PowerPoint presentation on Satellite Networks.

1. SATELLITE NETWORKS
Presented by:
Krishna Kant Gupta
Semester: 6th
Roll no.: 16
Computer Networks (IT-604)
Year: 20137/18/2014 6:37:54 PM
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2. • Introduction
• Artificial Satellites over Natural Satellites
• Orbits
• Types Of Satellite Orbits
• Footprint
• Categories of Satellite
i. GEO
ii. MEO
iii. LEO
• Advantages of Satellites
• Disadvantages of Satellites
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CONTENTS

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INTRODUCTION

4. We can install electronic equipment on the
satellite to regenerate the signal that has lost
its energy during travel.
The distance of natural satellites, such as the
Moon, from the Earth is huge, which create a
long delay in communication.
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ARTIFICIAL SATELLITES OVER NATURAL
ONE’S

5. An artificial satellite needs to have an orbit, the path in which it travels around
the Earth.
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SATELLITE ORBITS

6. Kepler’s Law: It determines the period
of satellite.
Period = C x distance1.5 sec.
Note:
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7. Example 1
What is the period of the moon according to Kepler’s law?
Solution
The moon is located approximately 384,000 km
above the earth. The radius of the earth is 6378
km. Applying the formula, we get
Period = (1/100) (384,000 + 6378)1.5 = 2,439,090s
= approx.(1 month)
Distance: 384000 km
Period: approx. 1month
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8. Example 2
According to Kepler’s law, what is the period of a
satellite that is located at an orbit approximately
35,786 km above the earth?
Solution
Applying the formula, we get
Period = (1/100) (35,786 + 6378)1.5 = 86,579 s
= 24 h
A satellite like this is said to be stationary to the earth.
The orbit, as we will see, is called a geosynchronous
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9. The area of the Earth’s surface from which an Earth Station can
transmit to or receive from a particular satellite.
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FOOTPRINT

10. Satellite
GEO
MEO
LEO
Based on the location of the orbits satellites are divided into
three categories:
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SATELLITE CATEGORIES

11. 11

Outer Van Allen Belt (15000-20000 km)
MEO (5 - 15K km)
GEO (35786 km)
LEO ( < 2K km)
Inner Van Allen Belt (1500-5000 km)
GEO: Geostationary Earth Orbit
MEO: Medium Earth Orbit
LEO: Low Earth Orbit
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SATELLITE ORBIT ALTITUDES

12. • Two Stations on Earth want to communicate through radio broadcast
but are too far away to use conventional means.
• One Earth Station sends a transmission to the satellite. This is called
a Uplink.
• The satellite Transponder converts the signal and sends it down to
the second earth station. This is called a Downlink.
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HOW SATELLITE WORKS?

13. Band
Downlink,
GHz
Uplink, GHz
Bandwidth,
MHz
Problems
L 1.5 1.6 15 Low bandwidth; crowded
S 1.9 2.2 70 Low bandwidth; crowded
C 4.0 6.0 500 Terrestrial Interference
Ku 11.0 14.0 500 Rain
Ka 20.0 30.0 3500 Rain, equipment cost
L-band and S-band: is used for Mobile Satellite Services and offers good penetration
through adverse weather conditions and foliage.
C-band: Public switched networks.
Ku-band and Ka-band: Rural telephony, satellite news gathering, high speed internet,
video conferencing, and multimedia.
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SATELLITE FREQUENCY BAND

14.  These satellites are in orbit 35,786 km above the earth’s surface along
the equator.
 Objects in Geostationary orbit revolve around the earth at the same
speed as the earth rotates. This means GEO satellites remain in the
same position relative to the surface of earth.
 One GEO satellite cannot cover the whole earth. It takes minimum of
three satellites equidistant from each other.
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GEOSTATIONARY EARTH ORBIT (GEO)

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SATELLITES IN GEOSTATIONARY ORBIT

16. • Advantages
 A GEO satellite’s distance from earth gives it a large coverage area,
almost a fourth of the earth’s surface.
 GEO satellites have a 24 hour view of a particular area.
 These factors make it ideal for satellite broadcast and other multipoint
applications.
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GEO (CONT.)

17. • Disadvantages
 A GEO satellite’s distance also cause it to have both a comparatively
weak signal and a time delay in the signal, which is bad for point to
point communication.
 GEO satellites, centered above the equator, have difficulty
broadcasting signals to near polar regions
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GEO (CONT.)

18. • A MEO satellite is in orbit somewhere between 5,000 km and 15,000 km
above the earth’s surface.
• 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 LEO satellites.
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MIDDLE EARTH ORBIT (MEO)

19. • Advantages
 A MEO satellite’s longer duration of visibility and wider footprint means
fewer satellites are needed in a MEO network than a LEO network.
 Shorter time delay and stronger signal than a GEO satellite
• Disadvantages
 A MEO satellite’s distance gives it a longer time delay and weaker signal
than a LEO satellite, though not as bad as a GEO satellite.
EXAMPLE: Global Positioning System (GPS).
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MEO (CONT.)

20. • Constructed and operated by US Department of Defense.
• There are 24 satellites in six orbits.
• Used for land, sea and air navigation to provide time and
locations for vehicles and ships.
• The satellites in each orbits are designed in such a way, at a
time minimum four satellites are visible from any point on the
Earth.
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GPS: EXAMPLE OF MEO

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ORBITS FOR GPS SATELLITE

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TRILATERATION

23. • Measuring the distance: The trilateration principle can find our location on
the earth if we know our distance from three satellites and know the position of
each satellite. The position of each satellite can be calculated by a GPS receiver.
The GPS receiver, then, needs to find its distance from at least three GPS
satellites. Suppose all GPS satellites and the receiver on the earth are
synchronized. Each of 24 satellites transmits a complex signal each having a
unique pattern. The receiver measures the delay between the signals from the
satellites and its copy of signals to determine the distances to the satellites.
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GPS: HOW IT WORKS ( CONT.)

24. • LEO satellites are much closer to the earth than GEO satellites, ranging
from 500 to 2000 km above the surface.
• Rotation period of 90 to 120 minutes, with speed 20,000 to 25,000
km/h.
• LEO satellites don’t stay in fixed position relative to the surface, and are
only visible for 15 to 20 minutes each pass.
• A network of LEO satellites is necessary for LEO satellites to be useful.
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LOW EARTH ORBIT (LEO)

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LEO SATELLITE SYSTEM

26. • Advantages
 A LEO satellite is proximity to earth compared to a GEO satellite gives it
a better signal strength and less of a time delay, which makes it better
for point to point communication.
 A LEO satellite’s smaller area of coverage is less of a waste of
bandwidth.
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LEO (CONT.)

27. • Disadvantages
 A network of LEO satellites is needed, which can be costly
 Atmospheric drag effects LEO satellites, causing gradual orbital
deterioration.
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LEO (CONT.)

28. • It has 66 satellites in 6 LEO orbits.
• Each have altitude of 750 km.
• Use to provide direct worldwide communication.
i.e. voice, data paging, fax, even navigation.
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IRIDIUM SYSTEM: EXAMPLE OF LEO

29. The original name, Iridium, came from the name
of the 77th chemical element; a more appropriate
name is Dysprosium (66th element)
Fact:
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30. • It has 48 satellites in 6 LEO orbits.
• Each have altitude of 1400 km.
• The ground station can create more powerful signals.
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GLOBALSTAR: EXAMPLE OF LEO

31. •It provides fiber-optic like (broadband channels, low error rate, and low delay)
communication
•It has 288 satellites in 12 LEO polar orbits.
• Each have altitude of 1350 km.
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TELEDESIC: EXAMPLE OF LEO

32. The project was started in 1990 by mobile phone pioneer
Craig McCaw and Microsoft founder Bill Gates.
About:
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The goal of Teledesic system is to provide broadband
Internet access for users all over the world
Goal:

33.  The coverage area of a satellite greatly exceeds that of a terrestrial
system.
 Transmission cost of a satellite is independent 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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ADVANTAGES OF SATELLITES

34.  Launching satellites into orbit is costly.
 Satellite bandwidth is gradually becoming used up.
 There is a larger propagation delay in satellite communication than
in terrestrial communication.
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DISADVANTAGES OF SATELLITES

35. THANK YOU....
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