METHOD FOR PRESERVIING ACTIVE STATE OF IDLE MODE SIGNALING REDUCTION (ISR) FUNCTION

An apparatus and method of a User Equipment (UE) for preserving an active state of an Idle Mode Signaling Reduction (ISR) function in a wireless communication network are provided. The method includes sending, by the UE, during an Inter-Radio Access technology (RAT)/System change, an area update request message to a node in the wireless communication network; receiving, by the UE, an area update accept message from the node; and setting, by the UE, a Temporary Identity Used in Next Update (TIN) parameter to a RAT-related Temporary Mobile Subscriber Identity (TMSI) to preserve the ISR function, in response to receiving the area update accept message, when a status of a periodic area update timer is deactivated.