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Les réseaux optiques ont connu une émergence importante dans le domaine des télécommunications, et ceci grâce à leur bande passante offerte. Actuellement, la technique la plus prometteuse est la commutation optique de rafales (OBS). D'une part, OBS permet une meilIeure exploitation de la bande passante, tout en ayant un degré de complexité inférieur à OPS (Optical Packet Switching), d'autre part, OBS offre une gestion des ressources beaucoup plus efficace, comparée à OCS (Optical Circuit Switching). Plusieurs études ont démontré que le mécanisme « load-balancing » permet d'équilibrer le trafic à travers les différents noeuds, réduisant ainsi la probabilité de congestion dans les réseaux OBS. Cependant, l'utilisation du « load-balancing » a mis en évidence d'autres problèmes, particulièrement au niveau de la couche TCP (Transmission Control Protocol). De là, « Source-ordering » a été proposé comme solution pour améliorer les performances de TCP, en effectuant l'ordonnancement des rafales au niveau des sources. Dans ce travail, nous nous proposons d'étudier et d'approfondir le mécanisme du « load-balancing » afin de maximiser le débit TCP. Notre défi consiste a trouver un concept permettant d'éviter la réception en désordre des segments IP, au niveau de la couche TCP, et par conséquent à réduire le nombre de FTOs (False Time Out) et de FFRs (False Fast Retransmit). Nous avons implémenté une nouvelle technique basée sur le mécanisme de résolution de contention proactive « load-balancing » qu'on a appelée « ordonnancement à la destination ». Les résultats obtenus montrent une amélioration importante du débit TCP lors de l'emploi du mécanisme d'ordonnancement à la destination. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Maximisation du débit TCP, OBS, TCP, Rafale, Résolution de contention, Mécanisme proactif, Chemins alternatifs, Equilibrage de charge.

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La interfaz radio de los sistemas de comunicaciones móviles es normalmente considerada como la única limitación de capacidad en la red de acceso radio. Sin embargo, a medida que se van desplegando nuevas y más eficientes interfaces radio, y de que el tráfico de datos y multimedia va en aumento, existe la creciente preocupación de que la infraestructura de transporte (backhaul) de la red celular pueda convertirse en el cuello de botella en algunos escenarios. En este contexto, la tesis se centra en el desarrollo de técnicas de gestión de recursos que consideran de manera conjunta la gestión de recursos en la interfaz radio y el backhaul. Esto conduce a un nuevo paradigma donde los recursos del backhaul se consideran no sólo en la etapa de dimensionamiento, sino que además son incluidos en la problemática de gestión de recursos. Sobre esta base, el primer objetivo de la tesis consiste en evaluar los requerimientos de capacidad en las redes de acceso radio que usan IP como tecnología de transporte, de acuerdo a las recientes tendencias de la arquitectura de red. En particular, se analiza el impacto que tiene una solución de transporte basada en IP sobre la capacidad de transporte necesaria para satisfacer los requisitos de calidad de servicio en la red de acceso. La evaluación se realiza en el contexto de la red de acceso radio de UMTS, donde se proporciona una caracterización detallada de la interfaz Iub. El análisis de requerimientos de capacidad se lleva a cabo para dos diferentes escenarios: canales dedicados y canales de alta velocidad. Posteriormente, con el objetivo de aprovechar totalmente los recursos disponibles en el acceso radio y el backhaul, esta tesis propone un marco de gestión conjunta de recursos donde la idea principal consiste en incorporar las métricas de la red de transporte dentro del problema de gestión de recursos. A fin de evaluar los beneficios del marco de gestión de recursos propuesto, esta tesis se centra en la evaluación del problema de asignación de base, como estrategia para distribuir el tráfico entre las estaciones base en función de los niveles de carga tanto en la interfaz radio como en el backhaul. Este problema se analiza inicialmente considerando una red de acceso radio genérica, mediante la definición de un modelo analítico basado en cadenas de Markov. Dicho modelo permite calcular la ganancia de capacidad que puede alcanzar la estrategia de asignación de base propuesta. Posteriormente, el análisis de la estrategia propuesta se extiende considerando tecnologías específicas de acceso radio. En particular, en el contexto de redes WCDMA se desarrolla un algoritmo de asignación de base basado en simulatedannealing cuyo objetivo es maximizar una función de utilidad que refleja el grado de satisfacción de las asignaciones respecto los recursos radio y transporte. Finalmente, esta tesis aborda el diseño y evaluación de un algoritmo de asignación de base para los futuros sistemas de banda ancha basados en OFDMA. En este caso, el problema de asignación de base se modela como un problema de optimización mediante el uso de un marco de funciones de utilidad y funciones de coste de recursos. El problema planteado, que considera que existen restricciones de recursos tanto en la interfaz radio como en el backhaul, es mapeado a un problema de optimización conocido como Multiple-Choice Multidimensional Knapsack Problem (MMKP). Posteriormente, se desarrolla un algoritmo de asignación de base heurístico, el cual es evaluado y comparado con esquemas de asignación basados exclusivamente en criterios radio. El algoritmo concebido se basa en el uso de los multiplicadores de Lagrange y está diseñado para aprovechar de manera simultánea el balanceo de carga en la intefaz radio y el backhaul.

Expanding the global Internet to include mobile devices is an exciting area of current research. Because of the vast size of the Internet, and because the protocols in it are already widely deployed, mobile devices must inter-operate with those protocols. Although most of the incompatiblities with mobiles have been solved, the protocols that deliver data reliably, and that account for the majority of Internet traffic, perform very poorly. A change in location causes a disruption in traffic, and disruption is dealt with by algorithms tailored only for stationary hosts. The Transmission Control Protocol (TCP) is the predominant transport-layer protocol in the Internet. In this thesis, we look at the performance of TCP in mobile environments. We provide a complete explanation for poor performance; we conduct a large number of experiments, simulations, and analyses that prove and quantify poor performance;and we propose simple and scalable solutions that address the limitations.

A proof of concept study into the working of network media capture and visualization through the use of Packet Capture in real-time. An application was developed that is able to capture tcp network packets; identify and display images in raw HTTP network traffic through the use of search, sort, error detection, timeout failsafe algorithms in real time. The application was designed for network administrators to visualize raw network media content together with its relevant network source \& address identifiers. Different approaches were tried and tested such as using Perl with GTK+ and Visual Studio C\# .Net. Furthermore two different types of image identification methods were used: raw magic string identification in pure tcp network traffic and HTTP Mime type identification. The latter being more accurate and faster. C# was seen as vastly superior in both speed of prototyping and final performance evaluation. The study presents a novel new way of monitoring networks on the basis of their media content through deep packet inspection

A set top box is an embedded device, much like a computer with limited capabilities. Its main purpose is to decode a video signal and output it to a TV. The set top box market is constantly growing and to be competitive in it, a set top box has to be able to do more than only TV. One way to make an attractive product is to give it an appealing user interface. This thesis is a part of a larger work at the company to find new ways to create graphical user interfaces. Its goal is to investigate what SVG implementations that exits, which one that is most suitable for an integration attempt and then perform the integration. Several SVG engines were investigated and one provided by the company was selected for integration. Three ways to integrate the SVG engine were identified. One of these alternatives was to extend the callback interface be- tween the engine and the underlying platform. Because of the good fit with the current architecture this alternative was chosen and implemented. As a part of this investigation a demo application suite of SVG content was also constructed. This investigation resulted in a working integration of the chosen SVG engine on the platform. It has also showed that SVG is a suitable language to build graphical user interfaces on set top boxes.

Factum Electronics AB develops and manufactures equipment for Digital Audio Broadcasting (DAB). The increasing availability of IP networks has made the possibility to distribute the DAB signal, which is traditionally distributed over dedicated telecom links, over an IP backbone an interesting issue. This thesis investigates the possibilities to do this. Since distribution over IP is an unreliable service, it discusses techniques that can be used to eliminate the lack of reliability in IP. It also examines the advantages and drawbacks of using IP multicast, which would make it possible for many receivers to take part of the same signal. During the work behind this thesis, a protocol was developed including features to make the distribution more reliable. A prototype application including a client and a server was constructed to test and evaluate the protocol. Implementation issues of the protocol and test results drawn from the application are described in this thesis.

The purpose of this thesis is to examine the possibilities of creating a MPEG-4-compatible set-top box for IP-networks based on open standards. Existing alternatives for transporting MPEG-4 over IP are evaluated and ISMA is found to be an important actor within the area. ISMA is a non-profit corporation formed to provide a forum for the creation of specifications that define an interoperable implementation for streaming rich media over IP-networks. Two different designs based on ISMA's recommendation are constructed and evaluated. The designs have different levels of complexity and the more complex design is found to be better due to its extended functionality. During the design process a number of problems related to this kind of set-top box are discovered. It is believed, however, that many of these problems will be solved within the near future.

With the Internet expansion, real-time transmission over Internet is becoming a new promising application. Successful real-time communication over IP networks requires reasonably reliable, low delay, low loss date transport. Since Internet is a non-synchronous packet switching network, high load and lack of guarantees on data delivery make real-time communication such as Voice and Video over IP a challenging application to become realistic on the Internet. This thesis work is composed of two parts within real-time voice and video communication: network simulation and measurement on the real Internet. In the network simulation, I investigate the requirement for the network"overprovisioning"in order to reach certain quality-of-service. In the experiments on the real Internet, I simulate real-time transmission with UDP packets along two different traffic routes and analyze the quality-of- service I get in each case. The overall contribution of this work is: To create scenarios to understand the concept of overprovisioning and how it affects the quality-of-service. To develop a mechanism to measure the quality-of-service for real-time traffic provided by the current best-effort network.