Towards the Personal Communicator (http://www.satcom.co.uk/article.asp?article=6)

Introduction

The pages which follow are the slides of 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.

The slides were created using Microsoft PowerPoint and converted to HTML. During conversion the 38 slides were combined into 7 sections.

You can navigate between these sections at will from the left hand side. However, bear in mind that for the slides to make the most sense, it is suggested that you read through them in order.

Please note that this presentation contains the lecturers notes, and so in some places are not complete. If you have any questions regarding these lectures please contact the author here.

"Beam me up Scottie"

SLIDE 1

Hello. As you've heard, I'm Mark Posen of RPC Telecom. I'm very pleased to have the opportunity to talk to you about one of the most exciting developments in satellite telecommunications for a long time. 

I was involved in Satellite Personal Communications, albeit in a relatively peripheral role, from the early days. I lead the project team of ETSI which studied the early proposals and identified where standardisation and regulation was needed in Europe to facilitate the free movement of equipment through the Union and to ensure that European regulatory requirements were met. I'll speak for around 45 minutes and then we'll have some time for questions.

SLIDE 2

"Beam me up, Scottie!" The pocket-sized personal communicator has long been the stuff of Sci-fi...

Notes:
So, where does this story start? Well, we are all very familiar with these particular gentlemen (Star Trek crew). They have a very well developed communications system. They are in permanent communications contact (except when necessary to develop the plot) with their ship wherever they are... in space... on the surface of a planet or even deep below its surface. Their "personal communicator's" are an essential part of their day-to-day lives and they really couldn't function without them, but does any of this have any relevance to the real World?

SLIDE 3

First a question. What do these people have in common?

  • A businessman traveling in Africa
  • A farmer on a Pacific island who exports his crops in a volatile international market
  • The director of an emergency team dealing with an earthquake in South America
  • Or even an IEE lecturer, stuck in a cutting on the M25 and late for a presentation!

Notes:
Well, let me put a question to you first of all... (slide) [apart from being a very contrived set of individuals that is] well...

SLIDE 4

Answer... 
They need access to good communications 

  • Independent of where they are
  • Independent of time of day
  • Independent of infrastructure availability

They need Personal Communications!
Satellite Personal Communications Networks (S-PCN) can provide this now (almost!).

Notes:
(slide) How do we define "PERSONAL COMMUNICATIONS"? well, we'll go on to see... first though, let me outline the structure of my presentation.

SLIDE 5

PP Presentation Outline

  • Concept - the personal communicator 
  • Proposals - specific plans
  • Implementation - Who? How? When?
  • The future...

Notes:
First I'll review the CONCEPT - what do we mean by PERSONAL COMMUNICATIONS? What is involved? How does S-PCN fit in? Then I'll look at some specific PROPOSALS real commercial projects - NOT R&D - being implemented right now I'll look briefly at how S-PCN will be IMPLEMENTED and then finally attempt a bit of crystal ball gazing to look at THE FUTURE.

Concept

SLIDE 6

Concept (1)

P.O.T.S.: 

  • 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"

Notes:
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.

SLIDE 7

Concept (2)

So, what is "Personal communications"?

-User oriented

-Characterised by

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

-"Universal Service Concept"

Notes:
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.

SLIDE 8

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

Notes:
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?

SLIDE 9

Concept (4) - Hand Held Terminal

-Main limitation on network design

-Small

-Low power

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

-Multi-mode for better network integration

Notes:
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.

SLIDE 10

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
  • GEO - ACES / APMT / THURAYA

Notes:
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...

Orbit Mechanics

SLIDE 11

Digression - Orbit Mechanics!

Notes:
By way of a digression lets look at some orbit mechanics! This figure shows a generalised orbit... remember Kepler from school! The planet is at one focus... orbiting body sweeps out equal areas in equal time... define apogee, perigee, period, inclination mention stability

SLIDE 12

Orbit Mechanics (2)

  • Geostationary (GSO/GEO) - 36,000 km / 24 hour period / <5 inclination
  • Geosynchronous (GSO/GEO) - as stationary but higher inclination
  • Low Earth Orbit - <2,000 km / 80 - 130 minutes period
  • Medium (Intermediate) Earth Orbit - 2,000 km - 10,000 km / 130 minutes - 6 hours period

Notes:
Here are the main classes of orbit...

SLIDE 13

Orbit Mechanics (3)

-Other orbits

  • Inclined Highly Elliptical (HEO)
  • Sub- and super-synchronous

-Combine orbits into "constellations"

  • groups of orbits to provide global or regional coverage
  • key to defining service characteristics

Notes:
...and here are a few more! The CONSTELLATION puts a number of satellites together to provide a COVERAGE.

SLIDE 14

Concept (6) - Network Configuration

-There is no "typical" S-PCN configuration

-Some things to be considered: 

  • routing in space or on the ground (ISLs?)
  • integrated into terrestrial network / overlay / stand-alone?
  • gateway distribution... politically difficult!

We'll not try and answer these now but will look at specific proposals...

Notes:
Let's touch on the network configuration. This is complex and could be an entire lecture in itself! Mention some key considerations. (slide)

SLIDE 15

Proposals (1)

We'll focus on three specific examples

Bear in mind some of the key issues:

  • NGSO vs. Super-GEO
  • CDMA vs. TDMA
  • ISL vs. non-ISL

Iridium

SLIDE 16

Iridium (1)

  • One of the first S-PCN proposals
  • Backed by Motorola
  • 66 satellites (originally 77) in 6 planes
  • ~780km polar LEO
  • Processing transponder
  • Complex network with in-space routing through ISL "crosslinks"
  • TDMA

Notes:
This was one of the first. Designed to be a satellite based wireless personal communications network supporting all kinds of services - voice, data, fax and paging.

SLIDE 17

Iridium (2) - Handset

  • Handset based on Motorola cellular technology
  • Little data publicly available!
  • Iridium state 1 hour talk time and 24 hours standby
  • Note the antenna!

Notes:
We've seen that the design is handset driven so lets look at the Iridium handset... it looks much like any "regular" cell phone (slide).

SLIDE 18

Iridium (3) - Satellite

Notes:
Developed by Motorola Satcom Division. 689kg. Complex "antenna farm" communications cross-link gateway. Around 5 years lifetime over 1 satellite per month built and launched "for ever". Effectively makes satellite construction into a production line business. In passing Teledesic proposal has 840 satellites in orbit - 10 - 15 per month!!! FOR EVER!

SLIDE 19

Iridium (4) - Network Overview

Notes:
Complex network configuration - explain briefly the key components.

SLIDE 20

Iridium (5) - Crosslink Routing

-Call routing across and along planes

Notes:
Worth mentioning the unique feature of the Iridium proposal. Call routing in space through "crosslinks" calls routed along a plane and between planes mention counter-rotating planes. Problem of routing across this boundary this feature makes Iridium very different and may pose some complex technological problems!

ICO

SLIDE 21

ICO (1)

-Proposal of INMARSAT - International Mobile Satellite Operator

-MEO Constellation

  • 10 satellites in 2 planes
  • 10,355 km (6 hour) orbit
  • 45 inclination

-Transparent Transponder

Notes:
In "competition" to Iridium is another proposal - ICO. Named after the choice of "intermediate circular" orbit proposed by INMARSAT - the long established mobile satellite operator.

SLIDE 22

ICO (2) - Constellation

Notes:
Orbit configuration is quite different from Iridium - only two planes, fewer satellites, coverage and handover will be very different especially satellite to satellite handover much less frequent.

SLIDE 23

ICO (3) - Constellation Coverage

Notes:
This shows the instantaneous global coverage of the constellation. Note that in general most highly populated areas are covered by a number of satellites simultaneously... important for redundancy and to deal with blocking. Generally 2 but sometimes 3 or even 4 satellites will be visible to a user and a SAN (satellite access node) at a time. Constellation gives high elevation angles (40-50) which is key for avoiding blockage.

SLIDE 24

ICO (4) - Satellite Coverage

-Coverage from a single satellite

-163 beams

Notes:
Each satellite has a complex multi-feed, multi-spot pattern. Frequencies can be reused many times. Bandwidth can be reallocated to key beams

SLIDE 25

ICO (5) - Satellite

  • Based on Hughes HS601 GEO bus
  • Digital beam forming
  • Digital channelisation
  • Supports 4,500 phone channels

SLIDE 26

ICO (6) - Network Configuration

Notes:
Users correspond with the space segment these then route calls through ICONET, an interconnected network of 12 SANs (Satellite Access Nodes). Gateways route calls onto the terrestrial network at most convenient point.

Globalstar

SLIDE 27

Globalstar (1)

  • Proposal of SS/Loral, Qualcomm, Alcatel - other partners, e.g. Vodafone
  • 56 satellite constellation in 8 planes
  • ~1,400 km inclined LEO orbit
  • Transparent transponder
  • no cross-linking

Notes:
Let's look at a third proposal. This is something of a halfway house between Iridium and ICO - 48 operational satellites with 8 spares (1 per plane). Each satellite weighs 450 kg and has a total transponder power of 1 kW. Lifetime is 7.5 years.

SLIDE 28

Globalstar (2) - Network

Notes:
Key point... transparent transponders and no crosslink ISLs.

SLIDE 29

Globalstar (3) - CDMA Soft Handover / Redundancy

Notes:
CDMA... signals relayed through more than one satellite at a time... blockage and handover is SOFT.

SLIDE 30

Globalstar (4) - Coverage

Notes:
Coverage resembles ICO but more satellites and much lower so more complex.

Implementation & The Future

SLIDE 31

Super-GEO Proposals

  • Regional
  • One or two highly complex satellites in GSO
  • Multiple spot beam coverage
  • Transparent transponder / Digital filtering

SLIDE 32

Implementation (1)

When is this all going to happen? - Very soon! First generation systems due for launch before 2000. Next generation systems by 2010

SLIDE 33

Implementation (2)

Iridium

  • First partial plane due about 2 weeks ago (launch postponed 3 times - will happen very soon now!) 
  • Following testing and concept proving, full constellation will be deployed over next couple of years.
  • BUT service only fully viable once entire constellation deployed.

Notes:
Note that Globalstar plans to start launching in 1997. ICO not sure... but likely to be in the same timeframe.

SLIDE 34

Implementation (3)

Super-GEOs

  • Still fighting for spectrum!
  • First systems should be launched in 1998-2000 timeframe
  • System is viable from first launch - key advantage of Super-GEO!

SLIDE 35

The future...

-Follow-on systems already on the drawing board

  • FPLMTS / IMT-2000
  • UMTS
  • integration with UPT

-Movement towards "Global Bandwidth on Demand" rather than simple cell phone replacement.

SLIDE 36

Conclusions

  • Personal Communications Networks are being implemented now as S-PCNs
  • Will provide all (most?) features of the "Personal Communicator"
  • Network developments being driven by demand for bandwidth
  • Potential to replace entire fixed network World-wide!

SLIDE 37

Questions? And now some time for questions...

If you have any questions on this lecture you can contact us here.

SLIDE 38

Acknowledgements

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Copyright 2002 Satcom Online (http://www.satcom.co.uk)
21/04/2018  01:18:39