1. Low Earth (LEO) Medium Earth (OEO) Satellite Systems
TLMN645 CLASS 11 FALL 2002
Low Earth (LEO)
Medium Earth (OEO)
Satellite Systems

2. FedEx Data Network
Created its own Digital Data Network in the 1980’s using a private land mobile wide area system called Digital Assisted Dispatch System (DADS)
System is based on an messaging standard on a 800 MHz network providing digital messaging to trucks 40,000 mobile voice units and 2,500 hand-held. 760 base stations

3. FedEx FUTURE WIRELESS NETWORK
Fedex’s intention is to move to the public network. “We're going to move to a public network structure because the coverage has gotten very robust, the cost has come down and the speed has gone up. We've hit a crossover point where going to the public network just makes a whole lot of sense. We will be looking at 2.5G and 3G networks as they get
deployed.

4. FedEx Use of ATT Wireless Data
Ken Pasley, FedEx's director of wireless systems development, said the AT&T Wireless General Packet Radio Service (GPRS) network "gives us significantly more bandwidth" than the company's private network and will allow FedEx to expand the types of applications used on tracking devices. The throughput of the GPRS network is approximately 20K to 40K bit/sec., compared with the 19.2K bit/sec. FedEx gets on its private nationwide network. This will allow couriers to send "fat" files such as digital signatures and could also support voice recognition technology,

6. Satellite-Related Terms
Earth Stations – antenna systems on or near earth
Uplink – transmission from an earth station to a satellite
Downlink – transmission from a satellite to an earth station
Transponder – electronics in the satellite that convert uplink signals to downlink signals

7. Ways to Categorize Communications Satellites
Coverage area
Global, regional, national
Service type
Fixed service satellite (FSS)
Broadcast service satellite (BSS)
Mobile service satellite (MSS)
General usage
Commercial, military, amateur, experimental

8. Classification of Satellite Orbits
Circular or elliptical orbit
Circular with center at earth’s center
Elliptical with one foci at earth’s center
Orbit around earth in different planes
Equatorial orbit above earth’s equator
Polar orbit passes over both poles
Other orbits referred to as inclined orbits
Altitude of satellites
Geostationary orbit (GEO)
Medium earth orbit (MEO)
Low earth orbit (LEO)

9. Satellite Orbits

10. Geometry Terms
Elevation angle - the angle from the horizontal to the point on the center of the main beam of the antenna when the antenna is pointed directly at the satellite
Minimum elevation angle
Coverage angle - the measure of the portion of the earth's surface visible to the satellite

11. Minimum Elevation Angle
Reasons affecting minimum elevation angle of earth station’s antenna (>0o)
Buildings, trees, and other terrestrial objects block the line of sight
Atmospheric attenuation is greater at low elevation angles
Electrical noise generated by the earth's heat near its surface adversely affects reception

12. Overview:GEO Orbit Advantages of the the GEO orbit
No problem with frequency changes
Tracking of the satellite is simplified
High coverage area
Disadvantages of the GEO orbit
Weak signal after traveling over 35,000 km
Polar regions are poorly served
Signal sending delay is substantial

13. Satellite GEO vs LEO
LEO
GEO

14. Overview:LEO Satellite Characteristics
Circular/slightly elliptical orbit under 2000 km
Orbit period ranges from 1.5 to 2 hours
Diameter of coverage is about 8000 km
Round-trip signal propagation delay less than 20 ms
Maximum satellite visible time up to 20 min
System must cope with large Doppler shifts
Atmospheric drag results in orbital deterioration

15. LEO SATELLITES
Source: Globalstar?

16. Overview: MEO Satellite Characteristics
Circular orbit at an altitude in the range of 5000 to 12,000 km
Orbit period of 6 hours
Diameter of coverage is 10,000 to 15,000 km
Round trip signal propagation delay less than 50 ms
Maximum satellite visible time is a few hours

17. Satellite MEO Medium Earth Orbit (10,000 Km)
LEO
GEO

19. GPS System

20. Orbit (Delay) Roundtrip delay GEO 1/4 sec. Or 250 ms LEO
delay 10 to 50 ms .
MEO
delay> 66 ms
Orbit (Delay)
Geostationary
22,000 miles
36,000 Km
Low Earth
(LEO)
400 miles
800 Km
MEO
Orbit
10,000 Km
Acceptable delay
for voice- 100 to 200 ms.

21. Required Power GEO (INMARSAT-A)-40 watt transmitter into 1.2 m dish
MEO (ICO) watts satellite power
LEO (Sat. GS 1000 w. IR w.)
Iridium .57 watts average
Globalstar 400 mw. (to gateway)

22. Technology: LEO-UPSIDE DOWN CELLULAR SYSTEM

23. Iridium System 48 satellites in 8 planes
TDMA (slots), voice 2.4/4.8 kb/s, data 2.4 kb/s
Operates around 1610 MHz, Inter-sat GHz .Users can go direct to satellite, return through gateways
end to end delay ms. Below the 400 ms required for voice.

24. Iridium Handsets (when first available)

25. Iridium Gateways

26. Why Iridium Failed? 1, 2. 3. 4.

27. Iridium Status
The Department of Defense, through its Defense Information Systems Agency (2000), awarded
Iridium Satellite LLC $72 million contract for 24 months of satellite communications services. This contract would provide unlimited airtime for 20,000 government users over the Iridium satellite network.
The contract includes options which, if exercised, would bring the cumulative value of this contract to $252 million and extend the period of performance to December 2007.

28. Globalstar 48 satellites with CDMA access
voice up to 9 kb/s in 1.25 MHz channels
No intersatellite links, “bent pipe”
Access by gateways-would take 200 to cover whole earth- deployment will be less than that. Service within 1000 miles of a gateway. Service area size of Alaska

29. Globalstar Orbits 48 satellites

30. Globalstar
Phone
Gateway

31. Globalstar Satellite

32. Globalstar Telephones
PREVIOUS
2002

33. Globalstar Status

34. Teledesic - Broadband Internet in the sky
24 active SATs.s in 12 planes km alt.
Broadband fixed and mobile Ka operation (18-31 GHz)
low bit error rates 10-10
Latency ms. Roundtrip < than 100 ms
Packet mode(512 bits), TDMA access
Operates from gateways( e.g.ISPs) with bit rates155 Mb/s to Gb/s

35. Teledesic Orbits

36. Multimedia-Teledesic On 1 October 2002, it was reported that Teledesic was officially suspending its satellite construction work.

37. MEO

38. Orbit (Delay) Roundtrip delay GEO 1/4 sec. Or 250 ms LEO
delay 10 to 50 ms .
MEO
delay> 66 ms
Orbit (Delay)
Geostationary
22,000 miles
36,000 Km
Low Earth
(LEO)
400 miles
800 Km
MEO
Orbit
10,000 Km
Acceptable delay
for voice- 100 to 200 ms.

39. ICO 10 satellites at 10,000 Km. First Satellite Launched June 2001
two and sometimes three in view
each satellite covers 30% earth’s surface
Two communication systems
S band spot beams (163 users) direct to mobiles
C band to Satellite Access Notes (SANs)
The air interface is expected to operate through ICO satellites at data rates of up to 144 kbps.

40. ICO Architecture
ICO's satellites use a bent-pipe architecture, In a bent-pipe system the satellite is used to relay communication between the end-user equipment and a ground station that is part of the terrestrial infrastructure. The terrestrial infrastructure, provides the connection to the destination network or end-user.

41. ICO Satellites

42. ICO Ground Segment C band

43. ICO Orbits

44. ICO Projected Markets Maritime Transportation Government
Oil, Gas, Construction
Individuals and small businesses
Rural and underserved in US and around the world

45. ICO Status 2001 First satellite successfully launched.
Company signs an agreement to acquire Constellation Communications Holdings, Inc. and is awaiting FCC approval and the satisfaction of certain other closing conditions to close these transactions

46. Example:LEO Status: Skybridge
Planned: 80 LEO satellites using frequency in Ku-band (12GHz to 15GHz), orbiting at an altitude of 1469km.Total capacity will be over 200Gbps. Data rate: from 16kbit/s to 2Mbit/s uplink and 16kbit/s to 20Mbit/s downlink.
Status:The LEO constellation projected 64 to 80 satellites and was originally expected to enter service in However, development of the LEO component is now on hold, and the brand will be used to offer service over leased GEO capacity.