1. A method for a spatial reuse operation by a station (STA) in a wireless local area network (WLAN) system, the method comprising:receiving a WLAN frame through a wireless medium;
setting a status of the wireless medium as busy when a received power level of the WLAN frame exceeds a first clear channel assessment (CCA) level;
determining whether the received WLAN frame is from a first basic service set (BSS) to which the STA belong or from a second BSS other than the first BSS; and
accessing the wireless medium for spatial reuse, when the received WLAN frame is from the second BSS, and when the received power level of the WLAN frame is below a second CCA level,
wherein the second CCA level is higher than the first CCA level.