Section: 5.5.2 De-registration procedure 5.5.2.1 General
Content: The de-registration procedure is used: a) by the UE to de-register for 5GS services over 3GPP access when the UE is registered over 3GPP access; b) by the UE to de-register for 5GS services over non-3GPP access when the UE is registered over non-3GPP access; c) by the UE to de-register for 5GS services over 3GPP access, non-3GPP access or both when the UE is registered in the same PLMN over both accesses; d) by the network to inform the UE that it is deregistered for 5GS services over 3GPP access when the UE is registered over 3GPP access; e) by the network to inform the UE that it is deregistered for 5GS services over non-3GPP access when the UE is registered over non-3GPP access; f) by the network to inform the UE that it is deregistered for 5GS services over 3GPP access, non-3GPP access or both when the UE is registered in the same PLMN over both accesses; g) by the network to inform the UE to re-register to the network; h) by the network to inform the UE supporting UAS service that it is deregistered for UAS services in 5GS; and i) by the network to inform the UE operating as MBSR that it is deregistered for MBSR in 5GS. The de-registration procedure with appropriate de-registration type shall be invoked by the UE: a) if the UE is switched off; b) as part of the eCall inactivity procedure defined in subclause 5.5.3; and c) as part of USIM removal. The de-registration procedure with appropriate de-registration type shall be invoked by the network: a) if the network informs whether the UE should re-register to the network. The de-registration procedure with appropriate access type shall be invoked by the UE: a) to de-register for 5GS services over 3GPP access when the UE is registered over 3GPP access; b) to de-register for 5GS services over non-3GPP access when the UE is registered over non-3GPP access; c) to de-register for 5GS services over 3GPP access, non-3GPP access or both when the UE is registered in the same PLMN over both accesses; d) to de-register for 5GS services over 3GPP access, if the UE is registered for disaster roaming over 3GPP access and has successfully registered over non-3GPP access on another PLMN; or e) to de-register for 5GS services if an event is triggered in the UE that would make the UE unavailable for a certain period of time and the UE is not able to store its 5GMM and 5GSM context. NOTE 1: If the UE is able to store its 5GMM and 5GSM contexts, the UE triggers the registration procedure for mobility and periodic registration update. The de-registration procedure with appropriate access type shall be invoked by the network: a) if the network needs to inform the UE that it is deregistered over 3GPP access when the UE is registered over 3GPP access; b) if the network needs to inform the UE that it is deregistered over non-3GPP access when the UE is registered over non-3GPP access; or c) if the network needs to inform the UE that it is deregistered over 3GPP access, non-3GPP access or both when the UE is registered in the same PLMN over both accesses. If the de-registration procedure is triggered due to USIM removal, the UE shall indicate "switch off" in the de-registration type IE. If the de-registration procedure is requested by the network for a UE that has an emergency PDU session, the AMF shall not send a DEREGISTRATION REQUEST message to the UE and indicate to the SMF to release all non-emergency PDU sessions as specified in 3GPP TS 23.502[ Procedures for the 5G System (5GS) ]  [9]. If the de-registration procedure for 5GS services is performed, a local release of the PDU sessions over the indicated access(es), if any, for this particular UE is performed. If a PDU session that will be released is associated with one or more multicast MBS sessions, the UE is considered as removed from the associated multicast MBS sessions. The UE is allowed to initiate the de-registration procedure even if the timer T3346 is running. NOTE 2: When the UE has no PDU sessions over non-3GPP access, or the UE moves all the PDU sessions over a non-3GPP access to a 3GPP access, the UE and the AMF need not initiate de-registration over the non-3GPP access. The AMF shall provide the UE with a non-3GPP de-registration timer. When the AMF enters the state 5GMM-DEREGISTERED for 3GPP access, the AMF shall delete the stored UE radio capability information or the UE radio capability ID, if any. When upper layers indicate that emergency services are no longer required, the UE if still registered for emergency services, may perform UE-initiated de-registration procedure followed by a re-registration to regain normal services, if the UE is in or moves to a suitable cell. If the UE is registered for onboarding services in SNPN, after completing the configuration of one or more entries of the "list of subscriber data", the UE should perform UE-initiated de-registration procedure. To prevent the UE registered for onboarding services in SNPN from staying on the ON-SNPN or to prevent a UE whose subscription only allows for configuration of SNPN subscription parameters in PLMN via the user plane, from staying registered indefinitely, when an implementation specific timer expires: - if the AMF considers that the UE is in 5GMM-IDLE, the AMF shall locally de-registers the UE; or - if the UE is in 5GMM-CONNECTED, the AMF shall initiate the network-initiated de-registration procedure (see subclause 5.5.2.3). NOTE 3: The value of the implementation specific timer for onboarding services needs to be large enough to allow a UE to complete the configuration of one or more entries of the "list of subscriber data" taking into consideration that configuration of SNPN subscription parameters in PLMN via the user plane or onboarding services in SNPN involves third party entities outside of the operator's network. NOTE 4: How to determine the completion of the configuration of one or more entries of the "list of subscriber data" is UE implementation specific. If the de-registration procedure is not due to switch off and upper layers request establishing an emergency PDU session before the de-registration procedure has been completed, the UE shall abort the de-registration procedure, perform local de-registration and initiate a registration procedure. If the UE in 5GMM-CONNECTED mode determines to obtain service on a higher priority PLMN due to SOR, then based on the conditions as specified in 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5] annex C, where applicable, the UE shall perform UE-initiated de-registration procedure. If the UE is registered for disaster roaming services, and the UE receives an indication of whether disaster roaming is enabled in the UE set to "Disaster roaming is disabled in the UE" in a UE parameters update transparent container, the UE shall perform UE-initiated de-registration procedure.