A method of transmitting uplink control information at a communication apparatus configured with a plurality of cells including a first cell and a second cell in a wireless communication system is provided. A first set of one or more Physical Downlink Shared Channel (PDSCH) signals is received within M downlink subframes through the first cell, where M≧1. A second set of zero or more PDSCH signals is received within N downlink subframes through the second cell, where N≧1. Acknowledgment information is transmitted on an uplink subframe. The acknowledgment information includes acknowledgment information for the first set and acknowledgment information for the second set. A PDSCH signal without a corresponding Physical Downlink Control Channel (PDCCH) signal is present among the first set.