A method, an apparatus, and a computer program product for wireless communication are provided in which a single channelization code may be utilized on an uplink channel for providing a HARQ ACK/NACK response corresponding to DC-HSDPA+MIMO. Here, the set of channelization codes includes four codeword groups, each codeword group corresponding to a scenario wherein a node B schedules a single transport block or dual transport blocks on each of the two downlink carriers. Thereby, each of the four codeword groups may be designed to have an improved distance property in comparison to the utilization of a single codeword group for all HARQ ACK/NACK hypotheses, reducing errors.