Method for channel sounding in wireless local area network and apparatus for the same

A responding station for channel sounding in a wireless local area network, the responding station comprising:

• a transceiver configured to transmit and receive a radio signal;
• and
• a controller operatively connected to the transceiver and configured to:
• control the transceiver to receive, from a requesting station, a null data packet announcement (NDPA) frame and a null data packet (NDP) frame for the channel sounding, wherein the NDP frame follows the NDPA frame;
• control the transceiver to receive, from the requesting station, a first poll frame;
• in response to the first poll frame, control the transceiver to transmit, to the requesting station, a first feedback data field including beamforming feedback information and signal to noise ratio (SNR) information;
• control the transceiver to receive, from the requesting station, a second poll frame including a segment retransmission bitmap field indicating at least one segment of the first feedback data field;
• and
• in response to the second poll frame, control the transceiver to transmit, to the requesting station, a second feedback data field including the at least one segment of the first feedback data field.