Sav's satellite communication
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It is the World's shortest and most easy presentation on satellite communication. When I fill that most presentation available on this matter is to big to remember, then I am deciding to make a PPT on a short format. It is short but enough for school/collage level presentation.
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Sav's satellite communication
- 1. Satellite Communication UNDER THE ESTEEMED GUIDANCE OF Dr. Sudip Dogra Teacher In Charge Dept of Electronics & communication Engineering Meghnad Saha Institute of Technology, Kolkata May 2018 ECE 3rd year
- 2. Group Leader
- 4. Contents Introduction Factor in satellite communication Types of satellite Modern types and future development Application of satellites Conclusion
- 5. Introduction
- 7. How do Satellites Work
- 11. Elevation Angle
- 12. Coverage Angle
- 13. Other impairments to satellite communication
- 15. GEO Satellite
- 16. LEO Satellite
- 17. MEO Satellite
- 20. Modern Types And Future Development
- 23. Telephone
- 24. Television
- 26. Amateur Radio
- 27. Internet Access
- 28. Military Uses
- 29. Conclusions: Satellite systems are not aimed to replace terrestrial system but at complementing them. GEO’s are ideal for TV and Radio broadcasting and they do not need handover because of its larger footprint. Lifetime of GEO’s are rather high, about 15 years. LEO’s need a network of satellites and are appropriate for voice communications. In LEO’s handover is frequent and routing is must. MEO’s are in between LEO’s and GEO’s in every Aspect.
- 30. Thank You Have a nice day
Editor's Notes
- A satellite is simply any body that moves around another (usually much larger) one in a mathematically predictable path called an orbit A communication satellite is a microwave repeater station in space that is used for telecommunication , radio and television signals The first man made satellite with radio transmitter was in 1957 There are about 750 satellites in the space, most of them are used for Communication.
- Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means. The two stations can use a satellite as a relay station for their communication One Earth Station sends a transmission to the satellite. This is called a Uplink. The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink
- The advantages of satellite communication over terrestrial communication are: The coverage area of a satellite greatly exceeds that of a terrestrial system. Transmission cost of a satellite is independent of the distance from the center of the coverage area. Satellite to Satellite communication is very precise. Higher Bandwidths are available for use.
- The disadvantages of satellite communication: Launching satellites into orbit is costly. Satellite bandwidth is gradually becoming used up. There is a larger propagation delay in satellite communication than in terrestrial communication
- Elevation Angle: The angle of the horizontal of the earth surface to the center line of the satellite transmission beam. This effects the satellites coverage area. Ideally, you want a elevation angle of 0 degrees, so the transmission beam reaches the horizon visible to the satellite in all directions. However, because of environmental factors like objects blocking the transmission, atmospheric attenuation, and the earth electrical background noise, there is a minimum elevation angle of earth stations.
- Coverage Angle: A measure of the portion of the earth surface visible to a satellite taking the minimum elevation angle into account. R/(R+h) = sin(π/2 - β - θ)/sin(θ + π/2) = cos(β + θ)/cos(θ) R = 6370 km (earth’s radius) h = satellite orbit height β = coverage angle θ = minimum elevation angle
- Other impairments to satellite communication: The distance between an earth station and a satellite (free space loss). Satellite Footprint: The satellite transmission’s strength is strongest in the center of the transmission, and decreases farther from the center as free space loss increases. Atmospheric Attenuation caused by air and water can impair the transmission. It is particularly bad during rain and fog.
- GEO LEO MEO Molniya Orbit Polar orbit
- These satellites are in orbit 35,863 km above the earth’s surface along the equator. Objects in Geostationary orbit revolve around the earth at the same speed as the earth rotates. This means GEO satellites remain in the same position relative to the surface of earth. Advantages A GEO satellite’s distance from earth gives it a large coverage area, almost a fourth of the earth’s surface. GEO satellites have a 24 hour view of a particular area. These factors make it ideal for satellite broadcast and other multipoint applications. Disadvantages A GEO satellite’s distance also cause it to have both a comparatively weak signal and a time delay in the signal, which is bad for point to point communication. GEO satellites, centered above the equator, have difficulty broadcasting signals to near polar regions
- LEO satellites are much closer to the earth than GEO satellites, ranging from 500 to 1,500 km above the surface. LEO satellites don’t stay in fixed position relative to the surface, and are only visible for 15 to 20 minutes each pass. A network of LEO satellites is necessary for LEO satellites to be useful Advantages A LEO satellite’s proximity to earth compared to a GEO satellite gives it a better signal strength and less of a time delay, which makes it better for point to point communication. A LEO satellite’s smaller area of coverage is less of a waste of bandwidth. Disadvantages A network of LEO satellites is needed, which can be costly LEO satellites have to compensate for Doppler shifts cause by their relative movement. Atmospheric drag effects LEO satellites, causing gradual orbital deterioration.
- A MEO satellite is in orbit somewhere between 8,000 km and 18,000 km above the earth’s surface. MEO satellites are similar to LEO satellites in functionality. MEO satellites are visible for much longer periods of time than LEO satellites, usually between 2 to 8 hours. MEO satellites have a larger coverage area than LEO satellites. Advantage A MEO satellite’s longer duration of visibility and wider footprint means fewer satellites are needed in a MEO network than a LEO network. Disadvantage A MEO satellite’s distance gives it a longer time delay and weaker signal than a LEO satellite, though not as bad as a GEO satellite
- Molniya Orbit Satellites Used by Russia for decades. Molniya Orbit is an elliptical orbit. The satellite remains in a nearly fixed position relative to earth for eight hours. A series of three Molniya satellites can act like a GEO satellite. Useful in near polar regions.
- Due to the rotation of the Earth, it is possible to combine the advantages of low-altitude orbits with global coverage, using near-polar orbiting satellites, which have an orbital plane crossing the poles. These satellites, termed Polar Orbiting Environmental Satelliites (POES) are launched into orbits at high inclinations* to the Earth's rotation (at low angles with longitude lines), such that they pass across high latitudes near the poles. Most POES orbits are circular to slightly elliptical at distances ranging from 700 to 1700 km (435 - 1056 mi) from the geoid. At different altitudes they travel at different speeds.
- High Altitude Platform (HAP) One of the newest ideas in satellite communication. A blimp or plane around 20 km above the earth’s surface is used as a satellite. HAPs would have very small coverage area, but would have a comparatively strong signal. Cheaper to put in position, but would require a lot of them in a network. A HAP can be a manned or unmanned airplane, a balloon, or an airship. All require electrical power to keep themselves and their payload functional. While current HAPS are powered by batteries or engines, mission time is limited by the need for recharging/refueling. Therefore, alternative means are being considered for the future. Solar cells are one of the best options currently being used under trial for HAPS .
- On airplanes, satellites offer phone communications in-flight. They provide the main operative use for voice communication in rural areas, especially during a disaster where phone lines have been compromised. Satellite communications are still used in many applications today. Remote islands such as Ascension Island, Saint Helena, Diego Garcia, and Easter Island, where no submarine cables are in service, need satellite telephones. Satellite phone systems can be accomplished by a number of means. On a large scale, often there will be a local telephone system in an isolated area with a link to the telephone system in a main land area
- Satellites do transmit television signals right to your home, but they are also the essential spine of broadcasting networks. Signals are sent from a central station that generates programming to smaller stations, which then deliver signals through cables or airwaves locally. A broadcasting satellite system is a type of communication satellite service that distributes video and audio stream via satellite, which also services direct-to-home satellite television. As television became the main market, its demand for simultaneous delivery of relatively few signals of large bandwidth to many receivers being a more precise match for the capabilities of geosynchronous comsats.
- Radio broadcasting works through wireless transmission across radio waves to reach its audience. Stations use radio networks to broadcast in a common radio format (such as broadcast syndication), but broadcasting can be done through satellite radio as well. Many vehicles have receivers built-in for this type of broadcasting. Ground stations transmit signals to satellites, and these signals are sent to radio receivers in cars and home. Satellite radio typically covers a wide area and is best suited for rural areas that may not have the population density for FM/AM service. Satellite radio offers audio broadcast 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.
- Amateur radio services (ham radio) are considered a hobby service by individuals that communicate across towns and the world. Called “hamsats,” over 70 amateur radio satellites were launched in the last four decades. Hobbyists are required to get FCC licensure in order to bounce signals off of the satellites that they build. Amateur radio operators have access to amateur satellites, which have been designed specifically to carry amateur radio traffic. Most such satellites operate as spaceborne repeaters, and are generally accessed by amateurs equipped with UHF or VHF radio equipment and highly
- For rural areas, satellites provide fast Internet service compared to ancient dial-up service, with specific satellites dedicated to the service. Satellite download speeds can even be up to ten times fasterthan the speed of a regular modem. 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.
- Satellites are used to guide the military in times of war or suspected terrorist attacks. Communications satellites are used for military communications applications, such as Global Command and Control Systems. Examples of military systems that use communication satellites are the MILSTAR, the DSCS, and the FLTSATCOM of the United States, NATO satellites, United Kingdom satellites (for instance Skynet), and satellites of the former Soviet Union. India has launched its first Military Communication satellite GSAT-7, its transponders operate in UHF, F, C and Ku band bands.[14] Typically military satellites operate in the UHF, SHF (also known as X-band) or EHF (also known as Ka band) frequency bands.