A base station apparatus configured to communicate with a terminal apparatus (21,22), the base station apparatus comprising: a transmission unit configured to transmit a data signal and information about measurement of receive power in a component carrier of an unlicensed band to the terminal apparatus (21,22), and a reception unit configured to receive a measurement result of the receive power from the terminal apparatus (21,22), wherein the transmission unit is configured to transmit the information about the measurement of the receive power using RRC, the information about the measurement of the receive power includes a time period for measuring the receive power, the transmission unit is configured to transmit the data signal with a component carrier of a licensed band in a first frame format, and to transmit the data signal with the component carrier of the unlicensed band in a second frame format, a radio frame in the first frame format and the second frame format is constituted by ten subframes, the first frame format is Time Division Duplex, TDD, constituted by an uplink and a downlink, the second frame format is a format used in the unlicensed band constituted only by a subframe of the downlink, the data signal is transmitted by Carrier Aggregation in which one primary cell and one or more secondary cells are used, the primary cell is a component carrier of the licensed band, at least one of the secondary cells is a component carrier of the unlicensed band, and the rest of the secondary cells is a component carrier of the licensed band, and the transmission unit is configured to perform, on the component carrier of the unlicensed band, Listen Before Talk before transmitting the data signal, characterized in that the transmission unit is configured to transmit a primary synchronization signal in the subframes #1 and #6 in the radio frame with the component carrier of the licensed band, and to transmit no primary synchronization signal in the subframes #1 and #6 in the radio frame with the component carrier of the unlicensed band. a transmission unit configured to transmit a data signal and information about measurement of receive power in a component carrier of an unlicensed band to the terminal apparatus (21,22), and a reception unit configured to receive a measurement result of the receive power from the terminal apparatus (21,22), wherein the transmission unit is configured to transmit the information about the measurement of the receive power using RRC, the information about the measurement of the receive power includes a time period for measuring the receive power, the transmission unit is configured to transmit the data signal with a component carrier of a licensed band in a first frame format, and to transmit the data signal with the component carrier of the unlicensed band in a second frame format, a radio frame in the first frame format and the second frame format is constituted by ten subframes, the first frame format is Time Division Duplex, TDD, constituted by an uplink and a downlink, the second frame format is a format used in the unlicensed band constituted only by a subframe of the downlink, the data signal is transmitted by Carrier Aggregation in which one primary cell and one or more secondary cells are used, the primary cell is a component carrier of the licensed band, at least one of the secondary cells is a component carrier of the unlicensed band, and the rest of the secondary cells is a component carrier of the licensed band, and the transmission unit is configured to perform, on the component carrier of the unlicensed band, Listen Before Talk before transmitting the data signal, characterized in that the transmission unit is configured to transmit a primary synchronization signal in the subframes #1 and #6 in the radio frame with the component carrier of the licensed band, and to transmit no primary synchronization signal in the subframes #1 and #6 in the radio frame with the component carrier of the unlicensed band.