4. GSM Network Areas

The GSM network is made up of geographic areas. As shown in Figure 3, these
areas include cells, location areas (LAs), MSC/VLR service areas, and public land
mobile network (PLMN) areas.

The cell is the area given radio coverage by one base transceiver station. The GSM
network identifies each cell via the cell global identity (CGI) number assigned to
each cell. The location area is a group of cells. It is the area in which the
subscriber is paged. Each LA is served by one or more base station controllers,
yet only by a single MSC (see Figure 4). Each LA is assigned a location area
identity (LAI) number.

An MSC/VLR service area represents the part of the GSM network that is covered
by one MSC and which is reachable, as it is registered in the VLR of the MSC (see


The PLMN service area is an area served by one network operator