Differential codebook for a wireless network, MIMO beamforming system using same, and method of reducing a quantization error in a MIMO beamforming system for a wireless network using same

Abstract

A differential codebook for a wireless network includes a plurality of codewords and [e 1 . . . e N s ] G as a center location of the plurality of codewords, where e k represents a column vector comprising a plurality of rows including a k-th row and in which an entry on the k-th row is one and entries on each of the plurality of rows except for the k-th row are zero, where G is any N s by N s unitary matrix including the identity matrix, and where N s , represents a number of spatial streams in the wireless network. At least two of the plurality of codewords are symmetric about the center location.

1 . A differential codebook for a wireless network, the differential codebook comprising:
 a plurality of codewords; and   [e 1  . . . e N     s   ] G as a center location of the plurality of codewords, where e k  represents a column vector comprising a plurality of rows including a k-th row and in which an entry on the k-th row is one and entries on each of the plurality of rows except for the k-th row are zero, G is any N s  by N s  unitary matrix including the identity matrix, and N s , represents a number of spatial streams in the wireless network,   wherein:
 at least two of the plurality of codewords are symmetric about the center location. 
   
     
     
         2 . The differential codebook of  claim 1  wherein:
 one of the plurality of codewords is at the center location.   
     
     
         3 . The differential codebook of  claim 2  wherein:
 the plurality of codewords are equidistant from the center location.   
     
     
         4 . The differential codebook of  claim 3  wherein:
 the plurality of codewords are equidistant from each other.   
     
     
         5 . The differential codebook of  claim 1  wherein:
 no codeword is at the center location.   
     
     
         6 . The differential codebook of  claim 5  wherein:
 the plurality of codewords are equidistant from the center location.   
     
     
         7 . The differential codebook of  claim 6  wherein:
 the plurality of codewords are equidistant from each other.   
     
     
         8 . The differential codebook of  claim 1  wherein:
 at least one entry of each column of the codewords is a real number.   
     
     
         9 . A MIMO beamforming system for a wireless network, the MIMO beamforming system comprising:
 a plurality of differential codebooks, each of which:
 has a codebook center and a plurality of codewords; 
 contains [e 1  . . . e N     s   ] G as a center location of the plurality of codewords, where e k  represents a column vector comprising a plurality of rows including a k-th row and in which an entry on the k-th row is one and entries on each of the plurality of rows except for the k-th row are zero, G is any N s  by N s  unitary matrix including the identity matrix, and N s , represents a number of spatial streams in the wireless network; and 
 contains at least two codewords that are symmetric about the center location and that are each separated from the codebook center by a separation distance, 
 wherein:
 the separation distance for each one of the plurality of differential codebooks is different from the separation distance for each other one of the plurality of differential codebooks. 
 
   
     
     
         10 . The MIMO beamforming system of  claim 9  wherein:
 for each one of the plurality of differential codebooks, one of the codewords is at the codebook center.   
     
     
         11 . The MIMO beamforming system of  claim 10  wherein:
 for each one of the plurality of differential codebooks, the plurality of codewords are equidistant from each other.   
     
     
         12 . The MIMO beamforming system of  claim 9  wherein:
 no codeword is at a center of any of the plurality of differential codebooks.   
     
     
         13 . The MIMO beamforming system of  claim 12  wherein:
 for each one of the plurality of differential codebooks, the plurality of codewords are equidistant from each other.   
     
     
         14 . The MIMO beamforming system of  claim 9  wherein:
 for each one of the plurality of differential codebooks, at least one entry of each column of the codewords is a real number.   
     
     
         15 . A method of reducing a quantization error in a MIMO beamforming system for a wireless network, the method comprising:
 defining a differential codebook comprising:
 a codebook center and a plurality of codewords; 
 [e 1  . . . e N     s   ] G as a center location of the plurality of codewords, where e k  represents a column vector comprising a plurality of rows including a k-th row and in which an entry on the k-th row is one and entries on each of the plurality of rows except for the k-th row are zero, G is any N s  by N s  unitary matrix including the identity matrix, and N s , represents a number of spatial streams in the wireless network; and 
 at least two codewords that are symmetric about the center location and that are each separated from the codebook center by a separation distance; and 
   constraining the separation distance to be less than a predetermined limit.   
     
     
         16 . The method of  claim 15  wherein:
 the predetermined limit is 20 degrees.   
     
     
         17 . The method of  claim 15  wherein:
 at least one entry of each column of the codewords is a real number.   
     
     
         18 . The method of  claim 15  wherein:
 one of the codewords is at the center location of the differential codebook; and   the plurality of codewords are equidistant from each other.   
     
     
         19 . The method of  claim 15  wherein:
 no codeword is at the center location; and   the plurality of codewords are equidistant from each other.