In a wireless communication network (10), HARQ acknowledgements, re- transmissions, and related signaling (e.g., channel quality reports) are performed on a Re-transmission Extension Carrier, REC, separate from the primary downlink traffic carrier(s). In various embodiments, the REC may comprise an aggregated wireless communication network channel, which may be cross-channel scheduled or may have its own scheduler. The REC may be Frequency Domain Duplex, FDD, or Time Domain Duplex, TDD, The REC may be dedicated to a main downlink carrier, or may be shared across a plurality of aggregated component carriers. The REC may be transmitted from the same base station (14) as one or more associated main carriers, or from a different base station (14). A shared REC may be operated in cooperative or contention modes. The REC may be implemented in unlicensed spectrum.