671 research outputs found

    Smart PIN: utility-based replication and delivery of multimedia content to mobile users in wireless networks

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    Next generation wireless networks rely on heterogeneous connectivity technologies to support various rich media services such as personal information storage, file sharing and multimedia streaming. Due to users’ mobility and dynamic characteristics of wireless networks, data availability in collaborating devices is a critical issue. In this context Smart PIN was proposed as a personal information network which focuses on performance of delivery and cost efficiency. Smart PIN uses a novel data replication scheme based on individual and overall system utility to best balance the requirements for static data and multimedia content delivery with variable device availability due to user mobility. Simulations show improved results in comparison with other general purpose data replication schemes in terms of data availability

    Mathematical analysis of scheduling policies in peer-to-peer video streaming networks

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    Las redes de pares son comunidades virtuales autogestionadas, desarrolladas en la capa de aplicaciĂłn sobre la infraestructura de Internet, donde los usuarios (denominados pares) comparten recursos (ancho de banda, memoria, procesamiento) para alcanzar un fin comĂșn. La distribuciĂłn de video representa la aplicaciĂłn mĂĄs desafiante, dadas las limitaciones de ancho de banda. Existen bĂĄsicamente tres servicios de video. El mĂĄs simple es la descarga, donde un conjunto de servidores posee el contenido original, y los usuarios deben descargar completamente este contenido previo a su reproducciĂłn. Un segundo servicio se denomina video bajo demanda, donde los pares se unen a una red virtual siempre que inicien una solicitud de un contenido de video, e inician una descarga progresiva en lĂ­nea. El Ășltimo servicio es video en vivo, donde el contenido de video es generado, distribuido y visualizado simultĂĄneamente. En esta tesis se estudian aspectos de diseño para la distribuciĂłn de video en vivo y bajo demanda. Se presenta un anĂĄlisis matemĂĄtico de estabilidad y capacidad de arquitecturas de distribuciĂłn bajo demanda hĂ­bridas, asistidas por pares. Los pares inician descargas concurrentes de mĂșltiples contenidos, y se desconectan cuando lo desean. Se predice la evoluciĂłn esperada del sistema asumiendo proceso Poisson de arribos y egresos exponenciales, mediante un modelo determinĂ­stico de fluidos. Un sub-modelo de descargas secuenciales (no simultĂĄneas) es globalmente y estructuralmente estable, independientemente de los parĂĄmetros de la red. Mediante la Ley de Little se determina el tiempo medio de residencia de usuarios en un sistema bajo demanda secuencial estacionario. Se demuestra teĂłricamente que la filosofĂ­a hĂ­brida de cooperaciĂłn entre pares siempre desempeña mejor que la tecnologĂ­a pura basada en cliente-servidor

    A credit-based approach to scalable video transmission over a peer-to-peer social network

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    PhDThe objective of the research work presented in this thesis is to study scalable video transmission over peer-to-peer networks. In particular, we analyse how a credit-based approach and exploitation of social networking features can play a significant role in the design of such systems. Peer-to-peer systems are nowadays a valid alternative to the traditional client-server architecture for the distribution of multimedia content, as they transfer the workload from the service provider to the final user, with a subsequent reduction of management costs for the former. On the other hand, scalable video coding helps in dealing with network heterogeneity, since the content can be tailored to the characteristics or resources of the peers. First of all, we present a study that evaluates subjective video quality perceived by the final user under different transmission scenarios. We also propose a video chunk selection algorithm that maximises received video quality under different network conditions. Furthermore, challenges in building reliable peer-to-peer systems for multimedia streaming include optimisation of resource allocation and design mechanisms based on rewards and punishments that provide incentives for users to share their own resources. Our solution relies on a credit-based architecture, where peers do not interact with users that have proven to be malicious in the past. Finally, if peers are allowed to build a social network of trusted users, they can share the local information they have about the network and have a more complete understanding of the type of users they are interacting with. Therefore, in addition to a local credit, a social credit or social reputation is introduced. This thesis concludes with an overview of future developments of this research work

    Scalable service for flexible access to personal content

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    On the Role of Helper Peers in P2P Networks

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