In the wireless LAN system, the station STA receives a frame and updates a corresponding Inter-BSS Network Allocation Vector (NAV) or Intra-BSS NAV according to whether the frame is an Inter-BSS (Basic Service Set) frame or an Intra-BSS frame. If the received frame cannot be distinguished from the Inter-BSS frame or the Intra-BSS frame, it updates the Inter-NAV, and after receiving the frame that cannot be distinguished from the Inter-BSS frame or the Intra-BSS frame, it receives the CF-End frame, and then the corresponding NAV is reset.