Methods and apparatus are described for a User Equipment (UE) to determine a set of resources available for transmitting an acknowledgement signal in an UpLink (UL) Component Carrier (CC) in response to reception of multiple DownLink (DL) Scheduling Assignments (SAs) transmitted from a base station with each DL SA being associated with a respective DL CC. The UL CC and a first DL CC establish a communication link when the UE is configured for communication over a single UL CC and a single DL CC.