Satellite comm as remains a realistic alternative in comms. this short note discussed brief history of satellite, as well as types, components, locations and lots more......enjoy!

1. UNIVERSITY OF NIGERIA, NSUKKA
FACULTY OF ENGINEERING
Department of Electronic Engineering
TOPIC
SATELLITE COMMUNICATION – A REALISTIC ALTERNATIVE
A TECHNICAL WRITING PREPARED IN FULFILLMENT FOR THE REQUIREMENT
OF THE COURSE ECE 491 (TECHNICAL WRITING AND SEMINAR)
BY
EZEONYIDO KINGSLEY LOTANNA
REG NO
2007/147192
SEMINAR SUPERVISOR
ENGR M.A. AHANEKU
NOVEMBER, 2011.

2. TITLE PAGE
SATELLITE COMMUNICATION – A REALISTIC ALTERNATIVE

3. DEDICATION
This work is dedicated to my parents Mr. and Mrs. Anthony Ezeonyido and to my beloved
siblings, who stood solidly behind me during the period of my research.
ii

4. ACKNOWLEDGEMENTS
I wish to acknowledge GOD ALMIGHTY for His love and kindness towards me and my
family, His uncountable favors and blessings, and His perfect peace. Without Him, this term
paper would have been impossible. I am also eternally indebted to my friend Precious Bonyi
Linus who helped me so much during the time of arrangement of this term paper. I would
also like to recognize the arduous help that was freely and generously given to me by friends.
And finally, I would like to thank my parents for their supports and encouragements during
this research work.
iii

5. PREFACE
Chapter one of this term paper gives an overall introduction, important features and brief
history of Satellite Communication.
Chapter two of this work invariably revealed the basic components and requirements that aid
the operations of Satellite Communication.
In chapter three, we see the Technological Overview of Satellite communication such as their
Characteristics and Error Correction for certain short comings associated with its construction
as well as Hybrid Network as an alternative method of signal Transmission without much
loss in energy.
Chapter four discussed the various applications and impacts of Satellite Communication in
modern technology, as well as conclusion based on the content of this work.
iv

6. ABSTRACT
This research work consequently addresses as well as explains the components and basic
working principles of satellite communication. It also describes the frequency and functional
requirements for the operation of communication satellites as well as their orbits in space.
Finally, this research work enumerated and explained some well-known applications and
impacts of satellite communication in the modern technology as they all are known proves
that makes Satellite Communication a REALISTIC ALTERNATIVE.
v

7. TABLE OF CONTENTS
TITLE PAGE……………………………………………...………………………………….. i
DEDICATION……………………………………………………………………………….. ii
ACKNOWEDGEMENT…………………………………………………………………….. iii
PREFACE…………..……………………………………………………………………….. iv
ABSTRACT…………………..……………………………………………………………… v
TABLE OF
CONTENT…..………………………………………………………………………………. vi
CHAPTER ONE: INTRODUCTION………………………………………………………... 1
1.1 BRIEF HISTORY OF SATELLITE COMMUNICATION............................................... 1
CHAPTER TWO: BASICS OF SATELLITE COMMUNICATION………………... 3
2.1: BASIC COMPONENTS (ELEMENTS) OF COMMUNICATION SATELLITE............ 3
2.1.1 The Satellite……………………………….....……………………………………….. 3
2.1.2: Ground Station……………………....………………………………..………………. 3
2.2 BASIC REQUIREMENTS FOR SATELLITE COMMUNICATION..………….…. 3
2.2.1 Functional Requirements ………………….………………………………………..... 3
2.2.2 Frequency Requirements…………………………………………………….…….…. 4
2.3 ORBITS OF SATELLITE……………………...……...……………………………... 6
CHAPTER THREE: TECHNOLOGICAL OVERVIEW………………………………….. 7
3.1 CHARACTERISTICS……………..……………………………………...………….. 7
3.2 ERROR CORRECTION TECHNIQUES……………………………………...…….. 7
3.3 HYBRID NETWORKS…………………………………………………..………….. 8
CHAPTER FOUR: SATELLITE COMMUNICATION AS A REALISTIC
ALTERNATIVE…………………………………………………… 10
4.1 APPLICATIONS OF SATELLITE COMMUNICATION……………………....….10
4.2 IMPACTS OF SATELLITE COMMUNCATION………………….………..…….. 12
4.3 CONCLUSION………………………………………………………………….….. 12
REFERENCES
vi

8. 1
CHAPTER ONE
INTRODUCTION
A communications satellite is an artificial satellite stationed in space for the purpose of
telecommunications. The use of satellite in communication system is very much a fact of
everyday in life. This is evidenced by many homes, which are equipped with antennas and
dishes. These antennas were used for reception of satellite signal for television. Satellites also
form an essential part of communication system worldwide carrying large amount of data and
telephone traffic in addition to television signals.
Satellites offer a number of important features, which are not readily available with others
means of communication. Some of them are enumerated below.
• Very large area of earth is visible from satellite (about 42%) i.e. communication is
possible beyond earth curvature (beyond line of sight)
• Satellite offers communication with remote communities in sparsely populated area,
which are difficult to access by other means of communication.
• ‘Satellite communication ignores political boundaries as well as geographical
boundaries’1.
• Satellite provides communication with moving aircraft from ground control station
across the country.
• ‘Satellite provides remote sensing i.e. detection of water pollution, oil field,
monitoring and reporting of weather conditions etc’2.
• For fixed (point-to-point) services, communications satellites provide a microwave
radio relay technology complementary to that of communication cables. ‘They are
also used for mobile applications such as communications to ships, vehicles, planes
and hand-held terminals’3, and for TV and radio broadcasting, for which application
of other technologies, such as cable television, is impractical or impossible.
1.1 BRIEF HISTORY OF SATELLITE COMMUNICATION
Since the primary role of a satellite is to reflect electronic signal, the first artificial satellite
was the Soviet Sputnik 1, launched on October 4, 1957, and equipped with an on-board radio-
transmitter that worked on two frequencies, 20.005 and 40.002 MHz .The first American
satellite to relay communications was Project SCORE in 1958, which used a tape recorder to
store and forward voice messages. It was used to send a Christmas greeting to the world from
U.S. President Dwight D. Eisenhower. NASA launched an Echo satellite in 1960; the 100-
foot (30m) aluminized PET film balloon served as a passive reflector for radio

9. 2
communications. Courier 1B, built by Philco, also launched in 1960, was the world’s first
active repeater satellite. With the launch of Alouette 1 in 1962 Canada became the third
country to put a man-made satellite into space. Because Canada did not have any domestic
launch capabilities of its own, Alouette 1, which was entirely built and funded by Canada,
was launched by the American National Aeronautics and Space Administration (NASA) from
Vandenberg AFB in California.
‘In 1962, the American telecommunications giant AT&T launched the world's first true
communications satellite, called Telstar. Since then, countless communications satellites have
been placed into earth orbit, and the technology being applied to them is forever growing in
sophistication.’4

10. 3
CHAPTER TWO
BASICS OF SATELLITE COMMUNICATION
2.1 BASIC COMPONENTS (ELEMENTS) OF COMMUNICATION SATELLITE
Every communications satellite in its simplest form (whether low earth or Geostationary)
involves the transmission of information from an originating ground station to the satellite
(the uplink), followed by a retransmission of the information from the satellite back to the
ground station (the downlink). Therefore satellite communications are comprised of 2 main
components:
2.1.1 The Satellite
The satellite itself is also known as the space segment, and is composed of three
separate units, namely the fuel system, the satellite and telemetry controls, and the
transponder. ‘The transponder includes the receiving antenna to pick-up signals from the
ground station, a broad band receiver, an input multiplexer, and a frequency converter
which is used to reroute the received signals through a high powered amplifier for
downlink.’5
2.1.2 The Ground Station
This is the earth segment. ‘The ground station's job is two-fold. In the case of an
uplink, or transmitting station, terrestrial data in the form of baseband signals, is passed
through a baseband processor, an up converter, a high powered amplifier, and through a
parabolic dish antenna up to an orbiting satellite. In the case of a downlink, or receiving
station, it works in the reverse fashion as the uplink, ultimately converting signals
received through the parabolic antenna to baseband signal.’6
2.2 BASIC REQUIREMENTS FOR SATELLITE COMMUNICATION
2.2.1 FUNCTIONAL REQUIREMENTS: These are core requirements for satellite
communication. In the absence any of the following functional requirements,
communication satellite would be as good as non-existing.
i. Power Supply: The primary electrical power for operating Satellite electronic
equipment is obtained from solar cells. Individual cells can generate small
amounts of power, and therefore array of cells in series-parallel connection are
required.
ii. Attitude Control: The attitude of a satellite refers to its Orientation in space.
Much of equipment carried abroad a satellite is there for the purpose of

11. 4
controlling its attitude. ‘Attitude control is necessary, for example, to ensure that
directional antennas point in the proper directions.’7 In the case of earth
environmental satellites the earth-sensing instrument must cover the required
regions of the earth, which also requires attitude control.
iii. Thermal control: Equipment in the satellite also generates heat which has to be
removed, and satellite's equipment should operate as near as possible in a stable
temperature environment. ‘Therefore to achieve this, Thermal blankets and
shields may be used to provide insulation while radiation mirrors are often used
to remove heat from communication payload (transponders, antenna, and
switching systems)’8
iv. TT&C subsystem: The Telemetry, Tracking, and Command (TT&C)
subsystem performs several routine functions abroad a spacecraft.
• Telemetry: The telemetry or "telemetering" function could be interpreted
as "measurement at a distance". Specifically, it refers to the overall operation
of generating an electrical signal proportional to the quantity being measured,
and encoding and transmitting this to a distant station. ‘Data that are
transmitted as telemetry signals includes attribute information (sun earth
sensors), environmental information (magnetic field intensity and direction),
and spacecraft information (temperatures and power supply voltages)’9.
• Tracking: Tracking is obviously important during the transmitter and drift
orbital phases of the satellite launch and it is necessary to be able to track the
satellites movements and send correction signals as well as know the satellite
range as required from time to time. This can be determined by measurement
of propagation delay of signals specially transmitted for ranging purposes.
• Command Systems: Command system receives instructions from ground
system of satellite and decodes the instruction and sends suitable commends to
other systems.
v. Transponders: A transponder is the series of interconnected units which forms
a single communication channel between the receiving and transmitting antennas
in a communication satellite. They perform the major functions of receiving
signals, conditioning the signals (suppressing noise, amplification), and re-
transmitting them back to the ground station.
2.2.2 FREQUENCY REQUIREMENTS: The communication between one point
and another depends upon frequency of the transmitted signal as well as mode of

12. 5
communication. This is to say that frequency requirement greatly depends upon
the mode of communication which are:
a) Small distance Communication
b) Long Distance Communication
Small Distance Communication: Frequencies up to approximately 10MHz can be used
for small distance communication through Ground Wave Propagation. As frequency
increases, the attenuation of ground wave increases (Earth starts behaving like absorber for
high frequency signals) because of which, it is not possible to establish a reliable
communication link through ground waves for frequencies more than 10MHz.
Long Distance Communication: The signals having frequency more than 30MHz are
passed through ionosphere and these are required to reflect back to earth by some artificial
medium for establishing reliable communication between transmitter and receiver. For
fulfilling the requirement of high frequency and long distance communication across the
globe, the artificial reflector (Satellite) above the ionosphere are required for transmitted
signal.
TO TV
Transmitted signals
FIGURE 1: Sky Wave Propagation OR Long Distance Communication
The table below shows the frequency allocation/ranges for Satellite Communication
Band Designation Nominal Frequency Range Principal uses
HF 3 -30 M Hz Short-wave Broadcast
VHF 30 -300 M Hz FM, TV
UHF 300 -3000 MHz TV, LAN, cellular, GPS
L 1 -2 GHz Radar, GSO satellites
TABLE 1: FREQUENCY ALLOCATION FOR SATELLITE COMMUNICATION

13. 6
2.3 ORBITS OF SATELLITE
1. Polar Orbits: The polar orbiting satellites orbit the earth in such a way as to cover
the north and south Polar Regions. The altitude of polar orbiting satellite is constant
over the polar region and it is approximately 1000 Km. The period of orbiting is about
1.5Hrs and at 90°inclination to ensure that satellite passes every region of earth.
Example: IRIDIUM, GLOBAL STAR etc.
2. Equatorial Orbit: The equatorial orbit has 0° inclination from Equator. The most
popular orbit is geostationary orbits which is present at 35786 Km from the Earth
surface. The satellite in geostationary orbit appears to be stationary with respect to
earth and period of satellite is 23Hrs, 56 minutes, 4 second means solar time (ordinary
clock time). One disadvantage (for some purposes) of the geosynchronous orbit is that
the time to transmit a signal from earth to the satellite and back is approximately
percentage of a second, that is the time required to travel 35786 Km up and 35786
Km back down at the speed of light. For telephone conversations, this delay can
sometimes be annoying but for data transmission and other uses it is not much
significant.

14. 7
CHAPTER THREE
TECHNOLOGICAL OVERVIEW
3.1 CHARACTERISTICS OF COMMUNICATION SATELLITE
Incorporating satellites into terrestrial networks is often hindered by three characteristics
possessed by satellite communication.
1. Latency (propagation delay): Due to the high altitudes of satellite orbits, the
time required for a transmission to navigate a satellite link (more than 2/10ths of a
second from earth station to earth station) could cause a variety of problems on a high
speed terrestrial network that is waiting for the packets.
2. Poor Bandwidth: Due to radio spectrum limitations, there is a fixed amount of
bandwidth allocable to satellite transmission.
3. Noise: Radio signals strength is in proportion to the square of the distance travelled.
Due to the distance between ground station and satellite, the signal ultimately gets
very weak. However this problem can be solved by using appropriate error correction
techniques.
3.2 ERROR CORRECTION TECHNIQUES
Due to the high noise present on a satellite link, numerous error correction techniques have
been devised, and they are;
1. Forward-error-correction (FEC): In this method a certain number of information symbols
are mapped to new information symbols, but in such a way as to get more symbols than were
original had. When these new symbols are checked on the receiving end, the redundant
symbols are used to decipher the original symbols, as well as to check for data integrity. ‘The
more redundant symbols that are included in the mapping, the better the reliability of the
error correction.’10
Disadvantage(s) of Forward-error-Correction
a. Waste of Bandwidth: The more redundant symbols that are used to achieve
better integrity, the more bandwidth that is wasted, this is to say that this error
correction technique uses relatively a large amount of redundant data and therefore
may not be the most efficient choice on a clear channel. ‘But when noise levels are
high, FEC can more reliably ensure the integrity of the data.’10
2. Automatic-repeat-request (ARR): In this method, data is broken into packets. Within each
packet is included an error checking key. This key is often of the cyclic redundancy check
(CRC) sort. If the error code reflects a loss of integrity in a packet, the receiver can request
the sender to resend that packet. ARR is not very good in a channel with high noise, since

15. 8
many retransmissions will be required, and the noise levels that corrupted the initial packet
will be likely to cause corruption in subsequent packets. ARR is more suitable to relatively
noise free channels.’10
ARR could be achieved using varieties of method as seen below;
i. Stop and Wait (SW):With this form of ARR, the sender must wait for an
acknowledgement of each packet before it can send a new one. This can take upwards
of 4/10ths of a second per packet since it takes 2/10ths seconds for the receiver to get
the packet an another 2/10th seconds for the sender to receive the acknowledgement.
ii. Go-back-N (GBN): This method of ARR is an improvement over “stop and wait”
in that it allows the sender to keep sending packets until it gets a request for a resend.
When the sender gets such a request, it sends packets starting at the requested packet
over again. It can again send packets until it receives another retransmit request, and
so on.
iii. Selective-repeat (SR): This ARR protocol is an improvement over GBN in that
it allows the receiver to request a retransmit of only that packet that it needs, instead
of that packet and all that follows it. The receiver, after receiving a bad packet and
requesting a retransmit, can continue to accept any good packets that are coming. This
method is the most efficient method for satellite transmissions of the three ARR
methods discussed.
Disadvantage(s) of Automatic-repeat-request (ARR)
a. Cost Effective: ARR methods can be demonstrated to provide a usable error
correction scheme, but it is also the most expensive, in terms of hardware. This is in
part due to the buffering memory that is required, but more importantly to the cost of
the receiver, which needs to be able to transmit re-requests. ‘Systems such as the
Digital Broadcast Satellites used for television signal distribution would become
inordinately expensive if they had to make use of ARR, since the home based receiver
would now need to be a transmitter, and the 18 inch dish would be inadequate for the
requirements of transmitting back to a satellite.’10
3.3 HYBRID NETWORKS
In today's global networking landscape, there are many ways to transmit data from one place
to another and one way to get around the need in ARR for the receiver to have to request
retransmit via an expensive and slow satellite link is to use a form of hybrid network.
‘A hybrid network is one that allows data to flow across a network, using satellite, wireless or
terrestrial, transparently.’10

16. 9
‘In one form of hybrid network, the receiver transmits its requests back to the sender via a
terrestrial link. Terrestrial link allows for quicker, more economical and less error prone
transmission from the receiver, and the costs associated with the receivers hardware are
greatly reduced when compared to the costs involved if it had to transmit back over the
satellite link.’11 ‘There are products on the market today that allow a home user to get internet
access at around 400MB via digital satellite, while its retransmit signals are sent via an
inexpensive modem or ISDN line.’12

17. 10
CHAPTER FOUR
SATELLITE COMMUNICATION AS A REALISTIC ALTERNATIVE
Satellite Communication has replaced other means of communication that were in existence
before its grand arrival. To prove this fact, applications and impacts of satellite
communication has been adopted as seen below:
4.1 APPLICATIONS OF SATELLITE COMMUNICATION
I. TRADITIONAL TELECOMMUNICATION (TELEPHONY)
The first and historically most important application for communication satellites was in
intercontinental long distance telephony. Since the beginnings of the long distance telephone
network, there has been a need to connect the telecommunications networks of one country to
another, and this has been accomplished in several ways. The fixed Public Switched
Telephone Network relays telephone calls from land line telephones to an earth station, where
they are then transmitted to a geostationary satellite, and then the downlink follows an
analogous path. ‘Improvements in submarine communications cables, through the use of
fibre-optics, caused some decline in the use of satellites for fixed telephony in the late 20th
century, but they still serve remote islands.’13
II. SATELLITE TELEVISION (TELEVISION SIGNALS)
Satellites have been used since the 1960's to transmit broadcast television signals between the
network hubs of television companies and their network affiliates. This free viewing of
corporate content by individuals led to scrambling and subsequent resale of the descrambling
codes to individual customers, which started the direct-to-home industry. The direct-to-home
industry has gathered even greater momentum since the introduction of digital direct
broadcast service.
• Direct Broadcast Satellite: A direct broadcast satellite is a communications satellite
that transmits to small DBS satellite dishes (usually 18 to 24 inches or 45 to 60 cm in
diameter). ‘Direct broadcast satellites generally operate in the upper portion of the
microwave Ku band. DBS technology is used for DTH-oriented (Direct-To-Home)
satellite TV services. DBS is commonly used in United States, United Kingdom, New
Zealand, South Africa etc.’14
• Fixed Service Satellites: FSS uses the C band, and the lower portions of the Ku
bands. ‘They are normally used for broadcast feeds to and from television networks
and local affiliate stations, as well as being used for distance learning by schools and
universities, business television (BTV), Videoconferencing, and general commercial

18. 11
telecommunications.’13 FSS satellites are also used to distribute national cable
channels to cable television head ends
III. MOBILE SATELLITE TECHNOLOGIES
Some manufacturers have introduced special antennas for mobile reception of DBS
television. Using Global Positioning System (GPS) technology as a reference, these antennas
automatically re-aim to the satellite no matter where or how the vehicle (on which the
antenna is mounted) is situated.
IV. GLOBAL POSITIONING SERVICES
Another Very Small Aperture Terminal (VSAT) oriented service, in which a small apparatus
containing the ability to determine navigational coordinates by calculating a triangulating of
the signals from multiple geosynchronous.
V. MARINE COMMUNICATIONS
In the maritime community, satellite communication systems provide good communication
links to ships at sea. These links use a VSAT type device to connect to geosynchronous
satellites, which in turn link the ship to a land based point of presence to the respective nation
telecommunications system.
VI. SATELLITE MESSAGING FOR COMMERCIAL JETS
Another service provided by geosynchronous satellites is the ability for a passenger on an
airborne aircraft to connect directly to a land based telecom network.
VII. SATELLITE RADIO
Satellite radio offers audio services in some countries, notably the United States. Mobile
services allow listeners to roam a continent, listening to the same audio programming
anywhere.
A satellite radio or subscription radio (SR) is a digital radio signal that is broadcast by a
communications satellite, which covers a much wider geographical range than terrestrial
radio signals.
VIII. SATELLITE INTERNET
After the 1990s, satellite communication technology has been used as a means to connect to
the Internet via broadband data connections. This can be very useful for users who are located
in remote areas, and cannot access a broadband connection, or require high availability of
services.

19. 12
4.2 IMPACTS OF SATELLITE COMMUNCATION
i. Very large area of earth is visible from satellite (about 42%) i.e. communication is
possible beyond earth curvature (beyond line of sight)
ii. Satellite offers communication with remote communities in sparsely populated
area, which are difficult to access by other means of communication.
iii. Satellite communication ignores political boundaries as well as geographical
boundaries.
iv. Satellite provides communication with moving aircraft from ground control
station across the country.
v. Satellite provides remote sensing i.e. detection of water pollution, oil field,
monitoring and reporting of weather conditions etc.
vi. For fixed (point-to-point) services, communications satellites provide a
microwave radio relay technology complementary to that of communication
cables. They are also used for mobile applications such as communications to
ships, vehicles, planes and hand-held terminals, and for TV and radio
broadcasting, for which application of other technologies, such as cable television,
is impractical or impossible.
4.3 CONCLUSION:
The discovery of Satellite Communication has significantly changed our communication
modes for better. Although the use of fibre-optics in submarine communication cables has
substantially leaped satellite communication of its initial glory, communication satellite
remains the best and easiest means of communication since its use and services have
inevitably filled communication gap globally. Hence it is a REALISTIC
ALTERNATIVE.

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Satellite Capacity," University of Maryland, 1995.
6. Elbert, Bruce R, The satellite communication applications handbook, Boston, MA: Artech
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... [et al.], Park Ridge, N.J., U.S.A. : Noyes Data Corp., c1995.
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Networks", directed by Daniel E. Friedman, 1995.
11. Vivek Arora, Narin Suphasindhu, John S. Baras, Douglas Dillon, "Effective Extensions of
Internet in Hybrid Satellite-Terrestrial Networks", University of Maryland at College Park &
Hughes Network Systems, Inc., 1996.
12. John S. Baras, ATM in Hybrid Networks, Center for Satellite and Hybrid Communication
Networks, 1996.
13. Michael J. Miller (Editor),Branka Vucetic (Editor),Les Berry (Editor) , "Satellite
Communications: Mobile & Fixed Services" Kluwer Academic Publishers, 1993.
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15. Lindberg, Bertil C., Digital broadband networks and services, New York : McGraw-Hill, 1995
16. Http://www.tutorialsweb.com/fundamentals-of-satellite-communications.htm
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