Terminal device and transmission method

An integrated circuit comprising circuitry, which, in operation:

• controls transmission, to a terminal, of downlink data in one or more component carriers including a first component carrier and a second component carrier that are aggregated in a carrier aggregation;
• and
• controls reception of a response signal, which is generated based on error detection results of the downlink data and which is transmitted, from the terminal, in a uplink control channel based on a mapping rule, wherein:
• the mapping rule associates the error detection results with one of a plurality of resources used for transmission of the uplink control channel, the plurality of resources including a first resource and a second resource;
• error detection results when the downlink data is transmitted only in the first component carrier are associated with the first resource that is mapped on the first component carrier;
• error detection results when the downlink data is transmitted only in the second component carrier are associated with the second resource that is mapped on the second component carrier;
• the first resource is associated with an index of one or more control channel elements in which downlink control information transmitted in the first component carrier is mapped;
• and
• the second resource is associated with an index of one or more control channel elements in which downlink control information transmitted in the second component carrier is mapped.