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History of satellite communication. 1945 - Arthur C. Clarke Extra Terrestrial Relays1957 - first satellite USSR's SPUTNIK- first reflecting communication satellite ECHO1962 Telstar launched, an important step1963 - first geostationary satellite SYNCOM1965 - first commercial geostationar
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1. Satellite Systems History
Basics
Localization
2. History of satellite communication 1945 - Arthur C. Clarke Extra Terrestrial Relays
1957 - first satellite USSRs SPUTNIK
- first reflecting communication satellite ECHO
1962 Telstar launched, an important step
1963 - first geostationary satellite SYNCOM
1965 - first commercial geostationary satellite Early Bird (INTELSAT I 68 kg): 240 duplex telephone channels or 1 TV channel, 1.5 years lifetime
1967-69 Intelsat II, III; 1200 phone channels
1976 - three MARISAT satellites for maritime communication; 40W power, 1.2 m antenna
3. History (Contd) 1982 first mobile satellite telephone system INMARSAT-A
1988 first satellite system for mobile phones and data communication INMARSAT-C; 600 bps, interface to X.25
1993 INMARSAT-M - first digital satellite telephone system; still very heavy equipment
1998 global satellite systems for small mobile phones Iridium & Globalstar
Currently about 200 geo satellites.
4. Applications Traditional
Weather, radio and TV broadcast
military satellites espionage, warning system
navigation and localization (GPS)
Telecommunication cable in the sky
global telephone connections & mobiles
backbone for global networks
remote/rural areas
extend cellular systems (AMPS, GSM UMTS), need low orbit satellites. Satellites transmit pictures using IR/visible light. Used for predicting hurricanes.
Radio & TV alternative to cable; satellite dishes 4 m diameter typical
GPS precision of some metres possible. Used in ships and aircraft, trucks and cars.
Can be used for fleet management, localisation of car in case of theft.
For telephony, satellites are being overtaken by transcontinental fibre links 10Gbps or even more in the laboratories. bandwidth. Also, shorter distances (10000 km v 72000 km), leading to lower propagation delay.
In the UMTS system, frequencies for the S-Band satellite segment are 1980-2010 MHz (up) and 2170-2200 (down).Satellites transmit pictures using IR/visible light. Used for predicting hurricanes.
Radio & TV alternative to cable; satellite dishes 4 m diameter typical
GPS precision of some metres possible. Used in ships and aircraft, trucks and cars.
Can be used for fleet management, localisation of car in case of theft.
For telephony, satellites are being overtaken by transcontinental fibre links 10Gbps or even more in the laboratories. bandwidth. Also, shorter distances (10000 km v 72000 km), leading to lower propagation delay.
In the UMTS system, frequencies for the S-Band satellite segment are 1980-2010 MHz (up) and 2170-2200 (down).
5. Satellite Functions Transponder
Receive on one frequency, repeat on another frequency (transparent transponder)
May amplify or regenerate (regenerative transponder)
Inter satellite routing
Error correction is essential
6. Classical satellite systems Foorprint area on the earths surface covered by satellite transmission. Smaller cells (spotbeams) are possible.
Within a footprint, direct communication is possible using mobiles
Between footprints, Intersatellite links or Gateway links are needed.
Real challenge is to have smooth handover between all possible systems UMTS, GSM, satelliteFoorprint area on the earths surface covered by satellite transmission. Smaller cells (spotbeams) are possible.
Within a footprint, direct communication is possible using mobiles
Between footprints, Intersatellite links or Gateway links are needed.
Real challenge is to have smooth handover between all possible systems UMTS, GSM, satellite
7. Satellite Networks
8. SATELLITE RECEPTION Footprint area on earths surface where signal can be received
LOS (Line of Sight) to the satellite necessary for connection
Attenuation depends on distance, elevation, frequency of carrier and atmosphere
High elevation means less absorption due to rain, fog, atmosphere and buildings; at least 10 degrees needed.
Uplink: connection base station - satellite
Downlink: connection satellite - base station
typically separated frequencies for uplink and downlink
Uplink: connection base station - satellite
Downlink: connection satellite - base station
typically separated frequencies for uplink and downlink
9. Signal Loss Calculation (qualitative only) Attenuation or power loss is determined by
gain of sending/receiving antennae
distance between sender and receiver
Carrier frequency
This affects data rates achievable
Only 10 bps may be achievable
with GEOs, compared to 10
Kbps at 100 km, 2GHz carrier
10. Atmospheric attenuation
11. Satellites - features GEO: geostationary, ~ 36000 km from the earth
LEO (Low Earth Orbit): 500 - 1500 km
MEO (Medium Earth Orbit) or ICO (Intermediate Circular Orbit): 6000 - 20000 km
HEO (Highly Elliptical Orbit) elliptical orbits
Microwave, line of sight; GHz range
Uplink and downlink different frequencies
12. Satellite orbit altitudes
13. Orbits II
15. Satellites in geosynchronous orbitTelephony, broadcast TV, Internet backbone
16. Geostationary satellites 35,786 km, equatorial (inclination 0°), 15 yrs life
24 hr period, synchronous to earth rotation
fix antenna positions, no adjusting necessary
large footprint (up to 34% of earth), limited frequency reuse; 3 satellites are enough to cover
bad elevations in areas with latitude above 60°
high transmit power 10KW, high latency (0.25 s)
not for global coverage for small mobile phones and data transmission,
suitable for radio & TV
17. MEOs used for GPS 18000 km altitude
24 to cover the earth
6 hrs to orbit
GPS based on triangulation need distance from 4 points
Used widely by all sorts of users
18. LEO global telephony Polar orbits, 500-2000 km
5-8 years lifetime
90-120 min to orbit
20000 25000 km/hr
8000 km diameter footprint
System of satellites = network of switches
Little Leos - < 1GHz, low data rate messaging
Big Leos (1-3 GHz) Globalstar, Iridium
Broadband Leos (like fibre) - Teledesic
19. LEO systems
visibility ~ 10 - 40 minutes, period of 95-120 min
global radio coverage possible, 50-200 satellites
latency similar to terrestrial long distance: 5 - 10 ms
smaller footprints (i.e. cells), better frequency reuse
handover necessary from one satellite to another
High elevation even in polar regions
more complex systems due to moving satellites
Need for routing
Further classified into little (100 bps), big (1 kbps) and broadband (Mbps)
Example Globalstart 48 satellite systemFurther classified into little (100 bps), big (1 kbps) and broadband (Mbps)
Example Globalstart 48 satellite system
20. LEOS ISL Inter Satellite Link
GWL Gateway Link
UML User Mobile Link
21. Iridium 1998 - present 66 satellites, 6 orbits, altitude 750 km.
Originally for global voice, data, fax, paging, navigation
Spectrum - 1.6 G, ISL 23 G
66 x 48 spot beams or cells
2000 cells to cover the earth
240 channels of 41 KHz each,
can support 253 440 users.
22. Globalstar 48 Satellites, 6 orbits
Altitude of 1400 km
Relaying uses earth stations as well as satellites bent pipe.
Ground stations can create stronger signals
Voice and data at 4.8 kbps
23. Teledesic planned but never materialised 288 satellites, 12 polar orbits,1350 km
BB channels Internet in the sky
8 satellites form a unit, earth stations are also used
Earth divided into several 10ks cells, each assigned a time slot to transmit
User terminals to communicate directly
155 M/1.2G up/down links Ka band
24. Routing between satellites, gateways, fixed networks: ISL or terrestrial? Reduced number of gateways needed with ISL
Best to forward connections or data packets within the satellite network as long as possible
Only one uplink and one downlink per direction needed for the connection of two mobile phones
25. PROBLEMS - ISL more complex focusing of antennas between satellites
satellites need routing software
high system complexity due to moving routers
higher fuel consumption, shorter lifetime
Iridium and Teledesic planned with ISL
Other systems use terrestrial gateways and also terrestrial networks
26. Localization of mobile stations Mechanisms similar to GSM, except base stations are satellites.
Gateways maintain registers with user data
HLR (Home Location Register): static user data
VLR (Visitor Location Register): (last known) location of the mobile station
SUMR (Satellite User Mapping Register):
satellite assigned to a mobile station
positions of all satellites
27. Localisation of Mobiles Registration of mobile stations
Mobiles signal received by several satellites, reported to gateway(s)
Localization of the mobile station is via the satellites position
requesting user data from HLR
updating VLR and SUMR
Calling a mobile station
localization using HLR/VLR similar to GSM
connection setup using SUMR & the appropriate satellite
28. Handover in satellite systems More complex, due to motion of satellites
Intra satellite handover
handover from one spot beam to another
mobile station still in the footprint of the satellite, but in another cell
Inter satellite handover
handover from one satellite to another satellite
mobile station leaves the footprint of one satellite
29. Handover (Contd.) Gateway handover
Handover from one gateway to another
mobile station still in the footprint of a satellite, but satellite moves away from the current gateway
Inter system handover
Handover from the satellite network to a terrestrial cellular network
mobile station can use a terrestrial network again which might be cheaper, have a lower latency.
30. Overview of LEO/MEO systems ICO = Intermediate Circular OrbitICO = Intermediate Circular Orbit