Methods and apparatuses are described for transmitting acknowledgement information in a communication system. A method includes receiving one or more data TBs in one or more downlink data channels over TTIs; generating acknowledgement information comprising four acknowledgement bits, jointly representing a state of reception results for the plurality of data TBs, if the UE is configured for reception of the downlink data channels from two cells, a number of the TTIs is three or four, and a number of the data TBs is greater than a number of the acknowledgement bits; generating acknowledgement information respectively representing a reception result for each data TB by a corresponding acknowledgement bit, if the UE is configured for reception of the downlink data channels from a single cell or two cells, and a number of the TTIs is one or two; encoding the acknowledgement bits; multiplexing the encoded acknowledgement bits with uplink data; and transmitting the multiplexed acknowledgement bits and the uplink data on an uplink data channel.