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

Abstract

A method and apparatus for calibration and channel state feedback to support transmit beamforming in a multiple-input multiple-output (MIMO) system are disclosed. For radio frequency (RF) calibration, a first station (STA) sends a calibration request to a second STA, and the second STA sends a sounding packet to the first STA. The first STA receives the sounding packet, performs at least one channel measurement and performs calibration based on the channel measurement. For channel state feedback, the first STA sends a channel state feedback request to the second STA. The second STA sends a sounding packet to the first STA. The first STA receives the sounding packet and performs at least one channel measurement with the sounding packet. The first STA then calculates a steering matrix for transmit beamforming based on the channel measurement.

1 . A method for calibration to support transmit beamforming in multiple-input multiple-output (MIMO) wireless communications, the method comprising:
 a first station (STA) sending a calibration request to a second STA;   the second STA sending a sounding packet to the first STA;   the first STA receiving the sounding packet and performing at least one channel measurement to generate a channel estimate;   the first STA generating a correction vector based on the channel estimate; and   the first STA applying the correction vector for calibration.   
     
     
         2 . The method of  claim 1  wherein the calibration request is transmitted as one of a higher layer message and a medium access control (MAC) layer message. 
     
     
         3 . The method of  claim 1  wherein the calibration request is transmitted as a physical layer control message. 
     
     
         4 . The method of  claim 3  wherein the calibration request is included in a shared control part. 
     
     
         5 . The method of  claim 3  wherein the calibration request is included in a dedicated control part. 
     
     
         6 . The method of  claim 1  wherein the sounding packet is a packet dedicated for sounding purposes. 
     
     
         7 . The method of  claim 1  wherein the sounding packet is a data packet. 
     
     
         8 . The method of  claim 1  further comprising:
 the first STA sending a second sounding packet along with a second calibration request to the second STA; 
 the second STA receiving the second sounding packet and performing at least one channel measurement to generate a second channel estimate; and 
 the second STA sending the second channel estimate to the first STA, wherein the first STA generates the first correction vector based on the first channel estimate and the second channel estimate. 
 
     
     
         9 . A method for calibration to support transmit beamforming in multiple-input multiple-output (MIMO) wireless communications for channel state feedback to support transmit beamforming, the method comprising:
 a first STA sending a channel state feedback request to a second STA;   the second STA sending a sounding packet to the first STA;   the first STA receiving the sounding packet and performing a channel measurement with the sounding packet; and   the first STA calculating a steering matrix for transmit beamforming based on the channel measurement.   
     
     
         10 . The method of  claim 9  wherein the channel state feedback request is transmitted as one of a higher layer message and a medium access control (MAC) layer message. 
     
     
         11 . The method of  claim 9  wherein the channel state feedback request is transmitted as a physical layer control message. 
     
     
         12 . The method of  claim 11  wherein the channel state feedback request is included in a shared control part. 
     
     
         13 . The method of  claim 11  wherein the channel state feedback request is included in a dedicated control part. 
     
     
         14 . The method of  claim 9  wherein the sounding packet is a packet dedicated for sounding purposes. 
     
     
         15 . The method of  claim 9  wherein the sounding packet is a data packet. 
     
     
         16 . The method of  claim 9  wherein the channel state feedback request is signaled implicitly. 
     
     
         17 . The method of  claim 9  wherein the second STA sends a channel state feedback response message along with the sounding packet. 
     
     
         18 . A station (STA) configured to obtain channel state feedback to support transmit beamforming in a multiple-input multiple-output (MIMO) wireless communication system, the STA comprising:
 a plurality of antennas;   a channel estimator for generating a channel estimate based on a sounding packet transmitted by a communication peer; and   a processor configured to send a channel state feedback request to a communication peer and calculate a steering matrix for transmit beamforming based on the channel estimate.