Mobile communication system, user terminal, base station, processor, and communication control method

A user terminal, which performs D2D communication under management of a base station, the D2D communication indicating direct device to device communication, comprising:

• a control unit that transmits a D2D buffer status report indicating an amount of non-transmitted data in the D2D communication to the base station.

A processor, which is provided in a user terminal that performs D2D communication under management of a base station, the D2D communication indicating direct device to device communication, performing:

• a process of transmitting, by the user terminal, a D2D buffer status report indicating an amount of non-transmitted data in the D2D communication to the base station.

A base station, which manages D2D communication that is direct device to device communication by a user terminal, comprising:

• a reception unit that receives a D2D buffer status report indicating an amount of non-transmitted data in the D2D communication from the user terminal.

A processor, which is provided in a base station that manages D2D communication that is direct device to device communication by a user terminal, performing:

• a process of receiving, by the base station, a D2D buffer status report indicating an amount of non-transmitted data in the D2D communication from the user terminal.

A communication control method in a mobile communication system, which includes a user terminal that performs D2D communication under management of a base station, the D2D communication indicating direct device to device communication, comprising:

• a step of transmitting, by the user terminal, a D2D buffer status report indicating an amount of non-transmitted data in the D2D communication to the base station.