A wireless terminal comprising: a wireless transceiver configured to wirelessly communicate with a base station; and at least one processor coupled to the wireless transceiver, wherein the at least one processor is configured, when a plurality of hybrid automatic repeat request, HARQ, ACK/NACK bits corresponding to a plurality of downlink component carriers, DL CCs, configured in the wireless terminal are transmitted on a single physical uplink control channel, PUCCH, on a single uplink component carrier, UL CC, to change, depending on the number of the plurality of DL CCs or the number of the plurality of HARQ ACK/NACK bits, a spreading rate to be applied to time-domain spreading of a plurality of modulation symbols generated from the plurality of HARQ ACK/NACK bits, characterized in that: the at least one processor is configured to selectively perform a plurality of time-domain spreading operations including first and second time-domain spreading operations to change the spreading rate, depending on the number of the plurality of DL CCs or the number of the plurality of HARQ ACK/NACK bits, the first time-domain spreading operation includes performing time-domain spreading on a single data block at a spreading rate of 2n by using a first length-2n spreading code sequence, wherein the single data block is to be mapped to predetermined 2n single-carrier FDMA, SC-FDMA, symbols within a single slot in accordance with a PUCCH format used to transmit the plurality of HARQ ACK/NACK bits, and the second time-domain spreading operation includes performing time-domain spreading on two data blocks at a spreading rate of n by using a second length-n spreading code sequence consisting of n elements of the first spreading code sequence and a third length-n spreading code sequence consisting of the remaining n elements of the first spreading code sequence, wherein the two data blocks are to be mapped to the predetermined 2n SC-FDMA symbols within the single slot in accordance with the PUCCH format. a wireless transceiver configured to wirelessly communicate with a base station; and at least one processor coupled to the wireless transceiver, wherein the at least one processor is configured, when a plurality of hybrid automatic repeat request, HARQ, ACK/NACK bits corresponding to a plurality of downlink component carriers, DL CCs, configured in the wireless terminal are transmitted on a single physical uplink control channel, PUCCH, on a single uplink component carrier, UL CC, to change, depending on the number of the plurality of DL CCs or the number of the plurality of HARQ ACK/NACK bits, a spreading rate to be applied to time-domain spreading of a plurality of modulation symbols generated from the plurality of HARQ ACK/NACK bits, characterized in that: the at least one processor is configured to selectively perform a plurality of time-domain spreading operations including first and second time-domain spreading operations to change the spreading rate, depending on the number of the plurality of DL CCs or the number of the plurality of HARQ ACK/NACK bits, the first time-domain spreading operation includes performing time-domain spreading on a single data block at a spreading rate of 2n by using a first length-2n spreading code sequence, wherein the single data block is to be mapped to predetermined 2n single-carrier FDMA, SC-FDMA, symbols within a single slot in accordance with a PUCCH format used to transmit the plurality of HARQ ACK/NACK bits, and the second time-domain spreading operation includes performing time-domain spreading on two data blocks at a spreading rate of n by using a second length-n spreading code sequence consisting of n elements of the first spreading code sequence and a third length-n spreading code sequence consisting of the remaining n elements of the first spreading code sequence, wherein the two data blocks are to be mapped to the predetermined 2n SC-FDMA symbols within the single slot in accordance with the PUCCH format. the at least one processor is configured to selectively perform a plurality of time-domain spreading operations including first and second time-domain spreading operations to change the spreading rate, depending on the number of the plurality of DL CCs or the number of the plurality of HARQ ACK/NACK bits, the first time-domain spreading operation includes performing time-domain spreading on a single data block at a spreading rate of 2n by using a first length-2n spreading code sequence, wherein the single data block is to be mapped to predetermined 2n single-carrier FDMA, SC-FDMA, symbols within a single slot in accordance with a PUCCH format used to transmit the plurality of HARQ ACK/NACK bits, and the second time-domain spreading operation includes performing time-domain spreading on two data blocks at a spreading rate of n by using a second length-n spreading code sequence consisting of n elements of the first spreading code sequence and a third length-n spreading code sequence consisting of the remaining n elements of the first spreading code sequence, wherein the two data blocks are to be mapped to the predetermined 2n SC-FDMA symbols within the single slot in accordance with the PUCCH format.