Upon receiving a first DCI that does not contain explicit indication about a group identifier and/or a new feedback indicator, the UE determines whether group-based acknowledgement feedback is active. If so, the allocates the first DCI to a default group. The UE determines whether to toggle a new feedback indicator value for the default group based on a comparison of field values in the first DCI and those in the default group. The UE then transmits on an uplink channel acknowledgement feedback of the first group to the base station for the downlink data according on the new feedback indicator.