A method and apparatus wherein the method comprises maintaining at least first and second Hybrid Automatic Repeat reQuest (HARQ) Process Groups (HPGs), receiving a downlink control information (DCI) message, using at least one of explicit information and implicit information associated with the DCI message to identify one of the HPGs, using at least one of explicit information and implicit information associated with the DCI message to identify a first carrier and generating a transmission of at least one data packet using the identified HPG to an access device via the carrier and a first uplink sub-frame.