A terminal device comprising: a measurement unit configured to, for a value of a channel quality indicator that is reported in a subframe n, derive an index of the channel quality indicator based on a channel state information reference resource; a transmission unit configured to report channel state information which comprises the channel quality indicator in the subframe n; and a reception unit configured to receive, via a higher layer signaling, a radio resource control, RRC, message indicating first uplink-downlink configuration information and to detect a physical downlink control channel, PDCCH, with second uplink-downlink configuration information, wherein in a time domain, the channel state information reference resource is defined by a subframe n - n CQI_ref, wherein for periodic reporting of the channel state information, the n CQI_ref is a smallest value that is equal to or greater than 4, such that the subframe n - n CQI_ref corresponds to a valid subframe, wherein the valid subframe satisfies criteria which include at least a criterion (i), wherein the criterion (i) stipulates that, in a case where multiple cells with different uplink-downlink configurations are aggregated and the terminal device is not capable of simultaneous reception and transmission in the aggregated multiple cells, the valid subframe in a primary cell is a downlink subframe or a special subframe that is indicated by an uplink-downlink configuration for a radio frame for the primary cell, the multiple cells including at least the primary cell and one or more secondary cells, wherein for one serving cell of the multiple cells, in a case where the reception unit detects the PDCCH with the second uplink-downlink configuration information, the uplink-downlink configuration for the radio frame is given by the second uplink-downlink configuration information, and in a case where the reception unit does not detect the PDCCH with the second uplink-downlink configuration information, the uplink-downlink configuration for the radio frame is given by the first uplink-downlink configuration information. a measurement unit configured to, for a value of a channel quality indicator that is reported in a subframe n, derive an index of the channel quality indicator based on a channel state information reference resource; a transmission unit configured to report channel state information which comprises the channel quality indicator in the subframe n; and a reception unit configured to receive, via a higher layer signaling, a radio resource control, RRC, message indicating first uplink-downlink configuration information and to detect a physical downlink control channel, PDCCH, with second uplink-downlink configuration information, wherein in a time domain, the channel state information reference resource is defined by a subframe n - n CQI_ref, wherein for periodic reporting of the channel state information, the n CQI_ref is a smallest value that is equal to or greater than 4, such that the subframe n - n CQI_ref corresponds to a valid subframe, wherein the valid subframe satisfies criteria which include at least a criterion (i), wherein the criterion (i) stipulates that, in a case where multiple cells with different uplink-downlink configurations are aggregated and the terminal device is not capable of simultaneous reception and transmission in the aggregated multiple cells, the valid subframe in a primary cell is a downlink subframe or a special subframe that is indicated by an uplink-downlink configuration for a radio frame for the primary cell, the multiple cells including at least the primary cell and one or more secondary cells, wherein for one serving cell of the multiple cells, in a case where the reception unit detects the PDCCH with the second uplink-downlink configuration information, the uplink-downlink configuration for the radio frame is given by the second uplink-downlink configuration information, and in a case where the reception unit does not detect the PDCCH with the second uplink-downlink configuration information, the uplink-downlink configuration for the radio frame is given by the first uplink-downlink configuration information.