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<p>This work describes a design of a multimedia content delivery system based on context, to provide multimedia information and other services according to the user location and his preferences. It focuses on mobility and the problem of different coherent and cohesive presentations depending on the available resources of the presentation environment.</p>

A evolução do portfolio de serviços das operadoras em direção a ofertas convergentes que combinam serviços de voz, dados e vídeo é uma tendência do setor de telecomunicações. É neste contexto que o conceito de Internet Protocol Television (IPTV) ganha um papel relevante, pois permite às operadoras oferecerem serviços de vídeo utilizando como base uma infra-estrutura de rede convergente baseada em Internet Protocol (IP). Entretanto, existem diversos desafios relacionados à introdução de serviços IPTV. A nova realidade que inclui os serviços de vídeo apresenta um patamar de complexidade superior ao dos serviços já conhecidos. No que diz respeito à tecnologia, existem questões que permeiam desde a adaptação da infra-estrutura de rede e sistemas existentes até a implantação de plataformas de vídeo, até então não usuais no ambiente das operadoras. Neste cenário de complexidade, a metodologia de análise técnico-econômica proposta neste trabalho se torna útil para suportar a tomada de decisão relacionada à introdução de serviços IPTV. A metodologia proposta visa gerar subsídios para a identificação das condições em que se verifica a viabilidade econômica do serviço tendo em vista aspectos relacionados ao próprio serviço e a arquitetura tecnológica que o suporta. Para isto, a metodologia abrange as seguintes atividades: definição do serviço; mapeamento de seus requisitos; análise da arquitetura tecnológica existente; delineamento e dimensionamento da arquitetura tecnológica que suportará os novos serviços; modelagem econômica; análise de sensibilidade e cenários; e, por fim, análise dos resultados. Além da proposição da metodologia de análise, este trabalho inclui a aplicação da metodologia proposta em um caso de referência representativo da realidade de uma operadora de telecomunicações. / The evolution towards integrated service offerings that combine voice, video and data is a key trend for telecommunications service providers. IP-based technology plays an important role on this scenario by enabling the delivery of video over a multiservice IP network, a service commonly known as Internet Protocol Television (IPTV). There are many challenges to a large scale roll out of IPTV services, though. When compared to traditional voice and data services, video services introduce a higher level of complexity to the service providers\' environment. The technology issues related to IPTV range from the upgrade of the existing networks and systems to the deployment of new technology platforms oriented to video services delivery, which are not common in a service provider\'s technology architecture. Within this context, the techno-economic analysis methodology presented in this work aims to support the decision process underlying the IPTV services launch by a telecommunications service provider. The proposed methodology leads to the identification of economic feasibility conditions associated to relevant services aspects and required technology infrastructure alternatives. The methodology encompasses the main following activities: services definition; services\' requirements identification; analysis of the existing technology architecture; design and dimensioning of the new technology infrastructure that will support the services; economic analysis; sensitivity and scenario analysis. Besides the methodology proposition, this work includes a case study illustrating its application to a fictional service provider.

A evolução do portfolio de serviços das operadoras em direção a ofertas convergentes que combinam serviços de voz, dados e vídeo é uma tendência do setor de telecomunicações. É neste contexto que o conceito de Internet Protocol Television (IPTV) ganha um papel relevante, pois permite às operadoras oferecerem serviços de vídeo utilizando como base uma infra-estrutura de rede convergente baseada em Internet Protocol (IP). Entretanto, existem diversos desafios relacionados à introdução de serviços IPTV. A nova realidade que inclui os serviços de vídeo apresenta um patamar de complexidade superior ao dos serviços já conhecidos. No que diz respeito à tecnologia, existem questões que permeiam desde a adaptação da infra-estrutura de rede e sistemas existentes até a implantação de plataformas de vídeo, até então não usuais no ambiente das operadoras. Neste cenário de complexidade, a metodologia de análise técnico-econômica proposta neste trabalho se torna útil para suportar a tomada de decisão relacionada à introdução de serviços IPTV. A metodologia proposta visa gerar subsídios para a identificação das condições em que se verifica a viabilidade econômica do serviço tendo em vista aspectos relacionados ao próprio serviço e a arquitetura tecnológica que o suporta. Para isto, a metodologia abrange as seguintes atividades: definição do serviço; mapeamento de seus requisitos; análise da arquitetura tecnológica existente; delineamento e dimensionamento da arquitetura tecnológica que suportará os novos serviços; modelagem econômica; análise de sensibilidade e cenários; e, por fim, análise dos resultados. Além da proposição da metodologia de análise, este trabalho inclui a aplicação da metodologia proposta em um caso de referência representativo da realidade de uma operadora de telecomunicações. / The evolution towards integrated service offerings that combine voice, video and data is a key trend for telecommunications service providers. IP-based technology plays an important role on this scenario by enabling the delivery of video over a multiservice IP network, a service commonly known as Internet Protocol Television (IPTV). There are many challenges to a large scale roll out of IPTV services, though. When compared to traditional voice and data services, video services introduce a higher level of complexity to the service providers\' environment. The technology issues related to IPTV range from the upgrade of the existing networks and systems to the deployment of new technology platforms oriented to video services delivery, which are not common in a service provider\'s technology architecture. Within this context, the techno-economic analysis methodology presented in this work aims to support the decision process underlying the IPTV services launch by a telecommunications service provider. The proposed methodology leads to the identification of economic feasibility conditions associated to relevant services aspects and required technology infrastructure alternatives. The methodology encompasses the main following activities: services definition; services\' requirements identification; analysis of the existing technology architecture; design and dimensioning of the new technology infrastructure that will support the services; economic analysis; sensitivity and scenario analysis. Besides the methodology proposition, this work includes a case study illustrating its application to a fictional service provider.

In a wireless and mobile communication paradigm, distribution and sharing of video content often occurs over unfriendly network environments constrained by lack of sufficient bandwidth, and prone to jitter, delay and packet losses. The research presented in this thesis proposed an assortment of application-specific optimizations designed to enable high-quality video communication over bandwidth constrained and unreliable channels. This assortment of solutions, termed herein as the Application Specific Video Coding and Delivery (ASVCD) toolkit, comprises of content and network adaptive approaches such as Region of Interest (ROI) video coding, Multiple Representation Coding (MRC), and Multiple Representation Coding of the Region of Interest (ROI + MRC). Thus, the effectiveness of ROI based video-coding in facilitating diagnostically lossless delivery of surgical videos over very low bandwidth channels was studied in this thesis. Furthermore, to facilitate error resilient video delivery over channels prone to burst losses and signal loss intervals, the MRC scheme was presented in this thesis. Finally, the thesis proposed a scheme for unequal protection of the ROI in the video by using the MRC scheme to effectively enable a distance learning application. To summarize, the ASVCD toolkit contributed in enabling high-quality video communications applications to become seamless and pervasive.

Future wireless networks will be required to support multimedia traffic in addition to traditional best-effort network services. Supporting multimedia traffic on wired networks presents a large number of design problems, particularly for networks that run connectionless data transport protocols such as the TCP/IP protocol suite. These problems are magnified for wireless links, as the quality of such links varies widely and uncontrollably. This dissertation presents new tools developed for the design and realization of wireless networks including, for the first time, analytical channel models for predicting the efficacy of error control codes, interleaving schemes, and signalling protocols, and several novel algorithms for matching and adapting system parameters (such as error control and frame length) to time-varying channels and Quality of Service (QoS) requirements.

Silicon alternatives to quartz crystal based oscillators to electronic system clocking are explored. A study of clocking requirements reveals widely different specifications for different applications. Traditional CMOS oscillator-based solutions are optimized for low-cost fully integrated micro-controller clock applications. The frequency variability of these clock generators is studied and techniques to compensate for this variability are proposed. The efficacy of these techniques in reducing variability is proven theoretically and experimentally. MEMS-resonator based oscillators, due to their exceptional quality factors, are identified as suitable integrated replacements to quartz based oscillators for higher accuracy applications such as data converter clocks. The frequency variation in these oscillators is identified and techniques to minimize the same are proposed and demonstrated. The sources of short-term variation (phase noise) in these oscillators are discussed and an inclusive theory of phase noise is developed. Techniques to improve phase noise are proposed. Findings from this research indicate that MEMS resonator based oscillators, may in future, outperform quartz based solutions in certain applications such as voltage controlled oscillators. The implications of these findings and potential directions for future research are identified.

Video frame rate up-conversion is an important issue for multimedia systems in achieving better video quality and motion portrayal. Motion-compensated methods offer better quality interpolated frames since the interpolation is performed along the motion trajectory. In addition, computational complexity, regularity, and memory bandwidth are important for a real-time implementation. Motion-compensated frame rate up-conversion (MC-FRC) is composed of two main parts: motion estimation (ME) and motion-compensated frame interpolation (MCFI). Since ME is an essential part of MC-FRC, a new fast motion estimation (FME) algorithm capable of producing sub-sample motion vectors at low computational-complexity has been developed. Unlike existing FME algorithms, the developed algorithm considers the low complexity sub-sample accuracy in designing the search pattern for FME. The developed FME algorithm is designed in such a way that the block distortion measure (BDM) is modeled as a parametric surface in the vicinity of the integer-sample motion vector; this modeling enables low computational-complexity sub-sample motion estimation without pixel interpolation. MC-FRC needs more accurate motion trajectories for better video quality; hence, a novel true-motion estimation (TME) algorithm targeting to track the projected object motion has been developed for video processing applications, such as motion-compensated frame interpolation (MCFI), deinterlacing, and denoising. Developed TME algorithm considers not only the computational complexity and regularity but also memory bandwidth. TME is obtained by imposing implicit and explicit smoothness constraints on block matching algorithm (BMA). In addition, it employs a novel adaptive clustering algorithm to keep the low-complexity at reasonable levels yet enable exploiting more spatiotemporal neighbors. To produce better quality interpolated frames, dense motion field at the interpolation instants are obtained for both forward and backward motion vectors (MVs); then, bidirectional motion compensation using forward and backward MVs is applied by mixing both elegantly.

Wireless multimedia sensor networks (WMSNs) are networks of interconnected devices that allow retrieving video and audio streams, still images, and scalar data from the environment. In a densely deployed WMSN, there exists correlation among the observations of camera sensors with overlapped coverage areas, which introduces substantial data redundancy in the network. In this dissertation, efficient communication schemes are designed for WMSNs by leveraging the correlation of visual information observed by camera sensors. First, a spatial correlation model is developed to estimate the correlation of visual information and the joint entropy of multiple correlated camera sensors. The compression performance of correlated visual information is then studied. An entropy-based divergence measure is proposed to predict the compression efficiency of performing joint coding on the images from correlated cameras. Based on the predicted compression efficiency, a clustered coding technique is proposed that maximizes the overall compression gain of the visual information gathered in WMSNs. The correlation of visual information is then utilized to design a network scheduling scheme to maximize the lifetime of WMSNs. Furthermore, as many WMSN applications require QoS support, a correlation-aware QoS routing algorithm is introduced that can efficiently deliver visual information under QoS constraints. Evaluation results show that, by utilizing the correlation of visual information in the communication process, the energy efficiency and networking performance of WMSNs could be improved significantly.

Thesis (Ed.D.)--Teachers College, Columbia University, 1996. / Typescript; issued also on microfilm. Accompanying materials in Spanish. Sponsor: Robert Taylor. Dissertation Committee: Robert McClintock. Includes bibliographical references (leaves 125-135).