User terminal and base station

A method performed at a user terminal used in a mobile communication system, comprising:

• receiving a measurement instruction to instruct measurement in an unlicensed band, from a base station;
• in response to reception of the measurement instruction, searching for a radio signal transmitted in a frequency channel included in the unlicensed band, even when a cell identifier of a measurement target cell is not designated in the measurement instruction;
• measuring reception power of the radio signal detected by the search;
• and
• transmitting a measurement report including an identifier of a transmission source of the detected radio signal and a measurement result of the reception power, to the base station.

A mobile communication system, comprising:

• a base station;
• and
• a user terminal comprising:
• a receiver configured to receive a measurement instruction to instruct measurement in an unlicensed band, from the base station;
• a controller configured to, in response to reception of the measurement instruction, search for a radio signal transmitted in a frequency channel included in the unlicensed band, and measure reception power of the radio signal detected by the search, even when a cell identifier of a measurement target cell is not designated in the measurement instruction;
• and
• a transmitter configured to transmit a measurement report including an identifier of a transmission source of the detected radio signal and a measurement result of the reception power, to the base station.