Question: What is the purpose of the guard timer used by the RAN in relation to the periodic RAN Notification Area Update timer value provided to the UE?
Option 1: To synchronize the RAN Notification Area Update timer values between the UE and the RAN.
Option 2: To aid the UE reachability management in the AMF by initiating the AN Release procedure upon expiry.
Option 3: To adjust the periodic RAN Notification Area Update timer value based on the UE's location.
Option 4: To monitor the UE's activity level and adjust the RAN Notification Area accordingly.
Explanation: The guard timer is used by the RAN to aid the UE reachability management in the AMF. When the periodic RAN Notification Area Update guard timer expires, the RAN initiates the AN Release procedure as specified in TS 23.502. This ensures that the AMF is informed about the UE's reachability status and can take necessary actions accordingly.