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, 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.

De nos jours, l’expérience de l'utilisateur appelé en anglais « User Experience » est devenue l’un des indicateurs les plus pertinents pour les fournisseurs de services ainsi que pour les opérateurs de télécommunication pour analyser le fonctionnement de bout en bout de leurs systèmes (du terminal client, en passant par le réseaux jusqu’à l’infrastructure des services etc.). De plus, afin d’entretenir leur part de marché et rester compétitif, les différents opérateurs de télécommunication et les fournisseurs de services doivent constamment conserver et accroître le nombre de souscription des clients. Pour répondre à ces exigences, ils doivent disposer de solutions efficaces de monitoring et d’estimation de la qualité d'expérience (QoE) afin d’évaluer la satisfaction de leur clients. Cependant, la QoE est une mesure qui reste subjective et son évaluation est coûteuse et fastidieuse car elle nécessite une forte participation humaine (appelé panel de d’évaluation). Par conséquent, la conception d’un outil qui peut mesurer objectivement cette qualité d'expérience avec une précision raisonnable et en temps réel est devenue un besoin primordial qui constitue un challenge intéressant à résoudre. Comme une première contribution, nous avons analysé l'impact du comportement d’un réseau sur la qualité des services de vidéo à la demande (VOD). Nous avons également proposé un outil d'estimation objective de la QoE qui utilise le système expert basé sur la logique floue pour évaluer la QoE à partir des paramètres de qualité de service de la couche réseau. Dans une deuxième contribution, nous avons analysé l'impact des paramètres QoS de couche MAC sur les services de VoD dans le cadre des réseaux sans fil IEEE 802.11n. Nous avons également proposé un outil d'estimation objective de la QoE qui utilise le réseau aléatoire de neurones pour estimer la QoE dans la perspective de la couche MAC. Pour notre troisième contribution, nous avons analysé l'effet de différents scénarios d'adaptation sur la QoE dans le cadre du streaming adaptatif au débit. Nous avons également développé une plate-Forme Web de test subjectif qui peut être facilement intégré dans une plate-Forme de crowd-Sourcing pour effectuer des tests subjectifs. Finalement, pour notre quatrième contribution, nous avons analysé l'impact des différents paramètres de qualité de service Web sur leur QoE. Nous avons également proposé un algorithme d'apprentissage automatique i.e. un système expert hybride rugueux basé sur la logique floue pour estimer objectivement la QoE des Web services / Today user experience is becoming a reliable indicator for service providers and telecommunication operators to convey overall end to end system functioning. Moreover, to compete for a prominent market share, different network operators and service providers should retain and increase the customers’ subscription. To fulfil these requirements they require an efficient Quality of Experience (QoE) monitoring and estimation. However, QoE is a subjective metric and its evaluation is expensive and time consuming since it requires human participation. Therefore, there is a need for an objective tool that can measure the QoE objectively with reasonable accuracy in real-Time. As a first contribution, we analyzed the impact of network conditions on Video on Demand (VoD) services. We also proposed an objective QoE estimation tool that uses fuzzy expert system to estimate QoE from network layer QoS parameters. As a second contribution, we analyzed the impact of MAC layer QoS parameters on VoD services over IEEE 802.11n wireless networks. We also proposed an objective QoE estimation tool that uses random neural network to estimate QoE from the MAC layer perspective. As our third contribution, we analyzed the effect of different adaption scenarios on QoE of adaptive bit rate streaming. We also developed a web based subjective test platform that can be easily integrated in a crowdsourcing platform for performing subjective tests. As our fourth contribution, we analyzed the impact of different web QoS parameters on web service QoE. We also proposed a novel machine learning algorithm i.e. fuzzy rough hybrid expert system for estimating web service QoE objectively

Les progrès des technologies de l'information et de la communication, des MEMS, des capteurs, actionneurs, etc. ont permis l’émergence de différents dispositifs biomédicaux. Ces nouveaux dispositifs, souvent embarqués, contribuent considérablement à l'amélioration du diagnostic et du traitement de certaines maladies, comme le diabète par exemple. Des dispositifs embarqués encore plus complexes sont en cours d’élaboration, leur mise en œuvre nécessite des années de recherche et beaucoup d’expérimentation. Le cœur artificiel, encore en phase de réalisation, est un exemple concret de ces systèmes complexes. La question de la fiabilité, du test de fonctionnement et de sureté de ces dispositifs reste problématique et difficile à résoudre. Plusieurs paramètres (patient, évolution de la maladie, alimentation, activité, traitement, etc.) sont en effet à prendre en compte et la conséquence d’une erreur de fonctionnement peut être catastrophique pour le patient. L'objectif de cette thèse est de développer des outils et des approches méthodologiques permettant la validation et le test au niveau système de ce type de dispositifs. Il s’agit précisément d’étudier la possibilité de modéliser et simuler d’une manière conjointe un dispositif médical ainsi que son interaction avec le corps humain, du moins la partie du corps humain concernée par le dispositif médical, afin de mesurer les performances et la qualité de services (QoS) du dispositif considéré. Pour atteindre cet objectif notre étude a porté sur plusieurs points. Nous avons d’abord mis en évidence une architecture simplifiée d’un modèle de corps humain permettant de représenter et de mieux comprendre les différents mécanismes du corps humain. Nous avons ensuite exploré un ensemble de métriques et une approche méthodologique générique permettant de qualifier la qualité de service d’un dispositif médical donné en interaction avec le corps humain. Afin de valider notre approche, nous l’avons appliquée à un dispositif destiné à la régulation du taux de sucre pour des patients atteints du diabète. La partie du corps humain concernée par cette pathologie à savoir le pancréas a été simulé par un modèle simplifié que nous avons implémenté sur un microcontrôleur. Le dispositif de régulation de l’insuline quant à lui a été simulé par un modèle informatique écrit en C. Afin de rendre les mesures de performances observées indépendantes d’un patient donné, nous avons étudiés différentes stratégies de tests sur différentes catégories de patients. Nous avons pour cette partie mis en œuvre un générateur de modèles capable de reproduire différents états physiologiques de patients diabétiques. L’analyse et l’exploitation des résultats observés peut aider les médecins à considérablement limités les essais cliniques sur des vrai patients et les focaliser uniquement sur les cas les plus pertinent. / A Biomedical research seeks good reasoning for solving medical problems, based on intensive work and great debate. It often deals with beliefs or theories that can be proven, disproven or often refined after observations or experiments. The problem is how to make tests without risks for patients, including variability and uncertainty on a number of parameters (patients, evolution of disease, treatments …). Nowadays, medical treatment uses more and more embedded devices such as sensors, actuators, and controllers. Treatment depends on the availability and well-functioning of complex electronic systems, comprising thousands of lines of codes. A mathematical representation of patient or device is presented by a number of variables which are defined to represent the inputs, the outputs and a set of equations describing the interaction of these variables. The objective of this research is to develop tools and methodologies for the development of embedded systems for medical fields. The goal is to be able to model and jointly simulate the medical device as well the human body, at least the part of the body involved in the medical device, to analyze the performance and quality of service (QoS) of the interaction of the device with the human body. To achieve this goal our study focused on several points described below. After starting by defining a prototype of a new global and flexible architecture of mathematical model of human body, which is able to contain required data, we begin by proposing a new global methodology for modeling and simulation human body and medical systems, in order to better understand the best way to model and simulate these systems and for detecting performance and the quality of services of all system components. We use two techniques that help to evaluate the calculated QoS value. The first one calculates an index of severity which indicates the severity of the case studied. The second one using a normalization function that represents the simulation as a point in order to construct a new error grid and use it to evaluate the accuracy of value measured by patients. Using Keil development tools designed for ARM processors, we have declared a new framework in the objective to create a new tester model for the glucose-insulin system, and to define the basic rules for the tester which has the ability to satisfy well-established medical decision criteria. The framework begins by simulating a mathematical model of the human body, and this model was developed to operate in the closed loop of the glucose insulin. Then, the model of artificial pancreas has been implemented to control the mathematical model of human body. Finally a new tester model was created in order to analyze the performance of all the components of the glucose-insulin system.. We have used the suitability of partially observable Markov decision processes to formalize the planning of clinical management.

Due to its significant advantage in spectral efficiency, multiple-antenna communication technology will undoubtedly be a major component in future wireless system implementations. However, the full exploitation of this technology also requires perfect feedback of channel state information (CSI) to the transmitter-- something that is not practically feasible. This motivates the study of limited feedback systems, where CSI feedback is rate limited. This thesis focuses on the optimal design of limited feedback systems for three types of communication channels: the relay channel, the single-user point-to-point channel, and the multiuser broadcast channel. For the relay channel, we prove the efficiency of the Grassmannian codebooks as the source and relay beamforming codebooks, and propose a method for CSI exchange between the relay and the destination when global CSI is not available at destination. For the single-user point-to-point channel, we study the joint power control and beamforming problem and address the channel magnitude and direction quantization codebook design problem. It is shown that uniform quantization of the channel magnitude (in dB scale) is asymptotically optimal regardless of the channel distribution. The analysis further derives the optimal split of feedback bandwidth between the magnitude and direction quantization codebooks. For the multiuser broadcast channel, we first prove the sufficiency of a product magnitude-direction quantization codebook for managing the multiuser interference. We then derive the optimal split of feedback bandwidth across the users and their magnitude and direction codebooks. The optimization results reveal an inherent structural difference between the single-user and multiuser quantization codebooks: a multiuser codebook should have a finer direction quantization resolution as compared to a single-user codebook. It is further shown that the users expecting higher rates and requiring more reliable communication should provide a finer quantization of their CSI. Finally, we determine the minimum required total feedback rate based on users' quality-of-service constraints and derive the scaling of the system performance with the total feedback rate.

Due to its significant advantage in spectral efficiency, multiple-antenna communication technology will undoubtedly be a major component in future wireless system implementations. However, the full exploitation of this technology also requires perfect feedback of channel state information (CSI) to the transmitter-- something that is not practically feasible. This motivates the study of limited feedback systems, where CSI feedback is rate limited. This thesis focuses on the optimal design of limited feedback systems for three types of communication channels: the relay channel, the single-user point-to-point channel, and the multiuser broadcast channel. For the relay channel, we prove the efficiency of the Grassmannian codebooks as the source and relay beamforming codebooks, and propose a method for CSI exchange between the relay and the destination when global CSI is not available at destination. For the single-user point-to-point channel, we study the joint power control and beamforming problem and address the channel magnitude and direction quantization codebook design problem. It is shown that uniform quantization of the channel magnitude (in dB scale) is asymptotically optimal regardless of the channel distribution. The analysis further derives the optimal split of feedback bandwidth between the magnitude and direction quantization codebooks. For the multiuser broadcast channel, we first prove the sufficiency of a product magnitude-direction quantization codebook for managing the multiuser interference. We then derive the optimal split of feedback bandwidth across the users and their magnitude and direction codebooks. The optimization results reveal an inherent structural difference between the single-user and multiuser quantization codebooks: a multiuser codebook should have a finer direction quantization resolution as compared to a single-user codebook. It is further shown that the users expecting higher rates and requiring more reliable communication should provide a finer quantization of their CSI. Finally, we determine the minimum required total feedback rate based on users' quality-of-service constraints and derive the scaling of the system performance with the total feedback rate.

Next generation wireless systems have an IP-based infrastructure with the support of heterogeneous access technologies. One research challenge for next generation all-IP based wireless systems is to design intelligent mobility management techniques that take advantage of IP-based technologies to achieve global roaming between various access networks. To support global roaming, next generation wireless systems require the integration and interoperation of heterogeneous mobility management techniques. Mobility in a hierarchical structure or multilayered environment should be supported. The objective of this study is to develop new mobility management techniques for global roaming support in next generation all-IP based wireless systems. More specifically, new schemes for location management and paging in Mobile IP for network layer mobility support, and new schemes for location management and handoff management in heterogeneous overlay networks for link layer mobility support are proposed and evaluated. For network layer mobility support, a distributed and dynamic regional location management mechanism for Mobile IP is proposed. Under the proposed scheme, the signaling burden is evenly distributed and the regional network boundary is dynamically adjusted according to the up-to-date mobility and traffic load for each terminal. Next, a user independent paging scheme based on last-known location and mobility rate information for Mobile IP is proposed. The proposed scheme takes the aggregated behavior of all mobile users as the basis for paging. For link layer mobility support, an IP-based system architecture for the integration of heterogeneous mobility management techniques is proposed. Three location management schemes under this IP-based architecture are proposed. All the three schemes support user preference call delivery which is a very important feature of next generation wireless communications. A threshold-based enhancement method is also proposed to further improve the system performance. Finally, a hybrid resource allocation scheme for handoff management in wireless overlay networks is proposed. Under this scheme, the overall system resources can be optimally allocated when mobile users are covered by multiple overlay networks.

In this thesis, we consider optimal control problems arising in high-speed integrated communication networks with Quality of Service (QOS) constraints. Integrated networks are expected to carry a large variety of traffic sources with widely varying traffic characteristics and performance requirements. Broadly, the traffic sources fall into two categories: (a) real-time sources with specified performance criteria, like small end to end delay and loss probability (sources of this type are referred to as Type 1 sources below), and (b) sources that do not have stringent performance criteria and do not demand performance guarantees from the network - the so-called Best Effort Type sources (these are referred to as Type 2 sources below). From the network's point of view, Type 2 sources are much more "controllable" than Type 1 sources, in the sense that the Type 2 sources can be dynamically slowed down, stopped or speeded up depending on traffic congestion in the network, while for Type 1 sources, the only control action available in case of congestion is packet dropping. Carrying sources of both types in the same network concurrently while meeting the performance objectives of Type 1 sources is a challenge and raises the question of equitable sharing of resources. The objective is to carry as much Type 2 traffic as possible without sacrificing the performance requirements of Type 1 traffic. We consider simple models that capture this situation. Consider a network node through which two connections pass, one each of Types 1 and 2. One would like to maximize the throughput of the Type 2 connection while ensuring that the Type 1 connection's performance objectives are met. This can be set up as a constrained optimization problem that, however, is very hard to solve. We introduce a parameter b that represents the "cost" of buffer occupancy by Type 2 traffic. Since buffer space is limited and shared, a queued Type 2 packet means that a buffer position is not available for storing a Type 1 packet; to discourage the Type 2 connection from hogging the buffer, the cost parameter b is introduced, while a reward for each Type 2 packet coming into the buffer encourages the Type 2 connection to transmit at a high rate. Using standard on-off models for the Type 1 sources, we show how values can be assigned to the parameter b; the value depends on the characteristics of the Type 1 connection passing through the node, i.e., whether it is a Variable Bit Rate (VBR) video connection or a Continuous Bit Rate (CBR) connection etc. Our approach gives concrete networking significance to the parameter b, which has long been considered as an abstract parameter in reward-penalty formulations of flow control problems (for example, [Stidham '85]). Having seen how to assign values to b, we focus on the Type 2 connection next. Since Type 2 connections do not have strict performance requirements, it is possible to defer transmitting a Type 2 packet, if the conditions downstream so warrant. This leads to the question: what is the "best" transmission policy for Type 2 packets? Decisions to transmit or not must be based on congestion conditions downstream; however, the network state that is available at any instant gives information that is old, since feedback latency is an inherent feature of high speed networks. Thus the problem is to identify the best transmission policy under delayed feedback information. We study this problem in the framework of Markov Decision Theory. With appropriate assumptions on the arrivals, service times and scheduling discipline at a network node, we formulate our problem as a Partially Observable Controlled Markov Chain (PO-CMC). We then give an equivalent formulation of the problem in terms of a Completely Observable Controlled Markov Chain (CO-CMC) that is easier to deal with., Using Dynamic Programming and Value Iteration, we identify structural properties of an optimal transmission policy when the delay in obtaining feedback information is one time slot. For both discounted and average cost criteria, we show that the optimal policy has a two-threshold structure, with the threshold on the observed queue length depending, on whether a Type 2 packet was transmitted in the last slot or not. For an observation delay k > 2, the Value Iteration technique does not yield results. We use the structure of the problem to provide computable upper and lower bounds to the optimal value function. A study of these bounds yields information about the structure of the optimal policy for this problem. We show that for appropriate values of the parameters of the problem, depending on the number of transmissions in the last k steps, there is an "upper cut off" number which is a value such that if the observed queue length is greater than or equal to this number, the optimal action is to not transmit. Since the number of transmissions in the last k steps is between 0 and A: both inclusive, we have a stack of (k+1) upper cut off values. We conjecture that these (k + l) values axe thresholds and the optimal policy for this problem has a (k + l)-threshold structure. So far it has been assumed that the parameters of the problem are known at the transmission control point. In reality, this is usually not known and changes over time. Thus, one needs an adaptive transmission policy that keeps track of and adjusts to changing network conditions. We show that the information structure in our problem admits a simple adaptive policy that performs reasonably well in a quasi-static traffic environment. Up to this point, the models we have studied correspond to a single hop in a virtual connection. We consider the multiple hop problem next. A basic matter of interest here is whether one should have end to end or hop by hop controls. We develop a sample path approach to answer this question. It turns out that depending on the relative values of the b parameter in the transmitting node and its downstream neighbour, sometimes end to end controls are preferable while at other times hop by hop controls are preferable. Finally, we consider a routing problem in a high speed network where feedback information is delayed, as usual. As before, we formulate the problem in the framework of Markov Decision Theory and apply Value Iteration to deduce structural properties of an optimal control policy. We show that for both discounted and average cost criteria, the optimal policy for an observation delay of one slot is Join the Shortest Expected Queue (JSEQ) - a natural and intuitively satisfactory extension of the well-known Join the Shortest Queue (JSQ) policy that is optimal when there is no feedback delay (see, for example, [Weber 78]). However, for an observation delay of more than one slot, we show that the JSEQ policy is not optimal. Determining the structure of the optimal policy for a delay k>2 appears to be very difficult using the Value Iteration approach; we explore some likely policies by simulation.

QoS routing is one of the major building blocks for supporting QoS in communication networks and, hence, a necessary component of future communication networks. Bandwidth- Constrained Routing Algorithm (BCRA) may help to satisfy QoS requirements such as end-to-end delay, delay-jitter etc when WFQ-like (Weighted Fair Queuing) scheduling mechanisms are deployed. The existing algorithms for bandwidth constrained routing suffer from high message overhead and have a high computational and space complexity. The work presented in the thesis, therefore, focuses on the different techniques that an be used to reserve bandwidth for a unicast connection with low protocol overhead in terms of number of messages. We have compared the performance of the proposed routing algorithms using simulation studies with other bandwidth constrained routing algorithms. The call blocking ratio and message overhead have been used as the performance metric to compare the proposed algorithm with the existing ones. We present three source routing algorithms for unicast connections satisfying the band- width requirement. The first two routing algorithms are based on the partitioning of the network. The link-state broadcasts are limited to the partition. In the first algorithm, the source node queries the other partitions for the state information on a connection request and computes the path based on the information received from the other partitions. The second algorithm is based on state aggregation. The aggregated state of other partitions is maintained at every node. The source node finds a feasible path based on the aggregated information. The path is expanded in every partition, if required, at the time of resource reservation. The third QoS routing algorithm uses the Distance Vector Tables to find a route for a connection. If the shortest path satisfies the bandwidth requirement, then it is selected; otherwise a random deviation is taken at the point where bandwidth requirement is not satisfied and shortest path algorithm is again followed. In all the three algorithms presented, the packets carry the entire path information to the destination node. Therefore, no per connection information is required to be maintained at the intermediate nodes. Simulation results indicate that the proposed algorithms indeed help educing the protocol overhead considerably, and at the same time they give comparable or better performance in terms of resource utilization across a wide range of workloads.