The Base Station Subsystem BSS provides the connection between the mobile stations and the Network Subsystem NSS. The NSS forwards user signals to other mobiles via the BSS or subscribers in the Public Switched Telephone Network (PSTN), and provides necessary customer data. The Operation & Maintenance Subsystem (OMS) monitors BSS and NSS performance, and remotely debugs occurring faults in the network elements.
Additional components such as interface elements to data networks, the Short Message Service Center or the Voice Mail System complete the GSM system architecture.