Towards the Personal Communicator

Presentation / Towards the Personal Communicator

Date Submitted: 06 June 2001

Written by RPC Telecommunications. Website:

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A short lecture presented to the Surrey Section of the IEE (the IEE is the British Institution of Electrical Engineers) by Mark C J Posen of RPC Telecommunications Ltd.

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 Printable Version
-Section 1
"Beam Me Up Scottie"
-Section 2
-Section 3
Orbit Mechanics
-Section 4
-Section 5
-Section 6
-Section 7
Implementation & The Future



Concept (1)


  • telephones are for places, not people 
  • "Some people, some places, some of the time" 

Cellular Networks

  • telephones are for people, in the right places
  • "all people, some places, some of the time"

Personal Communications

  • telephones are for people, not places
  • "all people, all places, all the time"

First let's look at the way in which telecommunications networks have evolved. POTS fixes 'phones to places - you may find the person you want at the place you call, but you can't be sure. This has led us to develop "add on" features to enhance network such as call forwarding and transfer. But phones still essentially fixed to places
CELLULAR NETWORKS broke the "fixed place" link. We carry our 'phones in our pockets and they are linked to us and (except when we forget and leave them at home!) not to places. BUT they don't work everywhere and are dependent on infrastructure... indoors... remote areas... overseas... won't always find us.
PERSONAL COMMUNICATIONS aims to break the final "infrastructure" link. The phone is truly linked to the person and not the place or the time and the link to Captain Kirk is made.


Concept (2)

So, what is "Personal communications"?

-User oriented

-Characterised by

  • Mobility
  • Location
  • Tailoring
  • Affordability and capacity
  • Security

-"Universal Service Concept"

Traditional telecommunications networks are just that... "network oriented". Features and services defined by the network and not the user but.. PCN's are more user oriented. 
Mobility - service independent of user location. 
Location - network identifies user location and addresses services there
Tailoring - service parameters under user control.
Affordability/Capacity - both critical because of widespread nature of service and expected deep penetration
Security - the same or enhanced beyond the fixed networks Universal Service - "anyone, anyplace, anytime" Leads us to Satellite-PCN.


Concept (3): S-PCN

-Satellite based (enhanced) network

-Hand held terminal / direct access

  • Small
  • Low power

-Orbit choice?

  • Low Earth Orbit
  • Medium Earth Orbit
  • Geostationary Earth Orbit

-Network configuration

Look at the definition of PCN and it soon becomes clear that delivery by satellite is a key way of achieving the service objectives. By basing a network entirely on satellite or by adding satellite as an overlay to a terrestrial based network we can achieve the universal service requirement. Some of the areas I'll try and explore... Hand-held terminal... impact on system design Orbit - does the choice matter? Network... how configured?


Concept (4) - Hand Held Terminal

-Main limitation on network design


-Low power

  • Maintain battery life
  • User safety (< 0.5 W average RF power)
  • Defines link and satellite design

-Multi-mode for better network integration

The whole network design is terminal driven... (slide) Because of low power availability from terminal defines absolutely the parameters of the satellite receiving system... antenna gain -> size -> link margin (coping with fades and blockage) Multimode important too... ability to route calls through terrestrial network (cheaper) if it is available.


Concept (5) - Choice of Orbit

-Does the orbit really matter?

-Clearly pros and cons for different orbits

-No consensus amongst designers!

  • LEO - Iridium / Globalstar
  • MEO - ICO

Much has been written about which orbit is "best" for S-PCN. I have a personal preference, but we'll come to that later. Test is probably that there is no consensus amongst the system designers. But we've introduced some terms that probably need to be clarified! so...

Next: Section 3 - Orbit Mechanics


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