Satellite communication systems use of orbiting satellites to relay communications signals from one satellite station to one or several other users. Satellite communication can be divided into categories of fixed satellite service, positioning systems, and mobile satellite communication systems.

There are three basic types of satellite systems: geosynchronous earth orbit (GEO), medium earth orbit (MEO), and low earth orbit (LEO). GEO satellites hover at approximately 22,300 miles above the surface of the earth. GEO satellites revolve along with the earth once a day; they appear stationary with respect to the earth. The high-gain antennas used to receive signals from 22 thousand miles away (usually called dish antennas) are pointed directly toward the satellite. MEO satellites are located closer to the earth than GEO satellites and do not as a rule require high-gain antennas. This is important as MEO satellites revolve around the earth several times per day and fixed antennas cannot be used. The newest satellite technology being deployed is LEO satellites. LEO satellites are located approximately 450 miles above the surface of the earth. Because these satellites are relatively close to the earth, portable phones with smaller antennas can be used.

Figure 9.26 shows the different types of satellite communication systems. The GEO satellite system is primarily used for television broadcast services, as their satellites appear stationary above the Earth. MEO and LEO systems are used for mobile communications as they are located much closer to the Earth. However, these satellites continuously move relative to the surface...