1. A method of transmitting data by an AP (access point) in a WLAN (Wireless Local Area Network) system, the method comprising:obtaining information related to an STA (Station) located in an OBSS (overlapping basic service set) among STAs associated with the AP;
determining whether to transmit the data via a downlink oriented channel or a normal channel different from the downlink oriented channel or whether to use at least a DCF (distributed coordination function) procedure and an EDCA (enhanced distributed channel access) procedure, the determination according to whether an STA associated with the AP is located in the OBSS; and
transmitting the data according to the determination,
wherein the data is transmitted via the downlink oriented channel without the DCF procedure and the EDCA procedure when no STA is located in the OBSS and when the downlink oriented channel is idle during a PIFS (point coordination function interframe space) duration or a DIFS (distributed coordination function interframe space) duration.