Glossary:Location Area Identity (LAI)
The Location Area Identity, abbreviated as LAI, consists of three elements where the first two parts of the code are always the same for a particular Mobile network operator (MNO).
For registration in the network, the Mobility Management Entity (MME) has to inform the MSC of the 2G/3G Location Area Identity in which the mobile device is currently ’theoretically’ located. Since this is only a theoretical value, it has to be computed out of the Tracking Area Identity (TAI), which is the corresponding identifier in LTE. In practice, this creates a dependency between the TAI and the LAI, that is, the location areas that describe a group of base stations in 2G/3G and LTE must be configured in a geographically similar way for the fallback to work later on.