[attachment=8819]
Satellite Communications
Overview
 Basics of Satellites
 Types of Satellites
 Capacity Allocation
Basics: How do Satellites Work
 Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means.
 The two stations can use a satellite as a relay station for their communication
 One Earth Station sends a transmission to the satellite. This is called a Uplink.
 The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink.
Basics: Advantages of Satellites
 The advantages of satellite communication over terrestrial communication are:
 The coverage area of a satellite greatly exceeds that of a terrestrial system.
 Transmission cost of a satellite is independent of the distance from the center of the coverage area.
 Satellite to Satellite communication is very precise.
 Higher Bandwidths are available for use.
Basics: Disadvantages of Satellites
 The disadvantages of satellite communication:
 Launching satellites into orbit is costly.
 Satellite bandwidth is gradually becoming used up.
 There is a larger propagation delay in satellite communication than in terrestrial communication
Basics: Factors in satellite communication
 Elevation Angle: The angle of the horizontal of the earth surface to the center line of the satellite transmission beam.
 This effects the satellites coverage area. Ideally, you want a elevation angle of 0 degrees, so the transmission beam reaches the horizon visible to the satellite in all directions.
 However, because of environmental factors like objects blocking the transmission, atmospheric attenuation, and the earth electrical background noise, there is a minimum elevation angle of earth stations.