1. City University
Course Title: Computer Networks
Course Code: CSE317
Topic Name: Satellite System
Submitted By
Nishat Tasnim Ali
ID:1834902591
Batch: 49th
Submitted To
Pranab Bandhu Nath
Senior Lecturer
Department of CSE
City University
2. Introduction to Satellite System
A satellite is an artificial object which is placed intentionally into an orbit of any
natural satellite. It is used for weather forecasting, digital transmission, scientific
research and development etc. It can also be specified like it is a wireless
specialized transmitter that is launched by rocket and placed on orbit around the
earth.
History of Satellite System
There is a very long history of satellite system.
1945- Arthur C. Clarke published essay called “Extra Terrestrial relays”.
1957- First Satellite called SPUTNIK.
1960-ECHO the first reflecting communication satellite.
1963-First Geostationary satellite SYNCOM.
1965- First Geostationary commercial satellite “Early Bird (INTEKSAT)”.
Its lifetime was 1.5 year.
1976- Three MARISAT launched for maritime communication.
1982- First telephone system mobile satellite called INMARSAT-A.
1988- First mobile phone and data communication satellite called
INMARSAT-C.
1993-First digital telephone system satellite.
1998-Global satellite systems for small mobile phones.
Characteristics of Satellite System
1. Provide connection between earth based base station and satellites.
2. It has a large footprint which covered 34% of earth surface.
3. The antennas are at fixed positions and used to provide smaller footprints
and higher transmitting power.
4. Several satellite are needed to ensure global coverage.
5. Satellites are placed in different altitudes because of their uses and their
weights are also dissimilar.
Types of Satellite
There are four different types of satellite:
1. GEO (Geostationary Earth Orbit):
It is placed at about 36,000 km above earth’s surface. These satellites
remain in the same position relative to the surface of earth and move
around with the same speed as earth rotates.
3. Example: All TV and radio broadcast satellites, weather satellites and
satellites that are the backbones for telephone network.
Advantages:
a) Three Geo satellites are enough to cover up almost any spot on earth.
b) Receivers and senders can use fixed antennas.
c) Ideal for TV and Radio broadcast.
d) Lifetime expectations are high, about 15 years.
e) Have 24 hour view of a particular area.
f) Don’t need any handover due to large footprints.
g) Don’t exhibit any Doppler shift as relative movement is zero.
Disadvantages:
a) Shading of the signals in cities cause of high buildings and low
elevation further away from the equator limits transmission delays.
b) Transmit power is high which causes problems for battery powered
devices.
c) These satellites can’t be used for small mobiles.
d) Transferring GEO is very expensive.
2. LEO (Low Earth Orbit):
It is placed at about 500-1500km above the earth surface.
LEO satellites do not stay in fixed position and are only visible for 15 to 20
minutes each pass.
Example: Hubble space telescope, the Spot family of satellites (Earth
imaging and survey) and military observation satellites.
Advantages:
a) LEO’s smaller footprints allow for better frequency reuse.
b) LEO’s small area coverage reduce waste of bandwidth.
c) These satellites give a better signal strength and less of a time delay.
d) Using advanced compression schemes, transmission rates of about
2,400 bit/s can be enough for voice communication.
4. Disadvantages:
a) The high number of satellites combined with fast movement cause
high complexity of whole satellite system.
b) The low latency via a single LEO is only half story.
c) These have short lifetime of about 5 to 8 years.
d) Need for routing of data packets from satellite to satellite for
communication around the world.
3. MEO ( Medium Earth Orbit):
It is placed at somewhere between 6,000 km to 20,000 km above earth’s
surface. They are similar to LEO in context of functionality.
Example: GPS (Altitude of 20,200 kilometers), GLONASS (Altitude of
19,100 kilometers) and Galileo (Altitude of 23,222 kilometers).
Advantages:
a) The system only requires a dozen satellites at 10,000 km at orbit which
is more than GEO and Less than a LEO.
b) These satellites move more slowly allowing a simple system design.
c) MEO can cover larger populations.
d) They have longer visibility and wide footprints which means fewer
satellites are needed in MEO.
Disadvantages:
a) Due to larger distance to earth delay increases to 70-80ms.
b) Need higher transmit power and special antennas for smaller footprints.
c) Distance give a longer time delay and weak signal than LEO.
4. HEO (High Earth Orbit):
They are the only non-circular orbit satellites. They operates with an
elliptical orbit with a maximum altitude and a minimum altitude.
They are used where high area coverage is required.
Example: Molnya, Tundra, Loopus, Archimedes and Borealis of the Ellipse
system.
5. Advantages:
a) They take medium round trip delay.
b) They observe less exposure to atmospheric drag than LEO.
c) They offers longer dwell time at some point in the sky.
Disadvantages:
a) Satellite System is more complex than other types.
b) Selected area coverage.
c) High propagation delay on one side of earth.
d) Expensive in manufacturing and launching.
References:
[1]https://www.rfwireless-world.com/Terminology/Advantages-and-
Disadvantages-of-HEO.html
[2] https://www.swiftutors.com/types-of-satellite-orbits.html
[3] https://www.javatpoint.com/types-of-satellite-systems
[4]https://www.everythingrf.com/community/what-is-the-medium-earth-
orbit#:~:text=The%20region%20of%20space%20in,Medium%20Earth%20
Orbit%20(MEO).&text=Some%20examples%20of%20satellites%20that,(A
ltitude%20of%2023%2C222%20kilometers).
[5] https://ieeexplore.ieee.org/document/5632684
[6]https://www.sciencedirect.com/topics/engineering/low-earth-
orbit#:~:text=Most%20of%20the%20LEO%20satellites,survey)%20and%2
0military%20observation%20satellites.
