Lecture 1, General Principles

Presentation / Lecture 1, General Principles

Date Submitted: 06 June 2001

Written by RPC Telecommunications Ltd.. Website: http://www.rpctelecom.com

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This is the first in a series of general satcom tutorial lectures submitted by RPC Telecommunications.

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 Printable Version
-Section 1
The pioneers of satellite communications
-Section 2
Historical Perspective
-Section 3
-Section 4
Advantages & Disadvantages of satellite communications.
-Section 5
Frequency bands & the Satellite Link.

Advantages & Disadvantages

  • Flexible (if transparent transponders)
  • Easy to install new circuits
  • Circuit costs independent of distance
  • Broadcast possibilities
  • Temporary applications (restoration)
  • Niche applications
  • Mobile applications (especially "fill-in")
  • Terrestrial network "by-pass"
  • Provision of service to remote or underdeveloped areas
  • User has control over own network
  • 1-for-N multipoint standby possibilities


  • Large up front capital costs (space segment and launch)
  • Terrestrial break even distance expanding (now approx. size of Europe)
  • Interference and propagation
  • Congestion of frequencies and orbit
When, and when not, to use satellites
When to use satellites:
  • When the unique features of satellite communications make it attractive
  • When the costs are lower than terrestrial routing
  • When it is the only solution


  • Communications to ships and aircraft (especially safety communications)
  • TV services - contribution links, direct to cable head, direct to home, SNG
  • Data services - private networks
  • Overload traffic
  • Delaying terrestrial investments
  • 1-for-N diversity
  • Special events

When to use terrestrial:

  • PSTN - satellite is becoming increasingly uneconomic for most trunk telephony routes
  • but, there are still good reasons to use satellites for telephony such as: thin routes, diversity, very long distance traffic and remote locations.
  • Land mobile/personal communications - in urban areas of developed countries new terrestrial infrastructure is likely to dominate (e.g. GSM, FLMPTS)
  • but, satellite can provide fill-in as terrestrial networks are implemented, also provide similar services in rural areas and underdeveloped countries

Next: Section 5 - Frequency bands & the Satellite Link.


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