Satellite Network 1

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  Very flexible bandwidth-on-demand capabilities  Flexible in terms of network configuration and capacity allocation  Broadcast, Point-to-Point and Multicast capabilities  Scalable 2

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

Orbits (cont.) 4  Outer Van Allen Belt ( km) MEO ( < 13K km) GEO (33786 km) LEO ( < 2K km) Inner Van Allen Belt ( km) GEO: Geosynchronous Earth Orbit MEO: Medium Earth Orbit LEO: Low Earth Orbit

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

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

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

Disadvantages of GSOs  Long propagation delays ( 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. 8

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

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

Highly Elliptical Orbit Satellites (HEOs)  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.  Examples: MOLNIYA, ARCHIMEDES (Direct Audio Broadcast), ELLIPSO. 11

Low Earth Orbit Satellites (LEOs)  Usually less than 2000 km ( km are favored).  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).  Examples:  Earth resource management (Landsat, Spot, Radarsat)  Paging (Orbcomm)  Mobile (Iridium)  Fixed broadband (Teledesic, Celestri, Skybridge) 12

Low Earth Orbit Satellites (LEOs) (cont.)  Little LEOs: 800 MHz range  Big LEOs: > 2 GHz  Mega LEOs: GHz 13

Comparison of Different Satellite Systems 14

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

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

Frequency Bands NarrowBand Systems  L-Band  GHz DL; GHz UL  S-Band  GHz DL; GHz UL  C-Band  GHz DL; GHz UL  X-Band  GHz DL; GHz UL 17

Frequency Bands (cont.) WideBand/Broadband Systems  Ku-Band  GHz DL; GHz UL (36 MHz of channel bandwidth; enough for typical Mbps applications)  Ka-Band  GHz DL; GHz UL (500 MHz of channel bandwidth; enough for Gigabit applications) 18

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

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

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

Space Environment Issues (cont.)  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.  Gravitation pulls the satellite towards earth.  Limited propulsion to maintain orbit (Limits the life of satellites; Drags an issue for LEOs).  Thermal Environment again limits material and electronics life. 22

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

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

Satellite Interworking Unit (SIU) 25

Payload Concepts  Bent Pipe Processing  Onboard Processing  Onboard Switching 26

Bent-Pipe Protocol Stack (Internet) 27 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

Onboard Processing Protocol Stack (Internet) 28 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

Onboard Switching Protocol Stack (Internet) 29 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