A network node configured to operate in an unlicensed communication spectrum includes a processor and a transceiver, the processor being configured to determine an identifier for subframe for an uplink control channel transmission, the uplink control channel transmission comprising at least HARQ-ACK information, wherein the subframe for the uplink control channel transmission is a function of at least an index of a subframe in a downlink control channel that is configured to transmit the identifier, and the identifier; and wherein the transceiver is configured to transmit the identifier in the downlink control channel.