Methods and apparatus are provided for a User Equipment (UE) configured to have multiple cells in a DownLink (DL) of a Time Division Duplex (TDD) communication system so as to determine a power of an acknowledgement signal that the UE transmits in a control channel and to determine a number of acknowledgement information bits that the UE multiplexes with data information bits in a data channel. A transmission power of the control signal is determined based on DL Assignment Index (DAI) Information Elements (IEs) in DL Scheduling Assignments (SAs) that the UE detects through multiple transmission time intervals and through the multiple configured DL cells. The number of acknowledgement information bits in the data channel is determined based on a DAI IE of an UpLink (UL) SA associated with the transmission of the data channel.