History of mobile networks

(1)

Tik-109/110.300

Telecommunications architectures:

History of mobile networks

(2)

Agenda

Access technologies

Technical questions in mobile telephony Generations

First generation networks

Second generation networks

Third/Fourth generation networks

Satellite phones

(3)

Access technologies

• How to share radio between mobiles?

• TDMA

• Time Division Multiple Access

• Send at different time

• FDMA

• Frequency Division Multiple Access

• Send using different frequency

(4)

Technical questions in mobile telephony

• Mobility management issues

• Mobility management

• Handover

• Security

• Radio issues

• Spectrum efficiency, Network planning

• Multipath propagation, Power control, Timing advance

• Error correction, Discontinuous transmission

• Service issues

(5)

Mobility management

• Is mobile on or off?

• Where is the mobile?

• Page the mobile

• Location updates

(6)

Handover

• Moving from one cell to another

• What is the most optimal cell for the mobile

• Local optimization

• Global optimization

• Movement prediction

• Decision making by network or mobile?

(7)

Security

• AAA: Authentication, Authorization and Access control

• Who is the mobile?

• What it is allowed to do?

• Who are allowed to access?

• Ciphering: Encryption of the data

• Wireline level security

(8)

Spectrum efficiency

• How many bits per hertz (of spectrum) is obtained ?

• What is the optimal coding technology?

• TDMA, CDMA, FDMA, …

• How much spectrum is available?

• How expensive is the spectrum?

• Used spectrum and usability of the spectrum

• 2.4GHz area (license free)

• GSM/UMTS spectrum

(9)

Network planning

• How many mobiles can be served?

• Behavior of a mobile?

• 1.2 calls per mobile per busy hour

• Data usage patterns?

• Where to put base stations?

• Building expandable radio networks

• Supporting hot spots

(10)

Multipath propagation

• Signal propagates with several path

• Directly (line of sight)

• Reflection, scattering, …

• Original signal and later coming copies are summed up or interfering each other

• Radio fading problems

(11)

Power control

• How much power to use in uplink/downlink direction?

• Interference of mobiles

• Open loop vs. closed loop power control

(12)

Timing advance

• How to control transmission so that each mobiles does not disturb the neighbors?

• A time window of a mobile’s transmission

• Collision of mobile’s packets

(13)

Error correction

• What happens, when the radio communication has errors?

• Surviving radio errors

• Forward error correction (FEC)

• FEC overhead (in GSM ~50%)

• Retransmission of data

• Problem with real time data

(14)

Discontinuous transmission

• People are speaking only part of the call time

• Typically 40% of the time

• Transmission is power consuming

• Transmission causes interference

(15)

Voice codec

• How to code voice as compact as possible?

• Voice quality vs. transfer rate

• GSM full rate/half rate/enhanced coding

• How to decode/encode voice independently of each other?

• Problem of various languages

• European vs. Asian languages

(16)

Generations

• First generation

• Analog mobile networks

• Voice services

• Second generation

• Digital mobile networks

• Voice services and slow speed data

• Wide coverage

• Third generation

• Mobile multimedia, limited coverage

(17)

First generation networks:

ARP

• In use: 1971->

• Frequency band: 150 MHz

• Channels: 80

• Technology/Modulation: Analog, FM

• Transmit power: 1-5W

• Handover during call: no

• Coverage: Finland, whole country

(18)

First generation networks:

NMT-450

• In use: 1982->

• Channels: 180

• Transmit power: 150mW, 1,5W, 15W

• Handover during call: Automatic, 1.4s

• Coverage: Nordic countries, some baltic countries, almost whole country

• Data service: 1200/4800 bps

(19)

First generation networks:

NMT-900

• In use: 1986->

• Channels: 400

• Transmit power: 100mW, 1W, 6W

• Handover during call: Automatic, 0.4s

• Coverage:

(20)

First generation networks:

Others

• AMPS: Advanced Mobile Phone System (USA)

• C-450, C-Netz (South Africa, Germany, Austria), 450 MHz

• N-AMPS: Narrowband Advanced Mobile Phone System (USA)

• NMT-F: French version of NMT900

• NTT: Nippon Telegraph and Telephone (Japan)

• RC2000: Radiocom 2000 (France)

• TACS: Total Access Communications System (UK, Japan)

(21)

Second generation networks: GSM

• Frequency band: 890-960 MHz

• Carrier interval: 200 kHz

• Access technology: TDMA

• Technology: Digital

• Transmit power: 125mW, 1W

• Coverage: Europe, Asia, ...

• Voice/data rate: 13 kbps / 9600 bps

(22)

Second generation networks: DCS/PCS

• Frequency band: 1710-1880 MHz (DCS)/ 1900 MHz (PCS)

• Transmit power: 125mW, 1W

• Coverage: Europe, Asia, ...

• Voice/data rate: 13 kbps / 9600 bps

• Channel bit rate: 270 833 bps

(23)

Second generation networks: IS-54

• Frequency band: 824-894 MHz

• Transmit power: 200mW, 600mW

• Coverage: USA

• Voice/data rate: 7,95 kbps

(24)

Second generation networks: IS-95

• Frequency band: 824-894

• Access technology: CDMA

• Transmit power: 600mW

• Coverage: USA

• Voice/data rate: 8 kbps (variable)

• Frame lengts: 20 ms

(25)

Second generation networks: PDC

• Frequency band: 810-1501

• Coverage: Japan

• Voice/data rate: 6.7 kbps

• Channel bit rate: 42 kbps

(26)

Third generation networks

• FPLMTS, UMTS, 3G, …

• http://www.3gpp.org/

(27)

Satellite phones

• LEO

• Low Earth Orbit

• MEO

• Medium Earth Orbit

• GEO

• Geo-stationary Earth Orbit

(28)

Links

• In English

• http://www.cnp-wireless.com/cellular.html

• http://www.gsmworld.com/index1.html

• http://www.cellular.co.za/celltech.htm

• http://www.cellular.co.za/statistics_global_by_standard.htm

• http://ccnga.uwaterloo.ca/~jscouria/GSM/gsmreport.html

• http://www.comms.eee.strath.ac.uk/~gozalvez/gsm/gsm.html

• http://www.hut.fi/~lahtima3/wlan.html

• In Finnish

• http://www.hut.fi/~then/matkapuhelin/index.html