A satellite is an object in orbit around the earth. Satellite wireless communication uses electromagnetic waves transmitted from one location on Earth to another or from one place on Earth to many stations within sight of the satellite in orbit.
The satellite wireless communications system consists of an uplink signal from the Earth station to the satellite. Once received by satellite, a transponder receives the signal, amplifies and demodulates it, and then transmits it back to Earth via a downlink.
The type of satellite orbit depends on the satellite’s application. There are geosynchronous orbits where the satellite retains a position above the Earth’s equator in sync with the rotation of the Earth. They are positioned at an altitude of 35,786 km. These satellites allow pointing the ground-based antenna once and leaving it there. Examples are weather monitoring, broadcasting, and military applications.
There are also low-earth-orbit (LEO) satellites at an altitude between 160 km and 1,600 km above Earth. Medium-earth-orbit (MEO) satellites operate from 10,000 to 20,000 km (6,300 to 12,500 miles) from Earth. This type of satellite appears overhead several times a day. Since it is at a low altitude, lower signal levels can be used for communication. A good example is the SpaceX Starlink satellite, providing service to many areas and soon worldwide. It orbits approximately 342 (550 kilometers) above Earth.
The advantages of satellite wireless communication are the broad coverage along with high speed and bandwidth. The disadvantages are the high cost of building and placing them into orbit. Plus, it’s very challenging, if not impossible, to repair a satellite in orbit.
