IMSI attach

IMSI attach procedure is used to indicate the IMSI as active in the network.

The IMSI attach procedure is used only if the Location Area Identification

stored on a SIM card is the same as the one which is actually broadcasted on

the BCCH of the current serving cell e.g. when MS is switched off and on in

the same area. Otherwise a normal location updating procedure is invoked.

The parameters broadcasted in system information messages on BCCH

indicates whether IMSI attach/detach procedures are allowed in the cell. If the

IMSI attach procedure is not allowed in the serving cell MS performs normal

locating updating instead.