Apparatus and method for managing user plane function in wireless communication system

An access and mobility management function (AMF) in a wireless communication system, the AMF comprising:

• a transceiver;
• and
• at least one processor configured to:
• receive, from a user equipment (UE) with a packet data network (PDN) connection established, a registration request message including first single-network slice selection assistance information (S-NSSAI) associated with the PDN connection,
• determine second S-NSSAI associated with a packet data unit (PDU) session corresponding to the PDN connection, based on the first S-NSSAI, and
• transmit the second S-NSSAI to a session management function (SMF), wherein the second S-NSSAI is used for N4 session modification between the SMF and a user plane function (UPF).

A wireless communication system, the system comprising:

• a session management function (SMF);
• and
• an access and mobility management function (AMF) configured to:
• receive, from a user equipment (UE) with a packet data network (PDN) connection established, a registration request message including first single-network slice selection assistance information (S-NSSAI) associated with the PDN connection,
• determine second S-NSSAI associated with a packet data unit (PDU) session corresponding to the PDN connection, based on the first S-NSSAI, and
• transmit the second S-NSSAI to the SMF, and
• wherein the SMF is configured to transmit the second S-NSSAI to a user plane function (UPF) for N4 session modification.