2. CONTENTCONTENT
INTRODUCTION
SATELLITE COMM. SYSTEM
PRINCIPLES OF SATELLITE COMMUNICATION
SATELLITE FUNDAMENTALS
ADVANTAGES & DISADVATAGES
APPLICATIONS OF SATELLITE COMMUNICATION
CONCLUSION
REFERENCE
3. INTRODUCTIONINTRODUCTION
A satellite is basically aA satellite is basically a
self-contained communications systemself-contained communications system
with the ability to receive signals fromwith the ability to receive signals from
Earth and to retransmit those signalsEarth and to retransmit those signals
back with the use of a transponder—anback with the use of a transponder—an
integrated receiver and transmitter ofintegrated receiver and transmitter of
radio signals. A satellite has to withstandradio signals. A satellite has to withstand
the shock of a launch into orbit at 28,100 km (17,500 miles)the shock of a launch into orbit at 28,100 km (17,500 miles)
an hour and a hostile space environment where it can bean hour and a hostile space environment where it can be
subject to radiation and extreme temperatures for itssubject to radiation and extreme temperatures for its
projected operational life, which can last up to 20 years. Inprojected operational life, which can last up to 20 years. In
addition, satellites have to be light, as the cost of launchingaddition, satellites have to be light, as the cost of launching
a satellite is quite expensive and based on weight.a satellite is quite expensive and based on weight.
5. Satellite communication is based on the concept of line of sight.
Radio waves travel in straight path between transmitter and
receiver antenna. This is line of sight communication as both the
antenna is in respect to line of sight. As earth is round, direct line
of sight communication is limited to approximately 75km
without repeater. A repeater is required for relaying signals over
long distances and satellite transponder works as repeater .
6. SATELLITE FUNDAMENTALSSATELLITE FUNDAMENTALS
Satellite system consists of two parts :
Space segment and
Ground segment
1 . Space Segment :-1 . Space Segment :-
It includes operational satellitesIt includes operational satellites
in space. A typical satellitein space. A typical satellite
consists of a bus and aconsists of a bus and a
communication payload.communication payload.
Payload provide essentialPayload provide essential
subsystems for providing communication services and thesubsystems for providing communication services and the
bus consists of all other subsystems( structural, thermal,bus consists of all other subsystems( structural, thermal,
power , attitude, control , propulsion , and telemetry ,power , attitude, control , propulsion , and telemetry ,
tracking , and command subsystems ) needed for operatingtracking , and command subsystems ) needed for operating
payload .payload .
7. Ground segments are installations that provide communications with
the satellites, and allow the operation of each particular constellation
spacecraft . They also include data archives and provide tools for the
community to access the data.
2. Ground segment :-2. Ground segment :-
10. Global Mobile Communication:-
The basic purpose of satellites for mobile communication is to
extend the area of coverage.
Cellular phone systems, such as AMPS and GSM (and their
successors) do not cover all parts of a country. Areas that are not
covered usually have low population where it is too expensive to
install a base station.
11. Military Satellites :-
These satellites are often used for gathering intelligence, as a
communications satellite used for military purposes, or as a
military weapon.
A satellite by itself is neither military nor civil. It is the kind of
payload it carries that enables one to arrive at a decision regarding
its military or civilian character.
Navigation Satellites :-
The system allows for precise localization world-wide, and with
some additional techniques, the precision is in the range of some
meters.
Ships and aircraft rely on GPS as an addition to traditional
navigation systems.
Many vehicles come with installed GPS receivers. e.g., for fleet
management of trucks or for vehicle localization in case of theft.
12. CONCLUSION:-
Basic fundamentals are discussed in this paper covering
all important issues regarding satellite communication
including satellite bus,payloads, coding and modulation
techniques.
Future satellite communications cannot prescind from the
evolution of terrestrial broadcast and broadband
communication systems.
13. [1] S. Scalise, L. Castanet, M. Luglio, M. Neri, et al., “Satellite
Channel Impairments”,
in Digital Satellite Communications edited by G.E. Corazza,
Springer, 2007.
[2] E. Lutz, M. Werner, and A. Jahn, Satellite Systems for Personal
and
Broadband Communications, Springer, 2000.
[3] S. Scalise, H. Ernst, and G. Harles, “Measurement and
Modelling of
the Land Mobile Satellite Channel at Ku-Band”, IEEE Transactions
onVehicular Technologies, to appear in Januray 2008.
