L’augmentation et le renforcement des usages d’Internet rend nécessaire l’évolution des réseaux existants. Cependant, on constate de fortes inégalités entre les zones urbaines, bien desservies et qui concentrent l’essentiel des investissements, et les zones rurales, mal desservies etdélaissées. Face à cette situation, les utilisateurs de ces zones se tournent vers d’autres moyensd’accès, et notamment vers les accès Internet par satellite. Cependant, ces derniers souffrentd’une limitation qui est le délai important induit par le temps de propagation du signal entre la terre et l’orbite géostationnaire. Dans cette thèse, nous nous intéressons à l’utilisation simultanée d’un réseau d’accès terrestre, caractérisé par un faible débit et un faible délai, et d’un réseau d’accès satellite, caractérisé par une forte latence et un débit plus important. D’autre part, les réseaux dediffusion de contenus ou CDNs, constitués d’un grand nombre de serveurs de cache, apportentune réponse à l’augmentation du trafic et des besoins en termes de latence et de débit.Cependant, localisés dans les réseaux de cœur, les caches restent éloignés des utilisateurs etn’atteignent pas les réseaux d’accès. Ainsi, les fournisseurs d’accès Internet (FAI) se sontintéressés au déploiement de ces serveurs au sein de leur propre réseau, que l’on appelle alorsTelCo CDN. La diffusion des contenus nécessite idéalement l’interconnexion des opérateurs CDNavec les TelCo CDNs, permettant ainsi la délégation de la diffusion à ces derniers. Ils sont alorsen mesure d’optimiser la diffusion des contenus sur leur réseau dont ils ont une meilleureconnaissance. Ainsi, nous nous intéresserons à l’optimisation de la livraison de contenus sur unréseau hybride satellite / terrestre intégré à une chaîne de livraison CDN. Nous nous attacheronsdans un premier temps à décrire une architecture permettant, grâce à l’interconnexion de CDNs,de prendre en charge la diffusion des contenus sur le réseau hybride. Dans un second temps,nous étudierons l’intérêt de la connaissance des informations apportées par le contexte CDN pour le routage sur une telle architecture. Dans ce cadre, nous proposerons un mécanisme de routage fondé sur la taille des contenus. Finalement, nous montrerons la supériorité de notre approche sur l’utilisation du protocole de transport multichemin MP-TCP

Made available in DSpace on 2014-06-11T19:25:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02Bitstream added on 2014-06-13T19:12:15Z : No. of bitstreams: 1 garcia_rv_me_guara.pdf: 930247 bytes, checksum: b94e8ad1078ac15ad366a27e55b66b3a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Uma abordagem analítica para o movimento rotacional de satélites artificiais estabilizados por rotação é apresentada, considerando os satélites em órbita elíptica e a influência do torque magnético residual. O torque magnético residual resulta da interação entre o campo magnético residual do satélite e o campo geomagnético, sendo este representado pelo modelo de quadripolo. As equações do movimento são descritas em termos do módulo da velocidade de rotação do satélite, da declinação e da ascensão reta do eixo de rotação do satélite. As componentes médias do torque residual em um sistema fixo no satélite são determinadas para um período orbital. Uma solução analítica para as equações do movimento é determinada, sendo válida para um período orbital. Por esta solução observa-se que o torque residual não afeta o módulo da velocidade de rotação, contribuindo apenas para as variações temporais da ascensão reta e declinação do eixo de rotação, associadas com a precessão e deriva do eixo de rotação do satélite. Aplicações são realizadas para os Satélites de Coleta de Dados Brasileiros SCD1 e SCD2, mostrando uma concordância entre os resultados obtidos pela teoria e os dados fornecidos pelo Centro de Controle de Satélites do INPE. O comportamento do erro gerado na direção do eixo de rotação do satélite é também apresentado, sendo que os desvios obtidos se mostram de acordo com as precisões requeridas para as missões destes satélites. / An analytical approach is show for attitude motion of the spin stabilized artificial satellite in an elliptic orbit. Residual magnetic torque is considered and the geomagnetic torque is defined by the quadripole model. The equations of motion are described by the magnitude of the spin velocity, right ascension and declination of the spin axis. The components of the averaged residual torque are computed for one orbital period in a satellite reference system. An analytical solution is presented and it is valid for one orbit period. By this solution it is possible to observe that the residual torque causes the precession and the drift of the spin axis, but it does not affect the magnitude of spin velocity. Some applications are done for Brazilian Satellite SCD1 and SCD2, and they show the agreement of the theory results and the data provide by INPE Satellite Control Center. The behavior of the error in the spin axis direction is also presented and this error agrees with the required precision of these satellite missions.

Résumé non disponible / Résumé non disponible

[pt] Este trabalho faz parte do projeto de um sistema distribuído de microcomputadores, MULTIPUC, em desenvolvimento no Laboratório de Engenharia e Sistemas de Computação (LESC) DA PUC/RJ. Neste trabalho descreve-se o projeto e desenvolvimento de duas máquinas: - O computador Central do MULTIPUC - controlador Inteligente de Comunicação O computador Central do MULTIPUC é baseado no microprocessador 8086 da Intel e sua finalidade é gerenciar os acessos dos microcomputadores satélites do MULTIPUC às memórias secundárias e dispositivos periféricos e ainda, a comunicação dos satélites entre si e com máquinas externas ao MULTIPUC. O Controlador Inteligente de comunicação é um processador dedicado à tarefas de comunicações externas e é baseado no microprocessador 8085 da Intel e no controlador programável de DMA 8237 da Intel. / [en] This work is part of a microcomputer network Project called MULTIPUC which hás been developed at the Laboratório de Engenharia e Sistemas de Computação (LESC). This work is a description of the design and implementation of two machine: - The MULTIPUC Central Computer - The communication Intelligent Controller The MULTIPUC Central Computer is based on the Intel 8086 microprocessor. Its main purpose is to manage the accesses of the MULTIPUC microcomputers called SATÉLITES to secundary memories and peripherals and also the communication of SATÉLITES among themselves and other computeres external to MULTIPUC. The communication Inteligent Controller is a processor dedicated to tasks of external communications and is based on the Intel 8085 microprocessor and the Intel 8237, programmable DMA Controller.

The emerging trend in distributed spacecraft systems of using multiple spacecraft which share functions as opposed to independent spacecraft has given opportunities for missions previously infeasible. Inter-satellite link (ISL) communications provide a direct link within the space segment without need of an intermediate ground segment to relay the data. As the distributed spacecraft systems (DSS) have become less exotic and more complex, the need and demand for inter-satellite antenna systems has increased and the requirements for the antenna systems more diverse and become more demanding. This document is a research of the antennas currently used for ISL, already flown or will be launched in the near future. While the emphasis is strongly in the antennas, the other parts of the ISL communications sub-systems are observed. To limit the scope of the work, optical cross links are not observed in this document. ISL used only for very close proximity, such as several kilometres, are given only limited scope as the main challenges on those do not involve antennas. Furthermore, the major emphasis is given to systems which can be seen as commercially important. This document is divided in five main sections and the conclusions. In the first section the features and the challenges of ISLs are described. In the second section a parametrisation system for antennas is defined and this system is used in following sections to describe the ISL sub-systems and antenna used in them. The third part is a survey of recently flown space missions with ISLs. The fourth section is a survey on the missions which are scheduled to fly in near future and a brief survey of the solutions offered by satellite service providers and manufacturers. Due to the limited technical data available, the fourth section contains far more reverse engineering and assumptions than the survey on legacy missions. The fifth section describes the several families of ISL suitable antennas under development and discusses about several topics which relate to the ISL antenna development. In this part also are defined several example antenna specifications and the applications of those. The study concludes that antennas suitable for inter-satellite links are not inherently different from ground segment communication antennas of the S/C. The major difference is the need for greater coverage, which can be attained by multiple antenna elements, beam steering or antenna pointing. Specific considerations are needed to be taken into account and often the use of ISLs will increase the technical challenges, but it can provide solutions for problems which cannot be solved otherwise. / çDie sich abzeichnende Entwicklung von Einzelsatellitensysteme hin zu Systemen mit einer Vielzahl an Plattformen gleicher Funktionalität, eröffnet Möglichkeiten für die Durchführung von Missionen die bisher als nicht praktikabel/undurchführbar bewertet wurden. Inter-satellite Link (ISL) Kommunikation stellt eine direkte Verbindung zwischen den einzelnen Komponenten eines Raumsegments zur Verfügung ohne auf ein zwischengeschaltetes Bodensegment zur Datenübertragung angewiesen zu sein. Die gestiegene Anwendungshäufigkeit und Komplexität von Distributed Spacecraft Systemen (DSS) bringen eine Erhöhung der Nachfrage bezüglich Antennen für die inter-satelliten Kommunikation mit sich, wobei die Anforderungen an diese vielfältiger und anspruchsvoller geworden sind. Diese Abschlussarbeit stellt eine Untersuchung bezüglich Antennensystemen dar, welche in der Vergangenheit, der Gegenwart sowie der nahen Zukunft ihre Verwendung in der ISL fanden und finden werden. Während auch die anderen Bestandteile eines ISL Kommunikation Subsystems betrachtet werden, liegt der Schwerpunkt der Studie maßgeblich auf den Antennen selbst. Um den Rahmen der Arbeit zu wahren wird auf die Betrachtung optischer Kommunikationssysteme verzichtet. Bei inter-satellite Link Systemen die zur Datenübertragung über kurze Distanzen von nur einigen Kilometern benutzt werden liegen die Herausforderungen nicht bei den Antennen, weswegen diese nur bedingt untersucht werden. Weiter werden besonders die Systeme betrachtet welche als wichtig für die kommerzielle Anwendung erachtet werden können. Diese Arbeit ist in insgesamt sechs Abschnitte unterteilt. Im ersten Kapitel werden zunächst die Eigenschaften und die Herausforderungen bezüglich ISLs erläutert. Ein System zur Parametrisierung von Antennen wird im zweiten Kapitel definiert um es in den folgenden Abschnitten zur Beschreibung der ISL Subsysteme anzuwenden. Eine Analyse der Instrumentierung vergangener Weltraummission mit ISL Systemen wird im dritten Kapitel durchgeführt, die Betrachtung zukünftiger Missionen erfolgt in Kapitel 4. Da für Letztere nur begrenzt technische Daten zur Verfügung stehen, beinhaltet das vierte Kapitel weitaus mehr Reverse Engineering und Annahmen als die Untersuchung abgeschlossener Missionen. Im fünften Kapitel werden verschiedenen, für die inter-satellite Kommunikation geeigneten Antennentypen beschrieben und unterschiedliche Themen bezüglich der ISL Antennenentwicklung diskutiert. Weiter werden in diesem Abschnitt verschiedene Antennenspezifikationen definiert und entsprechende Anwendungsbeispiele beschrieben. Im letzten Teil werden die gefundenen Erkenntnisse abschließend diskutiert. Die Untersuchung zeigt dass Antennen welche für die inter-satelliten Kommunikation geeignet sind, sich grundsätzlich nicht von gängigen Antennen zur Bodensegmentkommunikation des S/C unterscheiden. Der Hauptunterschied liegt in der Notwendigkeit einer größeren Abdeckung. Dies kann durch eine größere Anzahl von Antennenelementen, Strahlsteuerung oder Antennenausrichtung erreicht werden. Systemspezifische Erwägungen müssen in Betracht gezogen werden wobei die Anwendung von ISL Systemen die technischen Herausforderungen/Anforderungen erhöht. Im Gegenzug ermöglicht sie Lösungen für Probleme die auf andere Weise nicht behandelt werden können. / Une nouvelle tendance est apparue dans les systèmes décentralisés des satellites, consistant à utiliser plusieurs satellites qui partagent des fonctionnalités, plutôt que des satellites indépendants. Cela a rendu possible des missions qui étaient précédemment irréalisables. Le lien inter-satellite (ISL) permet en effet de communiquer directement dans l’espace, sans devoir utiliser le segment sol pour transmettre les données. Alors que les systèmes décentralisés des satellites (DSS) sont devenus moins exotiques et plus complexes, la nécessité et la demande de systèmes d’antennes inter-satellite se sont développées et les exigences pour les systèmes d’antennes se sont diversifiés et sont devenus plus contraignants. Ce document réalise une étude des différentes antennes actuellement utilisées pour le ISL, dont certaines sont déjà opérationnelles et d’autres seront lancées prochainement. Tandis qu’il met fortement l’accent sur les antennes en ellesmêmes, il étudie aussi les autres parties des sous-systèmes de communication ISL. Néanmoins, pour limiter la portée du document, les réticulations optiques ne sont pas abordées. De même, les ISLs utilisés pour les communications à faible portée, de l’ordre de quelques kilomètres, ne sont que brièvement évoquées, étant donné que les défis majeurs concernant ceux-ci n’impliquent pas les antennes. Au delà de ça, ce document met surtout l’accent sur les systèmes qui peuvent être vu comme commercialement importants. Ce document est divisé en cinq sections, en plus de la conclusion. Dans la première section sont décrit les caractéristiques et les challenges des ISLs. Dans la seconde section, un système de paramétrage pour les antennes est défini et ce système est utilisé dans les sections suivantes pour décrire les sous-systèmes ISLs ainsi que les antennes associées. La troisième partie donne un aperçu des récentes missions spatiales lancées avec ISLs. La quatrième section étudie quant à elle les missions prochainement programmées et donne un bref aperçu des solutions offertes par les fournisseurs et fabricants des services satellitaires. Dû à la limitation des donéees techniques disponibles, cette section est principalement basée sur l’ingénierie inverse et des hypothèses, comparé aux missions déjà lancées et discutées en section 3. Finalement, la cinquième section décrit les différentes familles d’antennes ISL sous développement et discute de plusieurs sujets liés à leur développement. Elle définit aussi plusieurs exemples de spécifications d’antennes, et les applications associées. L’étude conclut que les antennes adaptées pour les liens inter-satellite ne sont pas très différentes des antennes de communication au sol du satellite, la plus grande différence étant la nécessité d’une plus grande couverture réseau. Celle-ci peut être atteinte via l’utilisation de plusieurs antennes, l’orientation du faisceau ou le pointage de l’antenne. Des considérations particulières doivent être prises en compte et souvent, l’utilisation des ISLs augmente les défis techniques. Néanmoins, cela constitue une solution à des problèmes qui ne peuvent pas être résolus autrement.

In broadband multimedia satellite networks it is necessary to multiplex bursty streams of traffic with differing Quality of Service (QoS) requirements to maximise the utilisation of the satellite link bandwidth. Providing the desired QoS of each service, in a multi-service environment is a major challenge for satellite networks. Asynchronous Transfer Mode (ATM) which provides hard QoS guarantees is suitable for a multi-service satellite environment. ATM has been developed as a vehicle for multimedia communications and is widely regarded as one of the most important and fastest-growing communications technology of this decade. The design of suitable traffic and congestion control algorithms is one of the most important challenge for the success of an ATM-based satellite network. This thesis develops and optimises a traffic and congestion control mechanism which can provide users the required QoS for ATM over satellite networks. In order to provide QoS differentiation for end-to-end communication it is proposed to use both loss and delay priorities, which are determined form the required Cell Loss Rate (CLR) and Cell Transfer Delay (CTD) parameters, for each service class. A multiple shared buffer scheduling (MSBS) policy considering both delay and loss priorities, is proposed and evaluated for scheduling and discarding of ATM cells. It is shown that both the CTD and CLR requirements of ATM services can be met by the MSBS scheme. A combined preventive/reactive control scheme incorporating an adaptive Leaky Bucket (LB) is investigated for the satellite environment. It has been found that reactive control improves the cell loss due to congestion for time scales larger than the propagation delay. As the satellite air interface bandwidth is currently one of the most expensive commodities in the service provision, an adaptive MAC protocol that can support the ATM service classes whilst maximising the bandwidth utilisation, is proposed and evaluated. The mapping of ATM service classes to MAC classes and the use of a prioritised request queue provides the QoS differentiation required by ATM networks. It is shown that a pure reservation system performs poorly for very bursty user traffic. The user population which can be supported using Random Access (RA) for very bursty users with short burst duration is higher. The system throughput can be maximised, by making this protocol adaptive to changing traffic characteristics. It is shown that the utilisation of the frame capacity and the total number of users served can be improved by using this protocol.

Knowledge of distributions of aerosols is critical to human health, Earth's radiative budget, and air quality. However, the lack of sufficient direct measurements of aerosol type, number, mass concentrations and current limitations of satellite retrievals make it challenging to accurately model the aerosol variability. Such measurement gaps also hinder evaluation of aerosol source budget from emission inventories, modeling of aerosol chemistry, and sinks. In this context, the first study characterizes the potential of multivariate relationships between Aerosol Optical Depth (AOD), a quantity that represents light extinction by aerosols in the atmospheric column and a suite of surface and atmospheric parameters (e.g., vegetation, precipitation, fire characteristics) in order to assess trends in AOD anomalies for the U.S Southwest. This study covers the area that experiences North American Monsoon (NAM) and examines trends in AOD across different aerosol sources in this region such as dust storms, biomass burning, and anthropogenic emissions. We find that aerosols from anthropogenic processes and biomass burning exhibited a strong declining trend in AOD whereas trends along the NAM alley were obfuscated by the monsoon precipitation (sink) and convective dust storms (sources). In the second study, we develop constraints to improve characterization of anthropogenic apparent Elemental Carbon (ECa) using coemitted combustion products such as Carbon Monoxide (CO) and Nitrogen Oxides (NOx). We compare observational ratios of ECa vs CO and ECa vs NOx against those from emission inventories. We find that the observational ratios have increased at sites in the Urban-West due to increase in ECa from 2000-2007 to 2008-2015. Further, emission ratios do not match with observational ratios. We recommend that rigorous efforts are needed to better quantify and monitor the changes in these species in the Urban-West particularly for non-road and residential combustion sectors. The final study of this dissertation discusses a technique to produce forecasts of AOD by combining satellite retrievals and a chemical transport model in an analog based framework. We use model forecasts of AOD, particulate matter (PM) concentrations, and meteorological parameters from Weather Research and Forecasting model with Chemistry (WRF-Chem) to train the framework for choosing analogs (past forecasts similar to current simulations). MODIS Terra and Aqua satellite retrievals of AOD for analog days are then used in a Kalman Filter (KF) framework to determine the forecast error and referred to as KFAN. The analog based estimates better forecasts of AOD for the Western US compared to the East and the mean bias in AOD forecasts are reduced to the range of 0.001-0.1. The reduction in positive bias in AOD is drastic and the method captures the decrease in AOD from morning to afternoon. We find that higher root mean square error (RMSE) values in the East are due to the inability of KFAN to capture the AOD peaks during biomass burning episodes and AOD lows during days of high precipitation rates. A systematic statistical analysis using step-wise linear regression models also show that in the East, there is a stronger dependence of aerosol loading on meteorological factors such as air temperature, precipitation, and relative humidity. As a consequence, overall quality of the analogs in the East is impacted when uncertainties in the simulated meteorological fields are higher. Overall, this study shows that the correlative information from multi-satellite remote sensing retrievals and models provide additional constraints on aerosols using composition/source identification (e.g., aerosol type, landcover, emission sources, fuel consumption), coemitted gas phase species (e.g., CO and NOx), and meteorological parameters (e.g., wind speed, TPW). The synergy of information from these datasets can be beneficial for design of future remote sensing missions, deployment of ground networks, and studies related to feedbacks between meteorology and aerosols.

The upcoming launch of the German hyperspectral satellite: Environmental Mapping and Analysis Program (EnMAP) will provide potential for producing improved remotely sensed maps in areas of exposed bedrock in advance of Arctic geology programs. This study investigates the usefulness of this moderate resolution (30m) sensor for predictive lithological mapping using simulated imagery to classify a map area dominated by mafic and felsic volcanics and minor sedimentary and volcaniclastic rocks in the Hope Bay Greenstone Belt of the Northwest Territories. The assessment also included the classification of high resolution and fidelity airborne (ProSpecTIR–SPECIM Dual sensor) hyperspectral imagery for comparison to understand the impact of combined lower signal-to-noise ratio (SNR), and spectral and spatial resolutions associated with EnMap. The performance of both sensors was assessed through statistical analysis of the classification results based on partial unmixing of the data as well as common geological band indices. The results obtained from these analyses were compared to a detailed published geological map of the study area. Both sensors, the airborne ProSpecTIR–SPECIM and spaceborne EnMap, provided good results however despite the simulated EnMap data’s lower resolution and SNR, the results showed it to have greater statistical accuracy and to be visually representative of the mapped geology. The results demonstrated that EnMap satellite hyperspectral technology is an effective tool for mapping lithology in the Canadian North. The discrimination of rock compositions was successful when their occurrences were spatially large and abundant; however, it was identified that spectral similarity between unit classes and spectral variability within classes are critical factors in mapping lithology. / Graduate

Recently, wireless network technology has grown at such a pace that scientific research has become a practical reality in a very short time span. One mobile system that features high data rates and open network architecture is 4G. Currently, the research community and industry, in the field of wireless networks, are working on possible choices for solutions in the 4G system. The researcher considers one of the most important characteristics of future 4G mobile systems the ability to guarantee reliable communications at high data rates, in addition to high efficiency in the spectrum usage. On mobile wireless communication networks, one important factor is the coverage of large geographical areas. In 4G systems, a hybrid satellite/terrestrial network is crucial to providing users with coverage wherever needed. Subscribers thus require a reliable satellite link to access their services when they are in remote locations where a terrestrial infrastructure is unavailable. The results show that good modulation and access technique are also required in order to transmit high data rates over satellite links to mobile users. The dissertation proposes the use of OFDM (Orthogonal Frequency Multiple Access) for the satellite link by increasing the time diversity. This technique will allow for an increase of the data rate, as primarily required by multimedia applications, and will also optimally use the available bandwidth. In addition, this dissertation approaches the use of Cooperative Satellite Communications for hybrid satellite/terrestrial networks. By using this technique, the satellite coverage can be extended to areas where there is no direct link to the satellite. The issue of Cooperative Satellite Communications is solved through a new algorithm that forwards the received data from the fixed node to the mobile node. This algorithm is very efficient because it does not allow unnecessary transmissions and is based on signal to noise ratio (SNR) measures.

archives@tulane.edu / 1 / Sabrina Martinez