Method and apparatus for serving quality of service (QOS) flow in a wireless communication system

A network node, comprising:

• a control circuit;
• a processor installed in the control circuit;
• and
• a memory installed in the control circuit and operatively coupled to the processor;
• wherein the processor is configured to execute a program code stored in the memory to:
• transmit a first message with a DRB (Data Radio Bearer) configuration to a UE (User Equipment) for establishing a default DRB for a PDU (Protocol Data Unit) session, wherein the DRB configuration includes a QFI (QoS Flow Id) configuration set to a value indicating that a QFI field is present in uplink for the default DRB;
• after the transmitting, establish the default DRB with a presence of the QFI field in uplink;
• and
• receive a SDAP (Service Data Adaptation Protocol) PDU with the QFI field via the default DRB from the UE.

A method of a UE (User Equipment), comprising:

• receiving a first message with a DRB (Data Radio Bearer) configuration from a network node for establishing a default DRB for a PDU (Protocol Data Unit) session, wherein the DRB configuration includes a QFI (QoS Flow Id) configuration set to a value indicating that a QFI field is present in uplink for the default DRB;
• wherein after the receiving, the default DRB is established with a presence of the QFI field in uplink;
• and
• transmitting a SDAP (Service Data Adaptation Protocol) PDU with the QFI field via the default DRB to the network node.

A UE (User Equipment), comprising:

• a control circuit;
• a processor installed in the control circuit;
• and
• a memory installed in the control circuit and operatively coupled to the processor;
• wherein the processor is configured to execute a program code stored in the memory to:
• receive a first message with a DRB (Data Radio Bearer) configuration from a network node for establishing a default DRB for a PDU (Protocol Data Unit) session, wherein the DRB configuration includes a QFI (QoS Flow Id) configuration set to a value indicating that a QFI field is present in uplink for the default DRB;
• wherein after the receiving, the default DRB is established with a presence of the QFI field in uplink;
• and
• transmit a SDAP (Service Data Adaptation Protocol) PDU with the QFI field via the default DRB to the network node.