2010fall ch19 otgonbayar


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2010fall ch19 otgonbayar

  1. 1. Satellite Communications<br /> J.TC08D721 Ì.Îòãîíáàÿð<br /> J.TC07D031 Á.Áóðìàà<br />J.TC08D708 Ò.Öýíäñ¿ðýí<br />
  2. 2. contenter<br />Satellite communication<br />Transponders<br />Attitude Control Apparatus<br />Power Supply<br />Radio Relay Equipment<br />Low Earth Orbiting Satellite<br />Very Small Aperture Terminal<br />Satellite application issues<br />
  3. 3. 1998 LEO Iridium <br /> 2002 MEO Teledesic<br />1962 GEO Telstar<br />Satellite communication<br />
  5. 5. 1. domestic<br />2. regional<br />3. international<br />Satellite fall into:<br />
  6. 6.
  7. 7. The receiving station can be mobile, which offers coverage from a single<br /> satellite.<br /> Within the coverage range of a single satellite, circuit cost is independent<br /> of distance.<br />Large amounts of bandwidth are available over satellite circuits, making voice, video, and high-speed data circuits available.<br />Advantages<br />
  8. 8. <ul><li>A transponder is a radio relay station on board the satellite.</li></li></ul><li>Transponders<br />The downlinksignal is applied to a high-power amplifier, using a traveling wave tube orsolid-state amplifier as the output device. <br />Echostar 9 (also known as Telstar 13 and Intelsat<br />Americas 13), which was launched in August 2003, has 2 Ka-, 32 Ku-, and 24 C-bandtransponders. <br />
  9. 9. A spin-stabilized satellite rotates on its axis at about 100 rpm.<br /> three-axis stabilization, which<br />consists of a gyroscopic stabilizer inside the vehicle.<br />Attitude Control Apparatus<br />
  10. 10. Satellites are powered by solar batteries. Power is conserved by turning offunused equipment with signals from the Earth.<br />Solar cell life is a major factor that limits the workinglife of a satellite.<br />Power Supply<br />
  11. 11. Radio Relay Equipment<br />
  12. 12. Iridium launched commercial voice, fax, paging, and narrow-band data service in<br />2001, using a network of 66 operational satellites plus six in-orbit backups.<br />Satellites are connected via intersatellite links to the four nearest neighbors<br />and to an Earth station.<br />Low Earth Orbiting Satellite<br />
  13. 13. Very Small Aperture Terminal<br />
  14. 14. The hubs control demand assignment to the satellite and monitor and diagnose<br /> network performance. <br />Demand is allocated in one of the four ways<br />-pure aloha<br />-slotted aloha<br />-TDMA and spread spectrum. <br /> The first three methods generally are used<br /> on Ku-band and the last on C-band.<br />VSAT provides bandwidth as high as T1/E1 and as low as the customer needs to go.<br />
  15. 15. The remote station has an antenna and a receiving unit, which is about the<br /> size of a personal computer base unit.<br />The primary application for VSAT is data, although it can also carry voice<br />and video. <br />Typically, C-band VSATs carry 9.6 Kbps data, and Ku-band VSATs carry 56 or 64 Kbps data; some systems carry a full or fractional T1/E1.<br />The primary advantage of VSAT is its ability<br /> to support multiple locations.<br />
  16. 16. In one sense, satellite applications diminish as terrestrial and undersea fiber-optic<br /> circuits become more plentiful and economical, but satellite services are still<br /> uniquely suited for many applications.<br />SATELLITE APPLICATION ISSUES<br />
  17. 17. Thank you for<br />your attention<br />