Method for priority handling for buffer status reporting in a d2d communication system and device therefor

A user equipment (UE) for transmitting data in a wireless communication system, the UE comprising:

• a radio frequency (RF) module;
• and
• a processor configured to control the RF module, the processor configured to:
• generate a medium access control (MAC) protocol data unit (PDU) containing at least one of a power headroom report (PHR) and a sidelink buffer status report (BSR);
• and
• control the RF unit to transmit the MAC PDU using uplink (UL) resources allocated to the UE,
• wherein the processor is configured to generate the MAC PDU, based on the UL resources and a predefined relative priority of a logical channel prioritization procedure, and
• wherein the predefined relative priority includes a following relative priority in decreasing order:
• MAC control element for PHR;
• and
• MAC control element for sidelink BSR.