11 research outputs found

    The Calling Network: A Global Telephone Utility

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    There is a very large demand for basic telephone service in developing nations, and remote parts of industrialized nations, which cannot be met by conventional wireline and cellular systems. This is the world\u27s largest unserved market. We describe a system which uses recent advances in active phased arrays, fast-packet switching technology, adaptive routing, and light spacecraft technology, in part based on the work of the Jet Propulsion Laboratory and on recently-declassified work done on the Strategic Defense Initiative, to make it possible to address this market with a global telephone network based on a large low-Earth-orbit constellation of identical satellites. A telephone utility can use such a network to provide the same modem basic and enhanced telephone services offered by telephone utilities in the urban centers of fully-industrialized nations. Economies of scale permit capital and operating costs per subscriber low enough to provide service to all subscribers, regardless of location, at prices comparable to the same services in urban areas of industrialized nations, while generating operating profits great enough to attract the capital needed for its construction. The bandwidth needed to support the capacity needed to gain those economies of scale require that the system use Ka-band frequencies. This choice of frequencies places unusual constraints on the network design, and in particular forces the use of a large number of satellites. Global demand for basic and enhanced telephone service is great enough to support at least three networks of the size described herein. The volume of advanced components, and services such as launch services, required to construct and replace these networks is sufficient to propel certain industries to market leadership positions in the early 21st Century

    The mobile satellite service (MSS) systems for global personal communications

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    A worldwide interest has arisen on personal communications via satellite systems. The recently proposed mobile satellite service(MSS) systems are categorized four areas: geostationary earth orbit(GEO) systems, medium earth orbit(MEO) systems, low earth orbit(LEO) systems, and highly elliptical orbit(HEO) systems. Most of the systems in each category are introduced and explained including some technical details. The communication links and orbital constellations of some systems are analyzed and compared with different categories, and with different systems. Some economical aspects of the systems are mentioned. The regulatory issues about frequency spectrum allocation, and the current technical trends in these systems are summarized

    Routing algorithm for provision of end-to-end delay QoS for low earth orbit satellite networks

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    Master'sMASTER OF ENGINEERIN

    A Survey on Non-Geostationary Satellite Systems: The Communication Perspective

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    The next phase of satellite technology is being characterized by a new evolution in non-geostationary orbit (NGSO) satellites, which conveys exciting new communication capabilities to provide non-terrestrial connectivity solutions and to support a wide range of digital technologies from various industries. NGSO communication systems are known for a number of key features such as lower propagation delay, smaller size, and lower signal losses in comparison to the conventional geostationary orbit (GSO) satellites, which can potentially enable latency-critical applications to be provided through satellites. NGSO promises a substantial boost in communication speed and energy efficiency, and thus, tackling the main inhibiting factors of commercializing GSO satellites for broader utilization. The promised improvements of NGSO systems have motivated this paper to provide a comprehensive survey of the state-of-the-art NGSO research focusing on the communication prospects, including physical layer and radio access technologies along with the networking aspects and the overall system features and architectures. Beyond this, there are still many NGSO deployment challenges to be addressed to ensure seamless integration not only with GSO systems but also with terrestrial networks. These unprecedented challenges are also discussed in this paper, including coexistence with GSO systems in terms of spectrum access and regulatory issues, satellite constellation and architecture designs, resource management problems, and user equipment requirements. Finally, we outline a set of innovative research directions and new opportunities for future NGSO research

    Space-Based Information Infrastructure Architecture for Broadband Services

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    This study addressed four tasks: (1) identify satellite-addressable information infrastructure markets; (2) perform network analysis for space-based information infrastructure; (3) develop conceptual architectures; and (4) economic assessment of architectures. The report concludes that satellites will have a major role in the national and global information infrastructure, requiring seamless integration between terrestrial and satellite networks. The proposed LEO, MEO, and GEO satellite systems have satellite characteristics that vary widely. They include delay, delay variations, poorer link quality and beam/satellite handover. The barriers against seamless interoperability between satellite and terrestrial networks are discussed. These barriers are the lack of compatible parameters, standards and protocols, which are presently being evaluated and reduced

    Serviços pós-4G em redes de satélite LEO com recepção multi-pacote e com handover

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    Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de ComputadoresUm pacote com erros, quer seja devido à existência de colisões ou ruído no canal, é normalmente descartado e necessita de ser retransmitido, levando a perdas de desempenho. A junção do protocolo H-ARQ (Hybrid Automatic Retransmission reQuest) com técnicas de recepção multi-pacote e com diversidade temporal como o NDMA (Network Diversity Multiple Access), melhoram o desempenho, visto terem a capacidade de pedir transmissões extra e combinar todos os sinais recebidos no mesmo período. Contudo, o atraso provocado pelo tempo de ida e volta na comunicação com uma rede de satélites, limita o número de retransmissões que possam ser pedidas pelos terminais para garantir qualidade de serviço. Esta tese considera o desenho de um protocolo híbrido que combina H-ARQ com NDMA para redes satélites com tráfego atribuído a pedido. O protocolo S-NDMA (Satellite NDMA) é apresentado, juntamente com modelos analíticos para o seu desempenho. É analisada a sua eficiência energética, tendo em conta requisitos de qualidade de serviço (QoS). O sistema é feito para satélites de órbita baixa (LEO) e com SC-FDE (Single-Carrier with Frequency Domain Equalization). É feita também uma comparação de desempenhos deste esquema com H-NDMA (Hybrid-NDMA), mostrando que é eficiente em termos energéticos e que cumpre requisitos de QoS para serviços exigentes como videochamadas. São necessários vários satélites para cobrir uma vasta área do planeta. Como os satélites estão em constante movimento, a zona de cobertura associada a cada satélite também se desloca. Isto leva a uma necessidade do terminal móvel trocar constantemente de ligação para um novo satélite. Nesta dissertação são propostos dois esquemas para S-NDMA: o tradicional com interrupção temporária de ligação, e um novo com continuidade de ligação baseado em SIMO distribuído. São estudadas a viabilidade e desempenho dos dois esquemas, analisando-se a eficiência energética, o efeito de Doppler, o ponto óptimo de troca e o atraso no tempo na comunicação entre terminais móveis e satélites
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