The present invention relates to a wireless connection system that supports unlicensed bands. A method for performing backoff, methods for configuring a reservation signal transmission and a transmission opportunity section, and apparatus supporting the same. A method for performing a backoff operation in a wireless connection system supporting unlicensed bands, that is an embodiment of the present invention, may comprises the steps of: configuring a backoff counter N so as to perform a backoff operation; determining whether a current sub-frame is a back-off permitted section; performing a carrier sensing (CS) operation for checking if an unlicensed band is in an idle state if the sub-frame is within a backoff permitted section, for each CS unit; decreasing the backoff counter N by 1 after performing the CS operation; and transmitting a reservation signal or data using a U cell that is formed in an unlicensed band if the backoff counter value expires. In this regard, the CS operation is not performed in sub-frames except for the backoff permitted section and the backoff counter value can be maintained continuously.