal access to multimedia services anywhere, anytime and using any kind of terminal, the new generation of multimedia applications have to interact with their environment, on the one hand, to inform the underling network about their need in term of QoS, and on the other hand, to dynamically adapt their services according to the receiver terminal and the changing in network conditions. In this context, we have proposed a new Cross-layer based streaming system to transmit audio/video streams over 802.11 networks. This new system, called XLAVS (Cross layer Adaptive video streaming), actively communicates with all network layers and the end receiver to determine the optimal adaptation that optimize the QoS of audio/video streams. Our contributions focus mainly on the Cross-layer adaptations implemented on the XLAVS. These contributions are classified into two major categories: the bottom-up adaptations performed at the application level and the top-down adaptations performed at the 802.11 MAC level. In the first category, our proposals have revolved around: (1) a dynamic adaptation of video throughput according to the physical rate available in the 802.11 network and (2) a join FEC and video throughput adaptation steered by the signal strength and the loss ratio. In the second category, we have proposed two Cross-layer mechanisms at the 802.11 MAC level: (1) an adaptive 802.11 MAC fragmentation to find an optimal trade-off between the packet loss and the overhead introduced by the MAC layer and (2) a video frame grouping at MAC level that allows video stream to get access to the 802.11 channel proportionally to its throughput.

Les travaux développés dans cette thèse ont pour cadre général la mise en œuvre d’approches adaptatives permettant de faire évoluer la gestion du réseau en migrant d’une vue "centrée réseau" où l’on se contentait uniquement des paramètres issus du réseau lui-même, vers une vue "centrée utilisateur". Plus particulièrement, ces travaux se sont focalisés sur un des composants principaux de l’ensemble de la chaîne de traitement et de transport, celui de la sélection de la meilleure interface réseau embarquée dans le terminal mobile, l’objectif étant de répondre au mieux aux contraintes imposées par l’environnement. Ces travaux reposent sur une approche décisionnelle dynamique tenant compte de changements dans les paramètres réseaux et des besoins et préférences des utilisateurs au regard des services qui leur sont proposés. En effet, dans l’environnement actuel, se caractérisant par une multiplicité de technologies, d’applications et d’utilisateurs, les terminaux mobiles sont équipés de plusieurs interfaces réseaux. Ces derniers donnent ainsi la possibilité aux utilisateurs de pouvoir basculer dynamiquement d’une interface à une autre dans l’objectif d’assurer une connexion satisfaisant le mieux possible leurs besoins en termes de services en tout lieu, à tout moment et de la meilleure manière possible (ABC, Always Best Connected). Les approches mises en œuvre dans le cadre de la thèse ont permis d’associer simultanément chaque flux d’application à l’interface la plus appropriée de manière à optimiser les performances globales du système. Ainsi, ces travaux ont mené à la proposition d’approches hybrides ayant pour cadre de départ la technique TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) et en y intégrant des modèles issus de la théorie des fonctions de croyance. Pour l’association flux/interface, une proposition basée sur des algorithmes bio-inspirés a été faite dans le cadre de ces travaux. Les résultats obtenus, à la fois par simulation et sur un cas d’usage réel en lien avec le domaine de la santé connectée, ont montré l’efficacité des approches proposées / The work developed in this dissertation has as a general framework the implementation of adaptive user-centric approaches for network interface selection (NIS) and flow/interface association (FIA) in Heterogeneous Wireless Networks (HWNs). The NIS mechanism relies on a dynamic decision approach that considers the change in networks’ parameters and users’ needs and preferences for their current applications. In a heterogeneous environment, the mobile terminals that are equipped with multiple network interfaces provide the possibility for mobile end-users to switch among available network interfaces and select the one that best fulfills their needs anywhere at any time which is known as Always Best Connected (ABC). The approaches proposed in this thesis allowed to associate simultaneously each application flow to its suitable interface in a way that best maximizes the global system performance. This work has led to the proposal of hybrid approaches originating from TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) and integrating models from the belief functions theory for the NIS. Concerning the FIA, a proposal based on bio-inspired algorithms was made as part of this work. Experimental results based on synthetic datasets and an experimental test bed for health monitoring showed the effectiveness of the proposed approaches

Les systèmes d’exploitation utilisent très généralement une politique de « meilleur effort » (Best-effort) pour exécuter les applications. Tant que les ressources sont suffisantes, les applications s’exécutent normalement mais quand les ressources deviennent insuffisantes, des mécanismes de contrôle sont nécessaires pour continuer à obtenir des services de qualité acceptable. Cette thèse a pour objectif de gérer la QoS des applications distribuées. La première partie propose un middleware totalement décentralisé pour contrôler l’utilisation des ressources des applications distribuées. Cette approche se fonde sur une planification approximative et un schéma d’emprunt de ressources afin d’améliorer la QoS globale du système. Via ce schéma d’emprunt, chaque nœud construit localement une vue détaillée de la disponibilité des ressources dans le système. La présence da la connaissance de la disponibilité des ressources en local permet à chaque nœud de prendre localement des décisions et de planifier les tâches des applications. Pour un contrôle plus fin de l’exécution, la deuxième partie ajoute un support pour l’adaptation du comportement des applications. Le middleware utilise un modèle général des applications sous forme de graphe d’exécution décoré avec les besoins en ressources. Un chemin dans le graphe est une exécution possible de l’application avec une certaine utilité, et ce sont ces chemins qui fournissent les degrés de liberté dont le middleware a besoin pour adapter la consommation des ressources au contexte. Les applications coopèrent avec le middleware dans le processus de gestion de la QoS lors de l’admission puis durant toute l’exécution. Le middleware est le chef d’orchestre et c’est lui qui pilote et c’est lui qui pilote l’exécution des actions des applications (arcs dans le graphe) Pour valider notre approche, un prototype à base d’agents a été réalisé. Les résultats démontrent l’intérêt de notre approche. / Generally, Operating Systems control and execute applications based on a best effort policy. As long as resources are sufficient, applications are normally executed but when resources become scarce, control mechanisms (graceful degradation) are necessary to maintain acceptable QoS. This thesis aims to manage the QoS of distributed applications. The first part of the thesis proposes a fully decentralized middleware to control the use of resources of distributed applications. This approach is based on a resource borrowing schema and an approximate scheduling in order to improve the overall QoS provided by the system. Using this borrowing schema, each node locally constructs a comprehensive view of resources availability in the system. The local knowledge of resources availability makes it possible for each node to make decisions and to schedule the execution of the applications. To finely control execution, the second part of the thesis adds a support for behavior adaptation of applications. The middleware interprets a general model of applications as an execution graph enriched with resources requirements. Each application must be designed according to this model to be manageable by the middleware (intrusive approach). A path in the graph is a possible execution of application with a certain utility. These paths provide degrees of freedom needed by the middleware to adapt resource consumption to the context. During the QoS management process, applications cooperate with the middleware at admission and execution phase. The middleware guides and controls the execution of applications actions (edges in the execution graph). To validate our approach, a prototype based on agents has been implemented using JADE. The results show the interest of our approach.

Atualmente, os usuários desejam obter, fornecer, compartilhar e interagir com informações e serviços com conteúdo multimídia em qualquer lugar, a qualquer momento e com qualquer dispositivo. Para que isso seja possível, um dos grandes desafios é assegurar a QoS (Quality of Service) fim a fim (entre o usuário final e a organização provedora de serviço) para a disponibilização de serviços móveis e interativos com conteúdo multimídia para os usuários finais. Em geral esse tipo de serviço têm maior exigência de QoS, pois além dos parâmetros de redes, possuem parâmetros específicos para áudio, imagem e vídeo, além de exigirem sincronização de áudio e vídeo, e a QoS fim a fim deve considerar parâmetros de QoS sob a percepção do usuário final. Com isso, o objetivo deste trabalho é propor um método para o levantamento de parâmetros de QoS para o estabelecimento de USLAs (User Service Level Agreements - Acordo do Nível de Serviço do Usuário) entre a organização provedora de serviço e o usuário final para serviços móveis e interativos com conteúdo multimídia em um ambiente de convergência tecnológica. O método consiste em quatro passos: 1. identificação do serviço a ser oferecido ao usuário final e elaboração de um grafo em árvore, que tem como objetivo identificar outros serviços que podem compor o serviço a ser oferecido ao usuário final; 2. mapeamento dos parâmetros de QoS em um metamodelo; 3. validação do metamodelo, para que se possa extrair do metamodelo os parâmetros de QoS; 4. elaboração do USLA. Este trabalho propõe um primeiro passo para solucionar a falta de métodos padronizados para o estabelecimento de USLA para serviços móveis e interativos com conteúdo multimídia sob a percepção do usuário final. Além de facilitar a identificação e composição de serviços e parâmetros, por meio de um metamodelo que proporciona a integração de classes de serviços que podem ser facilmente reutilizadas e customizadas, de acordo, com o tipo de serviço oferecido pela organização provedora de serviço e pela necessidade do usuário final. / In these days the final users wish to obtain, to furnish and to interact using interactive services with multimedia content anywhere, anytime and with any kind of user device. One of the biggest challenges is to assure the End-to End Quality of Service (E2E QoS) in the delivering of the interactive and multimedia services for moving users. In general, this kind of users have more strict requirements needs, because, besides of the computer network parameters, they need specify specific parameters like sound, image and video and their synchronization, on the users\' point of the view - perceived QoS. The main objective of this thesis is to present the application of a method for eliciting the E2E QoS parameters aiming the establishment of the User Service Level Agreement - USLA between the service provider and the final user applied to interactive and mobile services with multimedia content, inserted on a technological convergence environment. The method is a four steps method that consists of (1) an identification of the service to be offered to the final user and the elaboration of a tree graph aiming the identification of the composition of the service by other services (2) mapping the QoS parameters in a metamodel (3) validation of the metamodel, and extraction of the E2E QoS parameters (4) elaboration the USLA. This thesis proposes a first step to solve the lack of standardized methods for the establishment of the USLA for interactive and mobile services with multimedia content under the users\' perception. Besides of facilitating the identification and the composition of services and parameters, using a metamodel, that provides the integration of classes of services, that can be easily reused and customized, according, with the type of service offered for the service provider to the final user.

A partir de revisão do histórico da regulação do segmento de distribuição de energia elétrica no Brasil, da revisão de conceitos de Teoria da Regulação, Distribuição de Energia Elétrica, Estrutura Tarifária, Regulação de Monopólios Naturais, Qualidade do Serviço Prestado, e Sustentabilidade Econômico-Financeira, assim como definições de Direito Administrativo, Teoria Geral de Concessões de Serviços Públicos e política de preço aplicada a monopólios naturais, aprende-se que o regime tarifário chamado de serviço pelo preço (price cap) foi adotado a partir da edição da Lei de Concessões, sendo abandonado o regime do custo do serviço (rate of return), praticado desde a década de 1950. Contudo, a distinção entre os dois regimes de regulação tarifária fica prejudicada devido às práticas do regulador, fato que ocorre não apenas no Brasil. Conforme estabelecem os contratos de concessão, as tarifas deveriam ser preservadas pela equação de equilíbrio inicial \'RPI +/- X\', sendo previstas revisões tarifárias periódicas, observadas as alterações na estrutura de custos e de mercado, os níveis de tarifas observados em empresas similares no contexto nacional e internacional, e estímulos ao ganho de eficiência e à modicidade tarifária. Passadas duas décadas da implantação do price cap, observa-se que o regulador incorporou práticas do rate of return, criando instrumentos de reposicionamento das tarifas de acordo com critérios e trajetórias de custos operacionais eficientes e componentes discricionários de cálculo do ganho de produtividade, dotando o processo de reajuste e revisão das tarifas de excessiva complexidade. Assim, buscando-se maior simplicidade e clareza nos processos tarifários, de modo a incentivar de forma mais adequada o investimento na melhoria da qualidade do serviço e na sustentabilidade da concessão, o presente trabalho propõe aperfeiçoamentos na metodologia tarifária com base em parâmetros de eficiência em relação à qualidade do serviço prestado, discutido no âmbito do Mecanismo de Incentivo à Melhoria da Qualidade (MIQ) por meio do componente \'Q\' do Fator X, e de eficiência em relação à gestão econômico-financeira (sustentabilidade), aferida por parâmetros utilizados amplamente no setor financeiro, tratados como elementos de uma política de incentivos para assegurar a trajetória de sustentabilidade da concessão. A partir do princípio contratual de que os processos tarifários consideram como receita da distribuidora a soma de uma parcela não gerenciável (VPA) e de parcela gerenciável (VPB), a busca por maior simplicidade e clareza diz respeito ao estrito cumprimento dos critérios contratuais, com retorno à prática da regulação de serviço pelo preço, como estabelecido pela Lei de Concessões. A aplicação dos aperfeiçoamentos propostos é realizada mediante estudos de caso de duas distribuidoras de energia elétrica em situações de qualidade e sustentabilidade distintas. O resultado ilustra que a qualidade e sustentabilidade do serviço podem ser parâmetros importantes para introdução de uma metodologia menos complexa e mais objetiva para reajuste e revisão das tarifas de fornecimento no Brasil. / The Tariff Regulation for public service distribution of electrical energy, called \"price cap\" was adopted in Brazil from the publication of Law 8.095/1995 (the Law of Concessions), therefore abandoning the \"return rate\" remuneration system practiced since the late 1950s. However, the distinction between price cap and return rate regulation was negatively affected due to practices of the regulatory agency (National Electric Energy Agency - ANEEL), which occurs not only in Brazil. As established in concession contracts, the tariffs should be preserved by the equation of initial balance \'RPI +/- X\', forecasting tariff reviews periodically by observing changes in the structure of the licensee\'s costs and market share, the levels of rates observed in similar businesses in the national and international context, as well as stimulating efficiency gains and controlling tariffs. After two decades of implementation of the system of price cap in Brazil, and after four cycles of periodic review of tariffs, it is observed that the regulator has incorporated practices of rate of return throughout the process, creating instruments of repositioning of tariffs in accordance with criteria of operational costs considered efficient and discretionary components of calculating the productivity gains (X Factor), giving the process of readjustment and revision of rates of excessive complexity. In search of greater simplicity and clarity in the tariff process in order to encourage more adequately the investment in improving the quality of service and sustainability, this Thesis presents proposals for the improvement of tariff methodology based on parameters efficiency in terms of quality of service, objectively measured by global indicators of continuity and efficiency in relation to the economic and financial management (sustainability), measured by parameters used widely in the financial sector. The improvement of the efficiency of quality is discussed under the Incentive to Quality Improvement Mechanism (MIQ) of the Brazilian tariff regulation through the \'Q\' component of Factor X. The improvements on the extent of economic and financial sustainability are treated as elements of an incentive policy to ensure a path of sustainability of the concession, given that the Brazilian regulator has not adopted explicit mechanisms of sustainability, except those specifically defined in the process of renewal of distribution concessions, pursuant to Presidential Decree n. 8.461/2015. From the contractual principle that tariff processes consider the distribution company Requested Revenue as the sum of an unmanageable portion (VPA) and manageable portion (VPB), the search for greater simplicity and clarity with respect the strict compliance with the contract criteria, returning to the practice of price cap regulation, as established by the Concessions Law. The implementation of improvements for the proposed tariff mechanisms is carried out through case studies relating to two electricity distribution companies in different quality and sustainability situations. The result of the study shows that the quality and sustainability of the service in the electricity distribution segment can be important parameters for introducing a less complex and more objective methodology for adjustment and review of electricity tariffs in Brazil.

O segmento das comunicações, já há alguns anos, vem passando por significativas transformações exigindo a interação entre ambientes tecnológicos convergentes heterogêneos, com qualidade na continuidade de serviços, para se manter competitivo, pois é este mercado que exige, constantemente, que mais recursos tecnológicos lhe sejam colocados à disposição. O ineditismo da proposta desenvolvida neste trabalho é a elaboração de um modelo para assegurar a continuidade da qualidade de serviço percebida pelo usuário final através de handover (ou handoff) vertical, o que caracteriza-se como uma necessidade de solução global, isto é, o modelo é genérico e independente da tecnologia, o que permite sua adoção em qualquer ambiente de rede existente aproveitando a capilaridade já disponível das redes legadas. É analisada também a situação na qual um usuário final esteja acessando simultaneamente serviços gerenciados por Provedores de Serviço distintos, o que conduz a duas situações possíveis: a) o usuário está acessando serviços distintos contratados a Provedores de Serviço diferentes; b) o usuário está acessando o mesmo serviço contratado a Provedores de Serviço distintos. Nesta última situação pode surgir a necessidade de disparar um processo de handover exigindo a decisão de qual dos Provedores o executará, de acordo com o SPHDA Service Providers Handover Decision Agreement. A metodologia adotada para o desenvolvido do modelo foi a RM-ODP - Reference Model for Open Distributed Processing, por abranger todos os aspectos técnicos e comerciais necessários à sua construção. / The sector of communications, for some years, has undergone significant changes requiring interaction between converging heterogeneous technology environments, with quality and continuity of services to stay competitive, because this market is that requires constantly more technological resources available. The novelty of the proposal developed in this work is the development of a model to ensure the continued quality of service perceived by end users via vertical handover (or handoff), which characterizes itself as a need for a global solution, i.e., the model is generic and technology independent, allowing its adoption in any network environment taking advantage of the capillary already available from legacy networks. It is also analyzed the situation in which an end user is simultaneously accessing services managed by different Service Providers, which leads to two possible situations: a) the user is accessing different services contracted to different Service Providers; b) the user is accessing the same service contracted to different Service Providers. In this last situation may be necessary to trigger a handover process requiring the decision of which the Providers shall execute it in accordance with the SPHDA - Service Providers Handover Decision Agreement. The methodology adopted for the model development was the RM-ODP - Reference Model for Open Distributed Processing, as it includes all technical and commercial aspects necessary for its construction.

Atualmente, as concessionárias de energia enfrentam vários desafios na tentativa de fornecer energia com qualidade e confiabilidade, por exemplo, redes de distribuição com pouco monitoramento e controle, envelhecimento dos ativos, atender a crescente demanda dos consumidores e satisfazer padrões de qualidade, entre outros. No Brasil, para atingir os índices de qualidade no fornecimento de energia estabelecidos pela Agência Nacional de Energia Elétrica (ANEEL), tem-se como alternativa aumentar a inteligência da rede com sistemas de tecnologia de informação (TI), além de utilizar Dispositivos Eletrônicos Inteligentes (IEDs), medidores inteligentes e sensores. Adicionalmente é necessário o emprego de uma infraestrutura de comunicação que forneça uma visibilidade abrangente das condições de carga e do estado do sistema de distribuição, permitindo fazer uso de técnicas de otimização e tomada de decisão para aumento da inteligência. O controle da tensão e o gerenciamento da potência reativa (Volt/VAr) são práticas de automação que podem ser empregadas nos sistemas de distribuição. Estas práticas ajudam a aumentar o benefício, a confiabilidade e a eficiência no fornecimento da qualidade do produto, minimizando os custos de operação e manutenção nas concessionárias. Na presente dissertação foi desenvolvida uma metodologia de controle Volt/VAr descentralizado (subestação), por meio da coordenação e controle dos transformadores com mudança de tap sob carga - LTC, dos bancos de capacitores localizados na subestação e ao longo dos alimentadores, bem como dos reguladores de tensão instalados ao longo dos alimentadores. Destaca-se a utilização da técnica de Estimação de Estados, a qual possibilita o uso da metodologia de controle Volt/VAr em tempo real. O algoritmo de otimização desenvolvido neste trabalho foi implementado através de simulações numa rede teste e numa rede real que permitem mostrar o potencial da formulação matemática desenvolvida. Os resultados da metodologia proposta comprovam a melhoria do perfil de tensão dos alimentadores da rede testada ao longo do dia, assim como uma diminuição das perdas técnicas, as quais chegaram a diminuir 7% em energia. Estes resultados foram alcançados sem ultrapassar a quantidade de operações definidas por dia nos diferentes dispositivos de controle. / Currently, power utilities face challenges in order to provide energy considering minimum requirements of power quality and reliability due to the absence of control and monitoring infrastructure, aging assets, growing demand, amongst others. In Brazil, the Agência Nacional de Energia Elétrica (ANEEL) establishes specific power quality and reliability indices. Power utilities should attend the limits for those indices by improving intelligence of network using IT systems, installing Intelligent Electric Devices (IEDs), smart meters and sensors, amongst others. Additionally, communication infrastructure is needed to provide the monitoring of load conditions and distribution system state. Optimization and decision-making tools are important for developing smart grids. Voltage control and reactive power management (Volt/VAr) are automation techniques that can be used in distribution systems. These practices lead to benefits for the utilities such as improvement of reliability and efficiency of the system, minimization of operation and maintenance costs, amongst others. In the present dissertation a methodology for decentralized control (Volt/VAr) was developed, through the coordination and control of load tap changers (LTCs) in power transformers and capacitors banks located at the substation, as well as capacitor banks and voltage regulators scattered throughout the feeders. State Estimation was utilized, which allows the application of the Volt/VAr Control methodology in real time environment. The optimization algorithm developed in this work was implemented through simulations in a test network and in a real network which validated the proposed methodology showing the potentiality of the mathematical model. The results of the proposed method showed voltage profile improvement over the day for the network tested as well as a 7% decrease in power energy losses. These results were achieved without exceeding the number of operations per day defined for all control devices.

Coreografias de serviços Web representam uma forma mais escalável e flexível de compor serviços do que uma abordagem centralizada como a orquestração, e seu papel na integração e comunicação de sistemas de larga escala é vital para os objetivos da SOC (Computação Orientada a Serviços) e da Internet do Futuro. Atualmente coreografias de serviços Web possuem vários desafios de pesquisa, dos quais a qualidade de serviço (QoS) e o monitoramento de coreografias de serviçosWeb são linhas importantes. O objetivo deste trabalho é propor e implementar um mecanismo de monitoramento não intrusivo de coreografias de serviços Web baseado em SLAs (Acordos de Nível de Serviço) que especificam as restrições de atributos de QoS de maneira probabilística. Esta dissertação propõe um mecanismo para coreografias de serviços Web que: (1) define requisitos de QoS; (2) especifica contratos probabilísticos sobre parâmetros de QoS usando SLA; e (3) realiza um monitoramento não intrusivo de coreografias de serviços Web para detectar violações de SLA. / Web services choreographies are a more scalable and flexible way to compose services than a centralized approach like orchestrations, and its role in the integration and communication of large-scale systems is vital for the goals of SoC (Service Oriented Computing) and Future Internet. Currently,Web services choreographies have several research challenges. From all challenges, quality of service (QoS) and monitoring of Web services choreography are important research lines. The goal of this work is to propose and implement a mechanism for non-intrusive monitoring of Web services choreography based on SLAs (Service Level Agreements) that define constraints of QoS attributes in a probabilistic way. This thesis proposes a mechanism for Web services choreographies that:(1) defines QoS requirements; (2) specifies probabilistic contracts on QoS parameters using SLAs; and (3) monitors, non-intrusively, the enactment of Web services choreographies to detect SLA violations.

L’émergence de petites caméras CMOS et de microphones MEMS, à coût et puissance réduits, a contribué au développement d’une technologie permettant la transmission de flux multimédia (audio, image, vidéo) : les réseaux de capteurs multimédia. Cette technologie, offrant de nouvelles perspectives d’applications potentielles où la collecte d’informations visuelles et/ou acoustiques apporte une plus- value certaine, suscite un intérêt manifeste. Avec des données multimédia, la qualité de service devient désormais une exigence fondamentale pour la transmission dans un environnement contraint en ressources. Dans le contexte spécifique de cette thèse, nous considérons un déploiement par voie aérienne d’une grande quantité de capteurs image pour des applications critiques de surveillance telles que la détection d’intrusion ou des opérations de recherche et sauvetage. La prise en compte de la criticité des applications constitue un aspect important de cette thèse, novateur par rapport aux contributions déjà effectuées dans le domaine. Nos travaux se fondent sur une méthode d’ordonnancement adaptatif de l’activité des capteurs image qui fournit, pour chacun d’entre eux, son ensemble de cover-sets. La détection d’un événement dans le réseau déclenche la transmission d’une large quantité d’informations visuelles, émanant de plusieurs sources pour résoudre les ambiguïtés. L’objectif de cette thèse est d’optimiser cette transmission simultanée d’images causant des désagréments sur le réseau. Nous avons tout d’abord proposé une stratégie de sélection des cover-sets pertinents à activer pour une transmission efficace des images capturées. Cette stratégie, basée sur des critères d’état et de voisinage, assure un compromis entre autonomie et criticité. Une extension multi-chemin de GPSR assure la remontée des images émises des sources sélectionnées au puits. Une seconde contribution, également une approche de sélection, se fonde sur les informations de chemins à 2 sauts pour la sélection des cover-sets. Contrairement à la précédente, elle accorde une priorité à la criticité par rapport à la préservation de l’énergie, même si cette préservation est faite de manière indirecte. Un protocole de routage multi-chemin T-GPSR essentiellement basé sur les informations à 2 sauts est associé à la seconde approche de sélection. Une étude de performances de la mobilité du puits sur les propositions basées sur les informations à 2 sauts constitue notre troisième contribution. / Recent advances of inexpensive and low-power CMOS cameras and MEMS mi- crophones have led to the emergence of Wireless Multimedia Sensor Networks (WMSNs). WMSNs promise a wide spectrum of potential applications which require to ubiquitously capture multimedia content (visual and audio information). To support the transmission of multimedia content in a resource constrained environment, WMSNs may require a certain level of quality of service (QoS) in terms of delay, bandwidth, jitter, reliability, quality level etc. In this thesis, we consider Wireless Image Sensor Networks (WISNs) where sensor nodes equipped with miniaturized visual cameras to provide accurate information in various geographical parts of an area of interest can be thrown in mass for mission-critical applications such as intrusion detection or search & rescue. An innovative and important aspect of this thesis is to take into account the criticality of applications. The network adopts an adaptive scheduling of image sensor node’s activity based on the application criticality level, where each node computes its cover-sets. So, event detection triggers the simulataneous transmission of a large volume of visual data from multiples sources to the Sink. The main objective of this thesis is to optimize this simultaneous transmission of images that can degrade network performance. With this goal in mind, we first proposed a multi-criteria approach to select the suitable cover-sets to be activated for reliable transmission of images in mission-critical applications. The proposed approach takes into account various parameters that affect the image quality at the Sink in a multi-hop transmission network and guarantees a compromise between autonomy and criticality. A modified version of GPSR routing protocol supporting the transmission of multimedia streams ensures the transfer of images from selected sources to the Sink. The second contribution consists in an optimized selection strategy based on 2-hop neighborhood information to determine the most relevant cover-sets to be activated to increase reliability for image transmission. This selection approach prioritizes the application’s criticality. A multipath extension of GPSR, called T-GPSR, wherein routing decisions are based 2-hop neighborhood information is also proposed. A performance study of the sink mobility on proposals based on 2-hop information is our third contribution.