gsm presentation nirma 25 august 2007
TRANSCRIPT
8/2/2019 GSM Presentation Nirma 25 August 2007
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Global System forMobile Communication
Presented By:Deepika SharmaDept.Of Computer Engg.
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Topics CoveredGSM Introduction
GSM Network Architecture
GSM BasicsChannelisation MethodsMultiple Access Methods
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GSM
Global S ystem for Mobile communication
Also called Global S tandard for Mobile communication
Standard defined by ETSI ( European TelecommunicationsS tandards Institute)
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What does GSM Offer?
Voice with better QualityServices (PIN, Call barring, Call forwarding, Calltransfer, Call waiting, Call Holding, Closed UserGroup)Value added services (SMS, MMS, Caller Tune etc)And of course - Mobility
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GSM Network Architecture
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GSM Network Architecture
BTS 3
BTS 2
BTS 1
BSC
PSTN N/W
HLR
VLR
AUC
EIR
SMSC
VMSC
MSC
OSS
NSS
BSSMS
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Mobile Station (MS)
Mobile S tation (MS) consist of two unitsMobile Hand set SIM - S ubscriber Identity Module
- Provides user an access to theNetwork.
- Each handset has unique identity no.
called IMEI ( International Mobile EquipmentIdentity)
- SIM is a removable module fits inside the Mobilehandset.
- Each SIM has unique number calledIMSI (International Mobile S ubscriber Identity).
- Also it stores Network specific information likeAuthentication Key (Ki), Local Area Identity (LAI).
- The SIM also stores other carrier specific data such as
SMSC ( S hort Message S ervice Centre) number,S ervice
P rovider Name (SPN), Value Added S ervice (VAS)applications.
- It contains the ROM of 6 to 16KB, RAM of 128 to256 bytes and EEPROM of 3 to 8KB.
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BTS has a set of Transceivers to talk to MS.
One BTS covers one or more than one cell.
Capacity of BTS depends on no of Transceivers.
BTS is connected to BSC via A’bis interface.
Transmission rate on A’bis is 2 Mbps.
Interface between MS & BTS is called Air I/f.
Speech Transmission rate on Air I/f is 13 Kbps.
BTS controls RF parameters of MS.
Each Transceiver has 8 TDMA channels to carry Voice & signalling.
Base Transceiver Station (BTS)
BTSAntenna
Arrangement
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Base Station Controller (BSC)
BSCBSC controls several BTSs.BSC manages channel allocation, Power Control of MS/BTS
& Handover of calls from one BTS to another BTS.
BSC is connected to MSC via A interface.
Transmission rate on A I/f is 2 Mbps.
Interface between BSC & BTS is called A’bis I/f.
BSC has database for all of its BTS’s parameters.
BSC provides path from MS to MSC.
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Mobile Switching Centre (MSC)
MSC manages all call related functions andBilling/Charging related information.
MSC is connected to HLR & VLR for subscriberidentification & routing incoming calls.
MSC capacity is in terms of no of subscribers.
MSC is connected to BSC at one end and with different
network on other end.
Call Detail Record (CDR) is generated for each & every
call in the MSC. MSC
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Visiting Location Register (VLR)
VLR
MSC
Active Subscriber is registered in VLR.
It has temporary data base of all the active subscribers used for their callrouting.
HLR validates subscriber before registration.
MSC ask VLR before routing incoming call.
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Home Location Register (HLR)
HLR
MSC
All Subscribers data is stored in HLR.
It has permanent data base of all the registered subscribers.
HLR has series of numbers for all subscribers.
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Authentication Centre (AUC)
HLR
MSC
Authentication is a process to verify the subscriber SIM.
Secret data & verification algorithm are stored in to the AUC.
AUC & HLR combined to authenticate the subscribers.
Subscriber authentication can be done on every call, if required.
AUC
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Equipment Identity Register (EIR)
EIR
MSC
All subscriber's mobile handset data is stored in EIR.
MSC asks mobile to send it IMEI & then checks it with data available in EIR.
EIR has different classification for mobile handsets like, White list,
Grey list & Black list.
According to category the MS can make calls or can be stopped from
making calls.
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Operation & Maintenance Centre (OMC)
OMCAll the network elements are connected to OMC.
OMC monitors health of all network elements &carry out maintenance operation, if required.
OMC link to BTSs are via parent BSC.
OMC keeps records of all the faults occurred.
OMC can also do Traffic analysis.
OMC may prepares MIS Report for the network.
VMSC & SMSC
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VMSC & SMSC
MSC
SMSC VMSC
Voice Mail Service Centre : To provide Voice Mail service.It has database for all the VMS subscribers & also stores voicemessages for them.
Short Message Service Centre : To provide text message service.
To send short messages from mobile to another mobile subscriber.Messages can also be sent by Manual Terminal connected to SMSC.
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GSMBASICS
Ch li ti
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Channelization
Channelisation can be done primarily by threemethods:
FDMA (Frequency Division Multiple Access)TDMA (Time Division Multiple Access)CDMA (Code Division Multiple Access)
FDMA
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FDMA
Frequency
Time
Power
Television Channels (Star, Zee, Sony,..)
TDMA
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TDMA
GSM has 8 timeslots on each 200 KHz channel
Frequency
Time
Power
Duplex Access Methods
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Duplex Access Methods
F1 F2 Frequency
Amplitude
Time
Tx Rx
Frequency Division Duplex (FDD)Transmit on one frequency and receive on another frequency
Time Division Duplex
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Time Division Duplex
Time Division DuplexTx and Rx is on the same frequency but on different times
E.g.. Walky Talky
F1 Frequency
Amplitude
Time
Tx
Rx
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GSMAir Interface
GSM Air Interface
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GSM Air Interface
Separate Bands for Uplink and Downlink
Downlink : 935- 960 MHzUplink : 890- 915 MHz