A User Equipment - UE - to support explicit mapping for Hybrid Automatic Retransmission re-Quest - HARQ - for Carrier Aggregation - CA - comprising: a type module configured to detect a type 2 set of DownLink - DL - sub-frames of a radio frame for a virtual HARQ-ACKnowledge - HARQ- ACK - bundling window, wherein the virtual HARQ-ACK bundling window comprises a type 1 set of DL sub-frames transmitted from a first Component Carrier - CC - and the type 2 set of DL sub-frames transmitted from an additional CC, and the type 2 set is bundled with the virtual HARQ-ACK bundling window for the first CC; a selection module configured to select a set of Physical Uplink Control CHannel - PUCCH - resources from multiple sets of PUCCH resources configured by Radio Resource Control - RRC - signaling depending on the Transmit Power Control - TPC - field value in the Downlink Control Information - DCI - format of a corresponding Physical Downlink Control CHannel - PDCCH - wherein each PUCCH resource in the set has a one-to-one relationship associated with a DL frame in the type 2 set; and an index module configured to index a PUCCH resource of the selected set of PUCCH resources to a channel value used in a legacy mapping table for HARQ-ACK multiplexing, wherein the PUCCH resource includes HARQ-ACK feedback for the type 2 set of the DL sub-frames; wherein the selection module selects a set of PUCCH resources with three PUCCH resources from four sets of PUCCH resources known to the UE, each set of PUCCH resources in the four sets of PUCCH resources comprising three PUCCH resources when M p ≥ M s + 2, where M p represents the bundling window size for a virtual HARQ-ACK bundling window for a Primary CC - PCC - and M s represents the bundling window size for a virtual HARQ-ACK bundling window for a Secondary CC - SCC - wherein each of the first CC and the additional CC being one of the PCC or the SCC to the exclusion of the other. a type module configured to detect a type 2 set of DownLink - DL - sub-frames of a radio frame for a virtual HARQ-ACKnowledge - HARQ- ACK - bundling window, wherein the virtual HARQ-ACK bundling window comprises a type 1 set of DL sub-frames transmitted from a first Component Carrier - CC - and the type 2 set of DL sub-frames transmitted from an additional CC, and the type 2 set is bundled with the virtual HARQ-ACK bundling window for the first CC; a selection module configured to select a set of Physical Uplink Control CHannel - PUCCH - resources from multiple sets of PUCCH resources configured by Radio Resource Control - RRC - signaling depending on the Transmit Power Control - TPC - field value in the Downlink Control Information - DCI - format of a corresponding Physical Downlink Control CHannel - PDCCH - wherein each PUCCH resource in the set has a one-to-one relationship associated with a DL frame in the type 2 set; and an index module configured to index a PUCCH resource of the selected set of PUCCH resources to a channel value used in a legacy mapping table for HARQ-ACK multiplexing, wherein the PUCCH resource includes HARQ-ACK feedback for the type 2 set of the DL sub-frames; wherein the selection module selects a set of PUCCH resources with three PUCCH resources from four sets of PUCCH resources known to the UE, each set of PUCCH resources in the four sets of PUCCH resources comprising three PUCCH resources when M p ≥ M s + 2, where M p represents the bundling window size for a virtual HARQ-ACK bundling window for a Primary CC - PCC - and M s represents the bundling window size for a virtual HARQ-ACK bundling window for a Secondary CC - SCC - wherein each of the first CC and the additional CC being one of the PCC or the SCC to the exclusion of the other.