1. SATELLITE NETWORKS Ian F. Akyildiz Broadband & Wireless Networking Laboratory School of Electrical and Computer Engineering Georgia Institute of Technology Tel: 404-894-5141; Fax: 404-894-7883 Email: ian@ece.gatech.edu Web: http://www.ece.gatech.edu/research/labs/bwn

2. IFA’2004 2 Why Satellite Networks ? Wide geographical area coverage From kbps to Gbps communication everywhere Faster deployment than terrestrial infrastructures Bypass clogged terrestrial networks and are oblivious to terrestrial disasters Supporting both symmetrical and asymmetrical architectures Seamless integration capability with terrestrial networks Very flexible bandwidth-on-demand capabilities Flexible in terms of network configuration and capacity allocation Broadcast, Point-to-Point and Multicast capabilities Scalable

3. IFA’2004 3 Orbits Defining the altitude where the satellite will operate. Defining the altitude where the satellite will operate. Determining the right orbit depends on proposed service characteristics such as coverage, applications, delay. Determining the right orbit depends on proposed service characteristics such as coverage, applications, delay.

4. IFA’2004 4 Orbits (cont.)  Outer Van Allen Belt (13000-20000 km) MEO ( < 13K km) GEO (33786 km) LEO ( < 2K km) Inner Van Allen Belt (1500-5000 km) GEO: Geosynchronous Earth Orbit MEO: Medium Earth Orbit LEO: Low Earth Orbit

5. IFA’2004 5 Types of Satellites HEO: var. (Molniya, Ellipso) LEO: < 2K km MEO: < 13K km (Odyssey, Inmarsat-P) GEO: 33786 km (Globalstar, Iridium, Teledesic) Geostationary/Geosynchronous Earth Orbit Satellites (GSOs) (Propagation Delay: 250-280 ms) Geostationary/Geosynchronous Earth Orbit Satellites (GSOs) (Propagation Delay: 250-280 ms) Medium Earth Orbit Satellites (MEOs) (Propagation Delay: 110-130 ms) Medium Earth Orbit Satellites (MEOs) (Propagation Delay: 110-130 ms) Highly Elliptical Satellites (HEOs) (Propagation Delay: Variable) Highly Elliptical Satellites (HEOs) (Propagation Delay: Variable) Low Earth Orbit Satellite (LEOs) (Propagation Delay: 20-25 ms) Low Earth Orbit Satellite (LEOs) (Propagation Delay: 20-25 ms)

6. IFA’2004 6 Geostationary/Geosynchronous Earth Orbit Satellites (GSOs) 33786 km equatorial orbit 33786 km equatorial orbit Rotation speed equals Earth rotation speed (Satellite seems fixed in the horizon) Rotation speed equals Earth rotation speed (Satellite seems fixed in the horizon) Wide coverage area Wide coverage area Applications (Broadcast/Fixed Satellites, Direct Broadcast, Mobile Services) Applications (Broadcast/Fixed Satellites, Direct Broadcast, Mobile Services)

7. IFA’2004 7 Advantages of GSOs Wide coverage Wide coverage High quality and Wideband communications High quality and Wideband communications Economic Efficiency Economic Efficiency Tracking process is easier because of its synchronization to Earth Tracking process is easier because of its synchronization to Earth

8. IFA’2004 8 Disadvantages of GSOs Disadvantages of GSOs Long propagation delays (250-280 ms). (e.g., Typical Intern. Tel. Call  540 ms round-trip delay. Echo cancelers needed. Expensive!) (e.g., Delay may cause errors in data; Error correction /detection techniques are needed.) Long propagation delays (250-280 ms). (e.g., Typical Intern. Tel. Call  540 ms round-trip delay. Echo cancelers needed. Expensive!) (e.g., Delay may cause errors in data; Error correction /detection techniques are needed.) Large propagation loss. Requirement for high power level. (e.g., Future hand-held mobile terminals have limited power supply.) Currently: smallest terminal for a GSO is as large as an A4 paper and as heavy as 2.5 Kg. Large propagation loss. Requirement for high power level. (e.g., Future hand-held mobile terminals have limited power supply.) Currently: smallest terminal for a GSO is as large as an A4 paper and as heavy as 2.5 Kg.

9. IFA’2004 9 Disadvantages of GSOs (cont.) Lack of coverage at Northern and Southern latitudes. Lack of coverage at Northern and Southern latitudes. High cost of launching a satellite. High cost of launching a satellite. Enough spacing between the satellites to avoid collisions. Enough spacing between the satellites to avoid collisions. Existence of hundreds of GSOs belonging to different countries. Existence of hundreds of GSOs belonging to different countries. Available frequency spectrum assigned to GSOs is limited. Available frequency spectrum assigned to GSOs is limited.

10. IFA’2004 10 Medium Earth Orbit Satellites (MEOs) Positioned in 10-13K km range. Positioned in 10-13K km range. Delay is 110-130 ms. Delay is 110-130 ms. Will orbit the Earth at less than 1 km/s. Will orbit the Earth at less than 1 km/s. Applications Applications –Mobile Services/Voice (Intermediate Circular Orbit (ICO) Project) –Fixed Multimedia (Expressway)

11. IFA’2004 11 Highly Elliptical Orbit Satellites (HEOs) From a few hundreds of km to 10s of thousands  allows to maximize the coverage of specific Earth regions. From a few hundreds of km to 10s of thousands  allows to maximize the coverage of specific Earth regions. Variable field of view and delay. Variable field of view and delay. Examples: MOLNIYA, ARCHIMEDES (Direct Audio Broadcast), ELLIPSO. Examples: MOLNIYA, ARCHIMEDES (Direct Audio Broadcast), ELLIPSO.

12. IFA’2004 12 Low Earth Orbit Satellites (LEOs) Usually less than 2000 km (780-1400 km are favored). Usually less than 2000 km (780-1400 km are favored). Few ms of delay (20-25 ms). Few ms of delay (20-25 ms). They must move quickly to avoid falling into Earth  LEOs circle Earth in 100 minutes at 24K km/hour. (5-10 km per second). They must move quickly to avoid falling into Earth  LEOs circle Earth in 100 minutes at 24K km/hour. (5-10 km per second). Examples: Examples: –Earth resource management (Landsat, Spot, Radarsat) –Paging (Orbcomm) –Mobile (Iridium) –Fixed broadband (Teledesic, Celestri, Skybridge)

13. IFA’2004 13 Low Earth Orbit Satellites (LEOs) (cont.) Little LEOs: 800 MHz range Little LEOs: 800 MHz range Big LEOs: > 2 GHz Big LEOs: > 2 GHz Mega LEOs: 20-30 GHz Mega LEOs: 20-30 GHz

14. IFA’2004 14 Comparison of Different Satellite Systems

15. IFA’2004 15 Comparison of Satellite Systems According to their Altitudes (cont.)

16. IFA’2004 16 Why Hybrids? GSO + LEO GSO + LEO –GSO for broadcast and management information –LEO for real-time, interactive LEO or GSO + Terrestrial Infrastructure LEO or GSO + Terrestrial Infrastructure –Take advantage of the ground infrastructure

17. IFA’2004 17 Frequency Bands Frequency Bands NarrowBand Systems L-Band  1.535-1.56 GHz DL; 1.635-1.66 GHz UL L-Band  1.535-1.56 GHz DL; 1.635-1.66 GHz UL S-Band  2.5-2.54 GHz DL; 2.65-2.69 GHz UL S-Band  2.5-2.54 GHz DL; 2.65-2.69 GHz UL C-Band  3.7-4.2 GHz DL; 5.9-6.4 GHz UL C-Band  3.7-4.2 GHz DL; 5.9-6.4 GHz UL X-Band  7.25-7.75 GHz DL; 7.9-8.4 GHz UL X-Band  7.25-7.75 GHz DL; 7.9-8.4 GHz UL

18. IFA’2004 18 Frequency Bands (cont.) WideBand/Broadband Systems Ku-Band  10-13 GHz DL; 14-17 GHz UL (36 MHz of channel bandwidth; enough for typical 50-60 Mbps applications) Ku-Band  10-13 GHz DL; 14-17 GHz UL (36 MHz of channel bandwidth; enough for typical 50-60 Mbps applications) Ka-Band  18-20 GHz DL; 27-31 GHz UL (500 MHz of channel bandwidth; enough for Gigabit applications) Ka-Band  18-20 GHz DL; 27-31 GHz UL (500 MHz of channel bandwidth; enough for Gigabit applications)

19. IFA’2004 19 Next Generation Systems: Mostly Ka-band Ka band usage driven by: Ka band usage driven by: –Higher bit rates - 2Mbps to 155 Mbps –Lack of existing slots in the Ku band Features Features –Spot beams and smaller terminals –Switching capabilities on certain systems –Bandwidth-on-demand Drawbacks Drawbacks –Higher fading –Manufacturing and availability of Ka band devices –Little heritage from existing systems (except ACTS and Italsat)

20. IFA’2004 20 Frequency Bands (cont.) New Open Bands (not licensed yet) GHz of bandwidth GHz of bandwidth Q-Band  in the 40 GHz Q-Band  in the 40 GHz V-Band  60 GHz DL; 50 GHz UL V-Band  60 GHz DL; 50 GHz UL

21. IFA’2004 21 Space Environment Issues Harsh  hard on materials and electronics (faster aging) Harsh  hard on materials and electronics (faster aging) Radiation is high (Solar flares and other solar events; Van Allen Belts) Radiation is high (Solar flares and other solar events; Van Allen Belts) Reduction of lifes of space systems (12-15 years maximum). Reduction of lifes of space systems (12-15 years maximum).

22. IFA’2004 22 Space Environment Issues (cont.) Debris (specially for LEO systems) (At 7 Km/s impact damage can be important. Debris is going to be regulated). Debris (specially for LEO systems) (At 7 Km/s impact damage can be important. Debris is going to be regulated). Atomic oxygen can be a threat to materials and electronics at LEO orbits. Atomic oxygen can be a threat to materials and electronics at LEO orbits. Gravitation pulls the satellite towards earth. Gravitation pulls the satellite towards earth. Limited propulsion to maintain orbit (Limits the life of satellites; Drags an issue for LEOs). Limited propulsion to maintain orbit (Limits the life of satellites; Drags an issue for LEOs). Thermal Environment again limits material and electronics life. Thermal Environment again limits material and electronics life.

23. IFA’2004 23 Basic Architecture Ring Wireless Terrestrial Network Internet LAN Ethernet Internet Ethernet Ring Mobile Network Public Network MAN SIU- Satellite Interface Unit SIU - Satellite Interworking Unit

24. IFA’2004 24 Basic Architecture (cont.) SIU - Satellite Interworking Unit

25. IFA’2004 25 Satellite Interworking Unit (SIU)

26. IFA’2004 26 Payload Concepts Bent Pipe Processing Bent Pipe Processing Onboard Processing Onboard Processing Onboard Switching Onboard Switching

27. IFA’2004 27 Bent-Pipe Protocol Stack (Internet) PhysicalSatellite Applications IP Network Medium Access Control Data Link Control Physical User Terminal TCP Applications IP Network Physical User Terminal TCP Medium Access Control Data Link Control

28. IFA’2004 28 Onboard Processing Protocol Stack (Internet) Satellite User Terminal Applications IP Network Medium Access Control Data Link Control Physical TCP User Terminal Applications IP Network Physical TCP Medium Access Control Data Link Control Physical Medium Access Control Data Link Control

29. IFA’2004 29 Onboard Switching Protocol Stack (Internet) Applications IP Network Medium Access Control Data Link Control Physical User Terminal TCP Applications IP Network Physical User Terminal TCP Medium Access Control Data Link Control Satellite Physical Medium Access Control Data Link Control Network

30. IFA’2004 30 Routing Algorithms for Satellite Networks Satellites organized in planes Satellites organized in planes User Data Links (UDL) User Data Links (UDL) Inter-Satellite Links (ISL) Inter-Satellite Links (ISL) Short roundtrip delays Short roundtrip delays Very dynamic yet predictable network topology Very dynamic yet predictable network topology –Satellite positions –Link availability Changing visibility from the Earth Changing visibility from the Earth http://www.teledesic.com/tech/mGall.htm

31. IFA’2004 31 Seam Seam –Border between counter-rotating satellite planes Polar Regions Polar Regions –Regions where the inter-plane ISLs are turned off LEO’s at Polar Orbits n E. Ekici, I. F. Akyildiz, M. Bender, “The Datagram Routing Algorithm for Satellite IP Networks”, IEEE/ACM Transactions on Networking, April 2001. n E. Ekici, I. F. Akyildiz, M. Bender, “A New Multicast Routing Algorithm for Satellite IP Networks”, IEEE/ACM Transactions on Networking, April 2002.

32. IFA’2004 32 Routing in Multi-Layered Satellite Networks

33. IFA’2004 33 Iridium Network

34. IFA’2004 34 Iridium Network (cont.)

35. IFA’2004 35 Iridium Network (cont.) 6 orbits 6 orbits 11 satellites/orbit 11 satellites/orbit 48 spotbeams/satellite 48 spotbeams/satellite Spotbeam diameter = 700 km Spotbeam diameter = 700 km Footprint diameter = 4021km Footprint diameter = 4021km 59 beams to cover United States 59 beams to cover United States Satellite speed = 26,000 km/h = 7 km/s Satellite speed = 26,000 km/h = 7 km/s Satellite visibility = 9 - 10 min Satellite visibility = 9 - 10 min Spotbeam visibility < 1 minute Spotbeam visibility < 1 minute System period = 100 minutes System period = 100 minutes

36. IFA’2004 36 Iridium Network (cont.) 4.8 kbps voice, 2.4 Kbps data 4.8 kbps voice, 2.4 Kbps data TDMA TDMA 80 channels /beam 80 channels /beam 3168 beams globally (2150 active beams) 3168 beams globally (2150 active beams) Dual mode user handset Dual mode user handset User-Satellite Link = L-Band User-Satellite Link = L-Band Gateway-Satellite Link = Ka-Band Gateway-Satellite Link = Ka-Band Inter-Satellite Link = Ka-Band Inter-Satellite Link = Ka-Band

37. IFA’2004 37 Operational Systems

38. IFA’2004 38 Operational Systems (cont.) Little LEOs

39. IFA’2004 39 Proposed and Operational Systems 1.ICO Global Communications (New ICO) nNumber of Satellites:10 nPlanes:2 nSatellites/Plane:5 nAltitude:10,350 km nOrbital Inclination:45° n Remarks: Service: Voice @ 4.8 kbps, data @ 2.4 kbps and higher Service: Voice @ 4.8 kbps, data @ 2.4 kbps and higher Operation anticipated in 2003 Operation anticipated in 2003 System taken over by private investors due to financial difficulties System taken over by private investors due to financial difficulties Estimated cost: $4,000,000,000 Estimated cost: $4,000,000,000 163 spot beams/satellite, 950,000 km 2 coverage area/beam, 28 channels/beam 163 spot beams/satellite, 950,000 km 2 coverage area/beam, 28 channels/beam Service link:1.98-2.01 GHz (downlink), 2.17-2.2 GHz (uplink); (TDMA) Service link:1.98-2.01 GHz (downlink), 2.17-2.2 GHz (uplink); (TDMA) Feeder link: 3.6 GHz band (downlink), 6.5 GHz band (uplink) Feeder link: 3.6 GHz band (downlink), 6.5 GHz band (uplink)

40. IFA’2004 40 Proposed and Operational Systems (cont.) 2.Globalstar nNumber of Satellites: 48 nPlanes:8 nSatellites/Plane:6 nAltitude: 1,414 km nOrbital Inclination: 52° n Remarks: Service: Voice @ 4.8 kbps, data @ 7.2 kbps Service: Voice @ 4.8 kbps, data @ 7.2 kbps Operation started in 1999 Operation started in 1999 Early financial difficulties Early financial difficulties Estimated cost: $2,600,000,000 Estimated cost: $2,600,000,000 16 spot beams/satellite, 2,900,000 km 2 coverage area/beam, 175 channels/beam 16 spot beams/satellite, 2,900,000 km 2 coverage area/beam, 175 channels/beam Service link:1.61-1.63 GHz (downlink), 2.48-2.5 GHz (uplink); (CDMA) Service link:1.61-1.63 GHz (downlink), 2.48-2.5 GHz (uplink); (CDMA) Feeder link: 6.7-7.08 GHz (downlink), 5.09-5.25 GHz (uplink) Feeder link: 6.7-7.08 GHz (downlink), 5.09-5.25 GHz (uplink)

41. IFA’2004 41 Proposed and Operational Systems (cont.) 3.ORBCOM nNumber of Satellites:36 nPlanes:42 nSatellites/Plane:22 nAltitude:775 km775 km nOrbital Inclination:45° 70° n Remarks: Near real-time service Near real-time service Operation started in 1998 (first in market) Operation started in 1998 (first in market) Cost: $350,000,000 Cost: $350,000,000 Service link:137-138 MHz (downlink), 148-149 MHz (uplink) Service link:137-138 MHz (downlink), 148-149 MHz (uplink) Spacecraft mass: 40 kg Spacecraft mass: 40 kg

42. IFA’2004 42 Proposed and Operational Systems (cont.) 4.Starsys nNumber of Satellites:24 nPlanes: 6 nSatellites/Plane: 4 nAltitude:1,000 km nOrbital Inclination:53° n Remarks: Service: Messaging and positioning Service: Messaging and positioning Global coverage Global coverage Service link:137-138 MHz (downlink), 148-149 MHz (uplink) Service link:137-138 MHz (downlink), 148-149 MHz (uplink) Spacecraft mass: 150 kg Spacecraft mass: 150 kg

43. IFA’2004 43 Proposed and Operational Systems (cont.) 5.Teledesic (original proposal) nNumber of Satellites: 840 (original) nPlanes: 21 nSatellites/Plane: 40 nAltitude:700 km nOrbital Inclination:98.2° n Remarks: Service: FSS, provision for mobile service (16 kbps – 2.048 Mbps, including video) for 2,000,000 users Service: FSS, provision for mobile service (16 kbps – 2.048 Mbps, including video) for 2,000,000 users Sun-synchronous orbit, earth-fixed cells Sun-synchronous orbit, earth-fixed cells System cost: $9,000,000,000 ($2000 for terminals) System cost: $9,000,000,000 ($2000 for terminals) Service link:18.8-19.3 GHz (downlink), 28.6-29.1 GHz (uplink) (K a band) Service link:18.8-19.3 GHz (downlink), 28.6-29.1 GHz (uplink) (K a band) ISL: 60 GHz ISL: 60 GHz Spacecraft mass: 795 kg Spacecraft mass: 795 kg

44. IFA’2004 44 Proposed and Operational Systems (cont.) 6.Teledesic (final proposal) nNumber of Satellites:288 (scaled down) nPlanes: 12 nSatellites/Plane: 24 nAltitude:700 km n Remarks: Service: FSS, provision for mobile service (16 kbps – 2.048 Mbps, including video) for 2,000,000 users Service: FSS, provision for mobile service (16 kbps – 2.048 Mbps, including video) for 2,000,000 users Sun-synchronous orbit, earth-fixed cells Sun-synchronous orbit, earth-fixed cells System cost: $9,000,000,000 ($2000 for terminals) System cost: $9,000,000,000 ($2000 for terminals) Service link:18.8-19.3 GHz (downlink), 28.6-29.1 GHz (uplink) (K a band) Service link:18.8-19.3 GHz (downlink), 28.6-29.1 GHz (uplink) (K a band) ISL: 60 GHz ISL: 60 GHz Spacecraft mass: 795 kg Spacecraft mass: 795 kg

45. IFA’2004 45 References Survey Paper Akyildiz, I.F. and Jeong, S., "Satellite ATM Networks: A Survey," IEEE Communications Magazine, Vol. 35, No. 7, pp.30-44, July 1997.Akyildiz, I.F. and Jeong, S., "Satellite ATM Networks: A Survey," IEEE Communications Magazine, Vol. 35, No. 7, pp.30-44, July 1997.