Abstract: A channel sounding method in a wireless local area network (WLAN) system is provided. The method, performed by a transmitter, includes transmitting a null data packet announcement (NDPA) frame to a receiver to initiate a channel sounding procedure; transmitting a null data packet (NDP) to the receiver and receiving a feedback frame. The feedback frame includes a plurality of segment frames and a channel feedback report. The channel feedback report is split into a plurality of feedback segments. Each of the plurality of feedback segments is respectively included in each of the plurality of segment frames. The each of the plurality of segment frames includes a first-segment subfield indicating whether the each of the plurality of feedback segment included is a first segment and a remaining-segment subfield indicating the number of remaining feedback segments.

Abstract: In a multi-user multiple input multiple output (MIMO) communication system using the same radio resource, a unitary matrix may be generated to remove interference signals and enhance a transmission capacity. The unitary matrix may be used for precoding. Vectors included in the unitary matrix may have a most similar direction to precoding vectors of target terminal devices and may be orthogonal to each other.

Abstract: A multiple-input multiple-output (MIMO) communication method and apparatus are provided. A MIMO communication apparatus includes a selected beamforming vector determining unit to determine a selected beamforming vector corresponding to a selected user, a performance information generating unit to generate performance information corresponding to where a non-selected beamforming vector is allocated to a non-selected user, and an additional beamforming vector selecting unit to select an additional beamforming vector corresponding to the non-selected user based on the performance information.