Method and apparatus for supporting QOS (quality of service) flow to DRB (data radio bearer) remapping for sidelink communication in a wireless communication system

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:
• establish a sidelink communication with a second UE;
• map a PC5 QoS (Quality of Service) flow of the sidelink communication to a first SL-DRB (Sidelink-Data Radio Bearer);
• transmit a PC5 RRC (Radio Resource Control) message to the second UE, wherein the PC5 RRC message indicates the PC5 QoS flow is mapped to a second SL-DRB;
• transmit an end-marker control PDU (Protocol Data Unit) to the second UE after successful transmission of the PC5 RRC message has been confirmed by lower layer(s) or after receiving a PC5 RRC complete message corresponding to the PC5 RRC message from the second UE;
• and
• remap the PC5 QoS flow of the sidelink communication to the second SL-DRB after successful transmission of the PC5 RRC message has been confirmed by lower layer(s) or after receiving the PC5 RRC complete message from the second UE.