Satellite systems

Satellite Systems

Satellite systems provide a unique way to connect communications networks using space vehicle(s) in orbit over the Earth. Satellites simply act as transport for communications much like cables, fiber optics or microwave systems that are the path between two communicators. Similar to cables that provide long distance communications, a satellite acts like a repeater to assure that the signal, video or voice communications that it is transporting remains as near to the original as possible. Repeaters in satellites take the weak signal it receives and restores it before passing back to the recipient.

Satellites are unique for communications for many reasons. The start up costs for satellite communications is very high, however the benefits are extremely good. For example, if a satellite is placed in orbit over the earth, it is capable of providing a communication connection between any two points within it’s view by simply having a transmitter and receiver at each of the two points (in the form of a satellite dish). The view of a typical satellite in orbit over the earth is 1/3 of the planet. As well, the multiple connections can be established. Depending on the capability of the satellite, thousands of paired connections can be established at one time between two points. The advantage of this over established point-to-point cable connections is a significant benefit of a satellite.

A satellite in space is limited by its design as to how many signals it can receive and retransmit based on the number of “transponders” it holds. However, one of the biggest communications advantages of a satellite is that the number of communication devices on the ground that can receive the signal and use it is not limited. This makes satellites an ideal system for broadcast uses. Even a small satellite with only a few transponders can provide a significant service. Satellite radio systems are simple. A signal is transmitted to a satellite and the satellite, acting as a simple repeater re-transmits the signal. If listeners on the earth have a receiver, there is no limit to the number of customers that can receive the signal. For more than 30 years, satellites have been providing voice and data communication service around the globe; however, the cost for equipment and services has been very high.

In 1997, the high cost of satellite equipment and services began to reduce dramatically. New high capacity satellites and digital technology allow for lower cost service and advanced messaging services. Early satellites used analog transmission. After the development of digital satellites, which offer more capacity, several more satellites were put into orbit, followed by the next-generation of low orbiting satellites. These new developments are rapidly bringing the cost of equipment down by over 75%.

This diagram 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 of the Earth.