The Wireless Communication System

Xihan Lu

Wireless Communication

 Cellular phone system  Cordless telephone system  Bluetooth  Infrared communication  Microwave communication  IEEE Wireless LANs (Wi-Fi)  Satellite communication

Why

“

Cellular

”

?

AMPS NMT TACS HCMTS

1G

Three Generations

GSM GPRS

2G

WCDMA CDMA2000 TD SCDMA

3G

1G

 Start early 80’s  Analogue technique  AMPT ( Advanced Mobile Phone System ): North America  NMT ( Nordic Mobile Telephony ): North Europe  TACS ( Total Access Communication Service ): Europe, China  HCMTS ( High Capacity Mobile Telephone System ): Japan

FDMA

 Frequency Division Multiple Access  Different carrier frequencies are assigned to different traffic channels(speech)  One carrier frequency can only carry one single speech channel at one time

FDMA

Shortage

 Voice information only  Unsafe （ eavesdropping ）  Waste of frequency resource

2G

 Start early 90’s  Digital technique  GSM : Global System of Mobilephone  GPRS : General Packet Radio Service  D-AMPS : Digital AMPS

GSM

 TD/FDMA: A mix of FDMA and TDMA  The whole useable spectrum was divided to many 200k Hz carrier frequencies —FD  Each carrier was divided into 8 timeslots (burst) —TD  Each burst is assigned to a user(a logical traffic channel)  One carrier frequency can carry up to 8 logical traffic channels (voice or data) at the same time  The maximum data communication rate is 14.4 kbps

FD / TDMA

Network Structure

BTS,BSC and MSC

 BTS & BSC: Base Transceiver System and Base Station Controller . Radio signal transceiver, a connection between handset and MSC  MSC: Mobile services Switching Center , switching center of the GSM network, and connect to other networks

   

Databases

HLR : Home Location Register , contains static information of subscribers and location update data VLR : Visitor Location Register , embedded in MSC to avoid delay, contains current location information of handsets AUC : Authentication Center , stores secret keys for authentication and encryption of the radio channel EIR : Equipment Identity Register , contains a list of all valid mobile equipment in the network, by its International Mobile Equipment Identity (IMEI)

GPRS

 Upgrade of existed GSM network  Improves the data communication ability

GPRS

Network nodes

 GGSN: Gateway GSM Support Node ,  Protocol transferring, data encapsulation, a connection to external networks  SGSN: Service GSM Support Node ,  Communicate with HLR and mobile handsets, authorization and admission control, charging, mobility management

Data communications

 In GSM, one user occupies one traffic channel to exchange voice/data information  In GPRS, up to 8 traffic channels(a whole carrier) can be dynamically combined together for one data communication application  The theoretically maximum data transmission rate: 14.4k bps * 8 = 115.2k bps

Advantages of GPRS

 Higher data rate  Seamless connection to internet  Packet switching rather than circuit switch, bandwidth is only used when the data is actually used, even though it is always connected  A primary step to 3G

shortage

 Not fast enough for the multimedia service  The data rate falls when the network is busy  Upgrade of handset

3G

3G-Standards

 Three CDMA standards approved by ITU:  Direct Spread CDMA(WCDMA) : Europe, Japan  Multi-Carrier CDMA(CDMA 2000) : North America  TD-Synchronous CDMA(CDMA TDD) : Europe, China

3G-CDMA

 Code Division Multi Address  Spread spectrum technology  Each single traffic channel occupies the whole spectrum, but distinguished by a unique digital code  Walsh code: an orthogonal 64 bit pattern, unique in the network

CDMA

Features

 Better voice quality  Up to 2 Mbps data communication rate  Increase battery life  Soft hand-off  Excellent data safety  More effective spectrum usage than 2G

Conclusion

Voice Quality Data communication Spectrum usage Communication safety

Conclusion

1G OK N/A X Weak 2G OK ~115K 5~6X OK 3G Good ~2M 10~20X Good

References

        www.gsmworld.com/technology/gprs/index.html

www.3gsmamericas.com/pdfs/EOF_Cannes_2003/Nortel_David_Smit h.pdf

http://www.fcc.gov/Bureaus/Wireless/Reports/fcc98091.pdf

www.rogers.com

http://www.itu.int/ITU D/ict/publications/wtdr_99/material/glossary.html

www.itu.int/home/imt.html http://www.boeschatt.at/Mobil/mobilfunk_html.php?gsm_netzarchitekt

ur.php

http://www.pt.com/products/gsmintro.html