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Communication Satellite

Communication Satellite. References. Joe Montana, “Introduction to Satellite Communication,” George Mason University, http://classweb.gmu.edu/jmontana/lecture01.ppt Tanenbaum, Computer Networks, 4 th edition, Prentice Hall. Important Milestones (1950’s) Putting the pieces together.

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Communication Satellite

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  1. Communication Satellite

  2. References • Joe Montana, “Introduction to Satellite Communication,” George Mason University, http://classweb.gmu.edu/jmontana/lecture01.ppt • Tanenbaum, Computer Networks, 4th edition, Prentice Hall.

  3. Important Milestones (1950’s) Putting the pieces together • 1957 First man-made satellite launched by former USSR (Sputnik, LEO). • 1958 First US satellite launched (SCORE). First voice communication established via satellite (LEO, lasted 35 days in orbit after batteries failed). http://classweb.gmu.edu/jmontana/lecture01.ppt

  4. Sputnik - I http://classweb.gmu.edu/jmontana/lecture01.ppt

  5. Important Milestones (1960’s) First satellite communications • 1960 First passive communication satellite launched into space (Large balloons, Echo I and II). • 1962: First non-government active communication satellite launched Telstar I (MEO). • 1963: First satellite launched into geostationary orbit Syncom 1 (comms. failed). • 1964: International Telecomm. Satellite Organization (INTELSAT) created. • 1965 First communications satellite launched into geostationary orbit for commercial use Early Bird (re-named INTELSAT 1). http://classweb.gmu.edu/jmontana/lecture01.ppt

  6. ECHO I http://classweb.gmu.edu/jmontana/lecture01.ppt

  7. Telstar I http://classweb.gmu.edu/jmontana/lecture01.ppt

  8. Intelsat I http://classweb.gmu.edu/jmontana/lecture01.ppt

  9. Important Milestones (1970’s) GEO applications development • 1972 First domestic satellite system operational (Canada). INTERSPUTNIK founded. • 1975 First successful direct broadcast experiment (one year duration; USA-India). • 1977 A plan for direct-to-home satellite broadcasting assigned by the ITU in regions 1 and 3 (most of the world except the Americas). • 1979 International Mobile Satellite Organization (Inmarsat) established. http://classweb.gmu.edu/jmontana/lecture01.ppt

  10. Important Milestones (1980’s) GEO applications expanded • 1981 First reusable launch vehicle flight. • 1982 International maritime communications made operational. • 1983 ITU direct broadcast plan extended to region 2. • 1984 First direct-to-home broadcast system operational (Japan). • 1987 Successful trials of land-mobile communications (Inmarsat). • 1989-90 Global mobile communication service extended to land mobile and aeronautical use (Inmarsat) http://classweb.gmu.edu/jmontana/lecture01.ppt

  11. Important Milestones (1990’s) • 1990-95: - Several organizations propose the use of non-geostationary (NGSO) satellite systems for mobile communications. - Continuing growth of VSATs* around the world. - Spectrum allocation for non-GEO systems. - Continuing growth of direct broadcast systems. DirectTV created. • 1997: - Launch of first batch of LEO for hand-held terminals (Iridium). - Voice service telephone-sized desktop and paging service pocket size mobile terminals launched (Inmarsat). • 1998: Iridium initiates services. • 1999: Globalstar Initiates Service. • 2000: ICO initiates Service. Iridium fails and system is sold to Boeing. * VSAT - Very Small Aperture Terminal - small, software-driven earth stations (typically 3-6 feet) used for the transmission of data, video, or voice via satellite. http://classweb.gmu.edu/jmontana/lecture01.ppt

  12. Iridium http://classweb.gmu.edu/jmontana/lecture01.ppt

  13. Communication Satellites Classified Based on Main orbit types • Geostationary Satellites • Medium-Earth Orbit Satellites • Low-Earth Orbit Satellites

  14. GEO 36,000 km MEO 5,000 – 15,000 km LEO 500 -1000 km Main orbit types http://classweb.gmu.edu/jmontana/lecture01.ppt

  15. Communication Satellites Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage.

  16. Coverage vs. Altitude Satellite Altitude (km) http://classweb.gmu.edu/jmontana/lecture01.ppt

  17. LEO, MEO and GEO Orbit Periods http://classweb.gmu.edu/jmontana/lecture01.ppt

  18. Minimum Delay for two hops http://classweb.gmu.edu/jmontana/lecture01.ppt

  19. GEO (GEOSTATIONARY ORBIT) • In the equatorial plane • Orbital Period = 23 h 56 min. 4.091 s = one Sidereal Day (defined as one complete rotation relative to the fixed stars) • Satellite appears to be stationary over a point on the equator to an observer • Radius of orbit, r, = 42,164.57 km NOTE: Radius = orbital height + radius of the earth Average radius of earth = 6,378.14 km http://classweb.gmu.edu/jmontana/lecture01.ppt

  20. Characteristic of Communication Satellite on the GEO • Synchronize to the earth's rotation period. • T=23h 56min 4.091s • Orbit altitude • H=36,000km • One satellite can cover 40% of the earth • All the surface of the earth can be covered by three satellites. • Fixed propagation delay • D=250msec~270ms http://www.soi.wide.ad.jp/class/20020032/slides/08/8.html

  21. Current GEO Satellite Applications • Broadcasting - mainly TV at present • DirecTV, PrimeStar, etc. • Point to Multi-point communications • VSAT, Video distribution for Cable TV • Mobile Services • Motient (former American Mobile Satellite), INMARSAT, etc. http://classweb.gmu.edu/jmontana/lecture01.ppt

  22. Satellite Navigation: GPS by MEO Satellite System • GPS is a medium earth orbit (MEO) satellite system • GPS satellites broadcast pulse trains with very accurate time signals • A receiver able to “see” four GPS satellites can calculate its position within 30 m anywhere in world • “You never need be lost again” • Every automobile and cellular phone will eventually have a GPS location read-out http://classweb.gmu.edu/jmontana/lecture01.ppt

  23. LEO (Low-Earth Orbit) SatellitesIridium (a) The Iridium satellites from six necklaces around the earth. (b) 1628 moving cells cover the earth.

  24. LEO Satellites in year 2000 • Several new systems are just starting service • Circular or inclined orbit with < 1400 km altitude • Satellite travels across sky from horizon to horizon in 5 - 15 minutes • Earth stations must track satellite or have omni-directional antennas • Constellation of satellites is needed for continuous communication. • Handoff needed. http://classweb.gmu.edu/jmontana/lecture01.ppt

  25. Satellite System Elements Space Segment Satellite Coverage Region SCC Earth Stations TT&C Ground Station Ground Segment http://classweb.gmu.edu/jmontana/lecture01.ppt

  26. Space Segment • Satellite Launching Phase • Transfer Orbit Phase • Deployment • Operation • TT&C - Tracking Telemetry and Command Station: Establishes a control and monitoring link with satellite. Tracks orbit distortions and allows correction planning. Distortions caused by irregular gravitational forces from non-spherical Earth and due to the influence of Sun and Moon forces. • SSC - Satellite Control Center, a.k.a.: • OCC - Operations Control Center • SCF - Satellite Control Facility Provides link signal monitoring for Link Maintenance and Interference monitoring. • Retirement Phase http://classweb.gmu.edu/jmontana/lecture01.ppt

  27. Ground Segment Collection of facilities, users and applications. FSS – Fixed Satellite Service MSS – Mobile Satellite Service Earth Station = Satellite Communication Station (air, ground or sea, fixed or mobile). http://classweb.gmu.edu/jmontana/lecture01.ppt

  28. Communication Satellites (2) The principal satellite bands.

  29. Current Trends in Satellite Communications • Bigger, heavier, GEO satellites with multiple roles • More direct broadcast TV and Radio satellites • Expansion into Ka, Q, V bands (20/30, 30/50, 46/56 GHz) • Massive growth in data services fueled by Internet • Mobile services: • May be broadcast services rather than point to point • Make mobile services a successful business? http://classweb.gmu.edu/jmontana/lecture01.ppt

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