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WELCOME

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LOW EARTH ORBIT NANO-SATELLITE

COMMUNICATION USING IRIDIUM NETWORK

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Contents

• Orbits• Types of satellites• Comparison of different satellites system• Iridium network• Iridium v/s other telecommunication networks• disadvantages• Applications• conclusion• reference

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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

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Orbits

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

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Types of Satellites• Geostationary/Geosynchronous Earth

Orbit Satellites (GSOs) (Propagation Delay: 250-280 ms)

• Medium Earth Orbit Satellites (MEOs) (Propagation Delay: 110-130 ms)

• Highly Elliptical Satellites (HEOs) (Propagation Delay: Variable)

• Low Earth Orbit Satellite (LEOs) • (Propagation Delay: 20-25 ms)

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Geostationary/Geosynchronous Earth Orbit

Satellites (GSOs)• 33786 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)

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Medium Earth Orbit Satellites (MEOs)

• Positioned in 10-13K km range.• Delay is 110-130 ms.• Will orbit the Earth at less than 1 km/s.• Applications

– Mobile Services/Voice (Intermediate Circular Orbit (ICO) Project)

– Fixed Multimedia (Expressway)

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Low Earth Orbit Satellites (LEOs)

• Usually less than 2000 km (780-1400 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)

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Low Earth Orbit Satellites (LEOs) (cont.)

• Little LEOs: 800 MHz range• Big LEOs: > 2 GHz• Mega LEOs: 20-30 GHz

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GEO vs. LEO• Geo-stationary Earth orbital satellite

– On a circular orbit in the equatorial plane at an altitude of 35786 km making 1 revolution in 24 hours.

– Unable to service north or south latitudes > 70 degree and has long propagation delay (270ms, one way)

– Need huge antenna for low-powered mobile terminals– No satellite tracking needed, relay communication 24

hours a day– Good for non RT, non-interactive application (i.e. TV

broadcasting)

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GEO vs. LEO• Low Earth Orbital satellites

– Excellent link feasibility with low delay due to low orbit

– Small coverage cell is obtainable with small on-board antenna

– Global coverage possible– Require large number of spacecraft (satellites)– Very complex space control system– Frequent handovers (~10 min between

satellites, ~1-2 min between beams)– Low minimum angle

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Comparison of Different Satellite Systems

LEO MEO GEO

Satellite Life 3-7 10-15 10-15

Hand-held Terminal Possible Possible Difficult

Propagation Delay Short Medium Long

Propagation Loss Low Medium High

Network Complexity Complex Medium Simple

Hand-off Very Medium None

Visibility of a Satellite

Short Medium Mostly Always

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Iridium Network

Low Earth Orbit Satellite System

True pole-to-pole coverage

66 Satellites in orbit

6 Orbits

Altitude of 780 Km

Minimum elevation angle – 8.2 0

Average satellite view time – 10 minutes

Access Scheme – FDMA and TDMA

Maximum number of users – 80 users per a diameter of 318 Km

Low cost availability for research purposes ( NSF sponsored)

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Cont…………..• Satellite speed = 26,000 km/h = 7 km/s

• Satellite visibility = 9 - 10 min

• System period = 100 minutes

• 4.8 kbps voice, 2.4 Kbps data

• TDMA

• 80 channels /beam

• 3168 beams globally (2150 active beams)

• Dual mode user handset

• User-Satellite Link = L-Band

• Gateway-Satellite Link = Ka-Band

• Inter-Satellite Link = Ka-Band

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IRIDIUM Satellite Configuration

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Iridium Based Data Communication

App 3

App 2

App 1

Mux High Bandwidth Link

Multiplexing

App 1

Inv-Mux

Low Bandwidth Links

Idea – Combine multiple Iridium channels in to a single logical link

Inverse Multiplexing

Distributes data from a single application over multiple links.

Increases the available bandwidth per application

Packet based inverse multiplexing solutions exist - Multi-link point-to-point

protocol (MLPPP)

Inverse multiplexing

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IRIDIUM vs. other satellite

telecommunication network

• Geographical coverage– Iridium: truly global with 66 satellites; Others

focuses on regions in the mid-latitudes (GlobalStar has 24 satellites, Odyssey has 9)

• Co-operation with terrestrial Networks– Iridium uses 1 gateway; GlobalStar and

Odyssey require maximum co-operation with terrestrial networks (no gateway, no service)

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IRIDIUM vs. other satellite

telecommunication network• Propagation delay

- Satellite to Earth: Iridium has the shortest

- Terrestrial Networks: Iridium has the shortest since it has less terrestrial trail

- Processing delay due to transmission systems and on-board processing: Iridium has the longest

- Voice coding and decoding time (system independent)

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IRIDIUM vs. other satellite

telecommunication network• Frequency bands and multiple access

techniques– Iridium has a greater capacity (~0.3 mErlang/km2)

than the Globalstar (~0.06 mErlang/km2) and Odyssey (~0.2 mErlang/km2)

– Iridium uses TDMA access technique to coexist with the other systems while Globalstar and Odyssey’s S-band downlink is share with ISM applications leading to service degradation in populated urban area

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IRIDIUM vs. other satellite telecommunication network

• Elevation angle and signal fading margin– Iridium (15 degree); Globalstar and Odyssey (30

degree 90% of the time)

– Iridium has a higher fading margin (16 dB for voice, 35 dB for pagaing); Globalstar and Odyssey has less than 10 dB for voice

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Disadvantages

• Increased number of call drops in Iridium-Iridium mode

• Varies with time and weather

• Increased call drops in presence of strong radio interference

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Applications

Communications data upload – up to 40 MB files

Radar data uploads – up to 55 MB files

Video conference - real time audio/video

Individual audio or video conference works with moderate quality with the

commonly available codecs

Outreach Use

Daily Journal logs uploaded

Daily Pictures uploaded

Video clips uploaded

Held video conference with science teachers/ virtual camp tour

Wireless Internet access

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Contd…….

• Fixed cellular telephone service

• Complementary and back up telephone service in fields of:

• • Retail

• • Manufacturing

• • Military

• • Government

• • Transportation

• • Insurance

• • Finance

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Conclusion

Signal Strength issues

Reduce the number of call drops

Reduce signal attenuation at the server

Server Software

GUI based server management software

Increase reliability during field operations

Ease of operation and use by non-technical personnel

Delay Tolerant Networks

Communication networks tolerant to inherent delays

Set of protocol and architectures well suited to intermittent links

Supports communication in heterogeneous sensor webs such as polar sensor web

Adapt the evolving DTN technologies to address polar communication issues?

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References

• Henric Boiardt, Christian Rodriguez; ‘Low Earth Orbit Nanosatellite Communication using Iridium’s Network’; IEEE A&E SYSTEMS MAGAZINE, September 2010.

• http://en.wikipedia.org/wiki/Iridium_satellite_constellation

• Gérard Maral, Michel Bousquet, Zhili Sun; ‘Satellite communications systems: systems, techniques and technology’; Wiley, 2009.