Radio terminal

A radio terminal configured to perform dual connectivity communication with a master base station and a secondary base station, comprising:

• a transmitter configured to transmit data of one bearer to the master and secondary base stations;
• and
• a controller including two transmission entities corresponding to the master and secondary base stations respectively and a higher entity located at a layer higher than a layer of the two transmission entities, wherein
• the controller is configured to perform a process of transmitting a buffer status report including information indicating a total data amount, to each of the master and secondary base stations,
• the total data amount includes a first data amount accumulated in a buffer of the corresponding transmission entity and a second data amount accumulated in a buffer of the higher entity, and
• the controller is configured to transmit the buffer status report in response to a trigger that the second data amount accumulated in the buffer of the higher entity falls below a predetermined amount.

A radio terminal configured to perform dual connectivity communication with a master base station and a secondary base station, comprising:

• a transmitter configured to transmit data of one bearer to the master and secondary base stations;
• and
• a controller including two transmission entities corresponding to the master and secondary base stations respectively and a higher entity located at a layer higher than a layer of the two transmission entities, wherein
• the controller is configured to perform a process of transmitting a buffer status report including information indicating a total data amount, to each of the master and secondary base stations,
• the total data amount includes a first data amount accumulated in a buffer of the corresponding transmission entity and a second data amount accumulated in a buffer of the higher entity, and
• the controller is configured to notify at least one of the master or secondary base stations of information indicating that there is no data to be transmitted, if there is no data to be transmitted for the bearer.