Satellite Radio Channels
A communication satellite links two or more earth microwave transmitter receiver, know as ground stations. The satellite receives transmission on one frequency band,
Regenerates the signal a repeater and transmits the signal on another frequency. Satellites can provide transmission rates in the gigabits per second range. Two types of satellites are used in communication geostationary satellites and low altitude satellites.
Geostationary satellite permanently remain above the same spot on earth. This stationary presence is achieved by placing he satellite in orbit at 36,000kilometers above earth surface. This huge distance from ground station through satellite back to ground stations introduces a substantial signal propagation delay of 250 milliseconds. Nevertheless satellite links which can operate at the speeds of hundreds of Mbps are often used in telephone networks and is the backbone of the internet.
Low altitude satellites are placed much closer to earth and do not remain permanently above one spot on earth. They rotate around earth just as the moon does.
To provide continuous coverage to an area many satellites need to be placed orbit. Low altitude satellite technology may be used be used for internet access sometimes in the future.