Submitted By :- Omkar Lokhande

CONTENTCONTENT

INTRODUCTION

SATELLITE COMM. SYSTEM

PRINCIPLES OF SATELLITE COMMUNICATION

SATELLITE FUNDAMENTALS

ADVANTAGES & DISADVATAGES

APPLICATIONS OF SATELLITE COMMUNICATION

CONCLUSION

REFERENCE

INTRODUCTIONINTRODUCTION

A satellite is basically a A satellite is basically a self-contained communications system self-contained communications system with the ability to receive signals from with the ability to receive signals from Earth and to retransmit those signalsEarth and to retransmit those signalsback with the use of a transponder—an back with the use of a transponder—an integrated receiver and transmitter ofintegrated receiver and transmitter ofradio signals. A satellite has to withstandradio signals. A satellite has to withstandthe 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 be an hour and a hostile space environment where it can be subject to radiation and extreme temperatures for its subject to radiation and extreme temperatures for its projected operational life, which can last up to 20 years. In projected operational life, which can last up to 20 years. In addition, satellites have to be light, as the cost of launching addition, 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.

SATELLITE COMMUNICATION SYSTEMSATELLITE COMMUNICATION SYSTEM

Image Showing Satellite Comm. System

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 .

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 satellite in space. A typical satellite consists of a bus and a consists of a bus and a communication payload. communication payload. Payload provide essentialPayload provide essential subsystems for providing communication services and the subsystems 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 operating tracking , and command subsystems ) needed for operating payload .payload .

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 :-

1.GEO 2. LEO 3.MEO 4.Sun Synchronous Orbit 5.Hohmann Transfer Orbit 6. Prograde Orbit 7.Retrograde Orbit 8. Polar Orbits

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.

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.

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.

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[2] E. Lutz, M. Werner, and A. Jahn, Satellite Systems for Personal andBroadband Communications, Springer, 2000.

[3] S. Scalise, H. Ernst, and G. Harles, “Measurement and Modelling ofthe Land Mobile Satellite Channel at Ku-Band”, IEEE Transactions onVehicular Technologies, to appear in Januray 2008.