Mobile Communications GSM

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Basic Services

Voice services (speech coding with protection)
» full rate: 13 / 12.2 kbit/s (original coder / enhanced full rate coder)
» half rate: 5.6 kbit/s (enhanced half rate coder)
♦ Data services (coding with different levels of protection)
» full rate: 9.6 / 4.8 / 2.4 kbit/s
» half rate: 4.8 / 2.4 kbit/s
♦ Enhanced data services
GPRS (General Packet Radio Service)
» various rates (typically up to 53.6 kbit/s)


GSM Architecture –Network Subsystem (NSS)
» Switching, mobility management,
» Interconnection to other networks, system control
» MSC - Mobile Switching Centre: Management of connections
» HLR - Home Location Register: Associated to each PLMN
» VLR - Visitor Location Register: Associated to each MSC
» GMSC - Gateway MSC: MSC providing interconnection to other
networks


GSM Architecture –Operation Subsystem (OSS)
» Centralized operation, management and maintenance of GSM subsystems
» OMC - Operation and Management
– Control of the radio and network subsystems
» AuC - Authentication Centre
– Security functions
» EIR - Equipment Identity Register
– Mobile station registration



SIM Card (Subscriber Identity
Module)
» Uniquely associated to a user
» Stores user and location addresses
– IMSI - International Mobile Subscriber Identity
– TMSI - Temporary Mobile Subscriber Identity
– LAI - Location Area Identification
» Supports authentication and encryption mechanisms
– PIN - Personal Identity Number
– PUK - PIN Unblocking Key
– Ki - subscriber secret authentication key
– A3 - authentication algorithm
– A8 - cipher key generation algorithm
» Contains personal data
– list of subscribed services
– RAM for user directory