18-08-2012, 05:12 PM
Communication Satellites
the physical layer.pdf (Size: 715.3 KB / Downloads: 91)
Communication Satellites
Geostationary Satellites
• Medium-Earth Orbit Satellites
• Low-Earth Orbit Satellites
• Satellites versus Fiber
Communication Satellites
Communication satellite can be thought of as a big
microwave repeater in the sky.
It contains several transponders, each of which
listens to some portion of the spectrum, amplifies
the incoming signal, and then rebroadcasts it at
another frequency to avoid interference with the
incoming signal.
Geostationary Satellites
maximum 180 satellites(360/2)
Orbit slot allocation is done by ITU(International
Telecommunication Union).
station keeping: The effects of solar, lunar and
planetary gravity tend to move them away from
their assigned orbit slots and orientation.
ITU has allocated certain frequency bands to
satellite users.
Medium-Earth Orbit Satellites
Takes around 6 hours to circle the earth.
Compared to GEOs they have smaller
footprint on the ground and requires less
powerfull transmitters to reach them.
Eg: GPS(Global Positioning System)
satellites orbiting at about 18,000 km.