Location area identity (LAI) is a concept used in mobile telecommunications networks. It is a unique identifier assigned to each location area of a Public Land Mobile Network (PLMN).[1]
This internationally unique identifier is used for location updating of mobile subscribers. It is composed of a three decimal digit mobile country code (MCC), a two to three digit mobile network code (MNC) that identifies a Subscriber Module Public Land Mobile Network (SM PLMN) in that country, and a location area code (LAC) which is a 16 bit number with two special values, thereby allowing 65534 location areas within one GSM PLMN.
The LAI is broadcast regularly through a broadcast control channel (BCCH). A mobile station (e.g. cell phone) recognizes the LAI and stores it in the SIM Card. If the mobile station is moving and notices a change of LAI, it will issue a location update request, thereby informing the mobile provider of its new LAI. This allows the provider to locate the mobile station in case of an incoming call.