Base station and user terminal

A user terminal which communicates with a base station by carrier aggregation which is applied to a first cell and a second cell, the base station managing the first cell allocated a licensed band requiring a license and the second cell allocated an unlicensed band not requiring a license, the user terminal comprising:

• a controller configured to perform a detection operation of a synchronization signal on all or part of the carrier, based on an instruction for the detection operation of the synchronization signal used for synchronization with the second cell, which is transmitted by at least one carrier among the unlicensed band, the instruction being performed from the base station through the first cell;
• and
• a transmitter configured to transmit a detection report indicating a result of the detection operation to the base station through the first cell.

A base station which manages a first cell and a second cell and communicates with a user terminal by carrier aggregation which is applied to the first cell and the second cell, the first cell being allocated a licensed band requiring a license and a second cell being allocated an unlicensed band not requiring a license, the base station comprising:

• a transmitter configured to transmit at least one carrier of the unlicensed band, a temporal timing in the carrier, and configuration information of the second cell to the user terminal through the first cell, the at least one carrier being determined based on a result of carrier sensing in the second cell.

A user terminal which communicates with a base station by carrier aggregation which is applied to a first cell and a second cell, the base station managing the first cell allocated a licensed band requiring a license and the second cell allocated an unlicensed band not requiring a license, the user terminal comprising:

• a receiver configured to receive at least one carrier of the unlicensed band, which is determined based on a result of carrier sensing in the second cell, a temporal timing in the carrier, and configuration information of the second cell, the result of carrier sensing being received from the base station through the first cell.