A permanent database containing subscriber profiles and their last known location.
Handles authentication, security, and location tracking. GSM – Architecture, Protocols and Services
Verifies user identities and provides security keys for encryption. Short Message Service (SMS)
Manages call control (CC), Short Message Service (SMS), and supplementary services. Services and Security GSM – Architecture, Protocols and Services
Support for data transmission, originally limited to 9.6 kbps but later improved through upgrades like GPRS and EDGE .