Why Satellite Communication 11

8/3/2019 Why Satellite Communication 11

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In general, a satellite is anything

that orbits something else, as, for example, the moon orbits the earth.In a communications context, asatellite is a specialized wireless

receiver/transmitter that islaunched by a rocket and placed inorbit around the earth. There arehundreds of satellites currently inoperation. They are used for suchdiverse purposes as weather forecasting, television broadcast,Amateur radio communications,Internet communications, and theGlobal Positioning System,(GPS).



WHAT IS COMMUNICATION?

Communication is a process of transferring information from one

entity to another and understood .



GEOSTATIONARY EARTH ORBIT(GEO)GEOSTATIONARY EARTH ORBIT(GEO)GEOSTATIONARY EARTH ORBIT(GEO)GEOSTATIONARY EARTH ORBIT(GEO)

LOW EARTH ORBIT(LEO)LOW EARTH ORBIT(LEO)LOW EARTH ORBIT(LEO)LOW EARTH ORBIT(LEO)

MEDIUM EARTH ORBIT(MEO)MEDIUM EARTH ORBIT(MEO)MEDIUM EARTH ORBIT(MEO)MEDIUM EARTH ORBIT(MEO)

TYPES OF SATELLITE



GEOSTATIONARY EARTH ORBIT

These satellites are in orbit35,863 km above the earth¶ssurface along the equator.

Objects in Geostationaryorbit revolve around theearth at the same speed asthe earth rotates. Thismeans GEO satellitesremain in the same positionrelative to the surface of earth.





Medium Earth Orbit (MEO)

A MEO satellite is in orbitsomewhere between 8,000km and 18,000 km above theearth¶s surface.

MEO satellites are similar toLEO satellites infunctionality.

MEO satellites are visible for much longer periods of time

than LEO satellites, usually between 2 to 8 hours.

MEO satellites have a larger coverage area than LEOsatellites.



In satellite communication, signaltransferring between the sender andreceiver is done with the help of satellite. Inthis process, the signal which is basically a beam of modulated microwaves is senttowards the satellite. Then the satelliteamplifies the signal and sent it back to the

receiver¶s antenna present on the earth¶ssurface. So, all the signal transferring ishappening in space.



ANOTHER NAME

FOR SATELLITE COMMUNICATION



When using a satelliteWhen using a satellitefor long distancefor long distancecommunications, thecommunications, thesatellite acts as asatellite acts as arepeater.repeater.

An earth stationAn earth stationtransmits the signal uptransmits the signal upto the satelliteto the satellite(uplink), which in turn(uplink), which in turnretransmits it to theretransmits it to thereceiving earth stationreceiving earth station

(downlink).(downlink). Different frequenciesDifferent frequencies

are used for are used for uplink/downlink uplink/downlink ..



WHEN TO USE SATELLITE COMMUNICATION?

When it is the only solutionexample: terrestrialcommunication is difficultin villages.

When the unique features of satellitecommunications make it attractive

example: long distance

communication

When the costs are lower than

terrestrial routing

Example: communication through

wiring medium



WHY SATELLITE COMMUNICATION?

To stay in touch with the rest of world we need a strongcommunication services and thatcommunication is made throughthe satellites

Satellite communication is usefulfor:

i. Inter country long distancetelephony.

ii. Electronic Media.

iii. Military Purpose.

iv. Internet.



EFFECT OF ATMOSPHERIC LOSSES ON SATELLITE

COMMUNICATION

1. Atmospheric absorption

2 . Atmospheric attenuation

3 . Traveling ionospheric

disturbances



ENERGY ABSORPTION BY ATMOSPHERIC GASES, WHICH VARIES WITH THE FREQUENCY OF THE RADIO WAVE



Atmospheric Attenuation

Rain is the main cause of atmospheric

attenuation (hail, ice and snow have

little effect on attenuation because of their low water content) .



Traveling Ionospheric Disturbances







Internet- High Speed.

- Useful for far away places.

Military- Uses geostationary satellites.

- Example: The Defense Satellite Communications System

(DSCS).



The advantages of satellite communicationover terrestrial communication are:

The coverage area of a satellite greatlyexceeds that of a terrestrial system .

Transmission cost of a satellite isindependent of the distance from the center of the coverage area . Satellite to Satellite communication is very precise . Higher Bandwidths are available for use

.



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Why Satellite Communication 11