This work focuses on the autonomous exploration of unknown areas by a swarm of mobile robots, referred to as agents. When an emergency happens within a building, it is dangerous to send human responders to search the area for hazards and victims. This motivates the need for autonomous agents that are able to coordinate with each other to explore the area as fast as possible. We investigate this problem from an algorithmic, rather than a robotics point of view, and thus abstract away from practical problems, such as obstacle detection and navigation over rough terrain. Our focus is on distributed algorithms that can cope with the following challenges: the topology of the area is typically unknown, communication between agents is intermittent and unreliable, and agents are not aware of their location in indoor environments. In order to address these challenges, we adopt the stigmergy approach, that is, we assume that the area is instrumented with small inexpensive sensors (called tags) and agents coordinate indirectly with each other by reading and updating the state of local tags. We propose three novel distributed algorithms that allow agents to explore unknown areas by coordinating indirectly through a tag-instrumented environment. In addition, we propose two mechanisms for discovering evacuation routes from critical points in the area to emergency exits. Agents are able to combine the tasks of area exploration and evacuation route discovery in a seamless manner. We study the proposed algorithms analytically, and evaluate them empirically in a custom-built simulation environment in a variety of scenarios. We then build a real testbed of agents and tags, and investigate practical mechanisms that allow agents to detect and localise nearby tags, and navigate toward them. Using the real testbed, we derive realistic models of detection, localisation and navigation errors, and investigate how they impact the performance of the proposed exploration algorithms. Finally, we design fault-tolerant exploration algorithms that are robust to these errors and evaluate them extensively in a simulation environment.

Neste trabalho projetamos e construímos um terminal de baixo custo para o sistema de automação de laboratórios em desenvolvimento no L.I.E. Para tanto, discutimos as diversas arquiteturas empregadas nos terminais buscando obter subsídios com vistas à escolha da mais adequada as aplicações cientificas que são típicas desse microcomputador. Também é feito um estudo comparativo dos diversos dispositivos empregados como terminais, bem como das funções que desempenham nas disposições convencionais dos centros computacionais. Procurou-se implementar um terminal de custo extremamente reduzido, mas capaz de ser facilmente expandido pela incorporação de módulos adicionais. Também foi objetivo do trabalho prover um projeto sólido para permitir facilmente uma vasta gama de alterações, variando desde a substituição de alguns componentes até a troca de todo o sistema operacional residente. Para tanto houve grande cuidado na documentação dos esquemas e da programação. O dispositivo construído mostrou-se bastante versátil, confiável e baixíssimo custo / In the present work we compare several devices used as terminals, as well as the roles they play on a conventional computing centre. Their various architectural aspects are also investigated, providing the ground basis for a terminal biased towards scientific aplications, which are typical of the microcomputer system developed at L.I.E.. We wanted a very low cost traminal that still retained the capability of beeing expanded by the inclusion of additional modules. A solid Project, able to handle the most severe alterations, ranging from the replacement of some ICs to the replacement of the entire resident operational system was aso wanted. To accomplish these goals a great care was taken on the Project documentation of the software as well as of the hardware. The device that was eventually build proved to be very versatile, reliable and low cost one

Em dezembro de 2007, a partir da cidade de São Paulo, as transmissões de televisão digital terrestre e aberta tiveram início no Brasil. Um avanço significativo do Sistema Brasileiro de TV Digital (SBTVD) foi a adoção do padrão H.264/AVC e o formato de vídeo 1080i para a codificação de vídeo em alta definição. A adoção em larga escala de tecnologia de alta definição tem sido um processo observado em vários mercados do mundo, e novos formatos superiores ao 1080i já estão sendo discutidos e propostos. Tendo em vista o que será a próxima geração da televisão, centros de pesquisa, como o centro japonês da emissora NHK, investigam os fatores humanos determinantes para caracterizar o sistema que deverá ser o último passo em tecnologia de televisão 2D. Já nomeado de UHDTV, este sistema deve contemplar resolução de 7680 pontos horizontais por 4320 pontos verticais, além de outras características ainda em estudo. Ao mesmo tempo, o trabalho aqui apresentado discute as ferramentas de suporte da escalabilidade na codificação multimídia como forma de evolução gradual dos formatos de vídeo na radiodifusão. Especificamente este trabalho sistematiza as ferramentas de escalabilidade do padrão H.264/AVC tendo em vista a sua aplicação ao SBTVD. Neste sentido, são discutidas as possibilidades de evolução do sistema frente à escalabilidade e são apresentados levantamentos experimentais da atual ocupação do espectro na cidade de São Paulo, evidenciando a disponibilidade de taxa para expansões. São apresentados também resultados iniciais relativos à codificação SVC, que apontam objetivamente as vantagens da escalabilidade sobre o simulcast, evidenciando que esta técnica pode ser utilizada no SBTVD para prover novos formatos de vídeo, tendo como premissa a compatibilidade com os atuais receptores que suportam o formato 1080i. O trabalho apresenta contribuições teóricas e experimentais na direção de adoção da escalabilidade no SBTVD, apontando também possíveis trabalhos futuros que, se realizados, poderão confirmar a transmissão de formatos superiores de vídeo nos próximos anos no SBTVD. / On December 2007, starting from São Paulo city, the open digital terrestrial transmissions were launched in Brazil. A significant improvement of the Brazilian Digital TV System (SBTVD) was the adoption of the H.264/AVC standard supporting the 1080i video format for the high definition video coding. Wide adoption of high definition technology has been a process that can be observed in lots of countries, and new video formats, beyond 1080i have already been discussed and proposed. With both eyes in the next generation of TV, research centers like Japanese broadcaster NHK investigate human factors that should drive the system specifications of this one that may be the last step in terms of 2D television technology. Named UHDTV, the system may support 7680 horizontal dots per 4320 vertical dots in terms of resolution among other features. At the same time, the work exposed here discusses tools that support multimedia coding scalability as a way of gradually improving video formats for broadcast. This work specially deals with the H.264/AVC standard scalability tools, aiming their use within SBTVD. Therefore, the evolution of the system is discussed based on scalability and experimental results related to the digital TV spectral occupation in São Paulo city are analyzed, showing that there is enough exceeding bit rate available for future expansion. Initial results related to SVC coding are also shown, objectively indicating that video scalability is more advantageous than simulcast and that this technique can be used in SBTVD to provide new video formats, keeping compatibility with current receivers that only support 1080i format. This work presents theoretical and experimental contributions towards the adoption of SVC in the SBTVD, pointing out some future works that, if executed, could confirm the transmission of new video format in SBTVD in the next years.

The phenomenal growth in the use of the World Wide Web often places a heavy load on networks and servers, threatening to increase Web server response time and raising scalability issues for both the network and the server. With the advances in the field of optical networking and the increasing use of broadband technologies like cable modems and DSL, the server and not the network, is more likely to be the bottleneck. Many clients are willing to receive a degraded, less resource intensive version of the requested content as an alternative to connection failures. In this thesis, we present an adaptive content delivery system that transparently switches content depending on the load on the server in order to serve more clients. Our system is designed to work for dynamic Web pages and streaming multimedia traffic, which are not currently supported by other adaptive content approaches. We have designed a system which is capable of quantifying the load on the server and then performing the necessary adaptation. We designed a streaming MPEG server and client which can react to the server load by scaling the quality of frames transmitted. The main benefits of our approach include: transparent content switching for content adaptation, alleviating server load by a graceful degradation of server performance and no requirement of modification to existing server software, browsers or the HTTP protocol. We experimentally evaluate our adaptive server system and compare it with an unadaptive server. We find that adaptive content delivery can support as much as 25% more static requests, 15% more dynamic requests and twice as many multimedia requests as a non-adaptive server. Our, client-side experiments performed on the Internet show that the response time savings from our system are quite significant.

"Modern computer applications from business decision support to scientific data analysis use visualization techniques. However, visual exploration tools do not scale well for large data sets, i.e., the level of clutter on the screen is typically unacceptable. To solve the problem of cluttering at the interface level, visualization tools have recently been extended to support hierarchical views of the data, with support for focusing and drilling-down using interactive selection. To solve the scalability problem, we now investigate how best to couple such a near real-time responsive visualization tool with a database management system. Our solution proposes a framework containing three major components: hierarchy encoding, caching and prefetching. Since the direct implementation of the visual user interactions on hierarchical data sets corresponds to recursive query processing, we have developed a hierarchy encoding method, called the MinMax tree, that pushes the on-line recursive processing step into an off-line precomputation step. The MinMax encoding scheme allows us to map the hierarchy to a 2-dimensional space and the recursive navigation operations at the interface level to 2-dimensional spatial range queries. These queries can then be answered efficiently using spatial indexes. To compliment this encoding scheme we employ a caching strategy that exploits user navigation characteristics to cache the nodes having high probability of being referenced again. Based on user characteristics we choose to implement two replacement policies one which exploits temporal locality (LRU) and the other exploits spatial locality (Distance). Also, to enhance the performance of the cache we propose using a prefetching mechanism that predicts and prefetches future user requests into the cache. Together the components form a comprehensive framework that scales the visualization tool to support navigation operations over large data sets. The techniques have been incorporated into XmdvTool, a free software package for multi-variate data visualization and exploration. Our experimental results quantify the effectiveness of each component and show that collectively the components scale the XmdvTool to support navigation operations over large data sets. Mainly, our experimental results show that together the components can achieve 63\% to 96\%reduction in response time latency even with limited system resources."

Distribution over the internet is destined to become a standard approach for live broadcasting of TV or events of nation-wide interest. The demand for high-quality live video with personal requirements is destined to grow exponentially over the next few years. Endsystem multicast is a desirable option for relieving the content server from bandwidth bottlenecks and computational load by allowing decentralised allocation of resources to the users and distributed service management. Network coding provides innovative solutions for a multitude of issues related to multi-user content distribution, such as the coupon-collection problem, allocation and scheduling procedure. This thesis tackles the problem of streaming scalable video on end-system multicast overlays with prioritised push-based streaming. We analyse the characteristic arising from a random coding process as a linear channel operator, and present a novel error detection and correction system for error-resilient decoding, providing one of the first practical frameworks for Joint Source-Channel-Network coding. Our system outperforms both network error correction and traditional FEC coding when performed separately. We then present a content distribution system based on endsystem multicast. Our data exchange protocol makes use of network coding as a way to collaboratively deliver data to several peers. Prioritised streaming is performed by means of hierarchical network coding and a dynamic chunk selection for optimised rate allocation based on goodput statistics at application layer. We prove, by simulated experiments, the efficient allocation of resources for adaptive video delivery. Finally we describe the implementation of our coding system. We highlighting the use rateless coding properties, discuss the application in collaborative and distributed coding systems, and provide an optimised implementation of the decoding algorithm with advanced CPU instructions. We analyse computational load and packet loss protection via lab tests and simulations, complementing the overall analysis of the video streaming system in all its components.

LoRaWAN is an open networking technology designed for IoT devices that al-lows wireless data transmission over longer ranges than some other wireless tech-nologies, like Wi-Fi or Bluetooth, for devices that are constrained in terms of size,price, and available power. The current design of roaming among networks in LoRaWANis heavily inspired by that of mobile networks, as the use of roaming agreementsis mandated. Roaming agreements create unnecessary administrative overhead thathinders deployments. A roaming model that is quicker and simpler to deploy couldsave money for current users, and could even attract new users to the technology.To circumvent the necessity of roaming agreements, a new, scalable and agreement-less roaming model should be proposed. In this thesis project a literature survey isconducted, investigating similar technologies to find hints or inspiration for a newroaming model. It is found that the broker software architecture pattern put in thecontext of roaming in LoRaWAN suits the requirements quite well, so the new roam-ing model has been developed based on that. A software simulation has been imple-mented to gather data regarding the scalability of the model. It has been found thatthe proposed model is both scalable, and agreement-less.

Em dezembro de 2007, a partir da cidade de São Paulo, as transmissões de televisão digital terrestre e aberta tiveram início no Brasil. Um avanço significativo do Sistema Brasileiro de TV Digital (SBTVD) foi a adoção do padrão H.264/AVC e o formato de vídeo 1080i para a codificação de vídeo em alta definição. A adoção em larga escala de tecnologia de alta definição tem sido um processo observado em vários mercados do mundo, e novos formatos superiores ao 1080i já estão sendo discutidos e propostos. Tendo em vista o que será a próxima geração da televisão, centros de pesquisa, como o centro japonês da emissora NHK, investigam os fatores humanos determinantes para caracterizar o sistema que deverá ser o último passo em tecnologia de televisão 2D. Já nomeado de UHDTV, este sistema deve contemplar resolução de 7680 pontos horizontais por 4320 pontos verticais, além de outras características ainda em estudo. Ao mesmo tempo, o trabalho aqui apresentado discute as ferramentas de suporte da escalabilidade na codificação multimídia como forma de evolução gradual dos formatos de vídeo na radiodifusão. Especificamente este trabalho sistematiza as ferramentas de escalabilidade do padrão H.264/AVC tendo em vista a sua aplicação ao SBTVD. Neste sentido, são discutidas as possibilidades de evolução do sistema frente à escalabilidade e são apresentados levantamentos experimentais da atual ocupação do espectro na cidade de São Paulo, evidenciando a disponibilidade de taxa para expansões. São apresentados também resultados iniciais relativos à codificação SVC, que apontam objetivamente as vantagens da escalabilidade sobre o simulcast, evidenciando que esta técnica pode ser utilizada no SBTVD para prover novos formatos de vídeo, tendo como premissa a compatibilidade com os atuais receptores que suportam o formato 1080i. O trabalho apresenta contribuições teóricas e experimentais na direção de adoção da escalabilidade no SBTVD, apontando também possíveis trabalhos futuros que, se realizados, poderão confirmar a transmissão de formatos superiores de vídeo nos próximos anos no SBTVD. / On December 2007, starting from São Paulo city, the open digital terrestrial transmissions were launched in Brazil. A significant improvement of the Brazilian Digital TV System (SBTVD) was the adoption of the H.264/AVC standard supporting the 1080i video format for the high definition video coding. Wide adoption of high definition technology has been a process that can be observed in lots of countries, and new video formats, beyond 1080i have already been discussed and proposed. With both eyes in the next generation of TV, research centers like Japanese broadcaster NHK investigate human factors that should drive the system specifications of this one that may be the last step in terms of 2D television technology. Named UHDTV, the system may support 7680 horizontal dots per 4320 vertical dots in terms of resolution among other features. At the same time, the work exposed here discusses tools that support multimedia coding scalability as a way of gradually improving video formats for broadcast. This work specially deals with the H.264/AVC standard scalability tools, aiming their use within SBTVD. Therefore, the evolution of the system is discussed based on scalability and experimental results related to the digital TV spectral occupation in São Paulo city are analyzed, showing that there is enough exceeding bit rate available for future expansion. Initial results related to SVC coding are also shown, objectively indicating that video scalability is more advantageous than simulcast and that this technique can be used in SBTVD to provide new video formats, keeping compatibility with current receivers that only support 1080i format. This work presents theoretical and experimental contributions towards the adoption of SVC in the SBTVD, pointing out some future works that, if executed, could confirm the transmission of new video format in SBTVD in the next years.

This thesis concentrates on RF/microwave characterization and modeling of planar spiral inductors and pad stack parasitics. The inductors varied in size from 1.9 to 15.3 nH. Several approaches were examined for modeling the planar spiral inductors. The approach developed herein is built around an existing composite model (available in commercial computer-aided design software), with added series and shunt impedances at both the input and output of the existing composite model. Artificial neural network (ANN) software was used to determine the correction impedance values. Another approach investigated was to model the S-parameters of the inductor using a space- mapping model of the input parameters for the existing model. The correction impedance modeling approach was theoretically sound but the level of accuracy need for the ANN model was not obtainable. The space mapping approach had merit but a substrate and parameter scalable model could not be achieved. A pad stack is a section of microstrip line that a surface mounted element is affixed to; these pad stacks are standardized for specific element sizes, so for example any 0805 (80 mils by 50 mils) element may have the same pad stack whether it is a capacitor, inductor or resistor. The pad stack models were necessary because a capacitor model originally developed at the University of South Florida did not include parasitic effects for different input connections. The pad stack parasitic models can be broken down into three types: dual-input, tri-input, and quad-input. Each of the dual- and tri- input models have input angles of either 0 degrees, 45 degrees, or 90 degrees. The models were developed using a combination of microstrip and lumped elements.

<p>A method for constructing a highly scalable bit stream for video coding is presented in detail and implemented in a demo application with a GUI in the Windows Vista operating system.</p><p>The video codec uses the Discrete Wavelet Transform in both spatial and temporal directions together with a zerotree quantizer to achieve a highly scalable bit stream in the senses of quality, spatial resolution and frame rate.</p> / <p>I detta arbete presenteras en metod för att skapa en mycket skalbar videoström. Metoden implementeras sedan i sin helhet i programspråken C och C++ med ett grafiskt användargränssnitt på operativsystemet Windows Vista.</p><p>I metoden används den diskreta wavelettransformen i såväl de spatiella dimensionerna som tidsdimensionen tillsammans med en nollträdskvantiserare för att åstakomma en skalbar videoström i avseendena bildkvalitet, skärmupplösning och antal bildrutor per sekund.</p>