Method for triggering a buffer status reporting in dual connectivity and a device therefor

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

• receiving, by a Medium Access Control (MAC) entity from an upper entity, a first indication indicating that a first amount of uplink data available for transmission in the upper entity is ‘0’, if the first amount of uplink data available for transmission in the upper entity is less than a threshold value;
• receiving, by the MAC entity from the upper entity, a second indication indicating a second amount of uplink data available for transmission in the upper entity, if the second amount of uplink data available for transmission in the upper entity is larger than or equal to the threshold value;
• and
• triggering, by the MAC entity, a buffer status reporting (BSR) when the second indication is received.

A User Equipment (UE) operating in a wireless communication system, the UE comprising:

• a Radio Frequency (RF) module;
• and
• a processor operably coupled with the RF module and configured to:
• configure a threshold value for a Packet Data Convergence Protocol (PDCP) entity associated with a first MAC entity for a first eNB and a second MAC entity for a second eNB for a radio bearer;
• check whether an amount of uplink data available for transmission in the PDCP entity is less than the threshold value;
• and
• indicate that the amount of uplink data available for transmission in the PDCP entity is ‘0’ to the second MAC entity, if the amount of uplink data available for transmission in the PDCP entity is less than the threshold value.

A User Equipment (UE) operating in a wireless communication system, the UE comprising:

• a Radio Frequency (RF) module;
• and
• a processor operably coupled with the RF module and configured to:
• receive, from an upper entity, a first indication indicating that a first amount of uplink data available for transmission in the upper entity is ‘0’, if the first amount of uplink data available for transmission in the upper entity is less than a threshold value;
• receive, from the upper entity, a second indication indicating a second amount of uplink data available for transmission in the upper entity, if the second amount of uplink data available for transmission in the upper entity is larger than or equal to the threshold value;
• and
• trigger a buffer status reporting(BSR) when the second indication is received.