The Cellular Communication System
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Transcript of The Cellular Communication System
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The Wireless Communication The Wireless Communication SystemSystem
Xihan Lu
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Wireless CommunicationWireless Communication
Cellular phone systemCordless telephone systemBluetoothInfrared communicationMicrowave communicationIEEE Wireless LANs (Wi-Fi)Satellite communication
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Why “Cellular”?Why “Cellular”?
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Three GenerationsThree Generations
AMPSNMTTACS
HCMTS
GSMGPRS
WCDMACDMA2000TD SCDMA
2G 3G1G
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1G1G
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
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FDMAFDMA
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
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FDMAFDMA
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ShortageShortage
Voice information onlyUnsafe ( eavesdropping )Waste of frequency resource
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2G2G
Start early 90’sDigital techniqueGSM : Global System of Mobilephone GPRS : General Packet Radio Service
D-AMPS : Digital AMPS
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GSM 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
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FD / TDMAFD / TDMA
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Network StructureNetwork Structure
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BTS,BSC and MSCBTS,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
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DatabasesDatabases 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)
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GPRSGPRS
Upgrade of existed GSM networkImproves the data communication ability
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GPRSGPRS
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Network nodesNetwork nodes
GGSN: Gateway GSM Support Node,Protocol transferring, data encapsulation, a
connection to external networksSGSN: Service GSM Support Node,Communicate with HLR and mobile
handsets, authorization and admission control, charging, mobility management
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Data communicationsData 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
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Advantages of GPRSAdvantages of GPRS
Higher data rateSeamless connection to internetPacket 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
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shortageshortage
Not fast enough for the multimedia serviceThe data rate falls when the network is busyUpgrade of handset
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3G3G
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3G-Standards3G-Standards
Three CDMA standards approved by ITU:Direct Spread CDMA(WCDMA) : Europe,
JapanMulti-Carrier CDMA(CDMA 2000) : North
AmericaTD-Synchronous CDMA(CDMA TDD) :
Europe, China
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3G-CDMA3G-CDMA
Code Division Multi AddressSpread spectrum technologyEach 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
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CDMACDMA
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FeaturesFeatures
Better voice qualityUp to 2 Mbps data communication rateIncrease battery lifeSoft hand-offExcellent data safetyMore effective spectrum usage than 2G
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ConclusionConclusion
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ConclusionConclusion
1G 2G 3G
Voice Quality OK OK Good
Data communication
N/A ~115K ~2M
Spectrum usage X 5~6X 10~20X
Communication safety
Weak OK Good
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ReferencesReferences
www.gsmworld.com/technology/gprs/index.html www.3gsmamericas.com/pdfs/EOF_Cannes_2003/
Nortel_David_Smith.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.ht
ml 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