Apparatus and method of uplink beamforming in wireless local area network system

A first device comprising:

• a transceiver;
• and
• processing circuitry configured to,
• transmit a first trigger frame to at least one second device through the transceiver, the first trigger frame requesting at least one sounding null data packet (NDP),
• transmit a feedback frame to the at least one second device through the transceiver, the feedback frame including feedback information generated based on the at least one sounding NDP, and
• transmit a second trigger frame to the at least one second device through the transceiver, the second trigger frame requesting at least one beamformed physical layer protocol data unit (PPDU),
• wherein each of the first trigger frame and the feedback frame comprises a sounding dialog token number field having a sounding sequence number.

A wireless communication method by a second device, the method comprising:

• transmitting a sounding null data packet (NDP) to a first device in response to receiving a first trigger frame requesting the NDP from the first device;
• generating a beam steering matrix based on feedback information included in a feedback frame received from the first device;
• and
• transmitting a beamformed physical layer protocol data unit (PPDU) to the first device based on the beam steering matrix in response to receiving a second trigger frame requesting the beamformed PPDU from the first device,
• wherein
• each of the first trigger frame and the feedback frame comprises a sounding dialog token number field having a sounding sequence number, and
• the generating the beam steering matrix generates the beam steering matrix in response to determining that a first sounding sequence number included in the first trigger frame matches a second sounding sequence number included in the feedback frame.