A method of wireless communication by a wireless device, comprising: selecting a countdown number within a size of a contention window including a plurality of slots before a target subframe, wherein the wireless device determines the target subframe by: measuring energy on subframes at different frequencies, checking each subframe and determining an energy level at different frequencies in each subframe, if the target subframe has not been selected, selecting a target subframe and a frequency in the target subframe that provide a low energy level, if the target subframe has been selected, determining whether the energy level at the target subframe and a frequency for the target subframe is high, if the energy level at the target subframe and at the frequency for the target subframe is high, reselecting another subframe as a new target subframe, wherein the energy level is low if the energy level is less than or equal to an energy threshold and high if the energy level is greater than the energy threshold; determining whether each slot of the plurality of slots is idle or utilized while waiting for the target subframe; counting down the countdown number during each of the determined idle slots; determining a congestion level based on a number of interruptions during the countdown of the countdown number; adjusting the size of the contention window based on the determined congestion level; determining whether the countdown number has reached a threshold number before the target subframe; and performing, when the countdown number is determined to have reached the threshold number, one of: deferring from transmitting until the target subframe, or transmitting a channel usage beacon signal, CUBS, until a next subframe or the target subframe. selecting a countdown number within a size of a contention window including a plurality of slots before a target subframe, wherein the wireless device determines the target subframe by: measuring energy on subframes at different frequencies, checking each subframe and determining an energy level at different frequencies in each subframe, if the target subframe has not been selected, selecting a target subframe and a frequency in the target subframe that provide a low energy level, if the target subframe has been selected, determining whether the energy level at the target subframe and a frequency for the target subframe is high, if the energy level at the target subframe and at the frequency for the target subframe is high, reselecting another subframe as a new target subframe, wherein the energy level is low if the energy level is less than or equal to an energy threshold and high if the energy level is greater than the energy threshold; measuring energy on subframes at different frequencies, checking each subframe and determining an energy level at different frequencies in each subframe, if the target subframe has not been selected, selecting a target subframe and a frequency in the target subframe that provide a low energy level, if the target subframe has been selected, determining whether the energy level at the target subframe and a frequency for the target subframe is high, if the energy level at the target subframe and at the frequency for the target subframe is high, reselecting another subframe as a new target subframe, wherein the energy level is low if the energy level is less than or equal to an energy threshold and high if the energy level is greater than the energy threshold; determining whether each slot of the plurality of slots is idle or utilized while waiting for the target subframe; counting down the countdown number during each of the determined idle slots; determining a congestion level based on a number of interruptions during the countdown of the countdown number; adjusting the size of the contention window based on the determined congestion level; determining whether the countdown number has reached a threshold number before the target subframe; and performing, when the countdown number is determined to have reached the threshold number, one of: deferring from transmitting until the target subframe, or transmitting a channel usage beacon signal, CUBS, until a next subframe or the target subframe. deferring from transmitting until the target subframe, or transmitting a channel usage beacon signal, CUBS, until a next subframe or the target subframe.