A base station (BS) in a wireless communication system is provided. The BS comprises a processor configured to determine frequency units within a frequency range for a bandwidth of an operating carrier, wherein a listen-before-talk (LBT) operation is performed over each of the frequency units; and determine, for each of the frequency units, a set of intended spatial transmit (TX) parameters and a set of spatial receiver (RX) parameters of the LBT operation; and determine a subset of the frequency units for a downlink transmission based on the LBT operation performed over each of the frequency units; and a transceiver operably connected to processor, which is configured to transmit, to a user equipment (UE), downlink channels using the bandwidth corresponding to the determined subset of the frequency units.