Method for estimating phase error in MIMO OFDM communications system

Abstract

A method for estimating a phase error existing in a receiver of a MIMO OFDM communications system is disclosed. The method includes executing Hermitian transpose on channel coefficient matrix of the MIMO OFDM communications system for generating Hermitian-transposed channel coefficient matrix, multiplying received signal matrix of the receiver with the Hermitian-transposed channel coefficient matrix for generating converted signals, summing products of the converted signals and complex conjugates of pilot signals corresponding to the converted signals for generating a sum result, and generating the phase error according to the sum result, the converted signals, and the complex conjugates of the pilot signals. The pilot signals are extracted from the received signal matrix.

1 . A receiver of a Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) communications system, the receiver comprising:
 means for executing Hermitian transpose on a channel coefficient matrix of the MIMO OFDM communications system for generating a Hermitian-transposed channel coefficient matrix;   means for multiplying the Hermitian-transposed channel coefficient matrix with the channel coefficient matrix for generating a product channel coefficient matrix;   means for adding a real constant to each element on diagonal of the product channel coefficient matrix for generating a constant-added product channel coefficient matrix;   means for inversing the constant-added product channel coefficient matrix for generating an inversed constant-added product channel coefficient matrix;   means for multiplying the inversed constant-added product channel coefficient matrix with the Hermitian-transposed channel coefficient matrix for generating a diversity gain matrix; and   means for generating the phase error according to the diversity gain matrix, a received signal matrix, and a pilot signal matrix.   
     
     
         2 . The receiver of  claim 1 , further comprising:
 means for converting radio frequency signals to digital signals; and   means for fast Fourier transforming the digital signals as the received signal matrix.   
     
     
         3 . The receiver of  claim 2 , wherein means for converting the radio frequency signals to digital signals comprises:
 means for down-converting the radio frequency signals to analog signals; and   means for converting the analog signals to the digital signals.   
     
     
         4 . The receiver of  claim 1 , wherein each element in the channel coefficient matrix represents a channel coefficient between one transmitting antenna and one receiving antenna of the MIMO OFDM communications system. 
     
     
         5 . The receiver of  claim 1 , wherein each element in the received signal matrix represents a received signal of one receiving antenna of the MIMO OFDM communications system, and each element in the pilot signal matrix represent a pilot signal contained in a received signal. 
     
     
         6 . The receiver of  claim 1 , wherein a value of the real constant is defined as the following equation: 
       
         
           
             
               
                 Z 
                 ≥ 
                 
                   100 
                   · 
                   
                     Max 
                      
                     
                       ( 
                       
                         
                           
                             ∑ 
                             
                               i 
                               = 
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                               N 
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                            
                           
                             
                                
                               
                                 h 
                                 
                                   i 
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                                   1 
                                 
                               
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                         , 
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               1 
                             
                             
                               N 
                               R 
                             
                           
                            
                           
                             
                                
                               
                                 h 
                                 
                                   i 
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                                
                             
                             2 
                           
                         
                         , 
                         ... 
                         
                             
                         
                         , 
                         
                             
                         
                          
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               1 
                             
                             
                               N 
                               R 
                             
                           
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                                   r 
                                 
                               
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                       ) 
                     
                   
                 
               
               ; 
             
           
         
       
       wherein Z represents the real constant, N R  represents a number of the receiving antennas, N T  represents a number of the transmitting antennas, and h ij  represents a channel coefficient between one transmitting antenna and one receiving antenna of the MIMO OFDM communications system. 
     
     
         7 . A method for estimating a phase error in a receiver of a MIMO OFDM communications system, the method comprising:
 executing Hermitian transpose on a channel coefficient matrix of the MIMO OFDM communications system for generating a Hermitian-transposed channel coefficient matrix;   multiplying the Hermitian-transposed channel coefficient matrix with the channel coefficient matrix for generating a product channel coefficient matrix;   adding a real constant to each element on diagonal of the product channel coefficient matrix for generating a constant-added product channel coefficient matrix;   inversing the constant-added product channel coefficient matrix for generating an inversed constant-added product channel coefficient matrix;   multiplying the inversed constant-added product channel coefficient matrix with the Hermitian-transposed channel coefficient matrix for generating a diversity gain matrix; and   generating the phase error according to the diversity gain matrix, a received signal matrix, and a pilot signal matrix.   
     
     
         8 . The method of  claim 7 , further comprising:
 converting radio frequency signals to digital signals; and   fast Fourier transforming the digital signals as the received signal matrix.   
     
     
         9 . The method of  claim 8 , wherein converting the radio frequency signals to digital signals comprises:
 down-converting the radio frequency signals to analog signals; and   converting the analog signals to the digital signals.   
     
     
         10 . The method of  claim 7 , wherein each element in the channel coefficient matrix represents a channel coefficient between one transmitting antenna and one receiving antenna of the MIMO OFDM communications system. 
     
     
         11 . The method of  claim 7 , wherein each element in the received signal matrix represents a received signal of one receiving antenna of the MIMO OFDM communications system, and each element in the pilot signal matrix represent a pilot signal contained in a received signal. 
     
     
         12 . The method of  claim 7 , wherein a value of the real constant is defined as the following equation: 
       
         
           
             
               
                 Z 
                 ≥ 
                 
                   100 
                   · 
                   
                     Max 
                      
                     
                       ( 
                       
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               1 
                             
                             
                               N 
                               R 
                             
                           
                            
                           
                             
                                
                               
                                 h 
                                 
                                   i 
                                    
                                   1 
                                 
                               
                                
                             
                             2 
                           
                         
                         , 
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               1 
                             
                             
                               N 
                               R 
                             
                           
                            
                           
                             
                                
                               
                                 h 
                                 
                                   i 
                                    
                                   
                                       
                                   
                                    
                                   2 
                                 
                               
                                
                             
                             2 
                           
                         
                         , 
                         ... 
                         
                             
                         
                         , 
                         
                           
                             
                               
                                   
                               
                               ∑ 
                             
                             
                               i 
                               = 
                               1 
                             
                             
                               N 
                               R 
                             
                           
                            
                           
                             
                                
                               
                                 h 
                                 
                                   iN 
                                   T 
                                 
                               
                                
                             
                             2 
                           
                         
                       
                       ) 
                     
                   
                 
               
               ; 
             
           
         
       
       wherein Z represents the real constant, N R  represents a number of the receiving antennas, N T  represents a number of the transmitting antennas, and h ij  represents a channel coefficient between one transmitting antenna and one receiving antenna of the MIMO OFDM communications system.