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SATELLITES

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Overview

IntroductionHistory

Working of a satelliteAdvantages and Disadvantages

Applications

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What is a satellite?•A satellite is a body that moves around another

(usually much larger) one in a mathematically predictable path called an orbit

•A communication satellite is a microwave repeater station in space that is used for telecommunication ,

radio and television signals

•The first man made satellite with radio transmitter was in 1957

•There are about 750 satellite in the space, most of them are used for communication

Picture from [4]

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HISTORY:

• The first satellites• Pioneer satellites• Geo’s• Early bird• Later communication satellites

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Communication satellites bring the world to you anywhere and any time…..

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Working…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 transmits the signals to the satellite. Up link frequency is the frequency at which

Ground Station is communicating with SatelliteThe satellite Transponder converts the signal and sends it down to the second earth station. This

frequency is called a Downlink frequency

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base stationor gateway

Classical satellite systemsInter Satellite Link (ISL)

Mobile User Link (MUL) Gateway Link

(GWL)

footprint

small cells (spotbeams)

User data

PSTNISDN GSM

GWL

MUL

PSTN: Public Switched Telephone Network

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Advantages:

•The coverage area of a satellite is greater than that of a terrestrial system

•Transmission cost of a satellite is independent of the distance from the center of the coverage area

•Higher Bandwidths are available for use•Weather images can be displayed

•Television broadcasts are uninterrupted•Used to track major developments such as

hurricanes 24hrs a day

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Disadvantages:

•Cost involved in launching satellites into orbit is too high

•Satellite bandwidth is gradually becoming used up•There is a larger propagation delay in satellite

communication than in terrestrial communication• It takes longer signal to to the earth

•Increased difficulty of telephonic conversations•GEO’s are not positioned in the farthest northen

and southern orbits

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Applications:General applications• Weather forecasting• Radio and TV broadcast broadcasting• Military• Satellites for navigation and localization (e.g. GPS)

In context of mobile communication• Global telephone backbones (get rid of large cables)• Connections for communication in remote places or

developing areas (for researchers in Antarctica)• Global mobile communication (satellites with lower orbits are

needed like LEO’s)

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Thank you