Satellite Network & Capacity Allocation

Frequency division multiple access (FDMA)

Time division multiple access (TDMA)

Code division multiple access (CDMA)

Frequency Bands

Classification of Satellite Orbits

Geostationary orbit (GEO)
Medium earth orbit (MEO)
Low earth orbit (LEO)


GEO Orbit:

* No problem with frequency changes.
* Tracking of the satellite is simplified.
* High coverage area.
* Disadvantages of the GEO orbit.
* Weak signal after traveling over 35,000 km.
* Polar regions are poorly served.
* Signal sending delay is substantial.


MEO Orbit:

* Circular orbit at an altitude in the range of 5000 to 12,000 km.
* Orbit period of 6 hours.
* Diameter of coverage is 10,000 to 15,000 km.
* Round trip signal propagation delay less than 50 ms.
* Maximum satellite visible time is a few hours.


LEO Orbit:

* Circular/slightly elliptical orbit under 2000 km.
* Orbit period ranges from 1.5 to 2 hours.
* Diameter of coverage is about 8000 km.
* Round-trip signal propagation delay less than 20 ms.
* Maximum satellite visible time up to 20 min.

Satellite Related Terms & Service Types

Earth Stations:

Antenna systems on or near earth.

Uplink:

Transmission from an earth station to a satellite.

Downlink:

Transmission from a satellite to an earth station.

Transponder:

Electronics in the satellite that convert uplink signals to downlink signals.



Coverage Area:

1) Global.
2) National.
3) Regional.



Service Types:

1) Fixed Service Satellite (FSS)
2) Broadcast Service Satellite (BSS)
3) Mobile Service Satellite (MSS)

Components of Satellite

Transponder & Antenna System:

The transponder is a high frequency radio receiver, a frequency down converter and a power amplifier, which is used to transmit the downlink signal.

The antenna system contains the antennas and the mechanism to position them correctly.


Power Package:


It is a power supply to the satellite.

The satellite must be powered either from a battery or a solar energy system.

A solar cell system supplies the power to run the electronics and change the batteries during the sunlight cycle and battery furnishes the energy during the eclipse.


Control and Information System & Rocket Thruster System:

The control and information system and the rocket thruster system are called the station keeping system.

The function of the station keeping system is to keep the satellite in the correct orbit with the antennas pointed in the exact direction desired.

Components of Satellite

•Transponder and Antenna System.

•Power Package.

•Control and Information System & Rocket Thruster System.

Satellite Communication

What is Satellite?


In general, a satellite is anything that orbits something else,

for example, the moon orbits the earth.

In a communications context, a satellite is a specialized wireless receiver/transmitter that is launched by a rocket and placed in orbit around the earth.

There are hundreds of satellites currently in operation.

They are used for such diverse purposes as:

1) Weather forecasting.
2) Television broadcast.
3) Radio communications.
4) Internet communications.
5) Global Positioning System (GPS).