Mu-mimo transmission method in wireless lan system

A device for performing sounding in a wireless local area network, the device comprising:

• a transceiver configured to receive and transmit radios signals;
• and
• a processor operatively coupled with the transceiver and configured to:
• control the transceiver to transmit a Multi-User Multiple Input Multiple Output (MU-MIMO) initiation message to each of a plurality of responding stations for initiating sounding feedback, the MU-MIMO initiation message including a plurality of dimension indications, each of the plurality of dimension indications indicating a dimension of a feedback matrix for a corresponding responding station;
• control the transceiver to transmit a Null Data Packet (NDP) to each of the plurality of responding stations after transmitting the MU-MIMO initiation message;
• and
• control the transceiver to receive a sounding frame from each of the plurality of responding stations, each sounding frame including information related to the feedback matrix for the corresponding responding station, the feedback matrix estimated based on the NDP and the dimension of the corresponding feedback matrix.

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

• receiving a Multi-User Multiple Input Multiple Output (MU-MIMO) initiation message from a requesting station for initiating sounding feedback, the MU-MIMO initiation message including a dimension indication that indicates a dimension of a feedback matrix for the responding station;
• receiving a Null Data Packet (NDP) from the requesting station after receiving the MU-MIMO initiation message;
• estimating a feedback matrix based on the NDP and the dimension of the feedback matrix;
• and
• transmitting a sounding frame to the requesting station, the sounding frame including information related to the feedback matrix.

A device for performing sounding in a wireless local area network, the device comprising:

• a transceiver configured to receive and transmit radio signals;
• and
• a processor operatively coupled with the transceiver and configured to:
• control the transceiver to receive a Multi-User Multiple Input Multiple Output (MU-MIMO) initiation message from a requesting station for initiating sounding feedback, the MU-MIMO initiation message including a dimension indication that indicates a dimension of a feedback matrix for the device;
• control the transceiver to receive a Null Data Packet (NDP) from the requesting station after receiving the MU-MIMO initiation message;
• estimate a feedback matrix based on the NDP and the dimension of the feedback matrix;
• and
• control the transceiver to transmit a sounding frame to the requesting station, the sounding frame including information related to the feedback matrix.