The Fascination of Mobile Communications - TU Wien · The Fascination of Mobile Communications...

INSTITUT FÜRNACHRICHTENTECHNIK UNDHOCHFREQUENZTECHNIK

The Fascination of Mobile Communications

Ernst BonekInstitut für Nachrichtentechnik und Hochfrequenztechnik,

Technische Universität Wien

Researchers NightSofia

25 September 2009

25 September 2009


• Safety

• Independence

• Convenience

• Use of down times

• Fun

• Recognition

• Attachment to groups

• Price

• …

Why are mobile phones attractive for you?

25 September 2009


What to expect

• A look back

• The physical and technological challenges

• Social and commercial aspects

• Some critical questions

• Why this fascination?

25 September 2009


Some important dates

• 1981 NMT 450 in Scandinavia– Östen Mäkitalo

• 1984 Divestiture of the Bell System (AT&T) in the US• 1986 „Beauty contest“ for pan-European system in

Paris => GSM• 1993 GSM in 13 European countries

– Thomas Haug• 2002 first commercial national UMTS network

worldwide (Mobilkom in Austria)

25 September 2009


NMT, C-Netz, Autotelefonnetz C

• Start November 1984• For vehicle operation („transportable“ = 10 kg)• Price appr. 8.000 DM = 4.000 €• First fully automatically switched mobile phone

system (cellular, cell radius 15 km)

25 September 2009


…but

• Analog• An individual carrier (= TX and RX) for each channel• Not encrypted• Incompatible over Europe, even in countries that

officially shared the same system (until 1991!)

Time

Frequency

Channel

25 September 2009


Mobile phone subscribers worldwide

Subscriber Growth

955m

2001 2002 2003 2004 2005 20

1134m

Source: www.gsmworld.com

1368m

25 September 2009


GSM (Global System for Mobile communication)

• A European invention

February 2004 (September 2009):

• 1 (?) Billion(s) users worldwide!= 70% (>90%) of all mobile phones

• 541 network operators in 197 (>210) countries(in more countries than Coca Cola!)

Source: www.gsmworld.com

25 September 2009


1991 alternatives: Iridium, Qualcomm CDMA (“narrowband”)• Political will among European countries• Digital

– Sven-Olof Öhrvik• Capacity (8 channels on each carrier)• SIM card• International roaming• Open standard

– Economies of scale– in contrast to US methodology:– No excessive patent royalties – Consensus instead of squeeze-out

competition like IBM, Microsoft,…– Six different 3G technologies

accepted in US

Why GSM made it

25 September 2009


What to expect

• A look back





25 September 2009


Why is mobile radio such a challenge

• Multipath propagation of electromagnetic waves

• Limited energy

• Limited spectrum

• Many and mobile users

25 September 2009


Wireline telephony

Local switch 1

Central office

Local switch 2

25 September 2009


Base station

Base station:Interface to publictelephone network

25 September 2009


25 September 2009


Multipath propagation : 5λ × 5λ; 2 GHz

25 September 2009


GSM radio access• FDM/TDMA

Time

Frequency

0 1 2 3 4 5 6 7

ChannelTime Slot

25 September 2009


Wireless channel response 1

25 September 2009


Wireless channel response 2

25 September 2009


d

GSM mobiles require just 0,000 000 000 000 1 watts forreception!

Power dwindling

25 September 2009




• Limited energy



25 September 2009


Limited energy

More transmit power – wider range but……less battery life…digital signal processing also power-

hungry

Efficient power amplifiers (Class C) require constant envelope modulation

Transmission speed (bandwidth) is also power-hungry!

25 September 2009


Save energy!The battery is the sore spot, so … save energy

wherever possible

• Discontinuous transmission (DTX)

• Mobile does not transmit in standby

• Receiver is also put to sleep-mode

• Transmit power control (TPC) jointly at mobile and base station

25 September 2009


Transmit power of mobile

SendeleistungHandy

Zeit

Einschalten“Senden” = grünes Telefon drücken

Telefonieren

2W

1W

0,1W

2W

1W

0,1W


Transmit power of mobiles, measuredGreen: ruralBlack: small townBlue: Stockholm outskirtsRed: Stockholm center

0,003 W (= 3 mW) 0,125 W 2,0 W

25 September 2009


Paradoxon #1

Closer base stations meanless exposure to electromagnetic fields!

25 September 2009


Batteries or…?Batteries are• heaviest part• most expensive part

Future solutions• resonant magnetic field charging• piezoelectric chargers• solar• movement• hydrogen fuel-cells

25 September 2009




• Limited energy



25 September 2009


2GHz 3GHz1GHz

GSM1800

GSM1800

DECT

UMTS UMTS

UMTS Satellite

GSM 900

TETRA ISM

D-Netz

IRIDIUM

300 MHz

872890

905 917935 960915

950 MHz 1900 1980 2010 2110 2170 2200

1710 1785 1805 1880 19001621.351626.5

410430433.5

434.79450 470

MHz

MHz

MHz

UHF Band

880 925

EGSM

Quelle:ERO, European Radiocommunications Office, erstellt:T. Neubauer, www.symena.com

TV

TV White Space

„Digital Dividend“

to be used for Mobile Broadband like HSDPA, HSUPA and LTE

Mobile radio services at 300 MHz to 3000 MHz

25 September 2009


The cellular principle

25 September 2009


Co-channel interference

Co-channel interference, the bane of mobile radio

25 September 2009


The cellular principle

• While it permits spectrum-saving frequency re-use, itleads to …

• …interference-limited mobile radio networks

25 September 2009




• Limited energy



25 September 2009


Where are all those mobiles?

• Home Location Register– Your operator knows in which location area you are in, but only if you

are switched on (stand-by)

• Location Update – If you don‘t move, your operator asks you every 5 hours: still there?

– Saves battery power!

• Roaming, Visitor Location Register– If you are not in your home network, you are registered in the VLR of

the foreign operator

25 September 2009


The SIM cardSubscriber Identity Module - a small semiconductor chip• Separated the telephone number from a specific terminal• Enables international roaming• Protects you against eavesdropping• You cannot make a call without it (except 112)

25 September 2009


What to expect

• A look back





25 September 2009


Which businesses profit

Enormous boost in productivity• Sales people• Construction• Service & repair• Centralize data and make them available for

employees and customers on demand• Stock brokers

25 September 2009


Some social changes

• Economic and social development through country-wide mobile broadband

• New jobs in mobile-related industries, less officepersonnel

• Work hours and spare time not so distinct any more

• Knowledge is / will be ubiquitously available

- … but will remain everbody‘s personal obligation

25 September 2009


Which new services?

• Internet access•Ubiquitous information retrieval

• Position• How to I get to where I want to be• Individual picture postcard

• Mobile TV … ?• E-commerce => m-commerce• Gaming• Central address book (presence-enabled)

Information or entertainment?

RecognitionSafety

25 September 2009


In only 4 years as many users as GSM after 10 years

1996 1998 2000 2002 20040

200

400

600

800

1,000

Mill

ions

wireline

mobile telephony Internet

Mobile Internet

Mobile Internet

Source: Ericsson

minutes

25 September 2009


Mobile telephony in million minutes in Austria

2009: >80% market

25 September 2009


Broadband internet access

25 September 2009


What next in technology?

Long Term Evolution (LTE) is the next step from UMTS & HSPA

Basic drivers for LTE are:

• Reduced latency• Higher user data rates• Improved system capacity and coverage• Cost-reduction

25 September 2009


•

• ITU-RIMT Advanced

„4G“

CDMA WLAN => WiMAX

Verizon (US) and KDDI (Japan) will switch to LTE

?

25 September 2009


Both WiMAX and LTE use OFDMA

25 September 2009


… and Multiple-Input Multiple-Output (MIMO)

m n

A MIMO system consists of several antenna elements, plus adaptive signal processing, at both transmitter and receiver, the combination of which exploits the spatial dimension of the mobile radio channel.

25 September 2009


Benefits of MIMO

• increase power• beamforming

Array Gain

• multiply data rates• spatially orthogonal

channels

SpatialMultiplexing • mitigate fading

• space-time coding

Diversity

But will the propagation channel supportwhat you devise?

25 September 2009


Diversity Structures

25 September 2009


IMT Advanced

REPORT ITU-R M.2135Guidelines for evaluation of radio interface technologies

for IMT-Advanced

ReferencesSTEINBAUER, M., MOLISCH, A. F. and BONEK, E. [August 2001] The double-directional radio channel.IEEE Ant. Prop. Mag., p. 51-63.

http://www.itu.int/publ/R-REP-M.2135/enhttp://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-M.2135-2008-PDF-E.pdf

http://www.itu.int/publ/R-REP-M.2135/en

http://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-M.2135-2008-PDF-E.pdf

25 September 2009


Tracing individual multipaths

25 September 2009


Tracing Individual Multipath

28.4o34m

40m

34m

15m

34m

35m

Metallic Fence

VW-Bus

0

25 September 2009


Tracing Individual Multipath

28.4o34m

40m

34m

15m

34m

35m

Metallic Fence

VW-Bus

0L

1

3

2

25 September 2009


What to expect

• A look back





25 September 2009


Some critical questions

• Can my call be overheard?

• Are mobile phones a health hazard?

• Can my position be located and tracked?

• Why are antennas so unwieldy?

• Why don’t operators share their masts?

25 September 2009


Can my conversation be overheard?

• de facto not without cooperation of your operator

• Only with judicial mandate

• It‘s easier to eavesdrop in the switching center thanon the radio interface

25 September 2009


Mobile radio receives and transmits

• Case 1: Terminal transmits close to your head

• Case 2: Everybody is exposedto electromagnetic fields

• Time division multiple access(GSM, DECT) entails waves that areswitched on and off

25 September 2009


Why you shouldn‘t be afraid

• We have lived for 50 years with the em fields of TV• World Health Organization (WHO) has set safe

exposure limits• No part of your body can get warmer by more than

0.1°C• Over 13 000 studies so far on biological emf effects• Over 600 studies dedicated on mobile radio signals• 10 years of mobile phone use have not shown any

harmful effects• All attempts to find a biophysical mechanism why low-

level em fields should be harmful have failed

25 September 2009


Precautionary principle• World Health Organization (WHO) recommendations

are precautionary!

• Safety factor of 50

• Mobile phones reach ~1/2 of WHO limit in worst case,base stations only ~1%

• Exaggeration of the „precautionary principle“ createselectrophobia

25 September 2009


Electrophobia

When fear is the opponent, science does not stand a chance.

http://www.who.int/mediacentre/factsheets/fs304/en/index.html

http://www.icnirp.de/documents/StatementEMF.pdf

http://ec.europa.eu/health/opinions2/en/electromagnetic-fields/l-2/index.htm#0

http://www.who.int/mediacentre/factsheets/fs304/en/index.html

25 September 2009


Can I be spotted and tracked?

• Cell radius in GSM: 150 – 35 000m – Necessary for call termination– Operators pass on this information only for law

enforcement– Higher precision with GPS– USA requests 911 emergency callers to be

located• in 3G (UMTS): higher precision possible

– Location-based services will come– But: you can decide!

25 September 2009


What to expect

• A look back





25 September 2009


The feedback loops of mobile communications

More users

Smaller cells

Less transmit power

Smaller terminalsLonger talk time

Miniaturization

Digital signalprocessing

Low-power circuits

Technology Network

Enhancedcapacity

Smart management

The UserM

ore

attra

ctiv

e!

25 September 2009


That we can speak to each othermakes us human.

Karl Jaspers(philosopher)

We become human beings bycommunicating.

Wolf Singer(brain researcher)

25 September 2009


Telecommunications

• Culture is based on communication

• Telecommunications extends our ability to communicate by transcending distance

• Mobile communications facilitates communicationanytime everywhere

25 September 2009


Erich Kästner‘s Vision in 1933

But most impressive was this: A gentleman, who was coasting in front of them on themoving sidewalk, steppeddown on the street, took a telephone from his pocket, spoke a number into themicrophone and said: „Gertrud, listen, I‘ll be an hour late fordinner tonight. I have to go to the lab first. See you, honey!“ Then he put away his pocketphone, stepped onto themoving belt again, continuedreading his book and off he went.

25 September 2009


Thank you!

http://www.nt.tuwien.ac.at/about-us/staff/ernst-bonek/

25 September 2009


My grandchildren

25 September 2009


Which picture is correct?

A

B

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