CHANNEL SOUNDING METHOD IN WIRELESS LOCAL AREA NETWORK SYSTEM AND APPARATUS FOR SUPPORTING THE SAME

A method for a channel sounding in a wireless local area network is provided. The method includes transmitting a null data packet announcement (NDPA) frame, to a plurality of receivers, the NDPA frame requesting a channel statement information feedback and announcing that a null data packet (NDP) frame is to be transmitted; transmitting the NDP frame being a basis of channel estimation for the plurality of receivers; receiving a first feedback frame from a first receiver among the plurality of receivers, transmitting a feedback poll frame to a second receiver; and, receiving a second feedback frame from the second receiver, the second feedback frame including second channel state information estimated by the second receiver. If the first receiver fails to perform the channel estimation, the first feedback frame is a null feedback frame. The null feedback frame is a feedback frame not including channel state information.