A satellite orbits the Earth in a circular or elliptical path – typically at a height of between 160 and 35,800 kilometers. Satellite communication requires a free line of sight between a satellite and a station or terminal on Earth. The satellite’s view of Earth and, accordingly, the area that can be served by it, varies according to the altitude of the satellite’s orbit. There are three primary altitudes where communication satellites are placed; see the image on the right.
Communication is conducted via radio frequencies
Satellites transmit information to receivers on Earth by way of radio waves, which means that high-quality communication can be made available to remote areas in the world without requiring large investments in terrestrial equipment. The frequency of the radio waves is significant for a number of
properties that are important in satellite communication:
- Frequency bands with a higher frequency typically have greater available bandwidth, which in theory entails higher data rates and higher total capacity.
- On the other hand, higher frequencies are affected and attenuated more by atmospheric effects and weather conditions.
The most common frequency bands used by GEO communication satellites are:
1. Ku- and Ka-bands (10 – 31 GHz):
The bands are typically used for TV broadcasting, VSAT networks, and maritime and aeronautical services. The Ku-band is the band used for Ovzon’s services.
2. C-band (4 – 6 GHz):
Generally used for TV broadcasting, data and voice communication, especially in areas of heavy precipitation.
3. L-band (1.5 – 1.6 GHz):
The L-band is used for purposes such as satellite phones. The relatively narrow spectrum entails major constraints on the total data rate.
4. X-band (8 – 12 MHz):
Mainly used for defense applications.
Historically, the satellite-based communication market has been divided into two segments: Fixed Satellite Service (FSS) and Mobile Satellite Service (MSS). These boundaries
are not as clearly defined as they once were, as increased investments in new satellites with steerable beams and small mobile terminals blur the dividing lines, a trend that is
expected to continue.