Mobility management#Location area
Location Area (LA) referred to in the mobile (GSM and UMTS), the current location of a mobile phone within range of a network.
Definition and properties
A location area is defined by the Location Area Identity (LAI ), consisting of Mobile Country Code (MCC ), Mobile Network Code (MNC ) and Location Area Code (LAC, a 2-byte identifier ). So: LAI = MCC MNC LAC.
A location area consists of a variable number of radio cells (BTS ) that are connected to the same Mobile services Switching Centre ( MSC ), usually they can be controlled even by the same base station controller ( BSC). In combination with the cell- ID (CID) that uniquely distinguishes the individual radio cells within a location area LAI CID is added to the global unique Global Cell Identifier ( GCID ).
The geographical size of a location area varies depending on the network density (number of BTS), conversation or data volume and individual fixed by the network operator configurations.
Locating in the mobile network
As long as a GSM mobile phone is in " idle mode" is, so no connection is active, the location area is the only location-based information that is known to the network. Switches the phone into a wireless cell belongs to a different location area, so find a venue instead of update, ie the network is informed that it is now in a different location area. If you change to another cell within the same location area, we find no location update instead. So that LA is the smallest addressable unit in a mobile phone can be called by means of paging.
The exact location of the mobile telephone in a GSM cellular network via the CID is the only network with the establishment of a connection, such as a phone call or sending or receiving a short message known. Using a "silent SMS", this operation can also be triggered without the user noticed this. In more recent mobile networks of the third generation, these include UMTS and CDMA2000, the Global Cell ID ( GCID ) can be determined by the network operator without "silent SMS".