A method of a hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback mechanism includes receiving at a user equipment (UE) one or more first downlink control informations (DCIs) associated with first downlink transmissions belonging to a first HARQ-ACK feedback group. One of the first DCIs requests one or more second HARQ-ACK feedback groups to be acknowledged over a HARQ-ACK transmission opportunity (TxOP). A HARQ-ACK feedback for the first HARQ-ACK feedback group and the one or more second HARQ-ACK feedback groups is transmitted over the HARQ-ACK TxOP.