The Wireless Communication System Xihan Lu Wireless Communication

The Wireless Communication System Xihan Lu

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

Why “Cellular”?

Three Generations AMPS NMT TACS HCMTS GSM GPRS WCDMA 2000 TD SCDMA 1 G 2 G 3 G

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

FDMA

Shortage l Voice information only l Unsafe （eavesdropping） l Waste of frequency resource

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

GSM l l l TD/FDMA: A mix of FDMA and TDMA The whole useable spectrum was divided to many 200 k 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 l BTS & BSC: Base Transceiver System and Base Station Controller. Radio signal transceiver, a connection between handset and MSC l 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 l VLR : Visitor Location Register, embedded in MSC to avoid delay, contains current location information of handsets l AUC : Authentication Center, stores secret keys for authentication and encryption of the radio channel l EIR : Equipment Identity Register, contains a list of all valid mobile equipment in the network, by its International Mobile Equipment Identity (IMEI) l

GPRS l Upgrade of existed GSM network l Improves the data communication ability

GPRS

Network nodes l GGSN: Gateway GSM Support Node, l Protocol transferring, data encapsulation, a connection to external networks l SGSN: Service GSM Support Node, l 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 l In GPRS, up to 8 traffic channels(a whole carrier) can be dynamically combined together for one data communication application l The theoretically maximum data transmission rate: 14. 4 k bps * 8 = 115. 2 k bps l

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

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

3 G

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

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

CDMA

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

Conclusion

Conclusion 1 G 2 G 3 G Voice Quality OK OK Good Data communication N/A ~115 K ~2 M Spectrum usage X 5~6 X 10~20 X Communication safety Weak OK Good

References l l l l www. gsmworld. com/technology/gprs/index. html www. 3 gsmamericas. com/pdfs/EOF_Cannes_2003/Nortel_David_Smit h. pdf http: //www. fcc. gov/Bureaus/Wireless/Reports/fcc 98091. pdf www. rogers. com http: //www. itu. int/ITUD/ict/publications/wtdr_99/material/glossary. html www. itu. int/home/imt. html http: //www. boeschatt. at/Mobil/mobilfunk_html. php? gsm_netzarchitek tur. php http: //www. pt. com/products/gsmintro. html