24.5013GPPNon-Access-Stratum (NAS) protocol for 5G System (5GS)Release 17Stage 3TS
The eCall inactivity procedure is performed only in 3GPP access and applicable only to a UE configured for eCall only mode as specified in 3GPP TS 31.102 . The procedure shall be started when:
a) the UE is in any 5GMM-REGISTERED substate except substates 5GMM-REGISTERED.PLMN-SEARCH or 5GMM-REGISTERED.NO-CELL-AVAILABLE;
b) the UE is in 5GMM-IDLE mode; and
c) one of the following conditions applies:
1) timer T3444 expires or is found to have already expired and timer T3445 is not running;
2) timer T3445 expires or is found to have already expired and timer T3444 is not running; or
3) timers T3444 and T3445 expire or are found to have already expired.
The UE shall then perform the following actions:
a) stop other running timers (e.g. T3511, T3512);
b) if the UE is currently registered to the network for 5GS services, perform a de-registration procedure;
c) delete any 5G-GUTI, TAI list, last visited registered TAI, list of equivalent PLMNs, and ngKSI; and
d) enter 5GMM-DEREGISTERED.eCALL-INACTIVE state.