A method for listen-before-talk (LBT) operation by an eNodeB (eNB) in a wireless communication network is provided. The method includes triggering an LBT request to transmit, to a user equipment (UE), at least one of an uplink (UL) grant or downlink (DL) data for UL transmission over an licensed assisted access (LAA), determining an adaptive contention window (CW) size includes a predetermined minimum value and maximum value for transmitting the DL data and UL grant, performing DL data and UL grant LBT operations in accordance with the adaptive CW size, performing a UL grant LBT operation that includes a higher priority than the DL data regardless of a level of quality of service (QoS) of the DL data to transmit a UL grant message to the UE, and multiplexing the UL grant with the DL data, and transmitting the multiplexed UL grant with the DL data transmission to the UE.