The Mobile Revolution
Professor Michael Walker
Group Research and Development Director
Vodafone Chair in Telecommunications,
Royal Holloway, University of London
© Vodafone Group 2004
WHO Base Stations & Wireless Networks, Geneva, June 2005
Contents
_ Global business context
_ How mobile phones have developed
_ Technology looking forward
_ Need for base stations
_ RF design for coverage
_ Field levels from base stations
_ Power levels from handsets
_ Handset SAR in real world
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Global mobile business context
700
600
Other
500
Subscriber
estimate 400
Dec 2004
millions 300
GSM
200
100
0
Europe
Asia
North
America
South
America
Arab
Africa
Russia
India
East
Central
Asia
_ More than 1.4 billion people, or 20% of the global population, have a
mobile phone, and more than 75% are GSM customers
_ 2 billion people in the world have yet to make a phone call - when it
happens it will most likely be on a mobile phone not a fixed line
_ Increasing proportion of revenue from non-voice
–
now over 17% for Vodafone globally 2004/5
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The beginning
_ In the 1970’s Bell Labs developed the Advanced Mobile
Phone Standard (AMPS) that initiated the Cellular
revolution
_ In the 1980’s Nordic Mobile Telephone standard was
deployed in the Scandinavian countries
_ In the mid 1980’s, UK Total Access Communications
System was developed based on AMPS
_ The following slides will take us through the revolution
from 1985 to present
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How mobile phones have developed
1985
1st January
Vodafone UK
network starts
1st “transportable”
Phone
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How mobile phones have developed
1986
Nokia “Talkman”
Weight - 4.8Kg
Price - £3000
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How mobile phones have developed
1987
Siemens C2
“Transportable”
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How mobile phones have developed
1989
Motorola MicroTAC
personal cellular phone.
The phone retails for an
estimated $3000
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How mobile phones have developed
1st GSM
mobile phone
1992
Motorola
International 3200
(>500g)
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How mobile phones have developed
1993
Panasonic
I series
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How mobile phones have developed
Vodafone UK Digital
data fax and short
text messaging
services
1994
Nokia 2140
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How mobile phones have developed
1995
1st sub 200g
mobile phone
Bosch M-cam
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How mobile phones have developed
1st PDA mobile
phone
1996
Nokia 9000
communicator
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How mobile phones have developed
1997
1st Colour display
Siemens S10
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How mobile phones have developed
1st Dual-band
mobile phone
1998
Siemens S15E
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How mobile phones have developed
1999
1st WAP capable
mobile phone
Nokia 7110
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How mobile phones have developed
1st mobile phone
to play MP3 files
2000
Samsung
SGH-100
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How mobile phones have developed
2001
1st 3G voice call - Vodafone & Ericsson
1st Active colour display – SonyEricsson T68
1st Bluetooth phone – Ericsson T39m
1st Polyphonic ring tones – Sony Z7
1st Integral FM radio – Nokia 8310
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How mobile phones have developed
1st Camera Phone
1st “Smart Phone”
2002
Nokia 7650
XDA
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How mobile phones have developed
2003
1st Vodafone 3G data card
1st Video recording phone – Nokia 3650
1st Dedicated game phone – Nokia N-Gage
1st Rotating screen – Samsung SGH-P400
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How mobile phones have developed
Vodafone launch
3G networks in
13 countries
2004
1st Two mega pixel
camera phone with optical
zoom – Sharp 902
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How mobile phones have developed
2005
3G Video Calling,
Internet browsing,
Full Track Music downloads,
Location based Services,
High Speed Data Access
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How mobile phones have developed
Mobile data access
Text message
FAX
Voice call
WAP
Wireless device connectivity
Increased data rate
Picture message
Video games
Video playback
Instant Email access
Fast Internet browsing
Video telephony
High Speed Data Access
Full Track Music downloads
Location based Services
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Looking forward - new ways of displaying content
Today
_ LCD display resolution progressing
towards VGA (640x480 pixels)
•
as good as the eye can resolve at typical
viewing distances…
•
…and capable of supporting DVD-quality
•
…but user experience degraded by small
display size
Tomorrow
_ Organic LED will improve image quality
_ 3D displays will compensate for small
physical display size by adding depth
_ But ultimately the need will be for larger
displays that fill the field of view and
support multiple viewing windows:
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•
Head-up displays (high-definition
resolution)
•
Micro-projectors
•
Pull-out displays (flexible/rollable)
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Looking forward - a multiplicity of local connectivity
Today
_
_
_
_
InfraRed
Bluetooth
Memory cards
USB
Tomorrow
_ All of the above with the addition of:
_ Near Field Communications
• device pairing & local network
configuration
• service discovery/initiation
_ WLAN (802.11b)
• Home and office connectivity
• Wireless extension of DSL in the home
• For both charging and synching content
to the terminal
_ UWB
• Wireless USB
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Mobile TV - bmco trials in Berlin
_ World’s first trial of MobileTV with interactive services
•
DVB-H/GSM terminals
•
friendly user group
•
proved technical feasibility and user demand/interest
•
insight into the nature of successful services
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Multimedia device – c 2009
Display
DVD quality (VGA)
DVB-H
broadcast
reception
Removable storage
128 MB <<<<<16 GB
Hard DD Storage
Processor
2 GB <<<<<< 50 GB
DVD quality video (H.264 decode)
Support for a range of audio and video codecs
Support for PS2-quality games
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Embedded Flash
6 MB <<<<128 MB
Part of Life
_ Health care use
•
Diabetes monitoring trial at Oxford University
•
Health monitoring trial for people with heart & lung problems in
Spain
•
Monitoring health of AIDS patients in South Africa
_ Peace of mind
•
Personal security for vulnerable
•
Controlled freedom for the young
•
Access to emergency services
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The need for base stations
_ Coverage
•
The local base station is the radio access to the network
_ Capacity
•
Each base station has capacity limited by spectrum bandwidth
•
Spectrum is limited and needs to be re-used across network
–
Interference from such re-use is a critical network design factor
_ Capability
•
There are physical limits to how far and how fast you can transmit a
bit
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Drivers for site density
Portable terminals = more sites
Terminal
Site density
Rooftop panel (10dBi)
1
Upstairs window, fixed (3dBi)
12
Outdoor laptop (0dBi)
60
Indoor laptop (0dBi) Suburban
230
Indoor laptop (0dBi) Urban
800
Higher frequencies = more sites
Faster data = more sites
3 Sector base station at 25m
to outdoor PC card
Data
Rate
Site
density
100Mb/s 0.21km
10Mb/s
50
0.41km
1Mb/s
100kb/s
2100MHz
3500MHz
4000MHz
15
3.6
0.78km
1.49km
1
2500MHz
Range
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The effect of frequency
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Factors affecting transmit power – GSM cell site
_ Max power per transmitter (100mW < ~10W)
•
depends on coverage needed.
_ Number of installed transmitters (2 < ~10)
•
designed to limit congestion <2%
_ One frequency per cell transmits all the time at max power
•
Broadcast Control Channel – but using only 2 of the 8 time slots
_ Other frequencies are used to provide the timeslots needed to support
calls at that time (“traffic”), at the power level needed for call (“power
control”) and when speaking (or sending data) to the user
(“discontinuous transmission”)
_ Even at busiest time of day not all frequencies are in use – and those
that are in use do not all operate at full power or continuously
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Impact on actual transmit power
_ Power control & DTX are each
likely to limit power to 50-70%
_ For a 6 transceiver cell,
maximum power output in busy
hour is likely to be 30% to 50%
maximum power
10
9
All @ 1W Max Power
8
Total Transmit Power (W)
_ Even without power control &
discontinuous transmission, the
peak power output at busiest
time is below the theoretical
maximum for cell
Total Transmit Power V No. GSM transceivers
for 2% blocking with DTX / PWC
No DTX or PWC
70% DTX & 70% PWC
7
50% DTX & 50% PWC
6
5
4
3
2
1
1
2
3
4
5
6
7
8
Number of GSM transceivers
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9
10
Measured transmit power
% Maximum power
90.0
Measured Max Active TRX
80.0
Max 70% DTX & 70% PWC
70.0
Max 50% DTX & 50% PWC
60.0
50.0
40.0
30.0
20.0
10.0
.0 01
0
02 - .00
.0 02
03 0 - .00
.0 03
04 0 - .00
.0 04
05 0 - .00
.0 05
06 0 - .00
.0 06
07 0 - .00
.0 07
08 0 - .00
.0 08
09 0 - .00
.0 09
10 0 - .00
.0 10
11 0 - .00
.0 11
12 0 - .00
.0 12
13 0 - .00
.0 13
14 0 - .00
.0 14
15 0 - .00
.0 15
16 0 - .00
.0 16
17 0 - .00
.0 17
18 0 - .00
.0 18
19 0 - .00
.0 19
20 0 - .00
.0 20
21 0 - . 00
.0 21
22 0 - .00
.0 22
23 0 - .00
.0 23
0 .0
-0 0
0.
00
0.0
01
.0
0
_ In any hour, the
maximum number
of active timeslots
noted and % of max
available
determined
100.0
00
Typical 6-transmitter
cell monitored over a
day.
Estimated % Maximum Power Output v Time,
6 transceiver cell.
Time
_ Effect of Power control & DTX each 50-70% max. per controlled
timeslot.
_ Shows for a 6 transceiver cell, maximum power output in busy hour is
likely to be ~30-40% of the theoretical capability of the cell
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Exposure guidelines and measurement standards
_ Specific Absorption Rate (SAR) is the measure of the rate of energy
deposited in the human body from an RF field.
_ International guidelines recommend max SAR for general public
•
ICNIRP – peak 2 W/kg in 10g head / trunk & 0.08 W/kg over whole body
•
IEEE – peak 1.6 W/kg in 1g head / trunk & 0.08 W/kg over whole body
•
Guidelines also specify frequency-dependent reference field levels
_ Current Standards define how to measure SAR
for handsets used against the ear: Global
(IEC), EU (CENELEC), US (IEEE)
_ IEC developing SAR measurement standard
for equipment used close to the body
•
Current US FCC measurement guidelines
_In EU, CENELEC are finalising standards on base station RF field
measurement. IEC / ITU are developing global base station standards
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Field levels are subject to a power law decay
Relative Field Power Flux v Relative Distance from Antenna
1
Releative Field Power Flux
1
10
100
0.1
0.01
1/d^2 Law
1/d^2.2 Law
0.001
0.0001
0.00001
Relative Distance from Antenna
_The RF Field decays rapidly as you move away from base station
_Ignoring antenna directivity, reflection & scatter effects, a point 10
times further away from a transmit antenna will have less than 1/100
power flux
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Exposure from base stations - observed
_RA* evaluated levels at 289
schools with/near base stations
UK RA cellular RF survey 2001 -> 2004
Highest levels measured from 289 Schools
100
_Measurements made in many
locations at each school
_Highest result for each school
were referenced to ICNIRP_GP.
80
Highest level
th
1/279
ICNIRP_GP
_Graph shows % of schools
below the ICNIRP_GP
compliance factor.
•
th
70
60
50
Median level
th
1/17970
ICNIRP_GP
40
Factor “1” = ICNIRP_GP
30
20
% of highest readings below factor
90
90% below 1/3485
ICNIRP_GP
10
Very low public RF exposure
0
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
Compliance Factor relative to ICNIRP_GP
*UK Radiocommunications Agency, now part of OFCOM
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1.E+00
Exposure from base stations – numbers game
_ 50 x ICNIRP_GP: exposure to 4
W/kg could produce a rise in
body temperature of 1°C
200 m
_ 5 x ICNIRP_GP: ICNIRP
recommends limiting exposure of
workers to 0.4 W/kg
20 m
_ ICNIRP: recommends limiting public
4m
exposure to 0.08 W/kg
_ Maximum field in any of the schools
surveyed was 1/279 x ICNIRP_GP
_ Median field for the schools surveyed
was 1/17970 x ICNIRP_GP
“Exposure levels from living near to mobile phone base
stations are extremely low, and the overall evidence
indicates that they are unlikely to pose a risk to health.”
AGNIR – January 2004
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1.4 cm
0.22 mm!
Effect of power control on the handset
_ Handset power set by network instructions
•
power control range for GSM is ~1000X (30dB) @ 3dB per 60ms
_ In-service communications loss from base station to handset varies by
~10,000,000 (70dB)
_ >> loss in larger area
further away from base
station
_ Explains observation
that most likely GSM
handset powers are at
max or min setting
_ 3G power control range
•
>70dB @ 2dB per 0.7ms
•
better match to
communications loss
30 dB GSM
i
(D
Power
Control
Range
s
s
70 dB Range of
lo
ath
Communications Loss
P
s
on
i
t
ica
un
m
m
Co
g
n
si
rea
c
In
GSM @
Min Power
r)
oo
d
n
,i
ter
t
u
Cl
e,
c
n
sta
GSM @
Max
Power
Population of each GSM power control setting*
* Output power levels from mobile phones in different geographical areas; implications for
exposure assessment; S Lonn, U Forssen, P Vecchia, A Ahlbom, M Feychting. Occup
Environ Med 2004;61:769–772. doi: 10.1136/oem.2003.012567
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SAR from Mobile Phones
_ Measured head-use SAR from compliance test varies
3X fold between products
•
Vodafone UK’s handsets 1.05 and 0.31 W/kg
_ Comparing head-compliance SAR values between products is not a
reliable guide to how SAR may vary between products for other
positions of use or in different operating bands
•
Vodafone retail store manager…
“I have a man in the store who wants a high SAR phone because he lives in a rural area and
said it was more powerful and would work better!”
_ UK MTHR research concludes that using a Personal Hands Free
with the lead wrapped around the phone gives a 60% reduction in
peak head SAR compared with phone used against the ear – a 2 or
3 fold factor SAR reduction.
_ Published data shows that a correctly-used PHF reduces peak head
SAR by 95% or more compared with phone used against the ear – a
20 fold factor SAR reduction.
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Moving away from the head
_ Vodafone supports research to assess effects
on SAR of
•
•
different body mounting positions
different operating frequency bands
_ Feeds international measurement standards
_ Empower users by giving effective advice on
how they may limit the SAR from their phone if
they are concerned
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Summary
_ The way people use mobile phones has changed
significantly over the last 30 years
_ Commercial drivers to use spectrum efficiently and to
maximise battery life work to reduce transmit power
_ Demands for coverage & capacity increase number of
base stations
_ GSM is spectrum efficient – but 3G is better, enabling
higher data rate services for similar power
_ Design of network impacts handset power - hence SAR
_ User actions are more effective in controlling exposure
from their handset than comparisons between different
products’ compliance-based SAR numbers
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Prof. Michael Walker
Vodafone Group R&D
Vodafone House
1 The Connection
Newbury
Berkshire
RG14 2FN
UK
mike.walker@vodafone.com
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