# Satellite networks

17 de Nov de 2019

### Satellite networks

1. SATELLITE NETWORKS PRESENTEDBY: MUKULSANAND (17010131) RAJEEVSANKHLA (17010132)
2. Content  Introduction  Artificial Satellites over Natural Satellites  Orbits  Types Of Satellite Orbits  Footprint  Categories of Satellite  GEO  MEO  L EO  Advantages of Satellites  Disadvantages of Satellites
3. What is satellite networks?  A satellite network is a combination of nodes, some of which are satellites, that provide from one point on the earth to another. A node in the network can be satellite, an Earth station etc.
4. Introduction
5. ARTIFICIAL SATELLITES OVER NATURAL ONE’S  We can install electronic equipment on the satellite to regenerate the signal that has lost its energy during travel.  The distance of natural satellites, such as the Moon, from the Earth is huge, which create a long delay in communication.
6. SATELLITE ORBITS
7. Kepler’s Law KEPLER’S LAW: IT DETERMINES THE PERIOD OF SATELLITE. PERIOD = C X DISTANCE1.5 SEC
8. Example 1 What is the period of the moon according to Kepler’s law? Solution The moon is located approximately 384,000 km above the earth. The radius of the earth is 6378 km. Applying the formula, we get Period =(1/100) (384,000 +6378)1.5 =2,439,090s=approx.(1 month)
9. Example 2 According to Kepler’s law, what is the period of a satellite that is located at an orbit approximately 35,786 km above the earth? Solution> Applying the formula, we get Period = (1/100) (35,786 +6378)1.5 =86,579 s = 24 h Asatellite like this is said to be stationary to the earth.earth. The orbit, as we will see, is called a geosynchronous orbit. 7/18/2014 6:37:54 PM 8
10. Footprint The area of the Earth’s surface from which an Earth Station can transmit to or receive from a particular satellite.
11. SATELLITE CATEGORIES Based on the location of the orbit satellites are divided into three categories: GEO MEO LEO
12. HOW SATELLITE WORKS Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means. One Earth Station sends a transmission to the satellite . This is calleda Uplink. The satellite Transponder converts the signal and sends it down tothe second earth station. This is called a Downlink.
13. Band Downlink, GHz Uplink, GHz Bandwidth, MHz Problems L 1.5 1.6 15 Low bandwidth; crowded S 1.9 2.2 70 Low bandwidth; crowded C 4.0 6.0 500 Terrestrial Interference Ku 11.0 14.0 500 Rain Ka 20.0 30.0 3500 Rain, equipment cost L-band and S-band: is used for Mobile Satellite Services and offers good penetration through adverse weather conditions andfoliage. C-band: Public switched networks. Ku-band and Ka-band: Rural telephony, satellite news gathering, high speed internet, SATELLITE FREQUENCY BAND video conferencing, and multimedia.
14. GEOSTATIONARY EARTH ORBIT (GEO) These satellites are in orbit 35,786 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. One GEO satellite cannot cover the whole earth. It takes minimum of three satellites equidistant from each other.
15. GEO (CONT.)  Advantages  AGEOsatellite’s distance from earth gives it a large coverage area, almost a fourth of the earth’s surface.  GEOsatellites have a 24hour view of a particular area.  These factors make it ideal for satellite broadcast and other multipoint applications.
16. GEO (CONT.)  Disadvantages  AGEOsatellite’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.  GEOsatellites, centered above the equator, have difficulty broadcasting signals to near polar regions
17. MIDDLE EARTH ORBIT (MEO)  A MEO satellite is in orbit somewhere between 5,000 km and 15,000 km above the earth’s surface.  MEO satellites are visible for much longer periods of time than LEOsatellites, usually between 2 to 8 hours.  MEO satellites have a larger coverage area than LEO satellites.
18. MEO (CONT.) • A MEO satellite’s longer duration of visibility and wider footprint means fewer satellites are needed in a MEO network than a LEO network. • Shorter time delay and stronger signal than a GEO satellite Advantages • A MEO satellite’s distance gives it a longer time delay and weaker signal than a LEO satellite, though not as bad as a satellite. Disadvantages EXAMPLE: Global Positioning System (GPS).
19. GPS: EXAMPLE OF MEO CONSTRUCTED AND OPERATED BY US DEPARTMENT OF DEFENSE. THERE ARE 24 SATELLITES IN SIX ORBITS. USED FOR LAND, SEA AND AIR NAVIGATION TO PROVIDE TIME AND LOCATIONS FOR VEHICLES AND SHIPS. THE SATELLITES IN EACH ORBITS ARE DESIGNED IN SUCH A WAY, AT A TIME MINIMUM FOUR SATELLITES ARE VISIBLE FROM ANY POINT ON THE EARTH.
20. GPS: HOW IT WORKS ( CONT.)  Measuring the distance: The trilateration principle can find our location on the earth if we know our distance from three satellites and know the positionof each satellite. The position of each satellite can be calculated by a GPSreceiver. The GPSreceiver, then, needs to find its distance from at least three GPS satellites. Suppose all GPSsatellites and the receiver on the earth are synchronized. Each of 24 satellites transmits a complex signal each having a unique pattern. The receiver measures the delay between the signals from the satellites and its copy of signals to determine the distances to the satellites.
21. • LEOsatellites are much closer to the earth than GEOsatellites, ranging from 500 to 2000 km above thesurface. • Rotation period of 90 to 120 minutes, with speed 20,000 to 25,000 km/h. • LEOsatellites don’t stay in fixed position relative to the surface, and are only visible for 15 to 20 minutes eachpass. • Anetwork of LEOsatellites is necessary for LEOsatellites to be useful. LOW EARTH ORBIT (LEO)
22. LEO SATELLITE SYSTEM
23. • Advantages  ALEO satellite is 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. LEO (CONT.)
24. • It has 66 satellites in 6 LEOorbits. • Each have altitude of 750 km. • Use to provide direct worldwide communication. i.e. voice, data paging, fax, even navigation. IRIDIUM SYSTEM: EXAMPLE OF LEO
25. • It has 48 satellites in 6 LEOorbits. • Each have altitude of 1400 km. • The ground station can create more powerful signals. GLOBALSTAR: EXAMPLE OF LEO
26. •It provides fiber-optic like (broadband channels, low error rate, and low delay) communication •It has 288 satellites in 12 LEOpolar orbits. • Each have altitude of 1350 km. TELEDESIC: EXAMPLE OF LEO
27.  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. ADVANTAGES OF SATELLITES
28.  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. DISADVANTAGES OF SATELLITES
29. Thank you...