Patent ID: 8891653

Claim:
A Multi-User-Multiple Input Multiple Output (MU-MIMO) transmission method performed by an Access Point (AP) in a Wireless Local Area Network (WLAN) system, the method comprising: transmitting an MU-MIMO initiation message to a destination station (STA) that is a target of a MU-MIMO transmission, the MU-MIMO initiation message including dimension indication information and informing that MU-MIMO transmission will be initiated; receiving a sounding frame as a response to the MU-MIMO initiation message; and performing MU-MIMO transmission on data by beamforming based on channel information obtained from the received sounding frame, wherein the sounding frame comprises precoded and virtualized channel information (H virtual ) between the AP and the destination STA, wherein a dimension of the H virtual is determined based on the dimension indication information and is lower than a dimension of channel information (H) between the AP and the STA, and wherein the dimension indication information includes at least information indicating a difference between the dimension of the H and the dimension of the H virtual , information indicating the dimension of the H virtual or information indicating a number of virtualized receive (Rx) antennas of the destination STA.