Methods are described for a Node B to transmit and for a User Equipment (UE) to receive ACKnowledgement (ACK) information associated with the use of Hybrid Automatic Repeat reQuest (HARQ), also known as HARQ-ACK signaling, in a communication system that includes multiple downlink component carriers or multiple uplink component carriers. An HARQ-ACK signal to a UE is in response to a data packet transmission from the UE and may consist of 2 information bits when the UE has 2 or more transmitter antennas. The HARQ-ACK signal is always located in the same downlink component carrier as the scheduling assignment resulting to the data packet transmission from the UE.