De-registration method in wireless communication system and apparatus therefor

1. A method of performing, by an access and mobility management function (AMF), an AMF-initiated deregistration procedure in a wireless communication system, the method comprising:

receiving, from a unified data management (UDM), a first message for requesting a removal of a subscriber's registration management (RM) context and at least one protocol data unit (PDU) of a user equipment (UE), the first message including (i) a reason of the removal and (ii) an access type,

wherein the access type is information for a target access of the AMF-initiated deregistration procedure;

performing the AMF-initiated deregistration procedure for all accesses corresponding to the access type, based on the reason of the removal being set to a subscription withdrawn of the UE;

transmitting, to the UE, a second message for requesting a deregistration, the second message including the access type,

wherein the access type is related to the AMF-initiated deregistration procedure, the AMF-initiated deregistration procedure being applicable to both a 3GPP access and non-3GPP access; and

transmitting, to a radio access network (RAN), a third message for releasing an N2 signaling connection, the third message including information for a cause set to the deregistration,

wherein the third message is transmitted based on (i) the access type and (ii) the N2 signaling connection being present between the UE and the RAN,

wherein the AMF-initiated deregistration procedure is explicit, and

wherein based on the AMF-initiated deregistration procedure being explicit, the procedure is performed by an operation and maintenance (O&M) intervention.

2. The method of claim 1 , further comprising:

paging the UE based on the second message for requesting the deregistration being transmitted through the 3GPP access and the UE being in a connection management (CM)-IDLE state in the 3GPP access.

3. The method of claim 1 , wherein the first message further includes a subscriber permanent identifier (SUPI) of the UE.

4. The method of claim 3 , further comprising:

transmitting, to the UDM, a first deregistration response message in response to the first message.

5. The method of claim 4 , further comprising:

requesting a session management function (SMF) to release an established PDU session based on the UE having a protocol data unit (PDU) session established through the target access.

6. The method of claim 5 , wherein the requesting to release the established PDU session includes transmitting a fourth message for requesting the release of the established PDU session to the SMF.

7. The method of claim 6 , wherein the fourth message includes the SUPI and an identifier of the PDU session to be released.

8. The method of claim 7 , wherein the SMF is a network entity that releases an Internet protocol (IP) address or a prefix allocated to the PDU session to be released and that releases user plane resources corresponding to the PDU session to be released.

9. The method of claim 7 , wherein:

the SMF is a network entity that transmits an N4 session release request message for requesting the release of an N4 session to a user plane function (UPF), and

the UPF is a network entity that releases all tunnel resources and contexts associated with the N4 session.

10. An access and mobility management function (AMF) performing an AMF-initiated deregistration procedure in a wireless communication system, the AMF comprising:

a transceiver;

at least one processor; and

at least one computer memory operably connectable to the at least one processor and storing instructions that, when executed by the at least one processor, perform operations comprising:

receiving, via the transceiver from a unified data management (UDM), a first message for requesting a removal of a subscriber's registration management (RM) context and at least one protocol data unit (PDU) of a user equipment (UE), the first message including (i) a reason of the removal and (ii) an access type,

wherein the access type is information for a target access of the AMF-initiated deregistration procedure,

performing the AMF-initiated deregistration procedure for all accesses corresponding to the access type, based on the reason of the removal being set to a subscription withdrawn of the UE,

transmitting, via the transceiver to the UE, a second message for requesting a deregistration, the second message including the access type,

wherein the access type indicates the AMF-initiated deregistration procedure is applicable to both a 3GPP access and non-3GPP access; and

transmitting, via the transceiver to a radio access network (RAN), a third message for releasing an N2 signaling connection, the third message including information for cause set to the deregistration,

wherein the third message is transmitted based on (i) the access type and (ii) the N2 signaling connection being present between the UE and the RAN,

wherein the AMF-initiated deregistration procedure is either explicit, and

wherein based on the AMF-initiated deregistration procedure being explicit, the procedure is performed by an orientation and mobility (O&M) intervention.