On-board processing satellite network architecture and control study

The market for telecommunications services needs to be segmented into user classes having similar transmission requirements and hence similar network architectures. Use of the following transmission architecture was considered: satellite switched TDMA; TDMA up, TDM down; scanning (hopping) beam TDMA; FDMA up, TDM down; satellite switched MF/TDMA; and switching Hub earth stations with double hop transmission. A candidate network architecture will be selected that: comprises multiple access subnetworks optimized for each user; interconnects the subnetworks by means of a baseband processor; and optimizes the marriage of interconnection and access techniques. An overall network control architecture will be provided that will serve the needs of the baseband and satellite switched RF interconnected subnetworks. The results of the studies shall be used to identify elements of network architecture and control that require the greatest degree of technology development to realize an operational system. This will be specified in terms of: requirements of the enabling technology; difference from the current available technology; and estimate of the development requirements needed to achieve an operational system. The results obtained for each of these tasks are presented

On-board processing satellite network architecture and control study

For satellites to remain a vital part of future national and international communications, system concepts that use their inherent advantages to the fullest must be created. Network architectures that take maximum advantage of satellites equipped with onboard processing are explored. Satellite generations must accommodate various services for which satellites constitute the preferred vehicle of delivery. Such services tend to be those that are widely dispersed and present thin to medium loads to the system. Typical systems considered are thin and medium route telephony, maritime, land and aeronautical radio, VSAT data, low bit rate video teleconferencing, and high bit rate broadcast of high definition video. Delivery of services by TDMA and FDMA multiplexing techniques and combinations of the two for individual and mixed service types are studied. The possibilities offered by onboard circuit switched and packet switched architectures are examined and the results strongly support a preference for the latter. A detailed design architecture encompassing the onboard packet switch and its control, the related demand assigned TDMA burst structures, and destination packet protocols for routing traffic are presented. Fundamental onboard hardware requirements comprising speed, memory size, chip count, and power are estimated. The study concludes with identification of key enabling technologies and identifies a plan to develop a POC model

Future benefits and applications of intelligent on-board processing to VSAT services

The trends and roles of VSAT services in the year 2010 time frame are examined based on an overall network and service model for that period. An estimate of the VSAT traffic is then made and the service and general network requirements are identified. In order to accommodate these traffic needs, four satellite VSAT architectures based on the use of fixed or scanning multibeam antennas in conjunction with IF switching or onboard regeneration and baseband processing are suggested. The performance of each of these architectures is assessed and the key enabling technologies are identified

Applications of satellite technology to broadband ISDN networks

Two satellite architectures for delivering broadband integrated services digital network (B-ISDN) service are evaluated. The first is assumed integral to an existing terrestrial network, and provides complementary services such as interconnects to remote nodes as well as high-rate multicast and broadcast service. The interconnects are at a 155 Mbs rate and are shown as being met with a nonregenerative multibeam satellite having 10-1.5 degree spots. The second satellite architecture focuses on providing private B-ISDN networks as well as acting as a gateway to the public network. This is conceived as being provided by a regenerative multibeam satellite with on-board ATM (asynchronous transfer mode) processing payload. With up to 800 Mbs offered, higher satellite EIRP is required. This is accomplished with 12-0.4 degree hopping beams, covering a total of 110 dwell positions. It is estimated the space segment capital cost for architecture one would be about $190M whereas the second architecture would be about$250M. The net user cost is given for a variety of scenarios, but the cost for 155 Mbs services is shown to be about $15-22/minute for 25 percent system utilization

Architectural Model for Evaluating Space Communication Networks

[ANGLÈS] The space exploration endeavor started in 1957 with the launch and operation of the first manmade satellite, the URSS Sputnik 1. Since then, multiple space programs have been developed, pushing the limits of technology and science but foremost unveiling the mysteries of the universe. In all these cases, the need for flexible and reliable communication systems has been primordial, allowing the return of collected science data and, when necessary, ensuring the well-being and safety of astronauts. To that end, multiple space communication networks have been globally deployed, be it through geographically distributed ground assets or through space relay satellites. Until now most of these systems have relied upon mature technology standards that have been adapted to the specific needs of particular missions and customers. Nevertheless, current trends in the space programs suggest that a shift of paradigm is needed: an Internet-like space network would increase the capacity and reliability of an interplanetary network while dramatically reducing its overall costs. In this context, the System Architecting Paradigm can be a good starting point. Through its formal decomposition of the system, it can help determine the architecturally distinguishing decisions and identify potential areas of commonality and cost reduction. This thesis presents a general framework to evaluate space communication relay systems for the near Earth domain. It indicates the sources of complexity in the modeling process, and discusses the validity and appropriateness of past approaches to the problem. In particular, it proposes a discussion of current models vis-à-vis the System Architecting Paradigm and how they fit into tradespace exploration studies. Next, the thesis introduces a computational performance model for the analysis and fast simulation of space relay satellite systems. The tool takes advantage of a specifically built-in rule-based expert system for storing the constitutive elements of the architecture and perform logical interactions between them. Analogously, it uses numerical models to assess the network topology over a given timeframe, perform physical layer computations and calculate plausible schedules for the overall system. In particular, it presents a newly developed heuristic scheduler that guarantees prioritization of specific missions and services while ensuring manageable computational times.[CASTELLÀ] El inicio de la carrera espacial se inició en 1957 con el lanzamiento y operación del primer satélite artificial, el Sputnik 1 de la URSS. Desde entonces se han desarrollado múltiples programas espaciales que han llevado al límite tanto la tecnología como la ciencia y han permitido desvelar los misterios del universo. En todos estos casos, la necesidad de sistemas de comunicación flexibles y fiables ha sido primordial con el fin de asegurar el retorno de los datos científicos recopilados y, en ciertos casos, garantizar la seguridad de los astronautas. Como consecuencia, múltiples redes de comunicaciones espaciales han sido desplegadas, ya sea a través de antenas globalmente distribuidas a través de la superficie terrestre o mediante satélites repetidores. Hasta ahora la mayoría de estos sistemas se ha basado en estándares tecnológicos maduros y testeados, los cuales se han adaptado con el fin de satisfacer las necesidades específicas de cada misión y cliente. Sin embargo, las tendencias actuales en el diseño de los nuevos programas espaciales indica que un cambio de paradigma es necesario: una red espacial a imagen de Internet permitiría incrementar la capacidad y fiabilidad de las comunicaciones interplanetarias y, a la vez, reducir dramáticamente sus costes. En este contexto, el paradigma de arquitectura de sistemas puede ser un buen punto de partida. Mediante la descomposición formal del sistema, puede ayudar a determinar las decisiones que tienen un impacto cabal en el diseño de la arquitectura así como identificar las áreas con tecnologías similares y de menor coste. Esta tesis presenta un marco teórico general para evaluar sistemas de comunicaciones espaciales para misiones que orbitan la Tierra. Adicionalmente, la tesis indica los principales orígenes de complejidad durante el modelado del sistema y presenta una discusión sobre la validez de anteriores estrategias para analizar el problema. En concreto, propone una comparación de anteriores modelos respecto el paradigma de arquitectura de sistemas y su grado de adecuación para evaluar y comprar arquitecturas. A continuación, la tesis introduce un modelo computacional para simular y evaluar el rendimiento de sistemas de repetidores por satélite. La herramienta utiliza un rule-based expert system específicamente diseñado con el fin de almacenar los principales elementos constitutivos de la arquitectura y comprender las interacciones lógicas entre ellos. Análogamente, el modelo usa métodos numéricos con el fin de calcular la evolución temporal de la topología de la red en un determinado intervalo de tiempo, así como su capa física y un posible programa de contactos. En concreto, presenta un nuevo scheduler heurístico que garantiza la correcta ordenación de las misiones y servicios a la vez que asegura un tiempo computacional aceptable.[CATALÀ] L'inici de la cursa espacial va iniciar-se l'any 1957 amb el llançament i operació del primer satèl·lit artificial, l'Sputnik 1 de la URSS. Des d'aleshores s'han dut a terme múltiples programes espacials que han portat al límit tant la tecnologia com la ciència i han permès desvelar els misteris de l'univers. En tots aquests casos, la necessitat de sistemes de comunicació flexibles i fiables ha sigut primordial per tal d'assegurar el retorn de les dades científiques recopilades i, en certs casos, garantir el benestar i seguretat dels astronautes. Com a conseqüència, múltiples xarxes de comunicacions espacials han sigut desplegades, ja sigui a través d'antenes globalment distribuïdes a través de la superfície terrestre o mitjançant satèl·lits repetidors. Fins ara la majoria d'aquests sistemes s'han basat en estàndards tecnològics madurs i testats, els quals s'han adaptat per tal de satisfer les necessitats específiques de cada missió i client. Això no obstant, les tendències actuals en el disseny dels nous programes espacials indica que un canvi de paradigma és necessari: una xarxa espacial a imatge d'Internet permetria incrementar la capacitat i fiabilitat de les comunicacions interplanetàries i, alhora, reduir dramàticament els seu costs. En aquest context, el paradigma d'arquitectura de sistemes pot ser un bon punt de partida. Mitjançant la descomposició formal del sistema, pot ajudar a determinar les decisions que tenen un impacte cabdal en el disseny de l'arquitectura així com permetre identificar àrees amb tecnologies similars i de menor cost. Aquesta tesi presenta un marc teòric general per avaluar sistemes de comunicacions espacials per missions orbitant la Terra. Addicionalment, la tesi indica els principals orígens de complexitat durant el modelatge del sistema i presenta una discussió sobre la validesa d'anteriors estratègies per analitzar el problema. En concret, proposa una comparació d'anteriors models respecte el paradigma d'arquitectura de sistemes i el seu grau d'adequació per avaluar i comparar arquitectures. A continuació, la tesi introdueix un model computacional per simular i avaluar el rendiment de sistemes de repetidors per satèl·lit. L'eina empra un rule-based expert system específicament dissenyat per tal d'emmagatzemar els principals elements constitutius de l'arquitectura i comprendre les interaccions lògiques entre ells. Anàlogament, el model utilitza mètodes numèrics per tal de calcular l'evolució temporal de la topologia de la xarxa en un determinat interval de temps, així com calcular la seva capa física i un possible programa de contactes. En concret, presenta un nou scheduler heurístic que garanteix la correcte ordenació de les missions i serveis tot assegurant un temps de computació acceptable

Satellite Networks: Architectures, Applications, and Technologies

Since global satellite networks are moving to the forefront in enhancing the national and global information infrastructures due to communication satellites' unique networking characteristics, a workshop was organized to assess the progress made to date and chart the future. This workshop provided the forum to assess the current state-of-the-art, identify key issues, and highlight the emerging trends in the next-generation architectures, data protocol development, communication interoperability, and applications. Presentations on overview, state-of-the-art in research, development, deployment and applications and future trends on satellite networks are assembled

Application of advanced on-board processing concepts to future satellite communications systems

An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development

Technology Directions for the 21st Century

New technologies will unleash the huge capacity of fiber-optic cable to meet growing demands for bandwidth. Companies will continue to replace private networks with public network bandwidth-on-demand. Although asynchronous transfer mode (ATM) is the transmission technology favored by many, its penetration will be slower than anticipated. Hybrid networks - e.g., a mix of ATM, frame relay, and fast Ethernet - may predominate, both as interim and long-term solutions, based on factors such as availability, interoperability, and cost. Telecommunications equipment and services prices will decrease further due to increased supply and more competition. Explosive Internet growth will continue, requiring additional backbone transmission capacity and enhanced protocols, but it is not clear who will fund the upgrade. Within ten years, space-based constellations of satellites in Low Earth orbit (LEO) will serve mobile users employing small, low-power terminals. 'Little LEO's' will provide packet transmission services and geo-position determination. 'Big LEO's' will function as global cellular telephone networks, with some planning to offer video and interactive multimedia services. Geosynchronous satellites also are proposed for mobile voice grade links and high-bandwidth services. NASA may benefit from resulting cost reductions in components, space hardware, launch services, and telecommunications services

A Survey of Satellite Communications System Vulnerabilities

The U.S. military’s increasing reliance on commercial and military communications satellites to enable widely-dispersed, mobile forces to communicate makes these space assets increasingly vulnerable to attack by adversaries. Attacks on these satellites could cause military communications to become unavailable at critical moments during a conflict. This research dissected a typical satellite communications system in order to provide an understanding of the possible attacker entry points into the system, to determine the vulnerabilities associated with each of these access points, and to analyze the possible impacts of these vulnerabilities to U.S. military operations. By understanding these vulnerabilities of U.S. communications satellite systems, methods can be developed to mitigate these threats and protect future systems. This research concluded that the satellite antenna is the most vulnerable component of the satellite communications system’s space segment. The antenna makes the satellite vulnerable to intentional attacks such as: RF jamming, spoofing, meaconing, and deliberate physical attack. The most vulnerable Earth segment component was found to be the Earth station network, which incorporates both Earth station and NOC vulnerabilities. Earth segment vulnerabilities include RF jamming, deliberate physical attack, and Internet connection vulnerabilities. The most vulnerable user segment components were found to be the SSPs and PoPs. SSPs are subject to the vulnerabilities of the services offered, the vulnerabilities of Internet connectivity, and the vulnerabilities associated with operating the VSAT central hub. PoPs are susceptible to the vulnerabilities of the PoP routers, the vulnerabilities of Internet and Intranet connectivity, and the vulnerabilities associated with cellular network access

Space-based Communications Infrastructure for Developing Countries

This study examines the potential use of satellites to augment the telecommunications infrastructure of developing countries with advanced satellites. The study investigated the potential market for using satellites in developing countries, the role of satellites in national information infractructures (NII), the technical feasibility of augmenting NIIs with satellites, and a nation's financial conditions necessary for procuring satellite systems. In addition, the study examined several technical areas including onboard processing, intersatellite links, frequency of operation, multibeam and active antennas, and advanced satellite technologies. The marketing portion of this study focused on three case studies: China, Brazil, and Mexico. These cases represent countries in various stages of telecommunication infrastructure development. The study concludes by defining the needs of developing countries for satellites, and recommends steps that both industry and NASA can take to improve the competitiveness of U.S. satellite manufacturing