Satellite communication 4th year

Contents… Communication Types of communication Frequency spectrum Basics of satellite communication Frequency bands Advantages and disadvantages Major problems Applications

Communication The technique which helps to transfer information from one place /node /terminal /device to another is called communication.

Types Of Communication Wired Wireless Mobile (890 MHz) Satellite (6/4 GHz) Remote (10^3 Hz)

Frequency Spectrum

Basics of satellite communication Satellite: A celestial body that orbits a planet

Why satellite communication? Microwave band of frequency is used High frequency waves travel in straight line Earth is curved Solution: satellite An earth station transmits the signal up to the satellite-called the up-link and is transmitted on one frequency. The satellite receives the signal and retransmits it on the down link which is on another frequency.

Using a satellite for long distance communications

Why not moon? concept proved by naval research lab in Washington D.C.by using moon in 1940’s. Surface of the moon is tough and uneven that most of the signal scatters back into space instead of bouncing back to earth. Moon can only reflect signals. Modern communication satellites actively rebroadcast the signal back to earth. Moon is only available for half of the day, and it keeps moving. Earth based antenna have to move to track it.

Frequency Bands Name of the freq. band Range of freq. 1.) L 1-2(GHz) 2.) S 2-4(GHz) 3.) C 4-8(GHz) 4.) X 8-12(GHz) 5.) Ka 12-18(GHz) 6.) K 18-26(GHz) 7.) Ku 26-40(GHz)

Advantages of satellite communication Provision of service to remote or underdeveloped area. Transmission cost is independent of distance. Higher bandwidth is available. Larger coverage area than terrestrial network. Independent from terrestrial infrastructure.

Disadvantages of Satellite Communication Making and launching a satellite is a complex and costly process. Difficulty in troubleshooting a satellite. Larger propagation delay is found in satellite communication.

Major problems in satellite communication Difficulty in designing and positioning a satellite. Less stability (due to difficulty in alignment and direction of antenna). Large power requirement. Harsh climate affect transmission of signals.

Applications Weather forecasting VSAT(very small aperture terminal) Communication Military and intelligence satellite Research and development Observation of distant stars and other objects in space GPS and navigation

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