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Satellite Constellation (satellite + constellation)
Selected AbstractsPriority-based adaptive routing in NGEO satellite networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2007Ömer Korçak Abstract In a non-geostationary satellite constellation with inter satellite links (ISLs), there could be many shortest paths between two satellites in terms of hop count. An efficient routing algorithm should effectively use these paths in order to distribute traffic to ISLs in a balanced way and to improve the performance of the system. This paper presents and evaluates a novel priority-based adaptive shortest path routing (PAR) scheme in order to achieve this goal. PAR sets the path towards the destination in a distributed manner, using a priority mechanism depending on the past utilization and buffering information of the ISLs. Moreover, to avoid unnecessary splitting of a flow and to achieve better utilization of ISLs, enhanced PAR (ePAR) scheme is proposed. This paper evaluates performance of the proposed techniques by employing an extensive set of simulations. Furthermore, since there are a number of ePAR parameters that should be adjusted depending on the network and traffic characteristics, a detailed analysis of ePAR scheme is provided to form a framework for setting the parameters. This paper also includes a method for adaptation of the proposed algorithms to minimum-delay path routing. Copyright © 2006 John Wiley & Sons, Ltd. [source] Efficient IP-multicast via Inmarsat BGAN, a 3GPP satellite networkINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2007Paul Febvre Abstract This paper outlines a number of challenges associated with supporting IP-multicast services efficiently across the Inmarsat Broadband Global Area Network (BGAN) 3GPP-based satellite network operating over the Imarsat-4 satellite constellation. The paper presents a network architecture that extends the 3GPP reference architecture to allow IP-multicast to be delivered when the Core Network is in a 3GPP Release-4 (non-MBMS compliant) configuration. This paper further extends the service and system concepts defined in 3GPP MBMS to provide improved flexibility and accountability, and improved scalability and efficiency when operating with the Inmarsat-4 BGAN TDM/TDMA air interface. This paper describes a number of radio resource management techniques that were deployed in a test system and the validation testing that was undertaken to support multimedia distribution and VoIP-based netted communications applications. The tuning of application and system behaviour to achieve acceptable performance is described in outline. Copyright © 2007 John Wiley & Sons, Ltd. [source] Theatre in the Sky: a ubiquitous broadband multimedia-on-demand service over a novel constellation composed of quasi-geostationary satellitesINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2006Tarik Taleb Abstract To meet an ever-growing demand for wideband multimedia services and electronic connectivity across the world, development of ubiquitous broadband multimedia systems is gaining a tremendous interest at both commercial and academic levels. Satellite networks will play an indispensable role in the deployment of such systems. A significant number of satellite communication constellations have been thus proposed using Geostationary (GEO), Medium Earth Orbit (MEO), or Low Earth Orbit (LEO) satellites. These constellations, however, either require a potential number of satellites or are unable to provide data transmission with high elevation angles. This paper proposes a new satellite constellation composed of Quasi-GeoStationary Orbit (Quasi-GSO) satellites. The main advantage of the constellation is in its ability to provide global coverage with a significantly small number of satellites while, at the same time, maintaining high elevation angles. Based on a combination of this Quasi-GSO satellites constellation and terrestrial networks, the paper proposes also an architecture for building a global, large-scale, and efficient Video-on-Demand (VoD) system. The entire architecture is referred to as a ,Theatre in the Sky'. Copyright © 2006 John Wiley & Sons, Ltd. [source] Capacity provisioning and failure recovery for Low Earth Orbit satellite constellationINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2003Jun Sun This paper considers the link capacity requirement for an LEO satellite constellation. We model the constellation as an N×N mesh-torus topology under a uniform all-to-all traffic model. Both primary capacity and spare capacity for recovering from a link or node failure are examined. In both cases, we use a method of ,cuts on a graph' to obtain lower bounds on capacity requirements and subsequently find algorithms for routing and failure recovery that meet these bounds. Finally, we quantify the benefits of path-based restoration over that of link-based restoration; specifically, we find that the spare capacity requirement for a link-based restoration scheme is nearly N times that for a path-based scheme. Copyright © 2003 John Wiley & Sons, Ltd. [source] Analyzing GPS signals to investigate path diversity effects of non-geostationary orbit satellite communication systemsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2002Hsin-Piao Lin Abstract The concept behind path diversity is that a user who can access several satellites simultaneously will be able to communicate more effectively than a user who could only access one. The success of this method depends on the environment, the satellite constellation, and diversity combining technology. This paper explores the path diversity effects of non-geostationary orbit (NGO) satellite personal communication services, for different degrees of user mobility, under various scenarios, using the constellation of the global positioning system (GPS). Measurements are taken near downtown Taipei. Three types of mobilities (fixed-point, pedestrian, and vehicular) are examined, and the switch diversity and maximum ratio combining method are applied to determine the path diversity gain and calculate bit error probability. The error probability performance of applying diversity schemes in coherent binary phase shift keying (BPSK) and non-coherent differential phase shift keying (DPSK) modulations over Rician fading channels are also analysed and evaluated by using the characteristic function method. The results show that fading can be significantly reduced and diversity greatly increased. A significant diversity gain and improvement in bit error rate (BER) can be expected in all cases by simply applying switch diversity scheme. Besides, for the maximum ratio combining method, the results imply that summing two satellite signals suffices to increase diversity and improve the bit error rate performance. Copyright © 2002 John Wiley & Sons, Ltd. [source] Performance evaluation of adaptive routing algorithms in packet-switched intersatellite link networksINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2002Mihael Mohor Abstract This paper addresses the performance evaluation of adaptive routing algorithms in non-geostationary packet-switched satellite communication systems. The dynamic topology of satellite networks and variable traffic load in satellite coverage areas, due to the motion of satellites in their orbit planes, pose stringent requirements to routing algorithms. We have limited the scope of our interest to routing in the intersatellite link (ISL) segment. In order to analyse the applicability of different routing algorithms used in terrestrial networks, and to evaluate the performance of new algorithms designed for satellite networks, we have built a simulation model of a satellite communication system with intersatellite links. In the paper, we present simulation results considering a network-uniform source/destination distribution model and a uniform source,destination traffic flow, thus showing the inherent routing characteristics of a selected Celestri-like LEO satellite constellation. The updates of the routing tables are centrally calculated according to the Dijkstra shortest path algorithm. Copyright © 2002 John Wiley & Sons, Ltd. [source] Triangular planar array of a pyramidal adaptive antenna for satellite communications at 1.7 GHzMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2009J. L. Masa-Campos Abstract Nowadays, satellite communications are basic for the human lifestyle. In this way, a smart, conformal, and multiarray antenna (GEODA) is being developed in order to receive signals from several satellites simultaneously in the 1.7 GHz working band. An adaptive beam system is able to follow the signals from the satellite constellation. The complex structure of the antenna is based in a 3D composition of planar arrays with triangular shape. These arrays are divided into subarrays of three patches (Cells), composing the single control element for the arrays main beam direction management. Fifteen cells (45 radiating elements) compose each triangular array of the GEODA antenna. In this article, a triangular array prototype is implemented and measured. Likewise, an individual characterization of the array components is presented. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2633,2639, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24692 [source] Satellite Remote Sensing as a Tool in Lahar Disaster ManagementDISASTERS, Issue 2 2002Norman Kerle At least 40,000 deaths have been attributed to historic lahars (volcanic mudflows). The most recent lahar disaster occurred in 1998 at Casita volcano, Nicaragua, claiming over 2,500 lives. Lahars can cover large areas and be highly destructive, and constitute a challenge for disaster management. With infrastructure affected and access frequently impeded, disaster management can benefit from the synoptic coverage provided by satellite imagery. This potential has been recognised for other types of natural disasters, but limitations are also known. Dedicated satellite constellations for disaster response and management have been proposed as one solution. Here we investigate the utility of currently available and forthcoming optical and radar sensors as tools in lahar disaster management. Applied to the Casita case, we find that imagery available at the time could not have significantly improved disaster response. However, forthcoming satellites, especially radar, will improve the situation, reducing the benefit of dedicated constellations. [source] Multimedia satellite communications experiments to the international space stationINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2002Carlo Matarasso Abstract In the present concept of the International Space Station ISS, it is planned to provide the communication services between the European Columbus module of the ISS and the ground equipment via the TDRS (tracking and data relay satellite) network provided by the American NASA (National Aeronautics and Space Agency). Especially because of its low uplink data rate, an unacceptable limitation of the communication services with Columbus is to be expected. In order to investigate possible improvements to this situation, the MEDIS proposal studies the feasibility of a 150 Mbps full duplex communication system to the Columbus Module on via two MEO satellites. A mixed topology with optical inter satellite links and Ka-band up/down-links shall be employed. Also possible liaisons with the Artemis mission will be considered. The MEDIS project is a collaboration of Astrium GmbH, which is project manager, Bosch SatCom, GMD-Fokus and the German Aerospace Center (DLR). The preparation phase of the project will investigate the concept of the communications infrastructure and the experiments that could be realized when the MEOs are launched. This stage has been completed in February 2001. An additional study phase followed, which will be completed with a presentation in July 2002. Briefly the following aspects have been studied by DLR in the preparation phase: the overall concept of experimental communication services for Columbus, the system requirements and network topology, the relevant protocol and hardware architectures, useful satellite constellations and link scenarios. Two phases could follow the preparation phase, in phase one the satellite will be launched and the link will be tested. In phase two the satellites will be connected to the ISS. Copyright © 2002 John Wiley & Sons, Ltd. [source] Theatre in the Sky: a ubiquitous broadband multimedia-on-demand service over a novel constellation composed of quasi-geostationary satellitesINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2006Tarik Taleb Abstract To meet an ever-growing demand for wideband multimedia services and electronic connectivity across the world, development of ubiquitous broadband multimedia systems is gaining a tremendous interest at both commercial and academic levels. Satellite networks will play an indispensable role in the deployment of such systems. A significant number of satellite communication constellations have been thus proposed using Geostationary (GEO), Medium Earth Orbit (MEO), or Low Earth Orbit (LEO) satellites. These constellations, however, either require a potential number of satellites or are unable to provide data transmission with high elevation angles. This paper proposes a new satellite constellation composed of Quasi-GeoStationary Orbit (Quasi-GSO) satellites. The main advantage of the constellation is in its ability to provide global coverage with a significantly small number of satellites while, at the same time, maintaining high elevation angles. Based on a combination of this Quasi-GSO satellites constellation and terrestrial networks, the paper proposes also an architecture for building a global, large-scale, and efficient Video-on-Demand (VoD) system. The entire architecture is referred to as a ,Theatre in the Sky'. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||