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

A base station for a mobile communication system, which includes a plurality of cells, wherein

• the plurality of cells includes:
• a device-to-device (D2D) supporting cell that supports D2D communication in which data communication is directly performed between user terminals;
• and
• a D2D non-supporting cell that does not support the D2D communication, the D2D supporting cell and the D2D non-supporting cell conforming with long term evolution (LTE) standards, and
• the base station comprises a control unit configured to:
• include the D2D non-supporting cell;
• transmit a system information block (SIB) from the D2D non-supporting cell not assigning radio resources for the D2D communication, the SIB indicating that the D2D communication to be performed by a user terminal is permitted in the base station;
• receive notification information from the user terminal that transmits the notification information in response to receiving the SIB from the D2D non-supporting cell, wherein the notification information indicates an interest in performing the D2D communication by the user terminal;
• receive a measurement report from the user terminal;
• and
• perform handover of the user terminal from the D2D non-supporting cell to the D2D supporting cell, based on the measurement report, after receiving the notification information from the user terminal.

A processor for a user terminal for a mobile communication system, which includes a plurality of cells, wherein

• the plurality of cells includes:
• a device-to-device (D2D) supporting cell that supports D2D communication in which data communication is directly performed between user terminals;
• and
• a D2D non-supporting cell that does not support the D2D communication, the D2D supporting cell and the D2D non-supporting cell conforming with long term evolution (LTE) standards and supporting LTE cellular communication,
• the processor is configured to perform processes of:
• receiving, from the D2D non-supporting cell of a base station not assigning radio resources for the D2D communication, a system information block (SIB), the SIB indicating that the D2D communication to be performed by the user terminal is permitted in the base station,
• transmitting notification information to the base station in response to receiving the SIB from the D2D non-supporting cell, the notification information indicating an interest in performing the D2D communication by the user terminal;
• in case that the user terminal is in an idle state, transitioning to a connected state to transmit the notification information in response to receiving the SIB from the D2D non-supporting cell;
• transmitting a measurement report to the base station, and
• performing handover of the user terminal from the D2D non-supporting cell to the D2D supporting cell, based on an instruction from the base station.