Precoder for spatial multiplexing, multiple antenna transmitter

Abstract

A method of spatially precoding data includes determining a transmission rank of a communication channel and selecting a set of one or more precoding filters derived from a single generator matrix based on said transmission rank. The method also includes precoding data for transmission to a remote device using said precoding filters in a predetermined order according to a predetermined precoding sequence. The precoding may include using different ones of said precoding filters during different precoding intervals in a predetermined precoding period of the predetermined precoding sequence. Additionally, precoding data for transmission may involve traversing an Orthogonal Frequency Division Multiplexing (OFDM) resource block in an alternating pattern during said predetermined precoding period.

What is claimed is: 
     
         1 . A method of spatially precoding data in a channel independent way, said method comprising:
 selecting a transmission rank based on a transmission rank of a communication channel ( 16 );   said method characterized by:   selecting a set of one or more precoding filters ( 124 ) derived from a single generator matrix based on said transmission rank; and   precoding data for transmission to a remote device ( 200 ) using said precoding filters in a predetermined order according to a predetermined precoding sequence, thus using different ones of said precoding filters during different precoding intervals in a precoding period of the predetermined precoding sequence.   
     
     
         2 . The method of  claim 1  wherein selecting a set of one or more precoding filters ( 124 ) derived from a single generator matrix based on said transmission rank comprises selecting one or more columns of the generator matrix for each precoding filter, and wherein the number of columns selected for each precoding filter equals the transmission rank. 
     
     
         3 . The method of  claim 2  wherein selecting a set of one or more precoding filters ( 124 ) derived from a single generator matrix based on said transmission rank further comprises selecting a set of precoding filters such that the minimum subspace distance between any two precoding filters in the set of precoding filters is maximized according to a predetermined distance criterion. 
     
     
         4 . The method of  claim 3  wherein the distance criterion comprises at least one of chordal, projection two-norm, or Fubini-Study distance. 
     
     
         5 . The method according to any of  claims 2 - 4 , wherein selecting a set of one or more precoding filters ( 154 ) derived from a single generator matrix based on said transmission rank comprises selecting the set of precoding filters such that each column of the generator matrix is used the same number of times. 
     
     
         6 . The method according to any of  claims 1 - 5 , wherein said generator matrix comprises a QPSK alphabet generator matrix. 
     
     
         7 . A transmitter ( 100 ) for transmitting spatially precoding data in a channel independent way comprising:
 a transmit controller ( 110 ) configured to determine a transmission rank of said communication channel and to select a set of one or more precoding filters ( 124 ) derived from a single generator matrix based on said transmission rank; and   a transmit signal processor ( 120 ) including a precoder ( 124 ) configured to precode said data for transmission using said precoding filters in a predetermined order according to a predetermined precoding sequence, thus using different ones of said precoding filters in different precoding intervals of a predetermined precoding period of the predetermined precoding sequence.   
     
     
         8 . The transmitter ( 100 ) of  claim 7  wherein the transmit signal processor ( 120 ) is further configured to select one or more columns of the generator matrix for each precoding filter, and wherein the number of columns in each precoding filter equals the transmission rank. 
     
     
         9 . The transmitter ( 100 ) of  claim 8  wherein the transmit signal processor ( 120 ) is further configured to select the set of filters that maximizes a minimum subspace distance between any two precoding filters in the set according to a predetermined distance criterion. 
     
     
         10 . The transmitter ( 100 ) of  claim 11  wherein the distance criterion comprises at least one of chordal, projection two-norm, or Fubini-Study distance. 
     
     
         11 . The transmitter ( 100 ) according to any of  claims 9 - 10 , wherein the transmit signal processor ( 120 ) is further configured to select the set of precoding filters such that the selected set of precoding filters uses each column of the generator matrix the same number of times. 
     
     
         12 . A method of receiving spatially precoded data, precoded in a channel independent way, received from a remote device ( 200 ), said method comprising:
 determining a transmission rank applied at a transmitter;   said method characterized by:   selecting a set of one or more combining filters ( 224 ) based on said transmission rank, wherein said combining filters corresponding to a set of precoding filters derived from a single generator matrix; and   combining said spatially precoded data using said combining filters in a predetermined order according to a predetermined combining sequence, thus using different ones of said combining filters during different combining intervals in a combining period of the predetermined combining sequence.   
     
     
         13 . The method of  claim 12  wherein selecting a set of one or more combining filters ( 224 ) derived from a single generator matrix based on said transmission rank comprises selecting one or more columns of the generator matrix for each combining filter, and wherein the number of columns selected for each combining filter equals the transmission rank. 
     
     
         14 . The method according to  claim 13 , wherein selecting a set of one or more combining filters ( 224 ) derived from a single generator matrix based on said transmission rank comprises selecting the set of combining filters such that each column of the generator matrix is used the same number of times. 
     
     
         15 . The method according to any of  claims 12 - 14  applied to an Orthogonal Frequency Division Multiplexing (OFDM) system wherein combining said spatially precoded data comprises traversing an OFDM resource block in an alternating pattern during said predetermined combining period. 
     
     
         16 . A receiver for receiving spatially precoded data, precoded in a channel independent way, said method comprising:
 a receive controller ( 210 ) configured to determine a transmission rank applied at a transmitter ( 100 ) and to select a set of one or more combining filters ( 224 ) derived from a single generator matrix based on said transmission rank; and   a receive signal processor ( 220 ) including a combiner ( 124 ) configured to combine said spatially precoded data using said combining filters in a predetermined order according to the predetermined combining sequence, thus using different ones of said combining filters in different combining intervals in a predetermined combining period of the predetermined combining sequence.   
     
     
         17 . The receiver of  claim 16  wherein said receive signal processor ( 220 ) is further configured to select one or more columns of the generator matrix for each combining filter, and wherein the number of columns selected for each combining filter equals the transmission rank. 
     
     
         18 . The receiver according to any of  claim 17 , wherein said receive signal processor ( 220 ) is further configured to select the set of combining filters ( 224 ) such that each column of the generator matrix is used the same number of times. 
     
     
         19 . The receiver according to any of  claims 16 - 18  applied to an Orthogonal Frequency Division Multiplexing (OFDM) system, wherein the receive signal processor ( 210 ) is configured to combine said precoded data while traversing an OFDM resource block in an alternating pattern during said predetermined combining period.