Method for transmitting a buffer status report in a wireless communication system and device therefor

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

• a radio frequency (RF) module including a transceiver configured to transmit/receive signals to/from a network;
• and
• a processor configured to process the signals,
• wherein the processor is configured to:
• receive, by the UE, a message including information on a number N of lower entities to report an upper entity buffer size of a radio bearer;
• and
• transmit the buffer status report to each of M scheduling nodes,
• wherein the UE is scheduled by M scheduling nodes,
• wherein the radio bearer comprises one upper entity and M lower entities, and the M lower entities are comprised in the radio bearer based on the M scheduling nodes, and
• wherein the buffer status report transmitted to each of the M scheduling nodes comprises a first buffer status report transmitted by N lower entities of the M lower entities and that includes the upper entity buffer size and a corresponding lower entity buffer size, and a second buffer status report that is transmitted by M−N lower entities other than the N lower entities and that includes the corresponding lower entity buffer size, and
• wherein N≤M, and M is larger than two.