Method and apparatus for processing feedback in a wireless communication system

Abstract

A method and apparatus for processing feedback implemented in a wireless transmit/receive unit (WTRU) comprises estimating a channel matrix. The effective channel is calculated and a precoding matrix is selected. Feedback bits are generated and transmitted.

What is claimed is: 
     
         1 . A wireless transmit/receive unit (WTRU) comprising:
 a channel estimator configured to estimate a channel matrix;   a feedback generator configured to:
 calculating a plurality of effective channels for a plurality of candidate precoding matrices, wherein each respective effective channel is determined based on a multiplication of the channel matrix and a respective candidate precoding matrix; 
 determine a metric for each of the plurality of effective channels; and 
 generate feedback bits based on a selected precoding matrix; and 
   a transmitter configured to transmit the feedback bits.   
     
     
         2 . The WTRU of  claim 1 , wherein each metric is determined based on at least one of: a signal to interference noise ratio (SINK) for a respective effective channel, a block error rate (BER) associated with the respective effective channel, or a channel capacity associated with the respective effective channel. 
     
     
         3 . The WTRU of  claim 1 , wherein the feedback generator is further configured to select the precoding matrix from the plurality of candidate precoding matrices based on the determined metrics, wherein the precoding matrix is selected based on being associated with a largest signal to interference ratio (SNIR). 
     
     
         4 . The WTRU of  claim 1 , wherein the feedback generator is further configured to determine the selected precoding matrix based on one of a singular value decomposition (SVD) or an eigen-value decomposition (EVD) of the channel matrix estimate. 
     
     
         5 . The WTRU of  claim 1 , wherein the feedback generator is further configured to quantize the selected precoding matrix using a predetermined codebook. 
     
     
         6 . The WTRU of  claim 1 , wherein the feedback bits comprise a codeword index. 
     
     
         7 . The WTRU of  claim 1 , wherein the transmitter is further configured to send a single bit, the single bit indicating an update that is to be applied to the selected precoding matrix. 
     
     
         8 . The WTRU of  claim 1 , wherein the feedback generator is further configured to construct the plurality of candidate precoding matrices using a discrete Fourier transform (DFT) matrix. 
     
     
         9 . The WTRU of  claim 8 , wherein the feedback generator is further configured such that the DFT matris is multiplied with different phase shifts. 
     
     
         10 . The WTRU of  claim 1 , wherein the feedback generator is further configured to update the selected precoding matrix. 
     
     
         11 . A method performed by a wireless transmit/receive unit (WTRU), the method comprising:
 estimating a channel matrix;   calculating a plurality of effective channels for a plurality of candidate precoding matrices, wherein each respective effective channel is determined based on a multiplication of the channel matrix and a respective candidate precoding matrix;   determining a metric for each of the plurality of effective channels;   generate feedback bits based on a selected precoding matrix; and   transmitting the feedback bits.   
     
     
         12 . The method of  claim 11 , wherein each metric is determined based on at least one of: a signal to interference noise ratio (SINR) for a respective effective channel, a block error rate (BER) associated with the respective effective channel, or a channel capacity associated with the respective effective channel. 
     
     
         13 . The method of  claim 11 , further comprising selecting the precoding matrix from the plurality of candidate precoding matrices based on the determined metrics, wherein the precoding matrix is selected based on being associated with a largest signal to interference ratio (SNIR). 
     
     
         14 . The method of  claim 11 , further comprising determining the selected precoding matrix based on one of a singular value decomposition (SVD) or an eigen-value decomposition (EVD) of the channel matrix estimate. 
     
     
         15 . The method of  claim 11 , further comprising quantizing the selected precoding matrix using a predetermined codebook. 
     
     
         16 . The method of  claim 11 , wherein the feedback bits comprise a codeword index. 
     
     
         17 . The method of  claim 11 , further comprising sending a single bit, the single bit indicating an update that is to be applied to the selected precoding matrix. 
     
     
         18 . The method of  claim 11 , further comprising construct the plurality of candidate precoding matrices using a discrete Fourier transform (DFT) matrix. 
     
     
         19 . The method of  claim 18 , further comprising multiplying the DFT matris with different phase shifts. 
     
     
         20 . The method of  claim 11 , further comprising updating the selected precoding matrix.