5.5.2.3.1 Network-initiated de-registration procedure initiation

The network initiates the de-registration procedure by sending a DEREGISTRATION REQUEST message to the UE (see example in figure 5.5.2.3.1.1).

NOTE 1: If the AMF performs a local de-registration, it will inform the UE with a 5GMM messages (e.g. SERVICE REJECT message or REGISTRATION REJECT message) with 5GMM cause #10 "implicitly de-registered" only when the UE initiates a 5GMM procedure.

The network may include a 5GMM cause IE to specify the reason for the DEREGISTRATION REQUEST message. The network shall start timer T3522. The network shall indicate whether re-registration is needed or not in the De-registration type IE. The network shall also indicate via the access type whether the de-registration procedure is:

• for 3GPP access only;
• for non-3GPP access only; or
• for 3GPP access, non-3GPP access or both when the UE is registered in the same PLMN for both accesses.

If the network de-registration is triggered due to network slice-specific authentication and authorization failure or revocation as specified in clause 4.6.2.4, then the network shall set the 5GMM cause value to #62 "No network slices available" in the DEREGISTRATION REQUEST message. In addition, if the UE supports extended rejected NSSAI, the AMF shall include the Extended rejected NSSAI IE in the DEREGISTRATION REQUEST message; otherwise, the AMF shall include the Rejected NSSAI IE in the DEREGISTRATION REQUEST message.

If the Extended rejected NSSAI IE is included in the DEREGISTRATION REQUEST message and mapped S-NSSAI(s) are required as specified in clause 4.6.1, the AMF shall provide mapped S-NSSAI(s) for the rejected NSSAI.

If the UE supports extended rejected NSSAI and the network de-registration is triggered due to mobility management based network slice admission control as specified in clause 4.6.2.5, then the network shall set the 5GMM cause value to #62 "No network slices available" in the DEREGISTRATION REQUEST message. In addition, the network may include a back-off timer value for each S-NSSAI with the rejection cause "S-NSSAI not available due to maximum number of UEs reached" in the Extended rejected NSSAI IE of the DEREGISTRATION REQUEST message.

NOTE 1A: If the network sets the 5GMM cause value to #62 "No network slices available" in the DEREGISTRATION REQUEST message, the network also includes the rejected NSSAI in the DEREGISTRATION REQUEST message and the rejected NSSAI includes all the S-NSSAI(s) which were included in the allowed NSSAI.

If the network de-registration is triggered for a UE supporting CAG due to CAG restrictions, the network shall set the 5GMM cause value to #76 "Not authorized for this CAG or authorized for CAG cells only" and should include the "CAG information list" in the CAG information list IE or the Extended CAG information list IE in the DEREGISTRATION REQUEST message.

NOTE 2: If the UE supports extended CAG information list, the CAG information list can be included either in the CAG information list IE or Extended CAG information list IE.

NOTE 3: It is unexpected for network to send REGISTRATION REJECT message to the UE with 5GMM cause value #76 in non-CAG cell and not indicate "Indication that the UE is only allowed to access 5GS via CAG cells" for the serving PLMN in the Extended CAG information list or the CAG information list.

If the network de-registration is triggered for a UE not supporting CAG due to CAG restrictions, the network shall operate as described in bullet g) of clause 5.5.2.3.5.

If the network de-registration is triggered because the network determines for:

• PLMN via satellite NG-RAN access; or
• PLMN via an NG-RAN access where the PLMN supports selected features that are normally applied in the satellite access and the UE has indicated NonSATLSP supported,

that the UE is in a location where the network is not allowed to operate, see 3GPP TS 23.502 [9], the network shall set the 5GMM cause value in the DEREGISTRATION REQUEST message to #78 "PLMN not allowed to operate at the present UE location".

If the UE which is not registered for disaster roaming service, supports access technology utilization control and the AMF needs to update the access technology utilization control information based on the operator policy, the AMF shall send the DEREGISTRATION REQUEST message over 3GPP access with the 5GMM cause value set to #15 "No suitable cells in tracking area" and include the Access technology utilization control IE. In the Access technology utilization control IE, the AMF shall indicate that the access technology of the NG-RAN cell on which the DEREGISTRATION REQUEST message is sent as restricted.

NOTE 3A: Other restricted access technologies can be indicated in the Access technology utilization control IE, if any.

If the network de-registration is triggered due to:

• an unsuccessful outcome of an ongoing UUAA-MM procedure;
• an UUAA revocation notification received from the UAS-NF for a UE supporting UAS service requesting UAS services; or
• the UE not allowed to use UAS services via 5GS due to a change of the aerial UE subscription information,

then the network shall set the 5GMM cause value in the DEREGISTRATION REQUEST message to #79 "UAS services not allowed".

NOTE 4: If the UE supporting UAS service has requested services other than UAS services, or if there are other ongoing network slice-specific authentication and authorization on pending NSSAIs, it is then an operator policy or configuration decision whether to keep the UE supporting UAS service registered to the network, but that UE supporting UAS services is not allowed to access UAS services via 5GS as specified in 3GPP TS 23.256 [6AB].

If the network de-registration is triggered for a UE supporting MINT due to a disaster condition no longer being applicable in the current location of the UE and the PLMN of the AMF is a forbidden PLMN of the UE, the network shall set the 5GMM cause value to #11 "PLMN not allowed" and may include a disaster return wait range in the Disaster return wait range IE in the DEREGISTRATION REQUEST message.

If the network de-registration is triggered for a UE supporting MINT due to a disaster condition no longer being applicable in the current location of the UE, and the PLMN of the AMF is an allowable PLMN of the UE, the network shall set the 5GMM cause value to #13 "Roaming not allowed in this tracking area" and may include a disaster return wait range in the Disaster return wait range IE in the DEREGISTRATION REQUEST message.

If the network de-registration is triggered because the AMF determines that, by UE subscription and operator's preferences, all of the TAIs received from the satellite NG-RAN are forbidden for roaming or for regional provision of service, the AMF shall include the TAI(s) in:

• the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE; or
• the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for regional provision of service" IE; or
• both;

in the DEREGISTRATION REQUEST message.

If the network de-registration is triggered because the AMF determines that the UE operating as an IAB-node by subscription is not authorized for IAB-node operation, the AMF shall set the 5GMM cause value to #36 "IAB-node operation not authorized" in the DEREGISTRATION REQUEST message.

If the network de-registration is triggered for a UE operating as MBSR due to the UE no longer being allowed to operate as MBSR based on the UE subscription and the local policy, and:

• if the UE is allowed to operate as a UE, then the network shall indicate "re-registration required" in the De-registration type IE of the DEREGISTRATION REQUEST message; or
• if the UE is not allowed to operate as a UE, then the network shall indicate "re-registration not required" in the De-registration type IE of the DEREGISTRATION REQUEST message based on the local policy.

If the network de-registration is triggered due to the UE that was not allowed for MBSR operation becoming allowed to operate as MBSR based on the UE subscription and the local policy, then the network shall indicate "re-registration required" in the De-registration type IE of the DEREGISTRATION REQUEST message.

The AMF shall trigger the SMF to release locally the PDU session(s) over the indicated access(es), if any, for the UE and enter state 5GMM-DEREGISTERED-INITIATED. If a PDU session is associated with one or more multicast MBS sessions, the SMF shall consider the UE as removed from the associated multicast MBS sessions.