Method and apparatus for reporting channel state information of multi-channel in wireless local area network system

A device configured to report channel state information (CSI) in a wireless local area network system, the device comprising:

• a radio frequency unit configured to transmit and receive radio signals;
• and
• a processor operatively coupled with the radio frequency unit and configured to:
• instruct the radio frequency unit to receive a sounding Physical layer Protocol Data Unit (PPDU) from a requesting station, and
• instruct the radio frequency unit to transmit a CSI report to the requesting station, the CSI report including CSI report information in a form of angles representing a beamforming feedback matrix that is estimated by the responding station based on the sounding PPDU,
• wherein, if the sounding PPDU is received via a plurality of contiguous channels, the beamforming feedback matrix is estimated based on all of the plurality of contiguous channels, and
• wherein, if the sounding PPDU is received via at least one of a plurality of non-contiguous channels, the beamforming feedback matrix is estimated based on only one of the plurality of non-contiguous channels.