ING. CARLOS EGAS1 Abril 2005 Sistemas de Comunicaciones Satelitales PARTE 1 Ing. Geovanni Brito M. Documento original del Ing. Carlo Egas Escuela Politecnica Nacional

2 Agenda Introduccción Segmento Espacial Segmento Terreno Balance del enlace Caso de estudio: Redes Vsat

ING. CARLOS EGAS3 Introduction The operation of microwave radio links, as discussed in previous lectures, are based on line-of-sight. Some digital microwave radio links operate over long distances, in excess of 100 km. The height of the microwave radio antenna is the main limiting factor on the link distance. Radio communication through satellite is one of the solutions for extending the range of communication.

ING. CARLOS EGAS4 Introduction - Cont. Radio communication by satellite is an outcome of research for increasing radio communication range and capabilities. Satellite Communication combines the missile and microwave technologies The space era started in 1957 with the launching of the first artificial satellite (sputnik). SYNCOM was the first Geostationary satellite, launched in 1963.

ING. CARLOS EGAS5 SPUTNIK On October 4, 1957 the Soviet Union launched Sputnik, the first man-made object ever sent into space...

ING. CARLOS EGAS6 Diameter: 0.71 m (2 ft 4 in) Panel Height: 0.39 cm (1 ft 3 in) Weight in Orbit: 35 kg (78 lb) SYNCOM

ING. CARLOS EGAS7 Satellite Communications: Advantages and Disadvantages AdvantagesDisadvantages  Wide area coverage  Broadcast medium  Mobility support  Distance insensitive  Mature technology  Cost  Risks  Security  Orbital congestion  Spectrum constraints

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9 Frequency Bands L-band (1 - 2 GHz) S-band (2 - 4 GHz) C-band (4 - 8 GHz) X-band ( GHz) Ku-band ( GHz) K-band ( GHz) Ka-band ( GHz)

ING. CARLOS EGAS10 BANDAS DE FRECUENCIAS Banda Rango (GHz) ServicioUsos VHF MHzFijoTelemetría UHF MHzMóvilNavegación, Militar L1 - 2Móvil Emisión de audio, radiolocalización. S2 - 4MóvilNavegación C4 - 8FijoVoz, datos, video, X8 - 12FijoMilitar Ku FijoVoz, datos, video, K Fijo Emisión de video, com. intersatélite Ka Fijo Emisión de video, com. intersatélite

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ING. CARLOS EGAS14 Mobile Satellite Systems(MSS) LEO, MEO Satellites - Ground tracks move at high speeds (e.g. 7 Km/s) - Even stationary users are relatively “mobile” - Users’ actual terrestrial mobility less significant Terrestrial Cellular - Fixed cells and mobile users Mobile Satellite System - Moving cells and low mobility users (e.g. Iridium) - Fixed cells, using steered beams (e.g. Teledesic)

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ING. CARLOS EGAS19 Satellite Orbits LEO MEO GEO LEO: km MEO:5, ,000 km GEO:36,000 km LEO: Low Earth Orbit MEO: Medium Earth Orbit GEO: Geostationary Earth Orbit

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ING. CARLOS EGAS25 LEO, MEO and GSO GSO: km Outer Van Allen Belt 13,000-20,000 Km MEO: 10,000-20,000 Km Inner Van Allen Belt 1,500-5,000 Km LEO: Below 1,500 Km

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ING. CARLOS EGAS27 LEO Circular Low Earth Orbit (LEO) The altitude of the satellite is constant and equals to several hundreds of kilometres. The period is of the order of one and half hours. The orbit is nearly 90o inclination, which guarantees that the satellite will pass over every region of the Earth. Used for observation and mobile satellites

ING. CARLOS EGAS28 “Little” LEO S and “Big” LEO S Little LEO S - Small size and low weight - Low bit-rate applications - VHF band  MHz (up), MHz (down) - Example: ORBCOMM  36 satellites in 6 orbits, about 800 Km altitude  90 lbs weight  2400 bps data

ING. CARLOS EGAS29 “Little” LEO S and “Big” LEO S Little LEO S - Voice and data, position location (RDSS) - L-band ( MHz) uplink - S-band ( MHz) downlink - Dual-mode: interworking with PSTN - Examples  IRIDIUM  GLOBALSTAR

ING. CARLOS EGAS30 MEO Circular Medium Earth Orbits (MEO), also named Intermediate Circular Orbits (ICO) The altitude is about 10,000 km and an inclination of about 50 o and period of 6 hours. With constellations of about 10 to 15 satellites, a continuous coverage of the World is guaranteed

ING. CARLOS EGAS31 MEO Systems Example: ICO (Intermediate Circular Orbit) An INMARSAT venture 12 satellites in 45º inclined orbits 10,400 Km altitude TDMA/FDD “Bent-pipe” – no onboard processing

ING. CARLOS EGAS32 GEO Circular orbit with zero inclination (equatorial) The satellite orbits around the Earth at altitude of 35,786 and in the same direction as the Earth. The period is equal to that of the rotation of the Earth and in the same direction. The satellite thus appears as a fixed point in the sky and ensures continuous operation as a radio relay in real time for the area of visibility of the satellite One satellite covers 43% of the Earth’s surface.

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ING. CARLOS EGAS34 Orbita Geoestacionaria Advantages Disadvantages - Non-steerable antenas - Full earth coverage - Fixed link parameters - Minimal doppler - Large distance - Path loss (distance) - High uplink power - Large round-trip delay - Congestion in GSO - Orbit / Frequency coordination

ING. CARLOS EGAS35 Orbital Speeds for Circular Earth Orbits

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ING. CARLOS EGAS39 Cuadro comparativo

ING. CARLOS EGAS40 Comparison of LEO, MEO and GEO Satellite Systems LEOMEOGEO Cost Life(Yrs) MS size Compexity Handoff Freq Dev Period High 3-7 Handheld High Hign Long Low Handheld Medium Portable Low Short

ING. CARLOS EGAS41 Elliptical Orbits ELLIPSO Satellite System - Proposed by Ellipsat - 15 satellites in elliptical orbits - 9 satellites in circular equatorial orbits - Extensive coverage of northern hemisphere MOLNYA - Early Russian non – GEO satellite

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