A UE is configured such that, when in MICO mode, the UE does not transmit certain messages (e.g., Service Request, periodic registration update message) whenever there is a risk that the certain message will not be routed to the UE's serving AMF. In some embodiments, the network (e.g., serving AMF) indicates to the UE in MICO mode an area (parts of, or the entire PLMN) that is covered by the serving AMF, the Within Serving AMF (WSA) area. While the UE is within the indicated WSA area, the UE in MICO mode may continue to use periodic registration area update or Service Requests (instead of the more extensive mobility registration update procedure) as there is no risk of addressing a new AMF in that area.