Computer Network | Global Mobile Satellite System

GMSS stands for Global Mobile Satellite System. An artificial body which is placed in an orbit around the earth for the purpose of communication is known as Communication satellite. GMSS is a system which consists of various artificial communication satellites orbiting around the earth for the purpose of communication.

Uplink and downlink frequencies must be different to avoid interference. Now, stations at the earth have greater power sources than that of satellite as it has only solar power. Also, higher frequency results in higher attenuation and to compensate with it more power is required. So, uplink uses higher frequency to penetrate the environment.

Satellite Orbits:

  1. LEO:
    LEO stands for Low Earth Orbit. The communication satellites in this orbit operates at a distance of about 500 to 1200 km above the earth’s surface and their orbital time period generally ranges between 95 to 120 minutes. Low Orbit Satellites makes global radio coverage possible.
  2. MEO:
    MEO stands for Medium Earth Orbit. The communication satellites in this orbit operates at a distance of about 5000 to 12000 km above the earth’s surface and their orbital time period is about 6 hours. Medium Orbit Satellites are used for land and sea navigation, for example Google Maps.
  3. GEO:
    GEO stands for Geostationary Earth Orbit. The communication satellites in this orbit operates at a distance of about 36000 km above the earth’s surface and their orbital time period is about 24 hours. Geostationary Orbit Satellites are used for radio broadcasting.

Case Studies:

  • IRIDIUM:
    Iridium satellite constellation contains 77 satellites. It was the first satellite constellation to offer satellite based Personal Communication Services (PCS). It provides voice and data services all over the globe. It is named after the element IRIDIUM whose atomic number is 77 and features the 77 satellites as electrons revolving around the earth as nucleus. Actually only 66 satellites are active orbiting in 6 orbital planes. Each plane is 30 degrees apart and contains 11 satellites.
  • GlobalStar:
    GlobalStar satellite constellation contains 24 LEO satellites and was set up by an American satellite company, GlobalStar Inc. It is a 2nd generation satellite constellation and is used for satellite phone and low-speed data communication. The 24 LEO satellites are orbiting in the planes which are inclined at an angle of 52 degrees and they doesn’t cover pole areas. It provides voice and data services.


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