A method of handling a communication operation for a communication device comprising performing a reception in a first subframe of a time-division duplexing (TDD) carrier from a network; and performing a transmission for responding the reception via a second subframe of a uplink (UL) carrier to the network; wherein the UL carrier is a frequency-division duplexing (FDD) UL carrier, or is another TDD carrier with an UL/downlink (DL) configuration where all subframes are UL subframes.