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The Global System for Mobile Communications (GSM)
GSM and the Architecture (block diagram)
Thank You!
1G
- 1st generation cellular standard
- Called AMPS, MTS, IMTS
- Introduced in 1980s
- Supports voice calls only
- Uses FDMA, analog modulation
- Bulkier handset
GSM
1)2ND GENERATION CELLULAR STANDARD
2)DEVELOPED IN 1991 BY EUROPEAN TELECOMMUNICATIONS
3)SUPPORTS VOICE AND DATA SERVICES
4)USES TDMA,DIGITAL MODULATION
5) 2G Handset is lower in cost
6) Gsm produces SIM card
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GSM Specifications
GSM Specifications
Uplink = 890-915 Mhz
Downlink = 935-960 MHz
Transfer rate = 9.6Kbps
No of carriers = 124
Carrier separation = 200KHz
Modulation = GMSK
Access method = TDMA/FDMA
Time slots = 8
GSM speed = 14.4Kbps
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GSM Architecture
GSM Architecture
Mobile station
Mobile Station
ME (Mobile Equipment)
-Hardware used by subscriber containing IMEI (International Mobile Equipment Identity)
SIM (Subscriber Identity Module)
-Detachable smartcard containing IMSI (International Mobile Subscriber Identity)
-Used to send and receive calls
Base Station Subsystem
Base Station Subsystem
BTS (Base Transceiver Station)
-Sends and receives signals from MS
-Encoding, Multiplexing, Encryption, Modulation
BSC (Base Station Controller)
-Controls group of BTS
-Allocation of radio channels
-Handover from one BTS to another
Network Switching Subsystem
Network Switching Subsystem
MSC (Mobile Switching Center)
-Heart of GSM network
-Management of mobile services like registration, authentication, etc.
-Performs call routing, call setuo and call switching
-Communicates with HLR,VLR,AUC and EIR
HLR VLR AUC EIR
HLR (Home location Register)
-Master database of subscriber’s current location and information
VLR (Visitor Location Register)
-Subser of HLR
-Local database for user’s visiting location in other domain
EIR (Equipment Identity Register)
-Database containing all valid handsets on network using IMEI number
- Marks IMEI as invlid, if handset is stolen
AUC (Authentication Center)
-Protected database that stores copy of IMSI number used for authentication and encryption task
-Protects from different types of frauds on network