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| The GSM network is made up of geographic areas. As shown in Picture 3, these areas include cells, location areas (LAs), MSC/VLR service areas, and public land mobile network (PLMN) areas. |
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| Picture 3. Network Areas |
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| 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 Picture 4). Each LA is assigned a location area identity (LAI) number. |
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| Picture 4. Location Areas |
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| 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 Picture 5). |
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| Picture 5. MSC/VLR Service Areas |
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| The PLMN service area is an area served by one network operator (see Picture 6). |
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| Picture 6. PLMN Network Areas |
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