A method for Acknowledgement / Negative Acknowledgement, ACK/NACK multiplexing based on Physical Uplink Control Channel, PUCCH, resource selection by a communication apparatus with a first Component Carrier, CC, and a second CC in a wireless communication system, the method comprising: monitoring a first Physical Downlink Control Channel, PDCCH, for scheduling the first CC, and a second PDCCH for scheduling the second CC, wherein a transmission mode of the first CC is configured as a Multiple Input Multiple Output, MIMO, mode and a transmission mode of the second CC is configured as a non-MIMO mode; identifying a Hybrid Automatic Repeat reQuest - Acknowledgement, HARQ-ACK, state related to the first and second CCs; and transmitting a modulation symbol using a PUCCH resource based on the HARQ-ACK state, according to a relation including: HARQ-ACK HARQ-ACK HARQ-ACK n PUCCH, i modulation symbol ACK ACK NACK/DTX n PUCCH, 0 a ACK NACK NACK/DTX n PUCCH, 0 b NACK ACK NACK/DTX n PUCCH, 0 c NACK NACK DTX n PUCCH, 0 d NACK NACK ACK n PUCCH, 2 a DTX DTX ACK n PUCCH, 2 a NACK NACK NACK n PUCCH, 2 d DTX DTX NACK n PUCCH, 2 d where HARQ-ACK and HARQ-ACK indicate Acknowledgement/Negative Acknowledgement/Discontinuous Transmission, ACK/NACK/DTX, responses to data blocks related to the first CC, HARQ-ACK indicates an ACK/NACK/DTX response to a data block related to the second CC, n PUCCH,0 indicates a PUCCH resource determined based on a resource of the first PDCCH when the first CC is a primary CC, n PUCCH,2 indicates a PUCCH resource determined based on a resource of the second PDCCH when the second CC is the primary CC, and "a", "b", "c" and "d" are same as modulation symbols defined for PUCCH format 1b ACK/NACK transmission. monitoring a first Physical Downlink Control Channel, PDCCH, for scheduling the first CC, and a second PDCCH for scheduling the second CC, wherein a transmission mode of the first CC is configured as a Multiple Input Multiple Output, MIMO, mode and a transmission mode of the second CC is configured as a non-MIMO mode; identifying a Hybrid Automatic Repeat reQuest - Acknowledgement, HARQ-ACK, state related to the first and second CCs; and transmitting a modulation symbol using a PUCCH resource based on the HARQ-ACK state, according to a relation including: HARQ-ACK HARQ-ACK HARQ-ACK n PUCCH, i modulation symbol ACK ACK NACK/DTX n PUCCH, 0 a ACK NACK NACK/DTX n PUCCH, 0 b NACK ACK NACK/DTX n PUCCH, 0 c NACK NACK DTX n PUCCH, 0 d NACK NACK ACK n PUCCH, 2 a DTX DTX ACK n PUCCH, 2 a NACK NACK NACK n PUCCH, 2 d DTX DTX NACK n PUCCH, 2 d where HARQ-ACK and HARQ-ACK indicate Acknowledgement/Negative Acknowledgement/Discontinuous Transmission, ACK/NACK/DTX, responses to data blocks related to the first CC, HARQ-ACK indicates an ACK/NACK/DTX response to a data block related to the second CC, n PUCCH,0 indicates a PUCCH resource determined based on a resource of the first PDCCH when the first CC is a primary CC, n PUCCH,2 indicates a PUCCH resource determined based on a resource of the second PDCCH when the second CC is the primary CC, and "a", "b", "c" and "d" are same as modulation symbols defined for PUCCH format 1b ACK/NACK transmission. <EOS>