Satellite Networks for Computer Networks, Study notes of Data Communication Systems and Computer Networks

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Satellite Networks

Computer Networks

Computer Science

and Engineering

Satellite Networks

A satellite network is a combination of nodes, some of which are satellites, that provides communication from one point on the Earth to another. A node in the network can be a satellite, an Earth station, or an end-user terminal or telephone. Satellite networks are communication systems that use satellites orbiting the Earth to transmit and receive data across long distances. They offer global coverage, making them ideal for connecting remote locations and providing services like internet, television, and telecommunication. Satellite networks consist of ground stations, satellite uplinks, transponders on satellites, and end-user devices. They are essential for various applications, including broadcasting, military communication, weather monitoring, and navigation systems like GPS.

Satellite Categories

Geosynchronous Orbit

(GEO) Satellite Systems

• Satellites in GEO orbit at the same speed as the Earth's rotation, appearing stationary from the ground.
• They are positioned approximately 35,786 km above the equator.
• GEO satellites provide continuous coverage over a specific geographic area, making them ideal for communication and broadcasting services. Advantages:
• Large area coverage, stay where they are at 35,786km (22,000miles) above the Earth.
• Satellite rotation is synchronous to Earth.
• Three satellites can cover the whole globe w i t h low systemcomplexity Disadvantages:
• Long propagation delay (~125 msec).
• High transmission power is required

Low Earth Orbit (MEO)

Satellite Systems

• LEO satellites orbit at altitudes ranging from a few hundred to around 2,000 km above the Earth's surface.
• They move at high speeds and complete one orbit in roughly 90 to 120 minutes.
• LEO satellites are commonly used for Earth observation, scientific research, and satellite internet constellations. Advantages:
• Short propagation delays (10- 15 msec).
• Low transmission power required low prices for satellite and equipment. Disadvantages:
• Small coverage spot.
• They have to be in the rotation to preserve their low altitude (90 mins period).
• A network of at least 6 LEO satellites is required to cover a region continuously.
• High system complexity due to the need for handovers and satellite tracking.

Global Position System

(GPS)

• Operated by the US Department of Defense.
• Orbiting at an altitude of about 18,000km.
• Consists of 24 satellites in 6 orbits; 32 by Dec 2012.
• At any time, about 9 (>4) satellites are visible from any point on Earth.
• A GPS receiver has an almanac that tells the currentposition of each satellite