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 ” ?

Three Generations AMPS NMT TACS HCMTS GSM GPRS WCDMA CDMA2000 TD SCDMA 2G3G1G

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

Conclusion 1G2G3G Voice Quality OK Good Data communication N/A~115K~2M Spectrum usage X5~6X10~20X Communication safety WeakOKGood

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