Communication related to multi-access PDU sessions

A method for performing communication related to a Multi Access (MA) Packet Data Unit (PDU) session, the method performed by a User Equipment (UE) and comprising:

• transmitting a Session Initiation Protocol (SIP) registration message including MA PDU session information to a network node of an Internet Protocol Multimedia Subsystem (IMS) network, to perform an IMS service through the MA PDU session,
• wherein the MA PDU session information includes first information indicating that an IMS service is performed through the MA PDU session;
• performing IMS registration procedure for the MA PDU session;
• and
• transmitting information that Packet Switch (PS) Data Off status is activated to the network node of the IMS network,
• wherein the MA PDU session information is used for the network node of the IMS network to generate second information on whether the IMS service for a SIP invite message is included in the PS Data Off exempt service,
• wherein the second information enables a Policy Control Function (PCF) node to update a Policy and Charging Control (PCC) rule,
• wherein the updated PCC rule includes a steering mode of the PCC rule for the IMS service being configured to Active Standby based on active access being non-3GPP access and standby access being not configured, based on that the IMS service is not included in the PS Data Off exempt service, and
• wherein the 3GPP PS Data Off prevents traffic via the 3GPP access except for traffic related to the 3GPP PS Data Off Exempt service, when the 3GPP PS Data Off is activated.

A network node configured to perform communication related to a Multi Access (MA) Packet Data Unit (PDU) session, the network node comprising:

• at least one processor;
• and
• at least one memory operably electrically connectable with the at least one processor and storing instructions that, when executed by the at least one processor, perform operations that include:
• receiving a Session Initiation Protocol (SIP) registration message including MA PDU session information from a User Equipment (UE),
• wherein the MA PDU session information includes first information that the UE performs an Internet Protocol Multimedia Subsystem (IMS) service through the MA PDU session established via both of 3rd generation partnership project (3GPP) access and non-3GPP access;
• transmitting the SIP registration message to an Application Server (AS);
• performing IMS registration procedure for the MA PDU session;
• receiving a SIP invite message related to the IMS service for the MA PDU session from the AS;
• and
• based on the received MA PDU session information, transmitting second information on whether the IMS service for the SIP invite message is included in Packet Data (PS) Data Off exempt service to a Policy Control Function (PCF) node,
• wherein the second information enables the PCF node to update a Policy and Charging Control (PCC) rule,
• wherein the updated PCC rule includes a steering mode of the PCC rule for the IMS service being configured to Active Standby based on active access being non-3GPP access and standby access being not configured, based on that the IMS service is not included in the PS Data Off exempt service, and
• wherein the 3GPP PS Data Off prevents traffic via the 3GPP access except for traffic related to the 3GPP PS Data Off Exempt service, when the 3GPP PS Data Off is activated.