The present invention is directed to a wireless communication system. Particularly, the present invention is directed to a method and an apparatus of transmitting ACK/NACK (acknowledgement/negative-ACK) signal at a user equipment in a wireless communication system, the method comprising: receiving a plurality of data blocks from a transmitting end; reserving a plurality of PUCCH (physical uplink control channel) resources for transmission of the ACK/NACK signal; mapping ACK/NACK hypothesis for the plurality of the data blocks to a PUCCH resource group including at least two reserved PUCCH resources; and transmitting at least two modulation symbols corresponding to the ACK/NACK hypothesis to the transmitting end via the PUCCH resource group.
