A base station apparatus for communicating with a terminal apparatus, the base station apparatus comprising: a transmission unit configured to transmit a downlink signal to the terminal apparatus by performing carrier aggregation using one primary cell and one or a plurality of secondary cells, and a reception unit configured to perform carrier sense, wherein the primary cell is a component carrier of a licensed band, and at least one secondary cell is a component carrier of an unlicensed band, a frame of the component carrier of the licensed band includes a transmission period of the downlink signal, the transmission period during which the downlink signal of the licensed band is transmitted includes a plurality of continuous subframes, a frame of the component carrier of the unlicensed band includes a transmission period of the downlink signal and a carrier sensing period, said carrier sensing period being included in a null period, said base station being characterized in that: the component carrier of the unlicensed band includes a plurality of frame structures, wherein priorities are configured by said base station for the plurality of frame structures, the transmission period during which the downlink signal of the unlicensed band is transmitted includes a plurality of continuous subframes, the number of the plurality of continuous subframes in the unlicensed band is equal to or less than the number of the plurality of continuous subframes in the licensed band, at least one subframe of the plurality of subframes in the unlicensed band includes the transmission period and the sensing period, the reception unit is configured to perform carrier sense during at least a part of the sensing period, and the base station is further configured to transmit information to said terminal apparatus indicating said configured priorities of the plurality of frame structures. a transmission unit configured to transmit a downlink signal to the terminal apparatus by performing carrier aggregation using one primary cell and one or a plurality of secondary cells, and a reception unit configured to perform carrier sense, wherein the primary cell is a component carrier of a licensed band, and at least one secondary cell is a component carrier of an unlicensed band, a frame of the component carrier of the licensed band includes a transmission period of the downlink signal, the transmission period during which the downlink signal of the licensed band is transmitted includes a plurality of continuous subframes, a frame of the component carrier of the unlicensed band includes a transmission period of the downlink signal and a carrier sensing period, said carrier sensing period being included in a null period, said base station being characterized in that: the component carrier of the unlicensed band includes a plurality of frame structures, wherein priorities are configured by said base station for the plurality of frame structures, the transmission period during which the downlink signal of the unlicensed band is transmitted includes a plurality of continuous subframes, the number of the plurality of continuous subframes in the unlicensed band is equal to or less than the number of the plurality of continuous subframes in the licensed band, at least one subframe of the plurality of subframes in the unlicensed band includes the transmission period and the sensing period, the reception unit is configured to perform carrier sense during at least a part of the sensing period, and the base station is further configured to transmit information to said terminal apparatus indicating said configured priorities of the plurality of frame structures. the component carrier of the unlicensed band includes a plurality of frame structures, wherein priorities are configured by said base station for the plurality of frame structures, the transmission period during which the downlink signal of the unlicensed band is transmitted includes a plurality of continuous subframes, the number of the plurality of continuous subframes in the unlicensed band is equal to or less than the number of the plurality of continuous subframes in the licensed band, at least one subframe of the plurality of subframes in the unlicensed band includes the transmission period and the sensing period, the reception unit is configured to perform carrier sense during at least a part of the sensing period, and the base station is further configured to transmit information to said terminal apparatus indicating said configured priorities of the plurality of frame structures.