Method and apparatus for calibration and channel state feedback to support transmit beamforming in a MIMO system

In a multiple-input multiple-output (MIMO) wireless communication system including a plurality of stations (STAs), a method for calibration to support transmit beamforming, the method comprising:

• a first STA sending a calibration request to a second STA;
• the second STA sending a first sounding packet to the first STA;
• the first STA sending a second sounding packet to the second STA;
• the first STA receiving the first sounding packet and performing at least one channel measurement to generate a first channel estimate estimating a channel matrix {tilde over (H)}BA of a channel from the second STA to the first STA based on the second sounding packet;
• the first STA generating a first correction vector based on the first channel estimate;
• the second STA receiving the second sounding packet and performing at least one channel measurement to generate a second channel estimate estimating a channel matrix {tilde over (H)}AB of a channel from the first STA to the second STA based on the first sounding packet;
• the second STA sending the second channel estimate to the first STA, wherein the first STA generates the second correction vector based on the first channel estimate and the second channel estimate;
• the first STA applying the first correction vector for calibration;
• the first STA sending the second correction vector to the second STA;
• and
• the second STA applying the second correction vector for calibration.