ARCHITECTURE OF THE GSM NETWORK

A GSM network is composed of several functional entities, whose functions and
interfaces are specified. Figure 1.1 shows the layout of a generic GSM network. The
GSM network can be divided into three broad parts. The Mobile Station is carried by the
subscriber. The Base Station Subsystem controls the radio link with the Mobile Station.
The Network Subsystem, the main part of which is the Mobile services Switching Center
(MSC), performs the switching of calls between the mobile users, and between mobile
and fixed network users. The MSC also handles the mobility management operations.
Not shown is the Operations and Maintenance Center, which oversees the proper
operation and setup of the network. The Mobile Station and the Base Station Subsystem
communicate across the Um interface, also known as the air interface or radio link. The
Base Station Subsystem communicates with the Mobile services Switching Center across
the A interface.