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

A relay 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:
• establish a PC5 unicast link with a remote UE;
• receive an identifier of a PC5 QoS flow and a first PC5 5G QoS Identifier (PQI) of the PC5 QoS flow from the remote UE for adding the PC5 QoS flow, wherein the first PQI indicates end-to-end QoS requirements of the PC5 QoS flow for traffic transmission between the remote UE and a network;
• derive a second PQI for the PC5 QoS flow and a 5G QoS Identifier (5QI) for a QoS flow according to the first PQI;
• transmit a Protocol Data Unit (PDU) Session Modification Request message to the network for adding the QoS flow, wherein the PDU Session Modification Request message includes an identifier of the QoS flow and the 5QI;
• receive a PDU Session Modification Command message from the network, wherein the PDU Session Modification Command message includes the identifier of the QoS flow and an authorized 5QI for the QoS flow;
• derive a third PQI for the PC5 QoS flow according to the authorized 5QI if the authorized 5QI is different from the 5QI;
• and
• transmit the identifier of the PC5 QoS flow and the second PQI to the remote UE if the authorized 5QI is same as the 5QI and the relay UE transmits the identifier of the PC5 QoS flow and the third PQI to the remote UE if the authorized 5QI is different from the 5QI.