Method and transmitter for transmitting signal and receiver thereof in wireless communication system

Abstract

A transmitter includes a layer mapper and a precoder. The layer mapper is configured to map 2 codewords to 3 layers to output a mapped set of 3 symbols. A first codeword is mapped into one layer, and a second codeword is mapped into two layers. The precoder is configured to precode the mapped set of 3 symbols using a precoding matrix that distributes the mapped set of 3 symbols across 4 antenna ports so that each codeword is distributed across 2 antenna ports.

What is claimed is: 
     
         1 . A method of transmitting a signal from an apparatus, the apparatus comprising a processor, the method comprising:
 mapping 2 codewords to 3 layers to output a mapped set of 3 symbols, wherein a first codeword is mapped into one of the 3 layers, and a second codeword is mapped into the other two of the 3 layers;   precoding, by the processor, the mapped set of 3 symbols using a precoding matrix that distributes the mapped set of 3 symbols across 4 antenna ports; and   transmitting a signal that comprises the precoded set of symbols,   wherein the precoding matrix is selected from a set of precoding matrices,   wherein each precoding matrix in the set of precoding matrices includes a first submatrix and a second submatrix,   wherein the first submatrices are 4-by-1 submatrices each having 4 rows and 1 column for the first codeword, the first submatrices each having 2 non-zero elements and 2 zero elements,   wherein the second submatrices are 4-by-2 submatrices each having 4 rows and 2 is columns for the second codeword, each column of the second submatrices having 1 non-zero element and 3 zero elements,   wherein the first submatrices are different from each other, and   wherein, in the selected precoding matrix, the 2 non-zero elements of the first submatrix and the 2 non-zero elements of the second submatrix are arranged in different rows from each other.   
     
     
         2 . The method of  claim 1 , wherein the first codeword is distributed across two antenna ports of the 4 antenna ports and the second codeword is distributed across the other two antenna ports of the 4 antenna ports. 
     
     
         3 . The method of  claim 1 , wherein, in the selected precoding matrix, the 2 non-zero elements of the first submatrix and the 2 non-zero elements of the second submatrix have the same absolute value. 
     
     
         4 . A wireless communication apparatus, comprising:
 a layer mapper to map 2 codewords to 3 layers to output a mapped set of 3 symbols, wherein a first codeword is mapped into one of the 3 layers, and a second codeword is mapped into the other two of the 3 layers;   a precoder to precode the mapped set of 3 symbols using a precoding matrix that distributes the mapped set of 3 symbols across 4 antenna ports; and   a transmitter to transmit a signal that comprises the precoded set of symbols,   wherein the precoding matrix is selected from a set of precoding matrices,   wherein each precoding matrix in the set of precoding matrices includes a first submatrix and a second submatrix,   wherein the first submatrices are 4-by-1 submatrices each having 4 rows and 1 column for the first codeword, the first submatrices each having 2 non-zero elements and 2 zero elements,   wherein the second submatrices are 4-by-2 submatrices each having 4 rows and 2 columns for the second codeword, each column of the second submatrices having 1 non-zero is element and 3 zero elements,   wherein the first submatrices are different from each other, and   wherein, in the selected precoding matrix, the 2 non-zero elements of the first submatrix and the 2 non-zero elements of the second submatrix are arranged in different rows from each other.   
     
     
         5 . The wireless communication apparatus of  claim 4 , wherein the first codeword is distributed across two antenna ports of the 4 antenna ports and the second codeword is distributed across the other two antenna ports of the 4 antenna ports. 
     
     
         6 . The wireless communication apparatus of  claim 4 , wherein, in the selected precoding matrix, the 2 non-zero elements of the first submatrix and the 2 non-zero elements of the second submatrix have the same absolute value. 
     
     
         7 . A method of receiving a signal from an apparatus, the apparatus comprising a processor, the method comprising:
 receiving, from a transmitter, a signal that comprises a precoded set of symbols distributed across 4 antenna ports, the precoded set of symbols being precoded using a precoding matrix of the transmitter;   decoding, by the processor, the precoded set of symbols into a set of 3 symbols using an inverse matrix of the precoding matrix; and   demapping the decoded set of 3 symbols in 3 layers to 2 codewords, wherein a first codeword is demapped from one of the 3 layers, and a second codeword is demapped from the other two of the 3 layers,   wherein the precoding matrix is selected from a set of precoding matrices,   wherein each precoding matrix in the set of precoding matrices includes a first submatrix and a second submatrix,   wherein the first submatrices are 4-by-1 submatrices each having 4 rows and 1 column for the first codeword, the first submatrices each having 2 non-zero elements and 2 zero elements,   wherein the second submatrices are 4-by-2 submatrices each having 4 rows and 2 columns for the second codeword, each column of the second submatrices having 1 non-zero element and 3 zero elements,   wherein the first submatrices are different from each other, and   wherein, in the selected precoding matrix, the 2 non-zero elements of the first submatrix and the 2 non-zero elements of the second submatrix are arranged in different rows from each other.   
     
     
         8 . The method of  claim 7 , wherein the first codeword is distributed across two antenna ports of the 4 antenna ports and the second codeword is distributed across the other two antenna ports of the 4 antenna ports. 
     
     
         9 . The method of  claim 7 , wherein, in the selected precoding matrix, the 2 non-zero elements of the first submatrix and the 2 non-zero elements of the second submatrix have the same absolute value. 
     
     
         10 . A wireless communication apparatus, comprising:
 a receiver to receive a signal that comprises a precoded set of symbols distributed across 4 antenna ports, the precoded set of symbols being precoded using a precoding matrix of a transmitter of the signal;   a post-decoder to decode the precoded set of symbols into a set of 3 symbols using an inverse matrix of the precoding matrix; and   a layer-demapper to demap the decoded set of 3 symbols in 3 layers to 2 codewords, wherein a first codeword is demapped from one of the 3 layers, and a second codeword is demapped from the other two of the 3 layers,   wherein the precoding matrix is selected from a set of precoding matrices,   wherein each precoding matrix in the set of precoding matrices includes a first submatrix and a second submatrix,   wherein the first submatrices are 4-by-1 submatrices each having 4 rows and 1 column for the first codeword, the first submatrices each having 2 non-zero elements and 2 zero elements,   wherein the second submatrices are 4-by-2 submatrices each having 4 rows and 2 columns for the second codeword, each column of the second submatrices having 1 non-zero element and 3 zero elements,   wherein the first submatrices are different from each other, and   wherein, in the selected precoding matrix, the 2 non-zero elements of the first submatrix and the 2 non-zero elements of the second submatrix are arranged in different rows from each other.   
     
     
         11 . The wireless communication apparatus of  claim 10 , wherein the first codeword is distributed across two antenna ports of the 4 antenna ports and the second codeword is distributed across the other two antenna ports of the 4 antenna ports. 
     
     
         12 . The wireless communication apparatus of  claim 10 , wherein, in the selected precoding matrix, the 2 non-zero elements of the first submatrix and the 2 non-zero elements of the second submatrix have the same absolute value.