Feature Description
The Access and Mobility Management Function (AMF) supports periodic registration to the UE to confirm its availability. The procedure is controlled in the UE by the periodic registration update timer, T3512.
The timer that is run in the AMF is called the Mobile Reachability (MR) timer. It is configurable but is different from T3512. T3512 is the configured in the UE, and the MR timer is set to 4 minutes higher than T3512.
The MR timer in the AMF is restarted every time the UE moves to IDLE state, and stopped when the AMF receives any message from the UE.
When the MR timer expires, the AMF stops paging the UE.
The periodic registration timer (T3512) is supported as per 3GPP TS 24.501 v15.0.0. Currently, in AMF, the T3512 timer expiry supports implicit deregistration.
The AMF sends the T3512 timer value in the Registration Accept or Registration Reject message to the UE and the UE uses this value to send the periodic registration information.