Abstract:
A method for transmission is provided to generate a plurality of reference signals for a plurality of antenna ports, with each reference signal corresponding to an antenna port; to map the plurality of reference signals to a plurality of physical antennas in accordance with a selected antenna port mapping scheme, with each reference signal corresponding to a physical antenna, and the plurality of physical antennas being aligned sequentially with equal spacing between two immediately adjacent physical antennas; to demultiplex information to be transmitted into a plurality of stream blocks; to insert a respective cyclic redundancy check to each of the stream blocks; to encode each of the stream blocks according to a corresponding coding scheme; to modulate each of the stream blocks according to a corresponding modulation scheme; to demultiplex the stream blocks to generate a plurality of sets of symbols, with each stream block being demultiplexed into a set of symbols; to map the plurality of sets of symbols into the plurality of antenna ports in accordance with a selected symbol mapping scheme; and to transmit the plurality of sets of symbols via the corresponding antenna ports, with each set of symbols being transmitted via a subset of antenna ports, with, within each subset of antenna ports, the distance between the physical antennas of the corresponding antenna ports being larger than the average distance among the plurality of physical antennas.

Description:
CLAIM OF PRIORITY 
       [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from a provisional application earlier filed in the U.S. Patent &amp; Trademark Office on 4 May 2007 and there duly assigned Ser. No. 60/924,222. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method for transmitting data in a communication system, and more specifically, a process and circuits for transmitting information by mapping antennas in a communication system. 
         [0004]    2. Description of the Related Art 
         [0005]    A typical cellular radio system includes a number of fixed base stations and a number of mobile stations. Each base station covers an geographical area, which is defined as a cell. 
         [0006]    Typically, a non-line-of-sight (NLOS) radio propagation path exists between a base station and a mobile station due to natural and man-made objects disposed between the base station and the mobile station. As a consequence, radio waves propagate while experiencing reflections, diffractions and scattering. The radio wave which arrives at the antenna of the mobile station in a downlink direction, or at the antenna of the base station in an uplink direction, experiences constructive and destructive additions because of different phases of individual waves generated due to the reflections, diffractions, scattering and out-of-phase recombination. This is due to the fact that, at high carrier frequencies typically used in a contemporary cellular wireless communication, small changes in differential propagation delays introduces large changes in the phases of the individual waves. If the mobile station is moving or there are changes in the scattering environment, then the spatial variations in the amplitude and phase of the composite received signal will manifest themselves as the time variations known as Rayleigh fading or fast fading attributable to multipath reception. The time-varying nature of the wireless channel require very high signal-to-noise ratio (SNR) in order to provide desired bit error or packet error reliability. 
         [0007]    The scheme of diversity is widely used to combat the effect of fast fading by providing a receiver with multiple faded replicas of the same information-bearing signal. 
         [0008]    The schemes of diversity in general fall into the following categories: space, angle, polarization, field, frequency, time and multipath diversity. Space diversity can be achieved by using multiple transmit or receive antennas. The spatial separation between the multiple antennas is chosen so that the diversity branches, i.e., the signals transmitted from the multiple antennas, experience fading with little or no correlation. Transmit diversity, which is one type of space diversity, uses multiple transmission antennas to provide the receiver with multiple uncorrelated replicas of the same signal. Transmission diversity schemes can further be divided into open loop transmit diversity and closed-loop transmission diversity schemes. In the open loop transmit diversity approach no feedback is required from the receiver. In one type of closed loop transmit diversity, a receiver knows an arrangement of transmission antennas, computes a phase and amplitude adjustment that should be applied at the transmitter antennas in order to maximize a power of the signal received at the receiver. In another arrangement of closed loop transmit diversity referred to as selection transmit diversity (STD), the receiver provides feedback information to the transmitter regarding which antenna(s) to be used for transmission. 
         [0009]    An example of open-loop transmission diversity scheme is the Alamouti 2×1 space-time diversity scheme. The Alamouti 2×1 space-time diversity scheme contemplates transmitting a Alamouti 2×2 block code using two transmission antennas using either two time slots (i.e., Space Time Block Code (STBC) transmit diversity) or two frequency subcarriers (i.e., Space Frequency Block Code (SFBC) transmit diversity). 
         [0010]    One limitation of Alamouti 2×1 space-time diversity scheme is that this scheme can only be applied to two transmission antennas. In order to transmit data using four transmission antennas, a Frequency Switched Transmit Diversity (FSTD) or a Time Switched Transmit Diversity (TSTD) is combined with block codes. 
         [0011]    The problem with combined SFBC+FSTD scheme and STBC+TSTD schemes is that only a fraction of the total transmission antennas and hence power amplifier capability is used for transmission in a given frequency or time resource. This is indicated by ‘0’ elements in the SFBC+FSTD and STBC+TSTD matrix given above. When the transmit power on the non-zero elements in the matrix is increased, bursty interference is generated to the neighboring cells degrading system performance. Generally, bursty interference manifests itself when certain phases of a frequency hopping pattern incur more interference than other phases. 
         [0012]    In the Third Generation Partnership Project Long Term Evolution (3GPP LTE) system, the downlink reference signals mapping for four transmission antennas determines that a transmission density on the third antenna port and the fourth antenna port is half of the density on the first antenna port and the second antenna port. This leads to weaker channel estimates on the third and the fourth antenna ports. 
         [0013]    Moreover, the antenna correlation depends upon, among other factors, angular spread and antennas spacing. In general, for a given angle spread, the larger the antenna spacing the smaller the correlation among the antennas. In a four transmission antenna 3GPP LTE system, the four antennas are usually aligned sequentially with equal spacing between two immediate antennas. Therefore, the correlation between the first antenna and the second antenna is larger than the correlation between the first antenna and the third antenna. Similarly, the correlation between the third antenna and the fourth antenna is larger than the correlation between the second antenna and the fourth antenna. Because smaller correlation among antennas means higher achievable diversity, this kind of antenna arrangement may result in degraded transmit diversity performance for the symbols transmitted via the first and the second antennas, and for the symbols transmitted via the third and the fourth antennas. 
       SUMMARY OF THE INVENTION 
       [0014]    It is therefore an object of the present invention to provide an improve method and an improved apparatus for transmitting information. 
         [0015]    It is another object to provide an improve method and an improved apparatus for transmitting information in order to improve the transmission performance and increase the system throughput. 
         [0016]    It is another object to provide an improve method and an improved apparatus for transmitting information in order to improve the transmission diversity performance. 
         [0017]    According to on aspect of the present invention, a method and an apparatus may be provided to include demultiplexing information to be transmitted into a plurality of stream blocks; inserting a respective cyclic redundancy check to each of the stream blocks; encoding each of the stream blocks according to a corresponding coding scheme; modulating each of the stream blocks according to a corresponding modulation scheme; demultiplexing the stream blocks to generate a plurality of sets of symbols, with each stream block being demultiplexed into a set of symbols; and transmitting the plurality of symbols via a plurality of antenna ports, with each set of symbols being transmitted via a subset of the plurality of antenna ports, and the antenna ports having weaker channel estimates being equally distributed among the plurality of subsets of antenna ports. 
         [0018]    When four symbols are transmitted via four antenna ports according to a transmission matrix where a first symbol and a second symbol are generated from a first stream block, a third symbol and a fourth symbol are generated from a second stream block, and the first and second antenna ports have higher channel estimates than the third and the fourth antenna ports, the transmission matrix may be expressed as: 
         [0000]    
       
         
           
             
               [ 
               
                 
                   
                     
                       T 
                       11 
                     
                   
                   
                     
                       T 
                       12 
                     
                   
                   
                     
                       T 
                       13 
                     
                   
                   
                     
                       T 
                       14 
                     
                   
                 
                 
                   
                     
                       T 
                       21 
                     
                   
                   
                     
                       T 
                       22 
                     
                   
                   
                     
                       T 
                       23 
                     
                   
                   
                     
                       T 
                       24 
                     
                   
                 
                 
                   
                     
                       T 
                       31 
                     
                   
                   
                     
                       T 
                       32 
                     
                   
                   
                     
                       T 
                       33 
                     
                   
                   
                     
                       T 
                       34 
                     
                   
                 
                 
                   
                     
                       T 
                       41 
                     
                   
                   
                     
                       T 
                       42 
                     
                   
                   
                     
                       T 
                       43 
                     
                   
                   
                     
                       T 
                       44 
                     
                   
                 
               
               ] 
             
             = 
             
               [ 
               
                 
                   
                     
                       S 
                       1 
                     
                   
                   
                     
                       - 
                       
                         S 
                         2 
                         * 
                       
                     
                   
                   
                     0 
                   
                   
                     0 
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     
                       S 
                       3 
                     
                   
                   
                     
                       - 
                       
                         S 
                         4 
                         * 
                       
                     
                   
                 
                 
                   
                     
                       S 
                       2 
                     
                   
                   
                     
                       S 
                       1 
                       * 
                     
                   
                   
                     0 
                   
                   
                     0 
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     
                       S 
                       4 
                     
                   
                   
                     
                       S 
                       3 
                       * 
                     
                   
                 
               
               ] 
             
           
         
       
     
         [0000]    where T ij  represents symbol transmitted on the ith antenna port and the jth subcarrier or jth time slot, S 1 , S 2 , S 3 , and S 4  represent the first through the fourth symbols respectively. 
         [0019]    According to another aspect of the present invention, a method and an apparatus may be provided to include generating four reference signals for four antenna ports, with each reference signal corresponding to an antenna port; mapping the four antenna ports to four physical antennas in accordance with a selected antenna port mapping scheme, with each antenna port corresponding to a physical antenna, with the four physical antennas being aligned sequentially with equal spacing between two immediately adjacent physical antennas, and the channel estimates of the third and the fourth antenna ports are weaker than the channel estimates of the first and the second antenna ports; demultiplexing information to be transmitted into two stream blocks including a first stream block and a second stream block; inserting a respective cyclic redundancy check to each of the two stream blocks; encoding each of the two stream blocks according to a corresponding coding scheme; modulating each of the two stream blocks according to a corresponding modulation scheme; demultiplexing a first stream block into a first symbol and a second symbol and demultiplexing a second stream block into a third symbol and a fourth symbol; and transmitting the four symbols via the four antenna ports according to a selected transmission matrix. 
         [0020]    The selected antenna port mapping scheme may be established such that a first antenna port is mapped to a first physical antenna, a second antenna port is mapped to a third physical antenna, a third antenna port is mapped to a second physical antenna, and a fourth antenna port is mapped to a fourth physical antenna. In this case, the transmission matrix may be established as: 
         [0000]    
       
         
           
             
               [ 
               
                 
                   
                     
                       T 
                       11 
                     
                   
                   
                     
                       T 
                       12 
                     
                   
                   
                     
                       T 
                       13 
                     
                   
                   
                     
                       T 
                       14 
                     
                   
                 
                 
                   
                     
                       T 
                       21 
                     
                   
                   
                     
                       T 
                       22 
                     
                   
                   
                     
                       T 
                       23 
                     
                   
                   
                     
                       T 
                       24 
                     
                   
                 
                 
                   
                     
                       T 
                       31 
                     
                   
                   
                     
                       T 
                       32 
                     
                   
                   
                     
                       T 
                       33 
                     
                   
                   
                     
                       T 
                       34 
                     
                   
                 
                 
                   
                     
                       T 
                       41 
                     
                   
                   
                     
                       T 
                       42 
                     
                   
                   
                     
                       T 
                       43 
                     
                   
                   
                     
                       T 
                       44 
                     
                   
                 
               
               ] 
             
             = 
             
               [ 
               
                 
                   
                     
                       S 
                       1 
                     
                   
                   
                     
                       - 
                       
                         S 
                         2 
                         * 
                       
                     
                   
                   
                     0 
                   
                   
                     0 
                   
                 
                 
                   
                     
                       S 
                       2 
                     
                   
                   
                     
                       S 
                       1 
                       * 
                     
                   
                   
                     0 
                   
                   
                     0 
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     
                       S 
                       3 
                     
                   
                   
                     
                       - 
                       
                         S 
                         4 
                         * 
                       
                     
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     
                       S 
                       4 
                     
                   
                   
                     
                       S 
                       3 
                       * 
                     
                   
                 
               
               ] 
             
           
         
       
     
         [0000]    where T ij  represents the symbol transmitted on the ith antenna port and the jth subcarrier or jth time slot, S 1 , S 2 , S 3 , and S 4  represent the first through the fourth symbols respectively. 
         [0021]    Alternatively, the selected antenna port mapping scheme may be established such that a first antenna port is mapped to a first physical antenna, a second antenna port is mapped to a second physical antenna, a third antenna port is mapped to a third physical antenna, and a fourth antenna port is mapped to a fourth physical antenna. In this case, the transmission matrix may be established as: 
         [0000]    
       
         
           
             
               [ 
               
                 
                   
                     
                       T 
                       11 
                     
                   
                   
                     
                       T 
                       12 
                     
                   
                   
                     
                       T 
                       13 
                     
                   
                   
                     
                       T 
                       14 
                     
                   
                 
                 
                   
                     
                       T 
                       21 
                     
                   
                   
                     
                       T 
                       22 
                     
                   
                   
                     
                       T 
                       23 
                     
                   
                   
                     
                       T 
                       24 
                     
                   
                 
                 
                   
                     
                       T 
                       31 
                     
                   
                   
                     
                       T 
                       32 
                     
                   
                   
                     
                       T 
                       33 
                     
                   
                   
                     
                       T 
                       34 
                     
                   
                 
                 
                   
                     
                       T 
                       41 
                     
                   
                   
                     
                       T 
                       42 
                     
                   
                   
                     
                       T 
                       43 
                     
                   
                   
                     
                       T 
                       44 
                     
                   
                 
               
               ] 
             
             = 
             
               [ 
               
                 
                   
                     
                       S 
                       1 
                     
                   
                   
                     
                       - 
                       
                         S 
                         2 
                         * 
                       
                     
                   
                   
                     0 
                   
                   
                     0 
                   
                 
                 
                   
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                     0 
                   
                   
                     
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                       3 
                     
                   
                   
                     
                       - 
                       
                         S 
                         4 
                         * 
                       
                     
                   
                 
                 
                   
                     
                       S 
                       2 
                     
                   
                   
                     
                       S 
                       1 
                       * 
                     
                   
                   
                     0 
                   
                   
                     0 
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     
                       S 
                       4 
                     
                   
                   
                     
                       S 
                       3 
                       * 
                     
                   
                 
               
               ] 
             
           
         
       
     
         [0000]    where T ij  represents the symbol transmitted on the ith antenna port and the jth subcarrier or jth time slot, S 1 , S 2 , S 3 , and S 4  represent the first through the fourth symbols respectively. 
         [0022]    According to yet another aspect of the present invention, a method and an apparatus may be provided to include generating a plurality of reference signals for a plurality of antenna ports, with each reference signal corresponding to an antenna port; mapping the plurality of antenna ports to a plurality of physical antennas in accordance with a selected antenna port mapping scheme, with each antenna port corresponding to a physical antenna, and the plurality of physical antennas being aligned sequentially with equal spacing between two immediately adjacent physical antennas; demultiplexing information to be transmitted into a plurality of stream blocks; inserting a respective cyclic redundancy check to each of the stream blocks; encoding each of the stream blocks according to a corresponding coding scheme; modulating each of the stream blocks according to a corresponding modulation scheme; demultiplexing the stream blocks to generate a plurality of sets of symbols, with each stream block being demultiplexed into a set of symbols; mapping the plurality of sets of symbols into the plurality of antenna ports in accordance with a selected symbol mapping scheme; and transmitting the plurality of sets of symbols via the corresponding antenna ports, with each set of symbols being transmitted via a subset of antenna ports, with, within each subset of antenna ports, the distance between the physical antennas of the corresponding antenna ports being larger than the average distance among the plurality of physical antennas. 
         [0023]    When two stream blocks are transmitted via four antenna ports, the selected antenna port mapping scheme may be established such that a first antenna port is mapped to a first physical antenna, a second antenna port is mapped to a third physical antenna, a third antenna port is mapped to a second physical antenna, and a fourth antenna port is mapped to a fourth physical antenna. In this case, the selected symbol mapping scheme may be established such that a first stream block is mapped to the first and the second antenna ports, and a second stream block is mapped to the third and the fourth antenna ports. 
         [0024]    Alternatively, when two stream blocks are transmitted via four antenna ports, the selected antenna port mapping scheme may be established such that a first antenna port is mapped to a first physical antenna, a second antenna port is mapped to a second physical antenna, a third antenna port is mapped to a third physical antenna, and a fourth antenna port is mapped to a fourth physical antenna. In this case, the selected symbol mapping scheme may be established such that a first stream block is mapped to the first and the third antenna ports, and a second stream block is mapped to the second and the fourth antenna ports, such that the third and the fourth antenna ports having weaker channel estimates are equally distributed between the first and the second stream blocks. 
         [0025]    According to still another aspect of the present invention, a method and an apparatus may be provided to include demultiplexing information to be transmitted into a plurality of stream blocks; inserting a respective cyclic redundancy check to each of the stream  1 I blocks; encoding each of the stream blocks according to a corresponding coding scheme; modulating each of the stream blocks according to a corresponding modulation scheme to generate a plurality of modulated symbols; dividing the plurality of modulated symbols into a plurality of groups of modulated symbols; selecting a subset of matrices from among six permuted versions of a selected Space Frequency Block Code matrix; repeatedly applying the selected set of matrices to the plurality of groups of modulated symbols to generate a plurality of transmit matrices, with each matrix corresponding to a group of modulated symbols and each matrix being applied to each pair of modulated symbols in the corresponding group of modulated symbols; and transmitting the plurality of transmit matrices via four transmission antennas using a plurality of subcarriers, with each transmit matrix using two subcarriers. 
         [0026]    The selected Space Frequency Block Code diversity matrix may be a Space Frequency Block Code Cyclic Delay Diversity (SFBC-CDD) matrix, and the six permutated versions may be expressed as: 
         [0000]    
       
         
           
             
               
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                               ) 
                             
                           
                         
                       
                     
                   
                 
                 ] 
               
             
             , 
           
         
       
     
         [0000]    where S 1  and S 2  are two modulated symbols, g=[k/2] is the group index of two subcarriers, k is the subcarrier index, and functions b 1 (g) and b 2 (g) are two pseudo-random phase shift vectors that are functions of the subcarrier group index g. 
         [0027]    Alternatively, the selected Space Frequency Block Code diversity matrix may be a Space Frequency Block Code Phase Switched Diversity (SFBC-PSD) matrix, and the six permutated versions may be expressed as: 
         [0000]    
       
         
           
             
               
                 C 
                 A 
               
               = 
               
                 [ 
                 
                   
                     
                       
                         S 
                         1 
                       
                     
                     
                       
                         - 
                         
                           S 
                           2 
                           * 
                         
                       
                     
                   
                   
                     
                       
                         S 
                         2 
                       
                     
                     
                       
                         S 
                         1 
                         * 
                       
                     
                   
                   
                     
                       
                         
                           S 
                           1 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                     
                       
                         
                           - 
                           
                             S 
                             2 
                             * 
                           
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         
                           S 
                           2 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                     
                       
                         
                           S 
                           1 
                           * 
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                   
                 
                 ] 
               
             
             , 
             
               
 
             
              
             
               
                 C 
                 B 
               
               = 
               
                 [ 
                 
                   
                     
                       
                         S 
                         1 
                       
                     
                     
                       
                         - 
                         
                           S 
                           2 
                           * 
                         
                       
                     
                   
                   
                     
                       
                         
                           S 
                           1 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                     
                       
                         
                           - 
                           
                             S 
                             2 
                             * 
                           
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         S 
                         2 
                       
                     
                     
                       
                         S 
                         1 
                         * 
                       
                     
                   
                   
                     
                       
                         
                           S 
                           2 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                     
                       
                         
                           S 
                           1 
                           * 
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                   
                 
                 ] 
               
             
             , 
             
               
 
             
              
             
               
                 C 
                 C 
               
               = 
               
                 [ 
                 
                   
                     
                       
                         S 
                         1 
                       
                     
                     
                       
                         - 
                         
                           S 
                           2 
                           * 
                         
                       
                     
                   
                   
                     
                       
                         
                           S 
                           1 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                     
                       
                         
                           - 
                           
                             S 
                             2 
                             * 
                           
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         
                           S 
                           2 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                     
                       
                         
                           S 
                           1 
                           * 
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         S 
                         2 
                       
                     
                     
                       
                         S 
                         1 
                         * 
                       
                     
                   
                 
                 ] 
               
             
             , 
             
               
 
             
              
             
               
                 C 
                 D 
               
               = 
               
                 [ 
                 
                   
                     
                       
                         
                           S 
                           1 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                     
                       
                         
                           - 
                           
                             S 
                             2 
                             * 
                           
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         
                           S 
                           2 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                     
                       
                         
                           S 
                           1 
                           * 
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         S 
                         1 
                       
                     
                     
                       
                         - 
                         
                           S 
                           2 
                           * 
                         
                       
                     
                   
                   
                     
                       
                         S 
                         2 
                       
                     
                     
                       
                         S 
                         1 
                         * 
                       
                     
                   
                 
                 ] 
               
             
             , 
             
               
 
             
              
             
               
                 C 
                 E 
               
               = 
               
                 [ 
                 
                   
                     
                       
                         
                           S 
                           1 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                     
                       
                         
                           - 
                           
                             S 
                             2 
                             * 
                           
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         S 
                         1 
                       
                     
                     
                       
                         - 
                         
                           S 
                           2 
                           * 
                         
                       
                     
                   
                   
                     
                       
                         
                           S 
                           2 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                     
                       
                         
                           S 
                           1 
                           * 
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         S 
                         2 
                       
                     
                     
                       
                         S 
                         1 
                         * 
                       
                     
                   
                 
                 ] 
               
             
             , 
             
               
 
             
              
             
               
                 C 
                 F 
               
               = 
               
                 [ 
                 
                   
                     
                       
                         
                           S 
                           1 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                     
                       
                         
                           - 
                           
                             S 
                             2 
                             * 
                           
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               1 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         S 
                         1 
                       
                     
                     
                       
                         - 
                         
                           S 
                           2 
                           * 
                         
                       
                     
                   
                   
                     
                       
                         S 
                         2 
                       
                     
                     
                       
                         S 
                         1 
                         * 
                       
                     
                   
                   
                     
                       
                         
                           S 
                           2 
                         
                          
                         
                            
                           
                             j 
                              
                             
                                 
                             
                              
                             k 
                              
                             
                                 
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                     
                       
                         
                           S 
                           1 
                           * 
                         
                          
                         
                            
                           
                             
                               j 
                                
                               
                                 ( 
                                 
                                   k 
                                   + 
                                   1 
                                 
                                 ) 
                               
                             
                              
                             
                               θ 
                               2 
                             
                           
                         
                       
                     
                   
                 
                 ] 
               
             
             , 
           
         
       
     
         [0000]    where S 1  and S 2  are two modulated symbols, k is the subcarrier index, and θ 1  and θ 2  are two fixed phase angles. 
         [0028]    According to a further aspect of the present invention, a method and an apparatus may be provided to include demultiplexing information to be transmitted into a plurality of stream blocks; inserting a respective cyclic redundancy check to each of the stream blocks; encoding each of the stream blocks according to a corresponding coding scheme; modulating each of the stream blocks according to a corresponding modulation scheme to generate a pair of modulated symbols; selecting a subset of matrices from among six permuted versions of a selected Space Frequency Block Code matrix; repeatedly transmitting the pair of symbols by applying the selected set of matrices to the pairs of modulated symbols, with each matrix being transmitted at a time slot. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying. drawings in which like reference symbols indicate the same or similar components, wherein: 
           [0030]      FIG. 1  illustrates an Orthogonal Frequency Division Multiplexing (OFDM) transceiver chain; 
           [0031]      FIG. 2  is an illustration of a Space Time Block Code transmission diversity scheme for two transmission antennas; 
           [0032]      FIG. 3  is an illustration of another Space Frequency Block Code transmission diversity scheme for two transmission antennas; 
           [0033]      FIG. 4  is an illustration of mapping of downlink reference signals in a contemporary 3 rd  Generation Partnership Project Long Term Evolution system; 
           [0034]      FIG. 5  illustrates an arrangement of four transmission antennas; 
           [0035]      FIG. 6  is an illustration of a Multiple Input Multiple Output (MIMO) transceiver chain; 
           [0036]      FIG. 7  illustrates a single codeword MIMO transmission scheme; 
           [0037]      FIG. 8  illustrates a multiple codeword MIMO transmission scheme; 
           [0038]      FIG. 9  illustrates a multiple codeword MIMO transmission scheme according to a first embodiment of the principles of the present invention; 
           [0039]      FIG. 10  illustrates a reference symbol mapping scheme in case of four transmission antennas according to a second embodiment of the principles of the present invention; 
           [0040]      FIG. 11  illustrates a multiple codeword MIMO mapping scheme according to a third embodiment of the principles of the present invention; 
           [0041]      FIG. 12  illustrates a reference symbol mapping scheme in case of four transmission antennas according to a fourth embodiment of the principles of the present invention; and 
           [0042]      FIG. 13  illustrates a multiple codeword MIMO mapping scheme according to a fifth embodiment of the principles of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]      FIG. 1  illustrates an Orthogonal Frequency Division Multiplexing (OFDM) transceiver chain. In a communication system using OFDM technology, at transmitter chain  110 , control signals or data  111  is modulated by modulator  112  and is serial-to-parallel converted by Serial/Parallel (S/P) converter  113 . Inverse Fast Fourier Transform (IFFT) unit  114  is used to transfer the signal from frequency domain to time domain. Cyclic prefix (CP) or zero prefix (ZP) is added to each OFDM symbol by CP insertion unit  116  to avoid or mitigate the impact due to multipath fading. Consequently, the signal is transmitted by transmitter (Tx) front end processing unit  117 , such as an antenna (not shown), or alternatively, by fixed wire or cable. At receiver chain  120 , assuming perfect time and frequency synchronization are achieved, the signal received by receiver (Rx) front end processing unit  121  is processed by CP removal unit  122 . Fast Fourier Transform (FFT) unit  124  transfers the received signal from time domain to frequency domain for further processing. 
         [0044]    The total bandwidth in an OFDM system is divided into narrowband frequency units called subcarriers. The number of subcarriers is equal to the FFT/IFFT size N used in the system. In general, the number of subcarriers used for data is less than N because some subcarriers at the edge of the frequency spectrum are reserved as guard subcarriers. In general, no information is transmitted on guard subcarriers. 
         [0045]    The scheme of diversity is widely used to combat the effect of fast fading by providing a receiver with multiple faded replicas of the same information-bearing signal. 
         [0046]    An example of open-loop transmission diversity scheme is the Alamouti 2×1 space-time block code (STBC) transmission diversity scheme as illustrated in  FIG. 2 . In this approach, during any symbol period, i.e., time period, a transmitter transmits two data symbols via two transmission antennas to a receiver. As shown in  FIG. 2 , during the first symbol interval t 1 , symbols S 1  and S 2  are respectively transmitted via antennas ANT  1  and ANT  2 . During the next symbol period t 2 , symbols −S* 2  and S* 1  are respectively transmitted via antennas ANT  1  and ANT  2 , where x* represents complex conjugate of x. After receiving the signals, the receiver performs a plurality of processes to recover original symbols S 1  and S 2 . Note that the instantaneous channel gains g 1  and g 2  for ANT  1  and ANT  2 , respectively, are required for processing at the receiver. Therefore, the transmitter needs to transmit separate pilot symbols via both the antennas ANT  1  and ANT  2  for channel gain estimation at the receiver. The diversity gain achieved by Alamouti coding is the same as that achieved in Maximum Ratio Combining (MRC). 
         [0047]    The 2×1 Alamouti scheme can also be implemented in a space-frequency block code (SFBC) transmission diversity scheme as illustrated in  FIG. 3 . As shown in  FIG. 3 , symbols S 1  and S 2  are respectively transmitted to a receiver via antennas ANT  1  and ANT  2  on a first subcarrier having frequency f 1  in an Orthogonal Frequency Division Multiplexing (OFDM) system, symbols −S* 2  and S* 1  are respectively transmitted via antennas ANT  1  and ANT  2  on a second subcarrier having frequency f 2 . Therefore a matrix of transmitted symbols from antennas ANT  1  and ANT  2  can be written as: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       [ 
                       
                         
                           
                             
                               T 
                               11 
                             
                           
                           
                             
                               T 
                               12 
                             
                           
                         
                         
                           
                             
                               T 
                               21 
                             
                           
                           
                             
                               T 
                               22 
                             
                           
                         
                       
                       ] 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               S 
                               1 
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 2 
                                 * 
                               
                             
                           
                         
                         
                           
                             
                               S 
                               2 
                             
                           
                           
                             
                               S 
                               1 
                               * 
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0048]    The received signal at the receiver on subcarrier having frequency f 1  is r 1 , and the received signal at the receiver on subcarrier having frequency f 2  is r 2 . r 1  and r 2  can be written as: 
         [0000]    
       
      
       r 
       1 
       =h 
       1 
       s 
       1 
       +h 
       2 
       s 
       2 
       +n 
       1  
      
     
         [0000]        r   2   =−h   1   s*   2   +h   2   s*   1   +n   2 ,   (2) 
         [0000]    where h 1  and h 2  are channel gains from ANT  1  and ANT  2  respectively. We also assume that the channel from a given antennas does not change between subcarrier having frequency f 1  and subcarrier having frequency f 2 . The receiver performs equalization on the received signals and combines the two received signals (r 1  and r 2 ) to recover the symbols S 1  and S 2 . The recovered symbols Ŝ 1  and Ŝ 2  can be written as: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             1 
                           
                           = 
                           
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 r 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                               
                                
                               
                                 r 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                           
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 
                                   
                                     
                                       h 
                                       1 
                                     
                                      
                                     
                                       s 
                                       1 
                                     
                                   
                                   + 
                                   
                                     
                                       h 
                                       2 
                                     
                                      
                                     
                                       s 
                                       2 
                                     
                                   
                                   + 
                                   
                                     n 
                                     1 
                                   
                                 
                                 ) 
                               
                             
                             + 
                             
                               
                                 
                                   h 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   
                                     
                                       
                                         - 
                                         
                                           h 
                                           1 
                                         
                                       
                                        
                                       
                                         s 
                                         2 
                                         * 
                                       
                                     
                                     + 
                                     
                                       
                                         h 
                                         2 
                                       
                                        
                                       
                                         s 
                                         1 
                                         * 
                                       
                                     
                                     + 
                                     
                                       n 
                                       2 
                                     
                                   
                                   ) 
                                 
                               
                               * 
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         1 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         2 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 n 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                               
                                
                               
                                 n 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             2 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 r 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                               
                                
                               
                                 r 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 ( 
                                 
                                   
                                     
                                       h 
                                       1 
                                     
                                      
                                     
                                       s 
                                       1 
                                     
                                   
                                   + 
                                   
                                     
                                       h 
                                       2 
                                     
                                      
                                     
                                       s 
                                       2 
                                     
                                   
                                   + 
                                   
                                     n 
                                     1 
                                   
                                 
                                 ) 
                               
                             
                             + 
                             
                               
                                 
                                   h 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   
                                     
                                       
                                         - 
                                         
                                           h 
                                           1 
                                         
                                       
                                        
                                       
                                         s 
                                         2 
                                         * 
                                       
                                     
                                     + 
                                     
                                       
                                         h 
                                         2 
                                       
                                        
                                       
                                         s 
                                         1 
                                         * 
                                       
                                     
                                     + 
                                     
                                       n 
                                       2 
                                     
                                   
                                   ) 
                                 
                               
                               * 
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         1 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         2 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 2 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 n 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                               
                                
                               
                                 n 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0000]    It can be seen that both of the transmitted symbols Ŝ 1  and Ŝ 2  achieve full spatial diversity, that is, the each of the transmitted symbols Ŝ 1  and Ŝ 2  completely removes the interference from the other one. 
         [0049]    For the case of four transmission antennas, orthogonal full-diversity block codes are not available. An example of quasi-orthogonal block code also known as ABBA code is given below: 
         [0000]    
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             T 
                             11 
                           
                         
                         
                           
                             T 
                             12 
                           
                         
                         
                           
                             T 
                             13 
                           
                         
                         
                           
                             T 
                             14 
                           
                         
                       
                       
                         
                           
                             T 
                             21 
                           
                         
                         
                           
                             T 
                             22 
                           
                         
                         
                           
                             T 
                             23 
                           
                         
                         
                           
                             T 
                             24 
                           
                         
                       
                       
                         
                           
                             T 
                             31 
                           
                         
                         
                           
                             T 
                             32 
                           
                         
                         
                           
                             T 
                             33 
                           
                         
                         
                           
                             T 
                             34 
                           
                         
                       
                       
                         
                           
                             T 
                             41 
                           
                         
                         
                           
                             T 
                             42 
                           
                         
                         
                           
                             T 
                             43 
                           
                         
                         
                           
                             T 
                             44 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             A 
                           
                           
                             B 
                           
                         
                         
                           
                             B 
                           
                           
                             A 
                           
                         
                       
                       ] 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               S 
                               1 
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 2 
                                 * 
                               
                             
                           
                           
                             
                               S 
                               3 
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 4 
                                 * 
                               
                             
                           
                         
                         
                           
                             
                               S 
                               2 
                             
                           
                           
                             
                               S 
                               1 
                               * 
                             
                           
                           
                             
                               S 
                               4 
                             
                           
                           
                             
                               S 
                               3 
                               * 
                             
                           
                         
                         
                           
                             
                               S 
                               3 
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 4 
                                 * 
                               
                             
                           
                           
                             
                               S 
                               1 
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 2 
                                 * 
                               
                             
                           
                         
                         
                           
                             
                               S 
                               4 
                             
                           
                           
                             
                               S 
                               3 
                               * 
                             
                           
                           
                             
                               S 
                               2 
                             
                           
                           
                             
                               S 
                               1 
                               * 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where T ij  represents the symbol transmitted on the ith antenna and the jth subcarrier or jth time slot (i=1,2,3,4, j=1,2,3,4) for the case of four transmission antennas. A and B are block codes given as below. 
         [0000]    
       
         
           
             
               
                 
                   
                     A 
                     = 
                     
                       
                         1 
                         
                           2 
                         
                       
                        
                       
                         [ 
                         
                           
                             
                               
                                 S 
                                 1 
                               
                             
                             
                               
                                 - 
                                 
                                   S 
                                   2 
                                   * 
                                 
                               
                             
                           
                           
                             
                               
                                 S 
                                 2 
                               
                             
                             
                               
                                 S 
                                 1 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     B 
                     = 
                     
                       
                         1 
                         
                           2 
                         
                       
                        
                       
                         [ 
                         
                           
                             
                               
                                 S 
                                 3 
                               
                             
                             
                               
                                 - 
                                 
                                   S 
                                   4 
                                   * 
                                 
                               
                             
                           
                           
                             
                               
                                 S 
                                 4 
                               
                             
                             
                               
                                 S 
                                 3 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0050]    The problem with quasi-orthogonal block codes is that the loss of orthogonality may result in inter-symbol interference and hence degrades system performance and throughput. 
         [0051]    Another example of orthogonal block code for four transmission antennas is SFBC with balanced Frequency Switched Transmit Diversity (FSTD). The code structure can be expressed as: 
         [0000]    
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             T 
                             11 
                           
                         
                         
                           
                             T 
                             12 
                           
                         
                         
                           
                             T 
                             13 
                           
                         
                         
                           
                             T 
                             14 
                           
                         
                       
                       
                         
                           
                             T 
                             21 
                           
                         
                         
                           
                             T 
                             22 
                           
                         
                         
                           
                             T 
                             23 
                           
                         
                         
                           
                             T 
                             24 
                           
                         
                       
                       
                         
                           
                             T 
                             31 
                           
                         
                         
                           
                             T 
                             32 
                           
                         
                         
                           
                             T 
                             33 
                           
                         
                         
                           
                             T 
                             34 
                           
                         
                       
                       
                         
                           
                             T 
                             41 
                           
                         
                         
                           
                             T 
                             42 
                           
                         
                         
                           
                             T 
                             43 
                           
                         
                         
                           
                             T 
                             44 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             A 
                           
                           
                             A 
                           
                         
                         
                           
                             
                               - 
                               B 
                             
                           
                           
                             B 
                           
                         
                       
                       ] 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               S 
                               1 
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 2 
                                 * 
                               
                             
                           
                           
                             
                               S 
                               1 
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 2 
                                 * 
                               
                             
                           
                         
                         
                           
                             
                               S 
                               2 
                             
                           
                           
                             
                               S 
                               1 
                               * 
                             
                           
                           
                             
                               S 
                               2 
                             
                           
                           
                             
                               S 
                               1 
                               * 
                             
                           
                         
                         
                           
                             
                               - 
                               
                                 S 
                                 3 
                               
                             
                           
                           
                             
                               S 
                               4 
                               * 
                             
                           
                           
                             
                               S 
                               3 
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 4 
                                 * 
                               
                             
                           
                         
                         
                           
                             
                               - 
                               
                                 S 
                                 4 
                               
                             
                           
                           
                             
                               - 
                               
                                 S 
                                 3 
                                 * 
                               
                             
                           
                           
                             
                               S 
                               4 
                             
                           
                           
                             
                               S 
                               3 
                               * 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
         [0052]    Other proposals found in the art for four transmission antennas transmit diversity combines Frequency Switched Transmit Diversity (FSTD) or Time Switched Transmit Diversity (TSTD) with block codes. In case of combined SFBC+FSTD scheme or STBC+TSTD scheme, the matrix of the transmitted symbols from the four transmission antennas are given as: 
         [0000]    
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             T 
                             11 
                           
                         
                         
                           
                             T 
                             12 
                           
                         
                         
                           
                             T 
                             13 
                           
                         
                         
                           
                             T 
                             14 
                           
                         
                       
                       
                         
                           
                             T 
                             21 
                           
                         
                         
                           
                             T 
                             22 
                           
                         
                         
                           
                             T 
                             23 
                           
                         
                         
                           
                             T 
                             24 
                           
                         
                       
                       
                         
                           
                             T 
                             31 
                           
                         
                         
                           
                             T 
                             32 
                           
                         
                         
                           
                             T 
                             33 
                           
                         
                         
                           
                             T 
                             34 
                           
                         
                       
                       
                         
                           
                             T 
                             41 
                           
                         
                         
                           
                             T 
                             42 
                           
                         
                         
                           
                             T 
                             43 
                           
                         
                         
                           
                             T 
                             44 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             S 
                             1 
                           
                         
                         
                           
                             - 
                             
                               S 
                               2 
                               * 
                             
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           
                             S 
                             2 
                           
                         
                         
                           
                             S 
                             1 
                             * 
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             3 
                           
                         
                         
                           
                             - 
                             
                               S 
                               4 
                               * 
                             
                           
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             4 
                           
                         
                         
                           
                             S 
                             3 
                             * 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
     
         [0053]    The receiver algorithms for detecting the signal S 1 , S 2 , S 3 , and S 4  can be expressed as: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       s 
                       ⋒ 
                     
                     1 
                   
                   = 
                   
                     
                       1 
                       2 
                     
                      
                     
                       { 
                       
                         
                           
                             h 
                             1 
                             * 
                           
                            
                           
                             ( 
                             
                               
                                 r 
                                 1 
                               
                               + 
                               
                                 r 
                                 3 
                               
                             
                             ) 
                           
                         
                         + 
                         
                           
                             h 
                             2 
                           
                            
                           
                             ( 
                             
                               
                                 r 
                                 2 
                                 * 
                               
                               + 
                               
                                 r 
                                 4 
                                 * 
                               
                             
                             ) 
                           
                         
                       
                       } 
                     
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       s 
                       ⋒ 
                     
                     2 
                   
                   = 
                   
                     
                       1 
                       2 
                     
                      
                     
                       { 
                       
                         
                           
                             h 
                             2 
                             * 
                           
                            
                           
                             ( 
                             
                               
                                 r 
                                 1 
                               
                               + 
                               
                                 r 
                                 3 
                               
                             
                             ) 
                           
                         
                         - 
                         
                           
                             h 
                             1 
                           
                            
                           
                             ( 
                             
                               
                                 r 
                                 2 
                                 * 
                               
                               + 
                               
                                 r 
                                 4 
                                 * 
                               
                             
                             ) 
                           
                         
                       
                       } 
                     
                   
                 
               
               
                 
                   ( 
                   9 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       s 
                       ⋒ 
                     
                     3 
                   
                   = 
                   
                     
                       1 
                       2 
                     
                      
                     
                       { 
                       
                         
                           
                             h 
                             3 
                             * 
                           
                            
                           
                             ( 
                             
                               
                                 r 
                                 3 
                               
                               - 
                               
                                 r 
                                 1 
                               
                             
                             ) 
                           
                         
                         + 
                         
                           
                             h 
                             4 
                           
                            
                           
                             ( 
                             
                               
                                 r 
                                 4 
                                 * 
                               
                               - 
                               
                                 r 
                                 2 
                                 * 
                               
                             
                             ) 
                           
                         
                       
                       } 
                     
                   
                 
               
               
                 
                   ( 
                   10 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       s 
                       ⋒ 
                     
                     4 
                   
                   = 
                   
                     
                       1 
                       2 
                     
                      
                     
                       { 
                       
                         
                           
                             h 
                             4 
                             * 
                           
                            
                           
                             ( 
                             
                               
                                 r 
                                 3 
                               
                               - 
                               
                                 r 
                                 1 
                               
                             
                             ) 
                           
                         
                         - 
                         
                           
                             h 
                             3 
                           
                            
                           
                             ( 
                             
                               
                                 r 
                                 4 
                                 * 
                               
                               - 
                               
                                 r 
                                 2 
                                 * 
                               
                             
                             ) 
                           
                         
                       
                       } 
                     
                   
                 
               
               
                 
                   ( 
                   11 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where h 1 , h 2 , h 3 , h 4  are channel gains from ANT  1 , ANT  2 , ANT  3  and ANT  4 , respectively; r 1 , r 2 , r 3 , and r 4  are the received signal for sub-carrier  1 ,  2 ,  3 , and  4 , respectively. r 1 , r 2 , r 3 , and r 4  can be expressed as follow. 
         [0000]        r   1   =h   1   s   1   +h   2   s   2   −h   3   s   3   −h   4   s   4    (12) 
         [0000]        r   2   =h   2   s*   1   −h   1   s*   2   −h   4   s*   3   +h   3   s*   4    (13) 
         [0000]        r   3   =h   1   s*   1   +h   1   s*   2   +h   3   s*   3   +h   4   s*   4    (14) 
         [0000]        r   4   =h   2   s*   1   −h   1   s*   2   +h   4   s*   3   −h   3   s*   4    (15) 
         [0054]    The problem with combined SFBC+FSTD scheme and STBC+TSTD schemes is that only a fraction of the total transmission antennas and hence power amplifier (PA) capability is used for transmission in a given frequency or time resource. This is indicated by ‘0’ elements in the SFBC+FSTD and STBC+TSTD matrix given above. When the transmit power on the non-zero elements in the matrix is increased, bursty interference is generated to the neighboring cells degrading system performance. 
         [0055]    The downlink reference signals mapping for four transmission antennas in the 3GPP LTE (3 rd  Generation Partnership Project Long Term Evolution) system is shown in  FIG. 4 . The notation R p  is used to denote a resource element used for reference signal transmission on antenna port p. It can be noted that density on antenna ports  2  and  3  is half the density on antenna ports  0  and  1 . This leads to weaker channel estimates on antenna ports  2  and  3  relative to channel estimates on antenna ports  0  and  1 . 
         [0056]    In case of combined SFBC+FSTD scheme or STBC+TSTD scheme for four transmission antennas, the symbols S 1  and S 2  are transmitted from antenna ports  0  and  1 , while symbols S 3  and S 4  are transmitted from antenna ports  2  and  3 . The received symbol estimates are given as: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             1 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 r 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                               
                                
                               
                                 r 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         1 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         2 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 n 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                               
                                
                               
                                 n 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             2 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 r 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                               
                                
                               
                                 r 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         1 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         2 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 2 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 n 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                               
                                
                               
                                 n 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             3 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 3 
                                 * 
                               
                                
                               
                                 r 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                               
                                
                               
                                 r 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         3 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         4 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                                 * 
                               
                                
                               
                                 n 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                               
                                
                               
                                 n 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             4 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 4 
                                 * 
                               
                                
                               
                                 r 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                               
                                
                               
                                 r 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         3 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         4 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 4 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                                 * 
                               
                                
                               
                                 n 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                               
                                
                               
                                 n 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   16 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where h 1 , h 2 , h 3 , h 4  denote channel gains from antenna port  0 ,  1 ,  2  and  3  respectively; r 1 , r 2 , r 3 , and r 4  are the received signal for sub-carriers  1 ,  2 ,  3 , and  4  in the case of SFBC+FSTD respectively, or for time slots  1 ,  2 ,  3 , and  4  in the case of STBC+TSTD, respectively. It can be seen that symbols S 1  and S 2  transmitted from antennas ports  0  and  1  benefit from more reliable channel estimates than symbols S 3  and S 4  transmitted from antenna ports  2  and  3 . This is because the reference signal density is twice as high on antenna ports  0  and  1  relative to antenna ports  2  and  3 , as shown in  FIG. 4 . This results in degraded performance on symbols S 3  and S 4  and thus impacting the system throughput. 
         [0057]    The antenna correlation depends upon, among other factors, angular spread and antennas spacing. In general, for a given angle spread, the larger the antenna spacing the smaller the correlation among the antennas. An example of antenna spacing for the case of four transmission antennas is shown in  FIG. 5 . The four transmission antennas are sequentially aligned in a row, with a distance of λ between neighboring antennas. It can be seen that the correlation between antenna ports ANTP 0  and ANTP 1  is larger than the correlation between antenna ports ANTP 0  and ANTP 2 . Similarly, the correlation between antenna ports ANTP 2  and ANTP 3  is larger than the correlation between antenna ports ANTP 1  and ANTP 3 . 
         [0058]    Assume that symbols from the combined SFBC+FSTD scheme or STBC+TSTD scheme are transmitted via the antennas shown in  FIG. 5 , the symbols can be expressed as: 
         [0000]    
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             T 
                             11 
                           
                         
                         
                           
                             T 
                             12 
                           
                         
                         
                           
                             T 
                             13 
                           
                         
                         
                           
                             T 
                             14 
                           
                         
                       
                       
                         
                           
                             T 
                             21 
                           
                         
                         
                           
                             T 
                             22 
                           
                         
                         
                           
                             T 
                             23 
                           
                         
                         
                           
                             T 
                             24 
                           
                         
                       
                       
                         
                           
                             T 
                             31 
                           
                         
                         
                           
                             T 
                             32 
                           
                         
                         
                           
                             T 
                             33 
                           
                         
                         
                           
                             T 
                             34 
                           
                         
                       
                       
                         
                           
                             T 
                             41 
                           
                         
                         
                           
                             T 
                             42 
                           
                         
                         
                           
                             T 
                             43 
                           
                         
                         
                           
                             T 
                             44 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             S 
                             1 
                           
                         
                         
                           
                             - 
                             
                               S 
                               2 
                               * 
                             
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           
                             S 
                             2 
                           
                         
                         
                           
                             S 
                             1 
                             * 
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             3 
                           
                         
                         
                           
                             - 
                             
                               S 
                               4 
                               * 
                             
                           
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             4 
                           
                         
                         
                           
                             S 
                             3 
                             * 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   ( 
                   17 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where T ij  represents the symbol transmitted on the ith antenna and the jth subcarrier or jth time slot, and i=1,2,3,4, j=1,2,3,4 for the case of four transmission antennas. Accordingly, symbols S 1  and S 2  are transmitted via ANTP 0  and ANTP 1 , while symbols S 3  and S 4  are transmitted via ANPT 2  and ANTP 3 . This results in degraded transmit diversity performance for symbols S 1  and S 2  because the correlation between ANTP 0  and ANTP 1  is higher compared to the correlation between ANTP 0  and ANTP 2 , or the correlation between ANTP 1  and ANTP 3 . Similarly, symbols S 3  and S 4  may also experience a degraded transmit diversity performance because ANTP 2  and ANTP 3  have higher correlation compared to the correlation between ANTP 0  and ANTP 2 , or the correlation between ANTP 1  and ANTP 3 . 
         [0059]    Another approach of transmit diversity scheme for four transmission antennas is called SFBC-Phase Switched Diversity (SFBC-PSD), where the transmit space-frequency code structure is given by: 
         [0000]    
       
         
           
             
               
                 
                   [ 
                   
                     
                       
                         
                           S 
                           1 
                         
                       
                       
                         
                           - 
                           
                             S 
                             2 
                             * 
                           
                         
                       
                     
                     
                       
                         
                           S 
                           2 
                         
                       
                       
                         
                           S 
                           1 
                           * 
                         
                       
                     
                     
                       
                         
                           
                             S 
                             1 
                           
                            
                           
                              
                             
                               
                                 jθ 
                                 1 
                               
                                
                               
                                 ( 
                                 g 
                                 ) 
                               
                             
                           
                         
                       
                       
                         
                           
                             - 
                             
                               S 
                               2 
                               * 
                             
                           
                            
                           
                              
                             
                               
                                 jθ 
                                 1 
                               
                                
                               
                                 ( 
                                 g 
                                 ) 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           
                             S 
                             2 
                           
                            
                           
                              
                             
                               
                                 jθ 
                                 2 
                               
                                
                               
                                 ( 
                                 g 
                                 ) 
                               
                             
                           
                         
                       
                       
                         
                           
                             S 
                             1 
                             * 
                           
                            
                           
                              
                             
                               
                                 jθ 
                                 2 
                               
                                
                               
                                 ( 
                                 g 
                                 ) 
                               
                             
                           
                         
                       
                     
                   
                   ] 
                 
               
               
                 
                   ( 
                   18 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where g=[k/2] is the group index of two subcarriers, and k is the subcarrier index. Functions b 1 (g) and b 2 (g) are two pseudo-random phase shift vectors that are functions of the subcarrier group index g, and they are known at Node-B (i.e., the base station) and all User Equipments (UEs). 
         [0060]    Another approach of transmit diversity scheme for four transmission antennas is called SFBC-Cyclic Delay Diversity (SFBC-CDD), where the transmit space-frequency code structure is given by: 
         [0000]    
       
         
           
             
               
                 
                   [ 
                   
                     
                       
                         
                           S 
                           1 
                         
                       
                       
                         
                           - 
                           
                             S 
                             2 
                             * 
                           
                         
                       
                     
                     
                       
                         
                           S 
                           2 
                         
                       
                       
                         
                           S 
                           1 
                           * 
                         
                       
                     
                     
                       
                         
                           
                             S 
                             1 
                           
                            
                           
                              
                             
                               j 
                                
                               
                                   
                               
                                
                               k 
                                
                               
                                   
                               
                                
                               
                                 θ 
                                 1 
                               
                             
                           
                         
                       
                       
                         
                           
                             - 
                             
                               S 
                               2 
                               * 
                             
                           
                            
                           
                              
                             
                               
                                 j 
                                  
                                 
                                   ( 
                                   
                                     k 
                                     + 
                                     1 
                                   
                                   ) 
                                 
                               
                                
                               
                                 θ 
                                 1 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           
                             S 
                             2 
                           
                            
                           
                              
                             
                               j 
                                
                               
                                   
                               
                                
                               k 
                                
                               
                                   
                               
                                
                               
                                 θ 
                                 2 
                               
                             
                           
                         
                       
                       
                         
                           
                             S 
                             1 
                             * 
                           
                            
                           
                              
                             
                               
                                 j 
                                  
                                 
                                   ( 
                                   
                                     k 
                                     + 
                                     1 
                                   
                                   ) 
                                 
                               
                                
                               
                                 θ 
                                 2 
                               
                             
                           
                         
                       
                     
                   
                   ] 
                 
               
               
                 
                   ( 
                   19 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where k is the subcarrier index, and b 1  and b 2  are two fixed phase angles. Note that in this case, a simple orthogonal detection algorithm does not exist, and either Maximum Likelihood (ML) receivers, or Minimum Mean Square Error (MMSE) receivers, or other advanced receivers are needed to capture diversity. 
         [0061]    Multiple Input Multiple Output (MIMO) schemes use multiple transmission antennas and multiple receive antennas to improve the capacity and reliability of a wireless communication channel. A MIMO system promises linear increase in capacity with K where K is the minimum of number of transmit (M) and receive antennas (N), i.e. K=min(M,N). A simplified example of a 4×4 MIMO system is shown in  FIG. 6 . In this example, four different data streams are transmitted separately from the four transmission antennas. The transmitted signals are received at the four receive antennas. Some form of spatial signal processing is performed on the received signals in order to recover the four data streams. An example of spatial signal processing is vertical Bell Laboratories Layered Space-Time (V-BLAST) which uses the successive interference cancellation principle to recover the transmitted data streams. Other variants of MIMO schemes include schemes that perform some kind of space-time coding across the transmission antennas (e.g., diagonal Bell Laboratories Layered Space-Time (D-BLAST)) and also beamforming schemes such as Spatial Division multiple Access (SDMA). 
         [0062]    The MIMO channel estimation consists of estimating the channel gain and phase information for links from each of the transmission antennas to each of the receive antennas. Therefore, the channel for M×N MIMO system consists of an N×M matrix: 
         [0000]    
       
         
           
             
               
                 
                   H 
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
                               h 
                               11 
                             
                           
                           
                             
                               h 
                               12 
                             
                           
                           
                             ⋯ 
                           
                           
                             
                               h 
                               
                                 1 
                                  
                                 M 
                               
                             
                           
                         
                         
                           
                             
                               h 
                               21 
                             
                           
                           
                             
                               h 
                               22 
                             
                           
                           
                             ⋯ 
                           
                           
                             
                               h 
                               
                                 2 
                                  
                                 M 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                           
                             ⋯ 
                           
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               h 
                               
                                 N 
                                  
                                 
                                     
                                 
                                  
                                 1 
                               
                             
                           
                           
                             
                               h 
                               
                                 M 
                                  
                                 
                                     
                                 
                                  
                                 2 
                               
                             
                           
                           
                             ⋯ 
                           
                           
                             
                               h 
                               NM 
                             
                           
                         
                       
                       ] 
                     
                     . 
                   
                 
               
               
                 
                   ( 
                   20 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where h ij  represents the channel gain from transmission antenna j to receive antenna i. In order to enable the estimations of the elements of the MIMO channel matrix, separate pilots are transmitted from each of the transmission antennas. 
         [0063]    An example of single-code word MIMO scheme is given in  FIG. 7 . In case of single-code word MIMO transmission, a cyclic redundancy check (CRC) is added to a single information block and then coding, for example, using turbo codes and low-density parity check (LDPC) code, and modulation, for example, by quadrature phase-shift keying (QPSK) modulation scheme, are performed. The coded and modulated symbols are then demultiplexed for transmission over multiple antennas. 
         [0064]    In case of multiple codeword MIMO transmission, shown in  FIG. 8 , the information block is de-multiplexed into smaller information blocks. Individual CRCs are attached to these smaller information blocks and then separate coding and modulation is performed on these smaller blocks. After modulation, these smaller blocks are respectively demultiplexed into even smaller blocks and then transmitted through corresponding antennas. It should be noted that in case of multi-code word MIMO transmissions, different modulation and coding can be used on each of the individual streams, and thus resulting in a so-called Per Antenna Rate Control (PARC) scheme. Also, multi-code word transmission allows for more efficient post-decoding interference cancellation because a CRC check can be performed on each of the code words before the code word is cancelled from the overall signal. In this way, only correctly received code words are cancelled, and thus avoiding any interference propagation in the cancellation process. In the 3GPP LTE for rank  4  or 4 layers transmission, codeword- 1  (CW 1 ) is transmitted from antenna ports ANTP 0  and ANTP 1 , while CW 2  is transmitted from antenna ports ANTP 2  and ANTP 3 . This results in weaker channel estimates and degraded performance for CW 2  due to lower density of ANTP 2  and ANTP 3  reference signal density. 
         [0065]    Similarly, codeword- 1  (CW 1 ) mapped to ANTP 0  and ANTP 1  experience less diversity because of higher correlation between ANTP 0  and ANTP 1 . Similarly, codeword- 2  (CW 2 ) mapped to ANTP 2  and ANTP 3  experience less diversity because of higher correlation between ANTP 2  and ANTP 3 . 
         [0066]    In a first embodiment according to the principles of the present invention, we describe an open-loop transmit diversity scheme where symbols S 1  and S 2  are transmitted via antennas ports ANTP 0  and ANTP 2  as shown in  FIG. 5 , while symbols S 3  and S 4  are transmitted over antenna ports ANTP 1  and ANTP 3 , as shown in  FIG. 5 . The transmit matrix is given as: 
         [0000]    
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             T 
                             11 
                           
                         
                         
                           
                             T 
                             12 
                           
                         
                         
                           
                             T 
                             13 
                           
                         
                         
                           
                             T 
                             14 
                           
                         
                       
                       
                         
                           
                             T 
                             21 
                           
                         
                         
                           
                             T 
                             22 
                           
                         
                         
                           
                             T 
                             23 
                           
                         
                         
                           
                             T 
                             24 
                           
                         
                       
                       
                         
                           
                             T 
                             31 
                           
                         
                         
                           
                             T 
                             32 
                           
                         
                         
                           
                             T 
                             33 
                           
                         
                         
                           
                             T 
                             34 
                           
                         
                       
                       
                         
                           
                             T 
                             41 
                           
                         
                         
                           
                             T 
                             42 
                           
                         
                         
                           
                             T 
                             43 
                           
                         
                         
                           
                             T 
                             44 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             S 
                             1 
                           
                         
                         
                           
                             - 
                             
                               S 
                               2 
                               * 
                             
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             3 
                           
                         
                         
                           
                             - 
                             
                               S 
                               4 
                               * 
                             
                           
                         
                       
                       
                         
                           
                             S 
                             2 
                           
                         
                         
                           
                             S 
                             1 
                             * 
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             4 
                           
                         
                         
                           
                             S 
                             3 
                             * 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   ( 
                   21 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where T ij  represents symbol transmitted on the ith antenna port and the jth subcarrier or jth time slot, and i=1,2,3,4, j=1,2,3,4 for the case of four transmission antennas. 
         [0067]    The received symbol estimates are given as: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             1 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 r 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                               
                                
                               
                                 r 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         1 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         3 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 n 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                               
                                
                               
                                 n 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             2 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 3 
                                 * 
                               
                                
                               
                                 r 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                               
                                
                               
                                 r 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         1 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         3 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 2 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                                 * 
                               
                                
                               
                                 n 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                               
                                
                               
                                 n 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             3 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 r 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                               
                                
                               
                                 r 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         2 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         4 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 n 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                               
                                
                               
                                 n 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             4 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 4 
                                 * 
                               
                                
                               
                                 r 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                               
                                
                               
                                 r 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         2 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         4 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 4 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                                 * 
                               
                                
                               
                                 n 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                               
                                
                               
                                 n 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   22 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where h 1 , h 2 , h 3 , h 4  denote channel gains from antenna ports  0 ,  1 ,  2  and  3  respectively; n 1 , n 2 , n 3 , and n 4  represents noise for sub-carriers  1 ,  2 ,  3 , and  4  in the case of SFBC respectively, or for time slots  1 ,  2 ,  3 , and  4  in the case of STBC, respectively. It can be seen that symbols S 1  and S 2  transmitted from antennas ports  0  and  2  experience a good channel estimate h 1  and a weak channel estimate h 3 . Similarly, symbols S 3  and S 4  transmitted from antenna ports  1  and  3  experience a good channel estimate h 2  and a weak channel estimate h 4 . This way the effect of weaker channel estimates is distributed across all the four symbols, S 1 , S 2 , S 3 , and S 4 . 
         [0068]    The Multi-code word MIMO scheme according to the principles of the current invention is shown in  FIG. 9 . The codeword  1  (CW 1 ) is mapped to antennas ports  0  and  2  while ICW 2  is mapped to antenna ports  1  and  3 . This way the effect of weaker channel estimates on antenna ports  2  and  3  is distributed across the  2  codeword transmission. 
         [0069]    In a second embodiment according to the principles of the present invention, reference symbols for the four transmission antennas are mapped as shown in  FIG. 10 . Reference signals R 0 , R 1 , R 2  and R 3  are mapped to physical antennas  1 ,  3 ,  2  and  4  respectively. In this case, each antenna port is defined by the reference signal transmitted on the port. That is, antenna port ANTP 0  is defined by reference signal R 0 , antenna port ANTP 1  is defined by reference signal R 1 , antenna port ANTP 2  is defined by reference signal R 2 , and antenna port ANTP 4  is defined by reference signal R 4 . Because reference signals R 0 , R 1 , R 2  and R 3  are mapped to physical antennas  1 ,  3 ,  2  and  4  respectively, antenna port ANTP 0  corresponds to physical antenna  1 , antenna port ANTP 2  corresponds to physical antenna  2 , antenna port ANTP  1  corresponds to physical antenna  3 , antenna port ANTP 3  corresponds to physical antenna  4 . The large spacing between physical antenna  1  and physical antenna  3  assures that antenna ports ANTP 0  and ANTP 1  have larger spacing than the case without the antenna port mapping, and hence smaller correlation. It should be noted that smaller correlation among antenna ports means higher achievable diversity. Similarly, ANTP 2  and ANTP 3  have larger spacing and hence smaller correlation. 
         [0070]    Now we assume the symbols in the combined SFBC+FSTD scheme or STBC+TSTD scheme are transmitted via the antenna ports shown in  FIG. 10 . In case of combined SFBC+FSTD scheme or STBC+TSTD scheme, the transmitted symbols from the antenna ports are given as: 
         [0000]    
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             T 
                             11 
                           
                         
                         
                           
                             T 
                             12 
                           
                         
                         
                           
                             T 
                             13 
                           
                         
                         
                           
                             T 
                             14 
                           
                         
                       
                       
                         
                           
                             T 
                             21 
                           
                         
                         
                           
                             T 
                             22 
                           
                         
                         
                           
                             T 
                             23 
                           
                         
                         
                           
                             T 
                             24 
                           
                         
                       
                       
                         
                           
                             T 
                             31 
                           
                         
                         
                           
                             T 
                             32 
                           
                         
                         
                           
                             T 
                             33 
                           
                         
                         
                           
                             T 
                             34 
                           
                         
                       
                       
                         
                           
                             T 
                             41 
                           
                         
                         
                           
                             T 
                             42 
                           
                         
                         
                           
                             T 
                             43 
                           
                         
                         
                           
                             T 
                             44 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             S 
                             1 
                           
                         
                         
                           
                             - 
                             
                               S 
                               2 
                               * 
                             
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           
                             S 
                             2 
                           
                         
                         
                           
                             S 
                             1 
                             * 
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             3 
                           
                         
                         
                           
                             - 
                             
                               S 
                               4 
                               * 
                             
                           
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             4 
                           
                         
                         
                           
                             S 
                             3 
                             * 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   ( 
                   23 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where T ij  represents symbol transmitted on the (i−1)th antenna port and the jth subcarrier or jth time slot, and i=1,2,3,4, j=1,2,3,4 for the case of four transmission antennas. That is, symbols T 11 , T 12 , T 13 , and T 14  are transmitted via antenna port ANTP 0  which corresponds to the physical antenna  1 , symbols T 21 , T 22 , T 23 , and T 24  are transmitted via antenna port ANTP 1  which corresponds to the physical antenna  3 , symbols T 31 , T 32 , T 33 , and T 34  are transmitted via antenna port ANTP 2  which corresponds to the physical antenna  2 , and symbols T 41 , T 42 , T 43 , and T 44  are transmitted via antenna port ANTP 3  which corresponds to the physical antenna  4 . 
         [0071]    The received symbol estimates are given as: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         s 
                         ^ 
                       
                       1 
                     
                     = 
                     
                       
                         
                           ( 
                           
                             
                               
                                  
                                 
                                   h 
                                   1 
                                 
                                  
                               
                               2 
                             
                             + 
                             
                               
                                  
                                 
                                   h 
                                   2 
                                 
                                  
                               
                               2 
                             
                           
                           ) 
                         
                          
                         
                           s 
                           1 
                         
                       
                       + 
                       
                         
                           h 
                           1 
                           * 
                         
                          
                         
                           n 
                           1 
                         
                       
                       + 
                       
                         
                           h 
                           2 
                         
                          
                         
                           n 
                           2 
                           * 
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         s 
                         ^ 
                       
                       2 
                     
                     = 
                     
                       
                         
                           ( 
                           
                             
                               
                                  
                                 
                                   h 
                                   1 
                                 
                                  
                               
                               2 
                             
                             + 
                             
                               
                                  
                                 
                                   h 
                                   2 
                                 
                                  
                               
                               2 
                             
                           
                           ) 
                         
                          
                         
                           s 
                           2 
                         
                       
                       + 
                       
                         
                           h 
                           2 
                           * 
                         
                          
                         
                           n 
                           1 
                         
                       
                       + 
                       
                         
                           h 
                           1 
                         
                          
                         
                           n 
                           2 
                           * 
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         s 
                         ^ 
                       
                       3 
                     
                     = 
                     
                       
                         
                           ( 
                           
                             
                               
                                  
                                 
                                   h 
                                   2 
                                 
                                  
                               
                               2 
                             
                             + 
                             
                               
                                  
                                 
                                   h 
                                   4 
                                 
                                  
                               
                               2 
                             
                           
                           ) 
                         
                          
                         
                           s 
                           3 
                         
                       
                       + 
                       
                         
                           h 
                           2 
                           * 
                         
                          
                         
                           n 
                           3 
                         
                       
                       + 
                       
                         
                           h 
                           4 
                         
                          
                         
                           n 
                           4 
                           * 
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         s 
                         ^ 
                       
                       4 
                     
                     = 
                     
                       
                         
                           ( 
                           
                             
                               
                                  
                                 
                                   h 
                                   2 
                                 
                                  
                               
                               2 
                             
                             + 
                             
                               
                                  
                                 
                                   h 
                                   4 
                                 
                                  
                               
                               2 
                             
                           
                           ) 
                         
                          
                         
                           s 
                           4 
                         
                       
                       + 
                       
                         
                           h 
                           4 
                           * 
                         
                          
                         
                           n 
                           3 
                         
                       
                       + 
                       
                         
                           h 
                           2 
                         
                          
                         
                           n 
                           4 
                           * 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   24 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where h 1 , h 2 , h 3 , h 4  denote channel gains from antenna ports  0 ,  1 ,  2  and  3  respectively; n 1 , n 2 , n 3 , and n 4  represents noise for sub-carriers  1 ,  2 ,  3 , and  4  in the case of SFBC respectively, or for time slots  1 ,  2 ,  3 , and  4  in the case of STBC, respectively. It can be seen that symbols S 1  and S 2  experience higher diversity due to larger spacing between antenna port  0  and antenna port  1 . Similarly, symbols S 3  and S 4  experience higher diversity due to larger spacing between antenna port  2  and antenna port  3  according to antenna ports to physical antennas mapping shown in  FIG. 10 . 
         [0072]    In a third embodiment according to the principles of the present invention shown in  FIG. 11 , CW 1  is mapped to ANTP 0  and ANTP 1  while CW 2  is mapped to ANTP 2  and ANTP 3  with antenna ports to physical antennas mapping as shown in  FIG. 10 . It can be seen that with this mapping of CW to antenna ports and the mapping of antenna ports to physical antenna mapping of  FIG. 10 , both codewords experience larger diversity compared to the case where ANTP 0 , ANTP 1 , ANTP 2  and ANTP 3  are mapped to physical antennas  1 ,  2 ,  3  and  4  respectively. 
         [0073]    In a fourth embodiment according to the principles of the present invention, reference symbols for the four transmission antennas are mapped as shown in  FIG. 12 . The reference signal R 0 , R 1 , R 2  and R 3  are mapped to physical antennas  1 ,  2 ,  3  and  4  respectively. For the open-loop transmit diversity scheme, symbols S 1  and S 2  are transmitted over antennas ports ANTP 0  and ANTP 2  while symbols S 3  and S 4  are transmitted over antenna ports ANTP 1  and ANTP 3  as given by the transmit matrix below: 
         [0000]    
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             T 
                             11 
                           
                         
                         
                           
                             T 
                             12 
                           
                         
                         
                           
                             T 
                             13 
                           
                         
                         
                           
                             T 
                             14 
                           
                         
                       
                       
                         
                           
                             T 
                             21 
                           
                         
                         
                           
                             T 
                             22 
                           
                         
                         
                           
                             T 
                             23 
                           
                         
                         
                           
                             T 
                             24 
                           
                         
                       
                       
                         
                           
                             T 
                             31 
                           
                         
                         
                           
                             T 
                             32 
                           
                         
                         
                           
                             T 
                             33 
                           
                         
                         
                           
                             T 
                             34 
                           
                         
                       
                       
                         
                           
                             T 
                             41 
                           
                         
                         
                           
                             T 
                             42 
                           
                         
                         
                           
                             T 
                             43 
                           
                         
                         
                           
                             T 
                             44 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             S 
                             1 
                           
                         
                         
                           
                             - 
                             
                               S 
                               2 
                               * 
                             
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             3 
                           
                         
                         
                           
                             - 
                             
                               S 
                               4 
                               * 
                             
                           
                         
                       
                       
                         
                           
                             S 
                             2 
                           
                         
                         
                           
                             S 
                             1 
                             * 
                           
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           
                             S 
                             4 
                           
                         
                         
                           
                             S 
                             3 
                             * 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   ( 
                   25 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where T ij  represents symbol transmitted on the (i−1)th antenna port and the jth subcarrier or jth time slot, and i=1,2,3,4, j=1,2,3,4 for the case of four transmission antennas. The received symbol estimates are given as: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             1 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 r 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                               
                                
                               
                                 r 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         1 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         3 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                                 * 
                               
                                
                               
                                 n 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                               
                                
                               
                                 n 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             2 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 3 
                                 * 
                               
                                
                               
                                 r 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                               
                                
                               
                                 r 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         1 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         3 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 2 
                               
                             
                             + 
                             
                               
                                 h 
                                 3 
                                 * 
                               
                                
                               
                                 n 
                                 1 
                               
                             
                             + 
                             
                               
                                 h 
                                 1 
                               
                                
                               
                                 n 
                                 2 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             3 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 r 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                               
                                
                               
                                 r 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         2 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         4 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                                 * 
                               
                                
                               
                                 n 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                               
                                
                               
                                 n 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         
                           
                             
                               s 
                               ^ 
                             
                             4 
                           
                           = 
                             
                            
                           
                             
                               
                                 h 
                                 4 
                                 * 
                               
                                
                               
                                 r 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                               
                                
                               
                                 r 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                     
                       
                         
                           = 
                             
                            
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         h 
                                         2 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         h 
                                         4 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                                
                               
                                 s 
                                 4 
                               
                             
                             + 
                             
                               
                                 h 
                                 4 
                                 * 
                               
                                
                               
                                 n 
                                 3 
                               
                             
                             + 
                             
                               
                                 h 
                                 2 
                               
                                
                               
                                 n 
                                 4 
                                 * 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   26 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where h 1 , h 2 , h 3 , h 4  denote channel gains from antenna ports  0 ,  1 ,  2  and  3  respectively; n 1 , n 2 , n 3 , and n 4  represents noise for sub-carriers  1 ,  2 ,  3 , and  4  in the case of SFBC respectively, or for time slots  1 ,  2 ,  3 , and  4  in the case of STBC, respectively. It can be seen that with the mapping of antenna ports to physical antennas shown in  FIG. 12  and symbol transmission matrix shown above, both the diversity within a symbol is maximized and also effect of channel estimates is distributed-evenly between the pair of symbols S 1  and S 2  and the pair of symbols S 3  and S 4 . 
         [0074]    In a fifth embodiment according to the principles of the present invention, as shown in  FIG. 13 , CW 1  is mapped to ANTP 0  and ANTP 2  while CW 2  is mapped to ANTP 1  and ANTP 3  using antenna ports to physical antenna mapping as shown in  FIG. 12 . In this case, both CW 1  and CW 2  experience larger diversity due to the spacing between antenna ports ANTP 0  and ANTP 2  and antenna ports ANTP 1  and ANTP 3 . Also, the effect of weaker channel estimates from antenna ports ANTP 2  and ANTP 3  is uniformly distributed on the two codewords. 
         [0075]    In a sixth embodiment according to the principles of the present invention, we derive the six permuted version of SFBC-PSD matrices: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       P 
                       A 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       P 
                       B 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       P 
                       C 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       P 
                       D 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       P 
                       E 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       P 
                       F 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     1 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     jθ 
                                     2 
                                   
                                    
                                   
                                     ( 
                                     g 
                                     ) 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   27 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where i=1, . . . , N, and N is the number of the symbols. While the transmitter maps the modulated symbols to the physical time-frequency OFDM resource, it select a subset of K (1≦K≦6) permuted matrices from the six permuted SFBC-PSD matrices. Afterward, the transmitter divides up the modulated signal into K parts, each of the K parts contains  2 M symbols, where M is an positive integer and M≧1. Each of the K parts uses a different permuted matrix from the subset of K matrices. One example is to let K=3, and let the three permuted matrices be P A ,P B ,P C . And we also assume there are  30  modulated symbols S 1 , S 2 , . . . , S 30 . The  30  modulated symbols are divided into 3 parts: the first part contains symbols S 1 , S 2 , S 7 , S 8 , S 13 , S 14 , S 19 , S 20 , S 25 , S 26 ; the second part contains symbols S 3 , S 4 , S 9 , S 10 , S 15 , S 16 , S 21 , S 22 , S 27 , S 28 ; and the third part contains symbols S 5 , S 6 , S 11 , S 12 , S 17 , S 18 , S 23 , S 24 , S 29 , S 20 . In this example, these three matrices P A ,P B ,P C  will be applied along the frequency dimension, in a pattern that repeats every 6 sub-carriers. That is, P A  is assigned to each pair of modulated symbols in the first part of modulated symbols, P B  is assigned to each pair of modulated symbols in the second part of modulated symbols, and P C  is assigned to each pair of modulated symbols in the third part of modulated symbols. 
         [0076]    In a seventh embodiment according to the principles of the present invention, the Node-B, i.e., the base station, selects a subset of K (1≦K≦6) permuted SFBC-PSD matrices for the purpose of Hybrid Automatic Repeat-reQuest (HARQ) transmission. Furthermore, the Node-B applies different SFBC-PSD matrices within this subset of K permuted SFBC-PSD matrices on different retransmissions of the packet. Noteworthy, this approach of applying permuted SFBC-PSD matrices on retransmissions apply to both Chase Combining and incremental redundancy. 
         [0077]    In an eighth embodiment according to the principles of the present invention, we derive the six permuted version of SFBC-CDD matrices: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       C 
                       A 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       C 
                       B 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       C 
                       C 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       C 
                       D 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   
                                     ( 
                                     
                                       k 
                                       + 
                                       1 
                                     
                                     ) 
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       C 
                       E 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                    
                   
                     
                       C 
                       C 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 
                                   S 
                                   1 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   
                                     S 
                                     2 
                                     * 
                                   
                                    
                                   
                                     ( 
                                     i 
                                     ) 
                                   
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     1 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 1 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   S 
                                   2 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 S 
                                 2 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                           
                             
                               
                                 S 
                                 1 
                                 * 
                               
                                
                               
                                 ( 
                                 i 
                                 ) 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   S 
                                   2 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   j 
                                    
                                   
                                       
                                   
                                    
                                   k 
                                    
                                   
                                       
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   S 
                                   1 
                                   * 
                                 
                                  
                                 
                                   ( 
                                   i 
                                   ) 
                                 
                               
                                
                               
                                  
                                 
                                   
                                     j 
                                      
                                     
                                       ( 
                                       
                                         k 
                                         + 
                                         1 
                                       
                                       ) 
                                     
                                   
                                    
                                   
                                     θ 
                                     2 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   21 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where k is the subcarrier index, and θ 1  and θ 2  are two fixed phase angles, i=1, . . . N, and N is the number of the symbols. While the transmitter maps the modulated symbols to the physical time-frequency OFDM resource, it select a subset of K (1≦K≦6) permuted matrices from the six permuted SFBC-CDD matrices. Afterward, the transmitter divides up the modulated signal into K parts, each uses a different permuted matrix from the subset of K matrices. One example is to let K=3, and let the three permuted matrices be C A ,C B ,C C . In this example, these three matrices will be applied along the frequency dimension, in a pattern that repeats every 6 sub-carriers. 
         [0078]    In a ninth embodiment according to the principles of the present invention, the Node-B select a subset of K (1≦K≦6) permuted SFBC-CDD matrices for the purpose of HARQ. Furthermore, the Node-B applies different SFBC-CDD matrices within this subset on different retransmissions of the packet. Noteworthy, this approach of applying permuted SFBC-CDD matrices on retransmissions apply to both Chase Combining and incremental redundancy. 
         [0079]    Note that the present invention does not limit the number of the antennas. That is, a communication system may have more than four transmission antennas. For example, two code words, CW 1  and CW 2  are transmitted via ten transmission antennas. Then CW 1  can be map to even numbered antenna ports, i.e., ANTP 0 , ANTP 2 , ANTP 4 , ANTP 6  and ANTP 8 , while CW 2  can be map to odd numbered antenna ports, i.e., ANTP 1 , ANTP 3 , ANTP 5 , ANTP 7  and ANTP 9 . For the case of SFBC-FSTD, we can create five pairs of symbols S 1  and S 2 , S 3  and S 4 , S 5  and S 6 , S 7  and S 8 , S 9  and S 10 . We can then map each pair to antennas to maximize transmit diversity gain. For example, the first pair S 1  and S 2  can be mapped to antenna ports  0  and  5 , the second pair S 3  and S 4  can be mapped to antenna ports  1  and  6 , and the last pair S 9  and S 10  to ports  4  and  9 . 
         [0080]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.