SATELLITE COMMUNICATION AND IT'S APPLICATION IN GPS

Satellite Communication & Its Application In GPS

Presented by:•Suchishmita Datta•Kakali Das•Arkaprava Jana

Outline• Introduction

• Orbit

• Types of Satellite

• Satellite subsystems

• System Design

• Choice of carrier

• Satellite link

• Capacity allocation

• VSAT

• Revolution

• Application

• Advantage & Disadvantage

• Conclusion

• Acknowledgement

Introduction

• A communication satellite is a station in space that is used for telecommunication, radio and television signals.

:A line joining a planet and the Sun sweeps out equal areas during equal intervals of time."

e=(s2 –r2)0.5 /s

Kepler’s Law

: “The orbit of every planet is an ellipse with the Sun at one of the two foci."

where s & r are the major & minor axis of elliptical path respectively, e = eccentricity,

"The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit."

[a=orbital constant]

1st Law2nd Law:

3rd law:

T2=aD3

Pioneers in Satellite Communication

• Konstantin Tsiolkovsky

• Hermann Noordung

• Arthur C. Clarke


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Types of Satellite Orbits

• Based on the inclination(i):

– Equatorial Orbit (i=0°)

– Polar Orbit (i=90°)

– Other orbits (0°<i<90°)

• Based on Eccentricity:

– Circular with centre at the earth’s centre

– Elliptical with one foci at earth’s centre

Based on Altitude:

• Low Earth Orbit (LEO).

• Geostationary Earth Orbit (GEO).

• Medium Earth Orbit (MEO).

• Highly Eccentric Orbit (HEO).

LEO (Low Earth Orbit)

• Circular/slightly elliptical orbit, 2000km

• Orbit period: 1.5 -2 km

• Diameter of coverage: 8000 km

• Signal propagation delay: <20 ms

• Maximum satellite visible time:20 min

• Atmospheric drag results in orbital

deterioration.

MEO (Medium Earth Orbit)

• Circular orbit: 2000-36000km

• Orbit period: 2-12hrs

• Diameter of coverage: 10,000-15,000km

• Signal propagation delay: <50ms

• GPS

GEO(Geostationary Earth Orbit)

• Circular , 36,000 km

• Orbital velocity:3 km/s

• Orbital period : 1436 min or 23.93 hrs

• High coverage area, stationary footprint

• Good for broadcasting TV

• Theoretically 3 geostationary satellites provides 100% earth coverage.(120 degree)

HEO(Highly Elliptical Orbit)

•Elliptic orbit with a low-altitude perigee and a high-altitude apogee(over 35,786 kilometres)

•i = 63.4°

•All traffic must be periodically transferred from the “setting” satellite to the “rising” satellite (Satellite Handover)

Other Orbits• Molniya Orbit Satellites:

i=63.4, orbital period = half sidereal dayUsed by Russia for decades.Molniya Orbit is an elliptical orbit. The satellite remains in a nearly fixed position relative to earth for eight hours.A series of three Molniya satellites can act like a GEO satellite.Useful in near polar regions

• High Altitude Platform (HAP):

Solar powered aerial platformsOperates in quasi-stationary position, alt. : 22kmAirship, AircraftHAPs would have very small coverage area, but would have a comparatively strong signal.Cheaper to put in position, but would require a lot of them in a networkAltitude selection above normal air traffic


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Types of Satellite

• Passive Satellite:

- Works as a reflector

- Works as a retransmitter

• Active Satellite:


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Satellite Sub-systems

• Altitude and Orbit control subsystem (AOCS)

• Telemetry, Tracking, Command and monitoring Subsystem (TTC&M)

• Power Subsystem

• Structural Subsystem

• Thermal Control Subsystem


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Satellite Systems Types:--

• Ground to ground system.

• Ground cross link ground system.

• Ground to relay platform system.

S1

ES2ES1

S1

S2

ES1

ES1

Relay Platfrom

ES

S1

Satellite System Elements

Ground Segment

•User , Terrestrial system

•Earth station

Space Segment

• Satellite Launching Phase , Transfer Orbit Phase , Deployment.

• Operation• TT&C -Telemetry,Tracking and Command Station• SCC - Satellite Control Center, a.k.a.:

• OCC - Operations Control Center• SCF - Satellite Control Facility

• Retirement Phase


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Frequency Coordination

Choice of frequency bands depends on:

• System Considerations(MSS and FSS).

• Organization level frequency planning

• Orbit frequency planning and coordination(INSAT).

Frequency Planning

• Primary Frequency Allocation.

• Secondary Frequency Allocation.

• Footnote Allocation.

Frequency Bands

Band Uplink Downlink Uses

L–Band 1GHz 2GHz MSS

S-Band 2GHz 4GHz MSS, NASA, Deep space research.

C-Band 4GHz 8GHz FSS.

X-Band 8GHz 12.5GHz FSS and in terrestrial imaging,

[Ex: military and meteorological

satellites].

Frequency Bands

Band Uplink Downlink Uses

Ku–Band 12.5GHz 18GHz FSS and BSS (DBS).

K-Band 18GHz 26.5GHz FSS and BSS.

Ka-Band 26.5GHz 40GHz FSS.

Millimeter 40GHz 300GHz -------


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Satellite Link

Uplink

Downlink

Transponder

Types of Link

Satellite Link Design

• The weight of satellite.

• The choice frequency band.

• Atmospheric propagation effects.

• Multiple access technique.

Design (Downlink Received Power)

Pr = EIRP + Gr - Lp - La - Lta - Lra dBW

Where:

EIRP(Equivalent isotropically radiated power)=10log10(PtGt)Dbw

Gr =10log10(4πAe/λ2)dB

Path Loss Lp =10log10[(4πR/λ)2]= 20log10[4πR/λ]dB

La =Attenuation in the atmosphere

Lta =Losses associated with transmitting antenna

Lra =Losses associated with receiving antenna

Design (Downlink Noise Power)

Pn=kTsBn watts.

N=k+Ts+Bn dBW

Where,K is Boltzmann's constant (-228.6 dBW/K/Hz)Ts is the system noise temperature in dBKBn is the noise Bandwidth of the receiver in dBHz

Design (Uplink Received Power)

Prxp=Pt+Gt+Gr-Lp-Lup dBW

Design (Uplink Noise Power)

Nxp=K+Txp+Bn dBW


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Capacity Allocation

• TDMA

Tf/N = b/R

• FDMA

µ = R/(N*b)

• CDMA

• ALOHA

DAMA

FAMA


• Orbit


• System Design


• Satellite link


• VSAT


• Revolution

• Application


• Conclusion

• Acknowledgement

VSAT

•VERY SMALL APERTURE TERMINAL

•Low or medium traffic

•Antenna diameter –1 to 3.7 meter

•Star topology


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Revolution of Satellites

• 1957

– October 4 : - First satellite Sputnik

– Sputnik 02

• 1958

– Project Score

• 1960

– First successful passive satellite: Echo 1

Revolution of Satellite• 1962

– First active satellite Telstar

• 1964

– INTELSAT

– Syncom 3

• 1974

− ATS-6

INDIAN Satellite

• 1975 - Aryabhata

• 2003 - INSAT-3A

• 2007 - INSAT-4B

• 2012 - Megha-Tropiques


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Application

• Amateur radio

• DSCS

• Fixed Service Satellite(FSS)

• Direct Broadcast Satellite

• SAT-PHONE

• INTERNET

• GPS

GPS

• Global Positioning System

• Network of 24 satellites

• Developed by DoD

• Operational 24 hours/day

• Available worldwide

• Land, sea and air

• Works in all weather conditions

GPS Satellite

• Weighs approximately 2,000 lbs

• Travels 7,000 mph

• 17 feet across with solar panels extended

• Orbit 12,500 miles above Earth

• Circle the Earth twice daily

How Does GPS Work?

HALDIA

DIAMOND HARBOUR

KOLKATA

ITME

Determining GPS Position

Satellite A

+

Satellite B

+

Satellite C

+

Determining GPS Position

Satellite A

Satellite B

+

+

Satellite C

+

How do we decide which one is our true location?

Satellite A

Satellite B

+

+


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Advantages

•Satellite can be used for broadcast purpose ( one to many) within the large covered area.

•Satellites are capable of handling very high bandwidth.

•It is possible to provide large coverage using satellite

•Satellite can provide signal to terrestrial uncovered pockets like valleys and mountainous regions.

•The cost of transmitting information through satellite is independent of distance involved.

Disadvantages

• Launching satellites into orbit is costly.

• Satellite bandwidth is gradually becoming used up.

• There is a larger propagation delay and noise interference in satellite communication

• Impossibility to repair and maintain


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

CONCLUSION

• The use of satellite technology, particularly in the use ofcommunications satellites has grown rapidly in the past thirtyyears. Each day more and more uses for the satellites arebeing discovered. Feeding this is the rapid advancement oftechnology that allows the quick implementation of theseuses.

• Satellites remain the best utilization used for communicationsdue to their speed and other advantages mentioned in thispresentation.


• Orbit



• System Design


• Satellite link


• VSAT

• Revolution

• Application


• Conclusion

• Acknowledgement

Acknowledgement

SATELLITE COMMUNICATION AND IT'S APPLICATION IN GPS

Technology

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