Apparatus and method for channel sounding

A first apparatus communicating with a second apparatus in a wireless local area network (WLAN) system, the first apparatus comprising:

• a channel estimator configured to estimate channels corresponding to a plurality of streams of each of a plurality of subcarriers by using a null data packet (NDP) received from the second apparatus;
• a discontinuity detector configured to perform, by stream units, cross correlation between beam steering matrixes corresponding to an adjacent subcarrier of the plurality of subcarriers by using the estimated channels, to determine interpolation target subcarriers of which a representative cross correlation value is less than a threshold value and which are sequentially listed with respect to an index;
• and
• an interpolator configured to perform an interpolation operation to generate pieces of angle information corresponding to the determined interpolation target subcarriers.

An operating method of a first apparatus communicating with a second apparatus in a wireless local area network (WLAN) system including the first apparatus and the second apparatus, the operating method comprising:

• receiving a null data packet (NDP) from the second apparatus;
• estimating channels corresponding to a plurality of streams of each of a plurality of subcarriers by using the NDP;
• performing, by stream units, a cross correlation between beam steering matrixes of adjacent subcarriers of the plurality of subcarriers by using the estimated channels;
• determining interpolation target subcarriers, of which a representative cross correlation value is less than a threshold value and which are sequentially listed with respect to an index, of the plurality of subcarriers;
• performing an interpolation operation to generate pieces of angle information in regard to the determined interpolation target subcarriers;
• and
• transmitting beamforming feedback, including the generated pieces of angle information, to the second apparatus.