Sattelite Comm

7/28/2019 Sattelite Comm

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Prepared and Presented by:

Manasi Bhalla

Priyanka Mehra


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A satellite is a self-containedcommunication

system with theability to receivesignals from Earth andto retransmit thosesignals back with use

of a transponder

anintegrated receiverand transmitterof radio signals


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Satellite communications use the very high-frequency range of 150 gigahertz to transmit and

receive signalsThe frequency ranges or bands are identified byletters: (in order from low to high frequency) L-,S-, C-, X-, Ku-, Ka-, and V-bands


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There are broadly three major types of satellite system

Fixed Satellite System

Mobile Satellite System

Research Satellite System


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Satellite communication has two main components:

The ground segment

The space segment


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The main components of a satellite consist of thecommunications system, which includes the

antennas and transponders that receive andretransmit signals, the power system, which includesthe solar panels that provide power, and thepropulsion system, which includes the rockets that

propel the satellite.


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The first artificial satellite was the Soviet Sputnik 1,launched on October 4, 1957 and equipped with anonboard radio-transmitter that worked on two

frequencies: 20.005 and 40.002 MHz.


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GEO satellites are synchronous with respect toearth. These satellites are placed in the space insuch a way that only three satellites are sufficient to

provide connection throughout the surface of theEarth (that is; their footprint is covering almost1/3rd of the Earth). The orbit of these satellites iscircular. This is because it revolves around the earthat the earth's own angular velocity (360 degreesevery 24 hours, in an equatorial orbit).


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Northern or southern regions of the Earth (poles) havemore problems receiving these satellites due to the lowelevation above a latitude of 60, i.e., larger antennas areneeded in this case. Shading of the signals is seen in citiesdue to high buildings and the low elevation further awayfrom the equator limit transmission quality. The transmit

power needed is relatively high which causes problemsfor battery powered devices. These satellites cannot beused for small mobile phones. The biggest problem forvoice and also data communication is the high latency aswithout having any handovers, the signal has to at least

travel 72,000 kms. Due to the large footprint, eitherfrequencies cannot be reused or the GEO satellite needsspecial antennas focusing on a smaller footprint.Transferring a GEO into orbit is very expensive.


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Th lli l d 500 1500k b


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These satellites are placed 500-1500kms abovethe surface of the earth. As LEOs circulate on alower orbit, hence they exhibit a much shorterperiod that is 95 to 120 minutes. LEO systemstry to ensure a high elevation for every spot onearth to provide a high quality communicationlink.


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Disadvantage


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MEOs can be positioned somewhere between LEOs and GEOs,both in terms of their orbit and due to their advantages and

disadvantages.

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: Again, due to the largerdistance to the earth, delay increases to about 7080 ms. the satellites need higher transmit power

and special antennas for smaller footprints


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The International Telecommunication Union (ITU), aspecialized agency of the United Nations, regulatessatellite communications. The ITU, which is based inGeneva, Switzerland, receives and approvesapplications for use of orbital slots for satellites.

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Sattelite Comm