Techniques for signaling acknowledgment status (e.g., ACK, NACK, or DTX) for up to four detected carriers according to 4C-HSDPA. In an exemplary embodiment, an ACK slot of an HS-DPCCH channel utilizes spreading factor 128 to accommodate two 10-symbol codewords per slot. The codewords may be dual-carrier codewords, enabling the acknowledgment status of up to four carriers to be signaled in each slot. A DTX-DTX codeword may be further provided to signal no detection of two carriers assigned to the same codeword. In an alternative exemplary embodiment, a codeword signaling acknowledgment status for two carriers may be repeated twice over a single slot.