Patent Document

[0001]    This application claims priority to the provisional patent application entitled “Time-Space Decoding”, Serial No. 60/322,869, filed Sep. 12, 2001. 
     
    
     TECHNICAL FIELD 
       [0002]    The present claimed invention relates to the field of communications. In particular, the present claimed invention relate to apparatus and methods for space-time processing and interference suppression techniques that will lead to an increased data rate and or capacity in CDMA based wireless communication systems. 
       BACKGROUND OF INVENTION 
       [0003]    Wireless communication systems are ubiquitous for personal and commercial uses. 
         [0004]    Demand continue to increase due to increase in quantity of users and increase in quantity of data desired (e.g., graphics, video, data, etc.). However there is a limit to the number of signals a communication system can accommodate per the number of orthogonal or quasi-orthogonal codes, for a direct sequence spread spectrum application. This is because the communication system is an interference limited and/or a code limited resource. 
         [0005]    The need arises to accommodate the increase in the quantity of users and quantity of data desired by the users with the limited resources of the communication system. 
         [0006]    One method of accommodating higher data rates is to use wideband transmissions, e.g., three data streams, that are combined at the receiver to produce the resultant signal. However, given the limitation in numbers of code sequences, a wideband system will simply consume the limited number of code resources faster. 
         [0007]    Consequently, a need arises to provide wideband transmission without the limitation of consuming code resources. 
         [0008]    In a DSSS communication system, multiple signals with different encoding sequences are transmitted simultaneously. To retrieve the desired data stream from the overall data signal, the specific code sequence used to encode the desired signal is reproduced at a receiver, and via the autocorrelation properties, used to detect the original data stream from the noise of and interference in the overall signal. However, in a system such as this, the multiple signals must be sufficiently weak to appear as noise when compared to the signal detected after correlating with the specific code sequence. 
         [0009]    Alternative paths exist between a transmitter and receiver due, e.g., to different reflections from objects such as buildings, mountains, trees, cars, etc. that provide duplicate signals at the receiver with unique time delays. These alternative paths or multipaths can be demodulated at the unique time delays and added up to improve the signal-to-noise ratio (SNR). However, in some cases, many or all of the multipaths provide very weak signals due to interference from other transmitters. 
         [0010]    Consequently a need arises to overcome the limitation of signal reception due to interference of other transmitters. 
         [0011]    One method used to Overcome this limitations is to use multiple antennas on a transmitter alone or to use multiple antennas on a transmitter and receiver. This provides additional multipaths for the signal that might overcome some of the geographical barriers as well as some interference suppression capability to the receiver. However, if different signals transmitted on the different antennas use different codes, then the code resource is used up quickly. Consequently, this model accomplishes little gain in the data rate. 
         [0012]    Thus, a need arises to overcome the limitation of using different code sequences to encode data for each of multiple antennas. 
         [0013]    Capacity is limited by the number of available codes. In particular, orthogonal or at least quasi-orthogonal code sequences must be used for each unique data stream being communicated. However, the number of orthogonal or quasi-orthogonal code sequences is limited for a given code sequence length. 
         [0014]    Thus the capacity of the communication system is limited. Consequently, a need arises for a method to satisfy additional transmission capacity while overcoming the limitation of different encoding sequences required for each data stream. 
       SUMMARY OF INVENTION 
       [0015]    In this invention, information symbols are transmitted simultaneously on independent streams using the same spreading code but from different transmit antennas at the transmitter. These simultaneous data stream could be intended for the same user (and thereby the data rate for any particular user can be increased) or for different users (thereby increasing the system capacity). Each stream of data can belong to a different signal constellation and use a different channel code. At the receiver, a number of receive antennas equal to at least the number of multiple data streams is used to separate the different data streams. We consider two different cases. The first one when no transmit diversity is used (this case can also include the case when transmit diversity with simple antenna weighting is used) and the second when transmit diversity with space-time block coding is used. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a schematic representation of an illustrative communication system that practices the invention; 
           [0017]      FIG. 2  is a block diagram of a transceiver that may be used in the practice of the invention; 
           [0018]      FIG. 3  is a block diagram of a pair of transmitters for use in practicing the invention; 
           [0019]      FIG. 4A  is a block diagram of a receiver used in practicing the invention; 
           [0020]      FIG. 4B  is a block diagram of details of a first embodiment of the receiver of  FIG. 4A ; 
           [0021]      FIG. 4C  is a block diagram of details of a second embodiment of the receiver of  FIG. 4A ; 
           [0022]      FIG. 5A  is a block diagram of a further detail of the block diagram of  FIG. 4B ; 
           [0023]      FIG. 5B  is a block diagram of a further detail of the block diagram of  FIG. 4C ; 
           [0024]      FIG. 6  is a block diagram of another detail of the receiver of  FIG. 4A ; 
           [0025]      FIG. 7  is a flow chart useful in understanding the operation of  FIG. 6 ; 
           [0026]      FIG. 8  is a block diagram of a pair of transmitters of an alternative embodiment of the invention; 
           [0027]      FIG. 9A  is a block diagram of a receiver for use in receiving signals transmitted by the transmitter of  FIG. 8 ; 
           [0028]      FIG. 9B  is a block diagram of details of a first embodiment of the receiver of  FIG. 9A ; 
           [0029]      FIG. 9C  is a block diagram of details of a second embodiment of the receiver of  FIG. 9A ; 
           [0030]      FIG. 10A  is a block diagram of a further detail of the block diagram of  FIG. 9B ; 
           [0031]      FIG. 10B  is a block diagram of a further detail of the block diagram of  FIG. 9C ; 
           [0032]      FIGS. 11A and 11B  are block diagrams of alternatives to  FIGS. 10 and 10B . 
           [0033]      FIG. 12  is a block diagram of another detail of the receiver of  FIG. 9A ; 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]      FIG. 1  is a schematic representation of apparatus  10  for use in practicing the invention. Apparatus  10  comprises at least first and second transmitters  20 ,  30  and a receiver  40 . Transmitter  20  has at least first and second antennas  22 ,  24  for transmitting signals; and transmitter  30  also has at least first and second antennas  32 ,  34  for transmitting signals. Receiver  40  has at least first and second antennas  42 ,  44  for receiving signals. The characteristics of the signal path from the first transmitter to the receiver are represented by the value h ij , where i identifies the receiver antenna number and j identifies the transmitter antenna number. Similarly, the characteristics of the signal path from the second transmitter to the receiver are represented by the value g ij . 
         [0035]    The invention may be practiced using additional antennas and additional transmitters but the number of antennas at the receiver  40  must be equal to at least the number of transmitters. 
         [0036]    As illustrated in  FIG. 1 , transmitters  20 ,  30  are located at base stations and receiver  40  is depicted as terminal equipment such as a mobile station. However, the invention may also be practiced in other configurations such as one where the transmitters are located at terminal equipment that are synchronized and the receiver at a base station. 
         [0037]      FIG. 2  depicts the major functions of an illustrative transceiver  200  that may be used in practicing the invention. Transceiver  200  comprises a receiver unit which includes a front-end processing block  202 , a modem  204  for demodulating the received signal, a codec  206  for decoding the received signal, a memory  208  and a parameter estimator block  212 . These elements are interconnected by a bus  207  and are controlled by a controller/microprocessor  210 . Signals received at antenna  201  are supplied to front-end processing block  202  and processed further by modem  204  and codec  206  under control of controller/microprocessor  210  and programs stored in memory  208 . Transmitter  214  has functional elements similar to those of the receiver section but operating in the opposite direction to generate a coded modulated signal that is provided to antenna  216  for transmission. 
         [0038]    General details about the operation of transceivers of the type shown in  FIG. 2  are well known. Specific details of the operation of such transceivers in the context of the present invention are set forth in the following discussion. 
         [0039]    An illustrative embodiment of a pair of 3GPP transmitters  321 ,  323  for use in practicing the invention is depicted in  FIG. 3 . As shown therein, transmitter  321  comprises a channel encoder  324   a , a modulator  326   a , a multiplier  327   a , a pulse shaper  328   a , and two multipliers  330   a  and  331   a . Transmitter  323  comprises the same functional elements which have been numbered the same but with a “b” suffix. While the elements of the two transmitters are functionally the same, the channel encoder  324   a ,  324   b  may use different channel codes and even different coding schemes; and the modulators  326   a ,  326   b  may use different signal constellations. The output of each modulator is a modulated signal that is suitable for spreading when multiplied by a spreading code in multiplier  327   a  or  327   b.    
         [0040]    Also shown in  FIG. 3  is a source  344  that provides the same spreading code to both multiplier  327   a  and multiplier  327   b . Also shown are sources  340   a ,  342 a,  340   b , and  342 b of weight w 11 , w 12 , w 21  and w 22 , respectively, which are provided to multipliers  330   a ,  331   a ,  330   b , and  331   b.    
         [0041]    In operation, a data stream from a source  301  is provided to a serial to parallel converter  303  that splits the data stream into first and second parallel data streams  325  and  327 , illustratively, by directing every other data symbol to transmitter  321  and the remaining data symbols to transmitter  323 . In  FIG. 3 , the data symbols directed to transmitter  321  are represented by the symbol “c” and the data symbols directed to transmitter  323  are represented by the symbol “s”. 
         [0042]    The first data stream is encoded by channel encoder  324   a , modulated by modulator  326   a  and spread by multiplier  327   a  to form a first spread data stream. The spread data stream is then pulse shaped by pulse shaper  328   a  and the resulting signal is applied in parallel to multipliers  330   a  and  331  a which weight the parallel signals by multiplying them with weights w 11  and w 12 . The weighted spread data streams are then supplied to antennas  332   a  and  334   a  for transmission. 
         [0043]    The second data stream is processed in similar fashion using the elements of transmitter  323  to produce a second spread data stream that has been spread with the same spreading code; and the second spread data stream is then applied in parallel to multipliers  330   b  and  331   b  which weight the parallel signals with weights w 21  and w 22 . The weighted spread data streams are then supplied to antennas  332   b  and  334   b  for transmission. 
         [0044]    An illustrative embodiment of a receiver  400  for receiving signals from multiple transmitters of the type shown in  FIG. 3  is shown in  FIG. 4A . Receiver  400  comprises first and second matched filters  414   a ,  414   b , a source  416  of a spreading code, first and second multipliers  417   a ,  417   b , a signal processing block  418 , first and second channel decoders  420   a ,  420   b , and a parallel to serial converter  422 . Optional feedback paths  421   a  and  421   b  provide decoded signals to signal processing block  418  that may be used for turbo decoding. To recover the data stream that is transmitted from the transmitters of  FIG. 3 , the spreading code supplied by source  416  is the same as that supplied by source  344 . 
         [0045]    Transmitted signals are received at antennas  412   a ,  412   b . The signals received at each antenna comprise the signals transmitted from all the antennas of all the transmitters communicating with the receiver. The signals received at each antenna are filtered by matched filter  414   a  or  414   b  and despread by multiplier  417   a  or  417   b  using the same spreading code. As a result, first and second despread signals are supplied to processing block  418 . In the system of the present invention, each despread signal contains information about both the first and second data streams originally supplied to transmitters  321  and  323 . 
         [0046]    Processing block  418 , which is shown in more detail in  FIGS. 4B ,  4 C,  5 A,  5 B and  6  below, suppresses signal interference and detects the data symbols of the first and second data streams in the received signals. These signals are then supplied to channel decoders  420   a ,  420   b  which decode the signals. The output of the decoders can then be recombined by parallel to serial converter  422  into a single serial stream, if desired, to reconstitute the original data stream delivered from source  301 . 
         [0047]    Further details of one embodiment of processing block  418  are shown in  FIG. 4B . Processing block  418  comprises a plurality of per finger interference suppression blocks  462   a - 462   n , first and second combiners  468   a ,  468   b , first and second tentative decision blocks  472   a ,  472   b , and interference cancellation and soft decision block  476 . 
         [0048]    The signals at the output of multipliers  417   a ,  417   b  include multipath signals that have propagated along different paths from the transmitters to the receiver and consequently have arrived at slightly different times. The stronger of these signals are supplied to different fingers of processing block  418 . The multipath signals from the first multiplier  417   a  are identified by the numbers  452   a ,  454   a , . . .  456   a  and those from the second multiplier  417   b  by numbers  452   b ,  454   b , . . .  456   b . For each finger, one signal from the first multiplier and one signal from the second multiplier are supplied to a per finger interference suppression block  462 . Channel information g about the channel from the second transmitter to the receiver and channel information h about the channel from the first transmitter to the receiver are supplied to all the per finger interference suppression blocks  462   a ,  462   b , . . .  462   n  from sources  416   a  and  416   b.    
         [0049]    Each per finger interference suppression block makes a preliminary decision as to the values of both the first and second data streams in the received signals and supplies these decisions via lines  464   a - n  and  466   a - n  to combiners  468   a  and  468   b , respectively. Combiners  468   a  and  468   b  combine the preliminary decisions from the per finger interference suppression blocks  462   a - n  and supply the results via lines  470   a ,  470   b  to tentative decision blocks  472   a ,  472   b . Channel decoder information is also supplied to blocks  472   a ,  472   b , from sources  422   a ,  422   b . The output of tentative decision blocks  472   a ,  472   b  is an estimate of the received signal and its reliability. This information is supplied via lines  474   a  and  474   b  to the iterative interference cancellation and soft decision block  476 . Channel information from sources  416   a  and  416   b  and received data signals from multipliers  417   a  and  417   b  are also supplied to block  476 . Illustratively, the data signals are the signals  452   a  and  452   b  which are also supplied to the first per finger interference suppression block  462   a . From this information, block  476  makes a soft decision as to the value of the first and second data streams in the received signals. 
         [0050]    To understand the operation of processing block  418 , it is helpful to represent the signal processing in mathematical terms. 
         [0051]    The signal received at antenna i can be written in the form 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         r 
                         i 
                       
                        
                       
                         ( 
                         
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         [0052]    
       25 
     
         [0000]    for the kth symbol and the lth finger. This can be rewritten as: 
         [0000]        r   i ( k,l )= {tilde over (h)}   i ( l )· c ( k )+ {tilde over (g)}   i ( l )· s ( k )+ n   i ( k,l )  i= 1,2   [2] 
         [0000]    where {tilde over (h)} and {tilde over (k)} are the channel gains for the channel from the first transmitter to the receiver and the channel from the second transmitter to the receiver. 
         [0053]    In the case of 3GPP, 
         [0000]        {tilde over (h)}   i ( l )= w   11   ·h   i1 ( l )+ w   12   ·h   i2 ( l ), where ∥ w   11 ∥ 2   +∥w   12 ∥ 2 =1   [3] 
         [0000]        {tilde over (g)}   i ( l )= w   21   ·g   i1 ( l )+ w   22   ·g   i2 ( l ), where ∥ w   21 ∥ 2   +∥w   22 ∥ 2 =1   [4] 
         [0000]    where w 11 , w 12  are the weights applied to the signals from transmitter  321  and w 21 , w 22  are the weights applied to the signals from transmitter  323 . 
         [0054]    On a per-finger signal model, for two antennas at the receiver, equation 2 can be rewritten as: 
         [0000]    
       
         
           
             
               
                 
                   
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         [0055]    And the overall signal model can be written as 
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         [0056]    We define a correlation matrix R for each finger as 
         [0000]    
       
         
           
             
               
                 
                   
                     
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                                   ) 
                                 
                               
                             
                           
                         
                         ] 
                       
                       
                         2 
                          
                         Lx2 
                       
                     
                   
                   , 
                   
                     i 
                     = 
                     1 
                   
                   , 
                   2 
                 
               
               
                 
                   [ 
                   9 
                   ] 
                 
               
             
           
         
       
     
         [0000]    H* is the conjugate transpose of H, I is the, identity matrix, and Γ l  is the signal to noise ratio in finger l. Further, we define 
         [0000]        {tilde over (h)}   l   ={tilde over (h)} ( l )=[ {tilde over (h)}   1 ( l )  {tilde over (h)}   2 ( l )] T  and  {tilde over (g)}   l   ={tilde over (g)} ( l )=[ {tilde over (g)}   1 ( l )  {tilde over (g)}   2 ( l )] T    [10] 
         [0057]    To obtain estimates of the values c l  and s l  for each finger l we need to find a set of weights 
         [0000]        w   c,l   =R   l   −1   ·{tilde over (h)}   l    w   s,l   =R   l   −1   ·{tilde over (g)}   l    [11] 
         [0000]    such that 
         [0000]        c   l   =w   c,l   *·r   l   =c+η   c,l    s   l   =w   s,l   *·r   l   =s+η   s,l    [12] 
         [0000]    where r l  is the received signal as specified by equation [2] and η is the effective noise. As indicated, these weights are obtained by determining the correlation matrix R, inverting the correlation matrix and multiplying it by {tilde over (h)}(l) or {tilde over (g)}(l). 
         [0058]    Illustrative apparatus for calculating the values c l  and s l  is shown in  FIG. 5A . The apparatus comprises a weight generation block  510  and multipliers  512  and  514 . Inputs to the weight generation block include the channel information specified in equation [9] and the signal to noise ratio or an estimate thereof. The received signal r l  is then multiplied by multipliers with weighting signals generated by block  510  as specified in equation [12]. 
         [0059]    The values c l  and s l  are supplied from each per finger interference suppression block  462   a - n  over lines  464   a - n  and  466   a - n  to combiners  468   a  and  468   b  where they are combined. The combined signals are then supplied to tentative decision blocks  472   a  and  472   b  where a minimum mean square error computation is performed to locate the minimum distance between the received signal and a point in the signal constellation. This computation is represented mathematically by 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       c 
                       tsd 
                     
                     = 
                     
                       
                         
                           arg 
                            
                           
                               
                           
                            
                           min 
                         
                         
                           
                             c 
                             c 
                           
                           ∈ 
                           
                             C 
                             c 
                           
                         
                       
                        
                       
                         
                           ∑ 
                           
                             l 
                             = 
                             1 
                           
                           L 
                         
                          
                         
                            
                           
                             
                               
                                 w 
                                 
                                   c 
                                   , 
                                   l 
                                 
                                 * 
                               
                               · 
                               
                                 r 
                                 l 
                               
                             
                             - 
                             
                               c 
                               c 
                               2 
                             
                           
                            
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       s 
                       tsd 
                     
                     = 
                     
                       
                         
                           arg 
                            
                           
                               
                           
                            
                           min 
                         
                         
                           
                             s 
                             c 
                           
                           ∈ 
                           
                             S 
                             c 
                           
                         
                       
                        
                       
                         
                           ∑ 
                           
                             l 
                             = 
                             1 
                           
                           L 
                         
                          
                         
                           
                              
                             
                               
                                 
                                   w 
                                   
                                     s 
                                     , 
                                     l 
                                   
                                   * 
                                 
                                 · 
                                 
                                   r 
                                   l 
                                 
                               
                               - 
                               
                                 s 
                                 c 
                               
                             
                              
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   13 
                   ] 
                 
               
             
           
         
       
     
         [0060]    In addition, the reliabilities, d c  and d s , of the estimates of c and s are also computed according to the formulas 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       d 
                       
                         c 
                         ^ 
                       
                     
                     = 
                     
                       
                         ∑ 
                         
                           l 
                           = 
                           1 
                         
                         L 
                       
                        
                       
                         
                            
                           
                             
                               
                                 w 
                                 
                                   c 
                                   , 
                                   l 
                                 
                                 * 
                               
                               · 
                               
                                 r 
                                 l 
                               
                             
                             - 
                             
                               c 
                               ^ 
                             
                           
                            
                         
                         2 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       d 
                       s 
                     
                     = 
                     
                       
                         ∑ 
                         
                           l 
                           = 
                           1 
                         
                         L 
                       
                        
                       
                         
                            
                           
                             
                               
                                 w 
                                 
                                   s 
                                   , 
                                   l 
                                 
                                 * 
                               
                               · 
                               
                                 r 
                                 l 
                               
                             
                             - 
                             
                               s 
                               ^ 
                             
                           
                            
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   14 
                   ] 
                 
               
             
           
         
       
     
         [0000]    The lower the value of d c  or d s , the more reliable is the estimate. 
         [0061]    The output of tentative decision block  472   a  is a noisy estimate of the received signal c and the reliability of this estimate, d c ; and the output of tentative decision block  472   b  is a noisy estimate of the received signal s and its reliability, d s . This information is supplied to iterative interference cancellation and soft decision block  476 . 
         [0062]    The iterative interference cancellation and soft decision block  476  is shown in detail at  FIG. 6 . This block performs the same operations on the signals received from tentative decision blocks  472   a  and  472   b , compares the results and picks the better one. In particular, as shown in  FIG. 7 , at step  701  it subtracts from the total received signal, r, the contribution to that signal arising from the estimated signal c or s and the associated channel gain {tilde over (h)} or {tilde over (g)}. What is left over is the contribution to the total received signal from the other signal and from noise. At step  702  it then makes an estimate of the value of the other signal using the same mean square error test used in the tentative decision blocks and also calculates the reliability of that estimate. At step  703  it then sums the calculated reliability for one symbol with the received reliability for the other symbol and at step  704  compares the two sums. The lower sum determines the final decision as to the value of the received signal. 
         [0063]    The apparatus of  FIG. 6  comprises first and second multipliers  608   a ,  608   b , first and second adders  610   a ,  610   b , first and second soft decision blocks  612   a ,  612   b , third and fourth adders  614   a ,  614   b  and reliability decision block  620 . Inputs include the soft decisions c and s, and reliabilities d c  and d s , the channel information h and g and the received signal r. Multiplier  608   a  multiplies the channel information h and the estimated signal c; and adder  610   a  determines the difference between the received signal and the contribution to that signal arising from the estimated signal c and the channel gain h. This calculation is represented as: 
         [0000]        x   2L×l   =r−{tilde over (h)}·ĉ   [15] 
         [0064]    Soft decision block  612   a  then makes a new estimate s l  of the signal s using a minimum mean square error determination. This is represented by 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       s 
                       ^ 
                     
                     1 
                   
                   = 
                   
                     
                       
                         arg 
                          
                         
                             
                         
                          
                         min 
                       
                       
                         
                           s 
                           c 
                         
                         ∈ 
                         
                           S 
                           c 
                         
                       
                     
                      
                     
                       
                          
                         
                           x 
                           - 
                           
                             
                               g 
                               ~ 
                             
                             · 
                             
                               s 
                               c 
                             
                           
                         
                          
                       
                       2 
                     
                   
                 
               
               
                 
                   [ 
                   16 
                   ] 
                 
               
             
           
         
       
     
         [0000]    Next, the overall reliability d 1  for the new estimate of s and the received estimate of c is determined by calculating the reliability for the new estimate of s and summing it at adder  614   a  with d c . This is represented by 
         [0000]        d   1   =d   c   +∥x−{tilde over (g)}·ŝ   1 ∥ 2    [17] 
         [0065]    In like fashion, a new estimate of c can be determined and the overall reliability d 2  of the new estimate of c and the received estimate of s can also be determined by multiplier  608   b , adders  610   b ,  614   b  and soft decision block  612   b , implementing the following equations: 
         [0000]    
       
         
           
             
               
                 
                   
                     y 
                     
                       2 
                        
                       Lx 
                        
                       
                           
                       
                        
                       1 
                     
                   
                   = 
                   
                     r 
                     - 
                     
                       
                         g 
                         ~ 
                       
                       · 
                       
                         s 
                         ^ 
                       
                     
                   
                 
               
               
                 
                   [ 
                   18 
                   ] 
                 
               
             
             
               
                 
                   
                     
                       c 
                       ^ 
                     
                     1 
                   
                   = 
                   
                     
                       
                         arg 
                          
                         
                             
                         
                          
                         min 
                       
                       
                         
                           c 
                           c 
                         
                         ∈ 
                         
                           C 
                           c 
                         
                       
                     
                      
                     
                       
                          
                         
                           y 
                           - 
                           
                             
                               h 
                               ^ 
                             
                             · 
                             
                               c 
                               c 
                             
                           
                         
                          
                       
                       2 
                     
                   
                 
               
               
                 
                   [ 
                   19 
                   ] 
                 
               
             
             
               
                 
                   
                     d 
                     2 
                   
                   = 
                   
                     
                       d 
                       s 
                     
                     + 
                     
                       
                          
                         
                           y 
                           - 
                           
                             
                               h 
                               ~ 
                             
                             · 
                             
                               
                                 c 
                                 ^ 
                               
                               1 
                             
                           
                         
                          
                       
                       2 
                     
                   
                 
               
               
                 
                   [ 
                   20 
                   ] 
                 
               
             
           
         
       
     
         [0066]    Finally, d 1  and d 2  are compared by reliability decision block  620 . If d 1 &lt;d 2 , then the new estimate of s and the original estimate of c are accepted and supplied as the outputs of the receiver. If d 2 &lt;d 1 , then the new estimate of c and the original estimate of s are accepted and supplied as the outputs of the receiver. 
         [0067]      FIG. 4C  depicts an alternative receiver  480  to that of  FIG. 4B . In this case, interference suppression is performed on a block basis rather than a per finger basis. Receiver  480  comprises a block interference suppression and combining subsystem  482 , first and second tentative decision blocks  484   a ,  484   b  and interference cancellation and soft decision block  486 . The inputs to receiver  480  and the outputs therefrom are the same as those of receiver  418  of  FIG. 4B . 
         [0068]    Details of the block interference suppression and combining subsystem  982  are set forth in  FIG. 4B . The subsystem comprises a weight generation block  530  and multipliers  532  and  534 . This subsystem is similar to the interference suppression block of  FIG. 5A  but the number of data signal inputs, and g and h channel gain inputs in each case is 2L where L is the number of fingers. In contrast, each interference suppression block of  FIG. 5A  has 2 data signal inputs and 2 inputs each for the G and H channel information. 
         [0069]    Similarly, the mathematical representation of the processing performed in subsystem  482  is similar to that of block  462  but the matrices are much larger. Thus, the correlation matrix R is defined by 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       R 
                       
                         2 
                          
                         L 
                          
                         
                             
                         
                          
                         x 
                          
                         
                             
                         
                          
                         2 
                          
                         L 
                       
                     
                     = 
                     
                       
                         HH 
                         * 
                       
                       + 
                       
                         
                           1 
                           
                             Γ 
                             l 
                           
                         
                         · 
                         I 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   where 
                 
               
               
                 
                   [ 
                   21 
                   ] 
                 
               
             
             
               
                 
                   
                     H 
                     
                       2 
                        
                       Lx 
                        
                       
                           
                       
                        
                       2 
                     
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             
                               h 
                               ~ 
                             
                             1 
                           
                         
                         
                           
                             
                               
                                 g 
                                 ~ 
                               
                               1 
                             
                              
                             
                                 
                             
                           
                         
                       
                       
                         
                           
                             
                               h 
                               ~ 
                             
                             2 
                           
                         
                         
                           
                             
                               g 
                               ~ 
                             
                             2 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   22 
                   ] 
                 
               
             
           
         
       
     
         [0000]    Further, we define 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       h 
                       
                         2 
                          
                         Lx 
                          
                         
                             
                         
                          
                         1 
                       
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 h 
                                 ~ 
                               
                               1 
                             
                           
                         
                         
                           
                             
                               
                                 h 
                                 ~ 
                               
                               2 
                             
                           
                         
                       
                       ] 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       g 
                       
                         2 
                          
                         Lx 
                          
                         
                             
                         
                          
                         1 
                       
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 g 
                                 ~ 
                               
                               1 
                             
                           
                         
                         
                           
                             
                               
                                 g 
                                 ~ 
                               
                               2 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   23 
                   ] 
                 
               
             
           
         
       
     
         [0070]    To obtain estimates of the values of c and s we need to final a set of weights 
         [0000]        w   c   =R   −1   ·{tilde over (h)} w   s   =R   −1   ·{tilde over (g)}   [24] 
         [0000]    such that 
         [0000]        c=w   c   *·r=c+η   c    s=w   s   *·r=s+η   s    [25] 
         [0071]    The estimates of c and s are supplied from subsystem  482  to tentative decision blocks  484   a  and  484   b ; and the operation of these blocks and the interference cancellation and soft decision block  486  is the same as that of the corresponding elements in  FIG. 4B . 
         [0072]    An alternative embodiment of the invention uses space-time block coding to code the transmitted signals. An illustrative embodiment of a pair of transmitters  821 ,  823  for use in practicing this embodiment of the invention is shown in  FIG. 8 . As shown therein, transmitter  821  comprises a channel encoder  824   a , a modulator  826   a , a space-time block coder  828   a , first and second multipliers  834   a ,  835   a , and pulse shapers  838   a ,  839   a . Transmitter  823  comprises the same functional elements which have been numbered the same but with a “b” suffix. While the elements of the two transmitters are functionally the same, the channel encoders  824   a  and  824   b  may use different channel codes and even different coding schemes; and the modulators  826   a  and  826   b  may use different signal constellations. 
         [0073]    Also shown in  FIG. 8  is a source  860  that provides the same spreading code to multipliers  834   a ,  835   a ,  834   b  and  835   b.    
         [0074]    In operation, a data stream from a source  801  is provided to a serial to parallel converter  803  that splits the data stream into first and second parallel data streams  825 ,  827 , illustratively, by directing every other data symbol to transmitter  821  and the remaining data symbols to transmitter  823 . In  FIG. 8 , the data symbols directed to transmitter  821  are represented by the symbol “c” and the data symbols directed to transmitter  823  are represented by the symbol “s”. 
         [0075]    The first data stream is encoded by channel encoder  824   a , modulated by modulator  826   a  and processed by space-time block coder  828   a  to produce first and second signals on output lines  830   a ,  831   a.  These signals are spread by multipliers  834   a ,  835   a  using a spreading code supplied by source  860 . The spread signals are then pulse shaped by pulse shapers  838   a ,  839   a  and supplied to antennas  850   a ,  851   a  for transmission. 
         [0076]    The second data stream is processed in similar fashion using the elements of transmitter  823  to produce two more spread data streams that have been spread using the same spreading code as that used to spread the data streams in transmitter  821 . The spread signals in transmitter  823  are then pulse shaped and supplied to antennas  850   b  and  851   b  for transmission. 
         [0077]    An illustrative embodiment of a receiver  900  for receiving signals from multiple transmitters of the type shown in  FIG. 8  is shown in  FIG. 9A . Receiver  900  comprises first and second matched filters  914   a ,  914   b , a source  916  of a spreading code, first and second multipliers  918   a ,  918   b , a space and time decoder and joint detection and interference suppression subsystem  920 , channel decoders  930   a ,  930   b  and parallel to serial converter  936 . Optional feedback paths  931   a  and  931   b  provide decoded signals to subsystem  920  that may be used for turbo decoding. To recover the data stream that is transmitted from the transmitters of  FIG. 8 , the spreading code supplied by source  916  is the same as that supplied by source  860 . 
         [0078]    Transmitted signals are received at antennas  912   a ,  912   b . The signals received at each antenna comprise the signals transmitted from all the antennas of all the transmitters communicating with the receiver. The signals received at each antenna are filtered by matched filter  914   a  or  914   b  and despread by multipliers  918   a  or  918   b  using the same spreading code. In the system of the present invention, each despread signal contains information about both the first and second data streams originally supplied to transmitters  821  and  823 . 
         [0079]    Subsystem  920 , which is shown in more detail in  FIG. 913  below, suppresses signal interference and space-time decodes the received signals. Soft decisions of a first substream and a second substream are supplied to channel decoders  930   a  and  930   b , respectively. The output of the decoders can then be combined by parallel to serial converter  936  into a single data stream, if desired, to reconstitute the original data stream delivered from source  801 . 
         [0080]    Further details of one embodiment of subsystem  920  are shown in  FIG. 9B . Subsystem  920  comprises a plurality of per finger interference suppression blocks  942   a - 942   n , first and second combiners  948   a ,  948   b , first and second tentative decision blocks  952   a ,  952   b , and interference cancellation and soft decision block  956 . 
         [0081]    The signals at the output of multipliers  918   a ,  918   b  include multipath signals that have propagated along different paths from the transmitters to the receiver and consequently have arrived at slightly different times. The stronger of these signals are supplied to different fingers of subsystem  920 . Illustratively, the multipath signals from the first multiplier  918   a  are identified by r 1×  and those from the second multiplier by r 2× . The second numeral in the subscript indicates the finger member. For each finger, one signal from the first multiplier and one signal from the second multiplier is supplied to a per finger interference suppression and space time decoder block  942 . Channel information g about the channel from the second transmitter to the receiver and channel information h about the channel from the first transmitter to the receiver are supplied to all the per finger interference suppression and space time decoder blocks  942   a - n.    
         [0082]    Each per finger block make a preliminary decision as to the values of first and second pairs of symbols (c 1 , c 2 ) and (s 1 , s 2 ) in the received signals and supplies these decisions via lines  944   a - n  and  946   a - n  to combiners  948   a  and  948   b , respectively. Combiners  948   a  and  948   b  combine the preliminary decisions from the per finger interference suppression and space time decoder blocks  942   a - n  and supply the results via lines  950   a ,  950   b  to tentative decision blocks  952   a ,  952   b . Feedback from the channel decoder is also supplied to these blocks. The output of tentative decision blocks  952   a ,  952   b  is an estimate of the received signals (c 1 , c 2 ; s 1 , s 2 ) and the reliability (d c , d s ) of the estimate. This information is supplied via lines  954   a  and  954   b  to iterative interference cancellation and soft decision block  956 . Channel information h and g and received signals are also supplied to block  956 . From this information, block  956  makes a soft decision as to the values of the first and second data streams in the received signals. 
         [0083]    As will be apparent, the organization of subsystem  920  as shown in  FIG. 9B  is similar to that of block  418  shown in  FIG. 4B  and much of the processing performed in subsystem  920  is also similar. 
         [0084]    The space-time block coder of  FIG. 8  operates on successive symbols, illustratively on pairs of symbols. Thus coder  828   a  operates on the pair of symbols (c 1 , c 2 ), and coder  828   b  operates on the pair, (s 1 , s 2 ). For each pair of symbols provided to the input of space time coder  828   a  the coder generates the complex conjugate of each symbol and rearranges them so as to provide on one output the pair (c 1 , −c 2 *) and on the other output the pair (c 2 , c 1 *), where the lefthand symbol in each pair is the first in time on the output. Illustratively, the pair (c 1 , −c 2 *) is output on line  830   a  and transmitted from antenna  850   a  and the pair (c 2 , c 1 *) is output on line  830   b  and transmitted from antenna  851   a.  In like fashion, space time coder  828   b  receives pairs of symbols (s 1 , s 2 ) and provides on output lines  830   b ,  831   b,  the pairs of symbols (s 1 , −s 2 *) and (s 2 , s 1 *). 
         [0085]    The received signals that are applied to each interference suppression block  942   a - 942   n  of  FIG. 9B  can be represented as 
         [0000]    
       
         
           
             
               
                 
                   
                     r 
                     
                       i 
                       , 
                       l 
                     
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
                               
                                 r 
                                 1 
                               
                                
                               
                                 ( 
                                 
                                   k 
                                   , 
                                   l 
                                 
                                 ) 
                               
                             
                           
                         
                         
                           
                             
                               
                                 r 
                                 2 
                                 * 
                               
                                
                               
                                 ( 
                                 
                                   
                                     k 
                                     + 
                                     1 
                                   
                                   , 
                                   l 
                                 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                     = 
                     
                       
                         
                           H 
                           il 
                         
                         · 
                         c 
                       
                       + 
                       
                         
                           G 
                           il 
                         
                         · 
                         s 
                       
                       + 
                       
                         n 
                         il 
                       
                     
                   
                 
               
               
                 
                   [ 
                   26 
                   ] 
                 
               
             
           
         
       
     
         [0000]    where I is the antenna number, k is time and I is the finger number and 
         [0000]    
       
         
           
             
               
                 
                   
                     H 
                     il 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             
                               h 
                               
                                 i 
                                  
                                 
                                     
                                 
                                  
                                 1 
                               
                             
                              
                             
                               ( 
                               l 
                               ) 
                             
                           
                         
                         
                           
                             
                               h 
                               
                                 i 
                                  
                                 
                                     
                                 
                                  
                                 2 
                               
                             
                              
                             
                               ( 
                               l 
                               ) 
                             
                           
                         
                       
                       
                         
                           
                             
                               h 
                               
                                 i 
                                  
                                 
                                     
                                 
                                  
                                 2 
                               
                               * 
                             
                              
                             
                               ( 
                               l 
                               ) 
                             
                           
                         
                         
                           
                             - 
                             
                               
                                 h 
                                 
                                   i 
                                    
                                   
                                       
                                   
                                    
                                   1 
                                 
                                 * 
                               
                                
                               
                                 ( 
                                 l 
                                 ) 
                               
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   27 
                   ] 
                 
               
             
             
               
                 
                   
                     G 
                     il 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             
                               g 
                               
                                 i 
                                  
                                 
                                     
                                 
                                  
                                 1 
                               
                             
                              
                             
                               ( 
                               l 
                               ) 
                             
                           
                         
                         
                           
                             
                               g 
                               
                                 i 
                                  
                                 
                                     
                                 
                                  
                                 2 
                               
                             
                              
                             
                               ( 
                               l 
                               ) 
                             
                           
                         
                       
                       
                         
                           
                             
                               g 
                               
                                 i 
                                  
                                 
                                     
                                 
                                  
                                 2 
                               
                               * 
                             
                              
                             
                               ( 
                               l 
                               ) 
                             
                           
                         
                         
                           
                             - 
                             
                               
                                 g 
                                 
                                   i 
                                    
                                   
                                       
                                   
                                    
                                   1 
                                 
                                 * 
                               
                                
                               
                                 ( 
                                 l 
                                 ) 
                               
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   28 
                   ] 
                 
               
             
             
               
                 
                   c 
                   = 
                   
                     [ 
                     
                       
                         
                           
                             c 
                              
                             
                               ( 
                               k 
                               ) 
                             
                           
                         
                       
                       
                         
                           
                             c 
                              
                             
                               ( 
                               
                                 k 
                                 + 
                                 1 
                               
                               ) 
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   29 
                   ] 
                 
               
             
             
               
                 
                   s 
                   = 
                   
                     [ 
                     
                       
                         
                           
                             s 
                              
                             
                               ( 
                               k 
                               ) 
                             
                           
                         
                       
                       
                         
                           
                             s 
                              
                             
                               ( 
                               
                                 k 
                                 + 
                                 1 
                               
                               ) 
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   30 
                   ] 
                 
               
             
           
         
       
     
         [0086]    For two antenna the received signals may be represented by 
         [0000]    
       
         
           
             
               
                 
                   
                     r 
                     l 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
                               r 
                               
                                 1 
                                 , 
                                 l 
                               
                             
                           
                         
                         
                           
                             
                               r 
                               
                                 2 
                                 , 
                                 l 
                               
                             
                           
                         
                       
                       ] 
                     
                     = 
                     
                       
                         
                           [ 
                           
                             
                               
                                 
                                   H 
                                   
                                     1 
                                      
                                     
                                         
                                     
                                      
                                     l 
                                   
                                 
                               
                               
                                 
                                   G 
                                   
                                     1 
                                      
                                     l 
                                   
                                 
                               
                             
                             
                               
                                 
                                   H 
                                   
                                     2 
                                      
                                     
                                         
                                     
                                      
                                     l 
                                   
                                 
                               
                               
                                 
                                   G 
                                   
                                     2 
                                      
                                     
                                         
                                     
                                      
                                     l 
                                   
                                 
                               
                             
                           
                           ] 
                         
                          
                         
                           [ 
                           
                             
                               
                                 c 
                               
                             
                             
                               
                                 s 
                               
                             
                           
                           ] 
                         
                       
                       + 
                       
                         [ 
                         
                           
                             
                               
                                 n 
                                 
                                   1 
                                   , 
                                   l 
                                 
                               
                             
                           
                           
                             
                               
                                 n 
                                 
                                   2 
                                   , 
                                   l 
                                 
                               
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
               
                 
                   [ 
                   31 
                   ] 
                 
               
             
           
         
       
     
         [0000]    which may be rewritten as 
         [0000]    
       
         
           
             
               
                 
                   
                     r 
                     
                       l 
                       , 
                       
                         4 
                          
                         x 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                   = 
                   
                     
                       
                         
                           
                             [ 
                             
                               
                                 H 
                                 
                                   l 
                                    
                                   
                                       
                                   
                                    
                                   4 
                                    
                                   x 
                                    
                                   
                                       
                                   
                                    
                                   2 
                                 
                                 ′ 
                               
                                
                               
                                   
                               
                                
                               
                                 G 
                                 
                                   l 
                                    
                                   
                                       
                                   
                                    
                                   4 
                                    
                                   x 
                                    
                                   
                                       
                                   
                                    
                                   2 
                                 
                                 ′ 
                               
                             
                             ] 
                           
                           
                             4 
                              
                             x 
                              
                             
                                 
                             
                              
                             4 
                           
                         
                          
                         
                           [ 
                           
                             
                               
                                 c 
                               
                             
                             
                               
                                 s 
                               
                             
                           
                           ] 
                         
                       
                       
                         4 
                          
                         
                             
                         
                          
                         x 
                          
                         
                             
                         
                          
                         1 
                       
                     
                     + 
                     
                       η 
                       
                         l 
                         , 
                         
                           4 
                            
                           
                               
                           
                            
                           x 
                            
                           
                               
                           
                            
                           1 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   32 
                   ] 
                 
               
             
           
         
       
     
         [0000]    In addition, 
         [0000]    
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             H 
                             
                               1 
                                
                               
                                   
                               
                                
                               l 
                             
                           
                         
                         
                           
                             G 
                             
                               
                                   
                               
                                
                               
                                 1 
                                  
                                 l 
                               
                             
                           
                         
                       
                       
                         
                           
                             H 
                             
                               2 
                                
                               l 
                             
                           
                         
                         
                           
                             G 
                             
                               2 
                                
                               l 
                             
                           
                         
                       
                     
                     ] 
                   
                   ≡ 
                   
                     A 
                     l 
                     ′ 
                   
                 
               
               
                 
                   [ 
                   33 
                   ] 
                 
               
             
           
         
       
     
         [0087]    It will be recognized that H le  and G le  are both orthogonal. Thus, 
         [0000]        H   il   *−H   il =δ h,il   −I , where δ h,il   =|h   i1 ( l ) 2   +|h   i2 ( l )| 2    [34] 
         [0000]        G   il   *−G   il =δ h,il   −I , where δ h,il   =|g   i1 ( l ) 2   +|g   i2 ( l )| 2    [35] 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         H 
                         il 
                         * 
                       
                       · 
                       
                         G 
                         il 
                       
                     
                     ≡ 
                     
                       B 
                       il 
                     
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             b 
                             
                               il 
                               , 
                               1 
                             
                           
                         
                         
                           
                             b 
                             
                               il 
                               , 
                               2 
                             
                           
                         
                       
                       
                         
                           
                             b 
                             
                               il 
                               , 
                               2 
                             
                             * 
                           
                         
                         
                           
                             - 
                             
                               b 
                               
                                 il 
                                 , 
                                 1 
                               
                               * 
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   36 
                   ] 
                 
               
             
           
         
       
     
         [0000]    It will be recognized that B il  is also orthogonal. 
         [0088]    Illustrative apparatus for calculating estimates of the signal pairs (c 1 , c 2 ) and (s 1 , s 2 ) is shown in  FIG. 10A . The apparatus comprises a pre-processing and weight generation block  1010 , multipliers  1012 ,  1014  and  1016  and space-time decoders  1022 ,  1024 . Inputs to the pre-processing and weight generation block  1010  include the channel information H and G and the signal to noise ratio. 
         [0089]    At each finger, the received signal r l  is multiplied at multiplier  1012  with the channel information represented by A l * (see equation 33) to yield 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       A 
                       l 
                       * 
                     
                      
                     
                       r 
                       l 
                     
                   
                   = 
                   
                     
                       r 
                       ~ 
                     
                     = 
                     
                       
                         
                           
                             [ 
                             
                               
                                 
                                   
                                     
                                       δ 
                                       
                                         h 
                                         , 
                                         l 
                                       
                                     
                                      
                                     
                                       · 
                                       I 
                                     
                                   
                                 
                                 
                                   
                                     B 
                                     l 
                                   
                                 
                               
                               
                                 
                                   
                                     B 
                                     l 
                                     * 
                                   
                                 
                                 
                                   
                                     
                                       δ 
                                       
                                         gh 
                                         , 
                                         l 
                                       
                                     
                                     · 
                                     I 
                                   
                                 
                               
                             
                             ] 
                           
                           
                             4 
                              
                             x 
                              
                             
                                 
                             
                              
                             4 
                           
                         
                          
                         
                           [ 
                           
                             
                               
                                 c 
                               
                             
                             
                               
                                 s 
                               
                             
                           
                           ] 
                         
                       
                       + 
                       
                         
                           η 
                           ~ 
                         
                         l 
                       
                     
                   
                 
               
               
                 
                   [ 
                   37 
                   ] 
                 
               
             
           
         
       
     
         [0000]    where 
         [0000]        B   l   *B   l =(| b   1l | 2   +|b   2l | 2 )· I=δ   b,l   ·I    [38] 
         [0090]    Sets of weights w* c,l  and w* s,l  are determined in pre-processing and weight generation block  1010  such that 
         [0000]        W   c,l   =[I−δ   g,l   −1   ·B   l ] 2×4    [39] 
         [0000]        W   s,l   =[I−δ   h,l   −1   ·B   l ] 2×4    [40] 
         [0091]    The weights are then multiplied in multipliers  1014  and  1016  with the output ñ l  from multiplier  1012  and decoded by space time decoders  1022 ,  1024  to produce estimates of the signal pair (c 1 , c 2 ) and (s 1 , s 2 ). This processing is represented by 
         [0000]        W   c,l   *·{tilde over (r)}   l   =r   c,l ={tilde over (δ)} h,l   ·c+ñ   c,l    [41] 
         [0000]        W   s,l   *·{tilde over (r)}   l   =r   s,l ={tilde over (δ)} g,l   ·s+ñ   s,l    [42] 
         [0000]    Since n c,l  and n s,l  are uncorrelated, white noise, the estimates of c and s are good soft decisions. These estimates are supplied by each finger to combiner  948   a  and  948   b  where the estimates are combined and supplied to first and second tentative decision blocks  952   a  and  952   b.    
         [0092]    Tentative decision blocks  952   a  and  952   b  operate in essentially the same fashion as tentative decision blocks  472   a  and  472   b  to generate an estimate of the received signal and its reliability, in this case operating on pairs of signals. A tentative decision as to the value of c and s is made using a mean square error computation to locate the minimum distance between the received signal and a point in the signal constellation. This computation is represented mathematically by 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         c 
                         ^ 
                       
                       tsd 
                     
                     = 
                     
                       
                         
                           arg 
                            
                           
                               
                           
                            
                           min 
                         
                         
                           
                             c 
                             c 
                           
                           ∈ 
                           
                             C 
                             c 
                           
                         
                       
                        
                       
                         
                           ∑ 
                           
                             l 
                             = 
                             1 
                           
                           L 
                         
                          
                         
                           
                              
                             
                               
                                 r 
                                 
                                   c 
                                   , 
                                   l 
                                 
                               
                               - 
                               
                                 
                                   δ 
                                   
                                     h 
                                     , 
                                     l 
                                   
                                 
                                 · 
                                 
                                   c 
                                   c 
                                 
                               
                             
                              
                           
                           2 
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         s 
                         ^ 
                       
                       tsd 
                     
                     = 
                     
                       
                         argmin 
                         
                           
                             s 
                             c 
                           
                           ∈ 
                           
                             S 
                             c 
                           
                         
                       
                        
                       
                         
                           ∑ 
                           
                             l 
                             = 
                             1 
                           
                           L 
                         
                          
                         
                           
                              
                             
                               
                                 r 
                                 
                                   s 
                                   , 
                                   l 
                                 
                               
                               - 
                               
                                 
                                   δ 
                                   
                                     g 
                                     , 
                                     l 
                                   
                                 
                                 · 
                                 
                                   s 
                                   c 
                                 
                               
                             
                              
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   43 
                   ] 
                 
               
             
           
         
       
     
         [0093]    In addition, the reliabilities d c  and d s  of the estimates of c and s are also computed according to the formulas 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       d 
                       
                         c 
                         ^ 
                       
                     
                     = 
                     
                       
                         ∑ 
                         
                           l 
                           = 
                           1 
                         
                         L 
                       
                        
                       
                         
                            
                           
                             
                               r 
                               
                                 c 
                                 , 
                                 l 
                               
                             
                             - 
                             
                               
                                 
                                   δ 
                                   ~ 
                                 
                                 
                                   h 
                                   , 
                                   l 
                                 
                               
                               · 
                               
                                 c 
                                 ^ 
                               
                             
                           
                            
                         
                         2 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       d 
                       
                         s 
                         ^ 
                       
                     
                     = 
                     
                       
                         ∑ 
                         
                           l 
                           = 
                           1 
                         
                         L 
                       
                        
                       
                         
                            
                           
                             
                               r 
                               
                                 s 
                                 , 
                                 l 
                               
                             
                             - 
                             
                               
                                 
                                   δ 
                                   ~ 
                                 
                                 
                                   g 
                                   , 
                                   l 
                                 
                               
                               · 
                               
                                 s 
                                 ^ 
                               
                             
                           
                            
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   44 
                   ] 
                 
               
             
           
         
       
     
         [0094]    The output of tentative decision block  952   a  is an estimate of the received signal pair (c 1 , c 2 ) and the reliability of this estimate, d c ; and the output of tentative decision block  952   b  is an estimate of the received signal pair (s 1 , s 2 ) and the reliability of this estimate, d s . This information is supplied to interference suppression and soft decision block  956 . 
         [0095]    The operation of interference suppression and soft decision block  956  is essentially the same as that of interference suppression and soft decision block  476 . This block performs the same operation on the signals received from tentative decision blocks  952   a  and  952   b , compares the results and picks the better one. This block comprises first and second multipliers  1208   a ,  1208   b , first and second adders  1210   a ,  1210   b , first and second soft decision blocks  1212   a ,  1212   b , third and fourth adders  1214   a ,  1214   b  and reliability decision block  1220 . The operation of this block is the same as that depicted in  FIG. 7  but the block is operating on signal pairs and not individual signals. 
         [0096]    The output of the block is a decision as to the value of signal pairs (c 1 , c 2 ) and (s 1 , s 2 ) which is provided to the channel decoders  930   a ,  930   b.    
         [0097]    As in the case of the receiver of  FIG. 4A , interference suppression can also be performed on a block basis. A receiver  980  for doing so is depicted in  FIG. 9C . Receiver  980  comprises a block interference suppression and space time decoding subsystem  982 , first and second tentative decision blocks  984   a ,  984   b , and interference cancellation and soft decision block  986 . The inputs to receiver  980  and the outputs therefrom are the same as those of receiver  900  of  FIG. 9B . 
         [0098]    Details of the block interference suppression and combining subsystem  982  are set forth in  FIG. 10B . The subsystem comprises a weight pre-processing and generation block  1030 , multipliers  1032 ,  1034  and  1036  and space-time decoders  1042 ,  1044  and  534 . This subsystem is similar to the interference suppression block of  FIG. 10  but the number of data signal inputs, and g and h channel gain inputs in each case is 4L where L is the number of fingers. In contrast, each interference suppression block of  FIG. 10A  has 4 data signal inputs and 4 inputs each for the G and H channel information. 
         [0099]    Similarly, the mathematical representation of the processing performed in subsystem  982  is similar to that of block  942  but the matrices are much larger. The signal model for the received signals at all the fingers is represented by 
         [0000]    
       
         
           
             
               
                 
                   
                     r 
                     
                       4 
                        
                       Lx 
                        
                       
                           
                       
                        
                       1 
                     
                   
                   = 
                   
                     
                       
                         
                           
                             
                               [ 
                               
                                 
                                   
                                     
                                       r 
                                       1 
                                     
                                   
                                 
                                 
                                   
                                     
                                       r 
                                       2 
                                     
                                   
                                 
                                 
                                   
                                     … 
                                   
                                 
                                 
                                   
                                     
                                       r 
                                       L 
                                     
                                   
                                 
                               
                               ] 
                             
                              
                             
                               [ 
                               
                                 
                                   
                                     
                                       H 
                                       1 
                                       ′ 
                                     
                                   
                                   
                                     
                                       G 
                                       1 
                                       ′ 
                                     
                                   
                                 
                                 
                                   
                                     
                                       H 
                                       2 
                                       ′ 
                                     
                                   
                                   
                                     
                                       G 
                                       2 
                                       ′ 
                                     
                                   
                                 
                                 
                                   
                                     … 
                                   
                                   
                                     … 
                                   
                                 
                                 
                                   
                                     
                                       H 
                                       L 
                                       ′ 
                                     
                                   
                                   
                                     
                                       G 
                                       L 
                                       ′ 
                                     
                                   
                                 
                               
                               ] 
                             
                           
                           
                             4 
                              
                             Lx 
                              
                             
                                 
                             
                              
                             4 
                           
                         
                          
                         
                           [ 
                           
                             
                               
                                 c 
                               
                             
                             
                               
                                 s 
                               
                             
                           
                           ] 
                         
                       
                       
                         4 
                          
                         x 
                          
                         
                             
                         
                          
                         1 
                       
                     
                     + 
                     
                       
                         [ 
                         
                           
                             
                               
                                 η 
                                 1 
                               
                             
                           
                           
                             
                               
                                 η 
                                 2 
                               
                             
                           
                           
                             
                               … 
                             
                           
                           
                             
                               
                                 η 
                                 L 
                               
                             
                           
                         
                         ] 
                       
                       
                         4 
                          
                         L 
                          
                         
                             
                         
                          
                         x 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                 
               
               
                 
                   [ 
                   45 
                   ] 
                 
               
             
           
         
       
     
         [0000]    or more simply 
         [0000]    
       
         
           
             
               
                 
                   r 
                   = 
                   
                     
                       
                         [ 
                         
                           
                             H 
                             ′ 
                           
                            
                           
                               
                           
                            
                           
                             G 
                             ′ 
                           
                         
                         ] 
                       
                        
                       
                         [ 
                         
                           
                             
                               c 
                             
                           
                           
                             
                               s 
                             
                           
                         
                         ] 
                       
                     
                     + 
                     η 
                   
                 
               
               
                 
                   [ 
                   46 
                   ] 
                 
               
             
           
         
       
     
         [0000]    where 
         [0000]      [H′ A′]≡A′  [47] 
         [0100]    The columns of H are orthogonal and the columns of G are orthogonal. In addition, 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       H 
                       l 
                       
                         ′ 
                         * 
                       
                     
                     · 
                     
                       H 
                       l 
                       ′ 
                     
                   
                   = 
                   
                     
                       
                         ∑ 
                         
                           i 
                           = 
                           1 
                         
                         2 
                       
                        
                       
                         
                           H 
                           il 
                           * 
                         
                         · 
                         
                           H 
                           il 
                         
                       
                     
                     = 
                     
                       
                         
                           ( 
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               2 
                             
                              
                             
                               δ 
                               
                                 h 
                                 , 
                                 il 
                               
                             
                           
                           ) 
                         
                         · 
                         I 
                       
                       = 
                       
                         
                           δ 
                           
                             h 
                             , 
                             il 
                           
                         
                         · 
                         I 
                       
                     
                   
                 
               
               
                 
                   [ 
                   48 
                   ] 
                 
               
             
             
               
                 
                   
                     
                       G 
                       l 
                       
                         ′ 
                         * 
                       
                     
                     · 
                     
                       G 
                       l 
                       ′ 
                     
                   
                   = 
                   
                     
                       
                         ∑ 
                         
                           i 
                           = 
                           1 
                         
                         2 
                       
                        
                       
                         
                           G 
                           il 
                           * 
                         
                         · 
                         
                           G 
                           il 
                         
                       
                     
                     = 
                     
                       
                         
                           ( 
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               2 
                             
                              
                             
                               δ 
                               
                                 g 
                                 , 
                                 il 
                               
                             
                           
                           ) 
                         
                         · 
                         I 
                       
                       = 
                       
                         
                           δ 
                           
                             g 
                             , 
                             il 
                           
                         
                         · 
                         I 
                       
                     
                   
                 
               
               
                 
                   [ 
                   49 
                   ] 
                 
               
             
             
               
                 
                   
                     
                       H 
                       l 
                       
                         ′ 
                         * 
                       
                     
                     · 
                     
                       G 
                       l 
                       ′ 
                     
                   
                   = 
                   
                     
                       
                         ∑ 
                         
                           i 
                           = 
                           1 
                         
                         2 
                       
                        
                       
                         
                           H 
                           il 
                           * 
                         
                         · 
                         
                           G 
                           il 
                         
                       
                     
                     = 
                     
                       
                         
                           ∑ 
                           
                             l 
                             = 
                             1 
                           
                           2 
                         
                          
                         
                           B 
                           il 
                         
                       
                        
                       
                         = 
                         Δ 
                       
                        
                       
                         
                           B 
                           l 
                         
                         = 
                         
                           [ 
                           
                             
                               
                                 
                                   b 
                                   
                                     l 
                                     , 
                                     1 
                                   
                                 
                               
                               
                                 
                                   b 
                                   
                                     l 
                                     , 
                                     2 
                                   
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   
                                     l 
                                     , 
                                     2 
                                   
                                   * 
                                 
                               
                               
                                 
                                   - 
                                   
                                     b 
                                     
                                       l 
                                       , 
                                       1 
                                     
                                     * 
                                   
                                 
                               
                             
                           
                           ] 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   50 
                   ] 
                 
               
             
           
         
       
     
         [0101]    The pre-processing operation of the pre-processing and weight generation block  1020  produces the values 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       A 
                       * 
                     
                      
                     r 
                   
                   = 
                   
                     
                       r 
                       ~ 
                     
                     = 
                     
                       
                         
                           
                             [ 
                             
                               
                                 
                                   
                                     
                                       δ 
                                       h 
                                     
                                     · 
                                     I 
                                   
                                 
                                 
                                   B 
                                 
                               
                               
                                 
                                   
                                     B 
                                     * 
                                   
                                 
                                 
                                   
                                     
                                       δ 
                                       g 
                                     
                                     · 
                                     I 
                                   
                                 
                               
                             
                             ] 
                           
                           
                             4 
                              
                             
                                 
                             
                              
                             x 
                              
                             
                                 
                             
                              
                             4 
                           
                         
                          
                         
                           [ 
                           
                             
                               
                                 c 
                               
                             
                             
                               
                                 s 
                               
                             
                           
                           ] 
                         
                       
                       + 
                       
                         η 
                         ~ 
                       
                     
                   
                 
               
               
                 
                   [ 
                   51 
                   ] 
                 
               
             
             
               
                 
                   
                     B 
                     
                       2 
                        
                       x 
                        
                       
                           
                       
                        
                       2 
                     
                   
                   = 
                   
                     
                       ∑ 
                       
                         
                           H 
                           l 
                           
                             ′ 
                             * 
                           
                         
                          
                         
                           G 
                           l 
                           ′ 
                         
                       
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               b 
                               1 
                             
                           
                           
                             
                               b 
                               2 
                             
                           
                         
                         
                           
                             
                               b 
                               2 
                               * 
                             
                           
                           
                             
                               - 
                               
                                 b 
                                 1 
                                 * 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   52 
                   ] 
                 
               
             
             
               
                 
                   
                     
                       δ 
                       h 
                     
                     = 
                     
                       ∑ 
                       
                         δ 
                         
                           h 
                           , 
                           l 
                         
                       
                     
                   
                    
                   
                       
                   
                    
                   
                     
 
                   
                    
                   
                     
                       δ 
                       g 
                     
                     = 
                     
                       ∑ 
                       
                         δ 
                         
                           g 
                           , 
                           l 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   53 
                   ] 
                 
               
             
             
               
                 
                   
                     
                       B 
                       l 
                       * 
                     
                      
                     
                       B 
                       l 
                     
                   
                   = 
                   
                     
                       
                         ( 
                         
                           
                             
                                
                               
                                 b 
                                 1 
                               
                                
                             
                             2 
                           
                           + 
                           
                             
                                
                               
                                 b 
                                 2 
                               
                                
                             
                             2 
                           
                         
                         ) 
                       
                       · 
                       I 
                     
                     = 
                     
                       
                         δ 
                         b 
                       
                       · 
                       I 
                     
                   
                 
               
               
                 
                   [ 
                   54 
                   ] 
                 
               
             
           
         
       
     
         [0000]    And the weight generation function produces the weights: 
         [0000]        W   c   =[I−δ   g   −1   ·B]   2×4    [55] 
         [0000]        W   s   =[I−δ   h   −1   ·B]   2×4    [56] 
         [0102]    The value A is supplied to multipler  1030  where it is multiplied with the received signal to produce {tilde over (r)} to produce the value 
         [0000]        r   c,l   =W   c   *·{tilde over (r)}   [57] 
         [0000]    and the weight W s * is supplied to multiplier  1034  where it is multiplied by {tilde over (r)} to produce the value 
         [0000]        r   s   =W   s   *·{tilde over (r)}   [58] 
         [0103]    The output of multiplier  1032  is supplied to ST decoder  1040  where an estimate of the signal pair (c 1 , c 2 ) is formed using the relation 
         [0000]        r   c ={tilde over (δ)} h   ·c+ñ   c    [59] 
         [0000]    and the output of multiplier  1034  is supplied to ST decoder  1042  where an estimate of the signal pair (s 1 , s 2 ) is formed using the relation 
         [0000]        r   s ={tilde over (δ)} g   ·s+ñ   s    [60] 
         [0000]    where 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       δ 
                       ~ 
                     
                     h 
                   
                   = 
                   
                     
                       
                         
                           δ 
                           h 
                         
                         · 
                         
                           δ 
                           g 
                         
                       
                       - 
                       
                         δ 
                         b 
                       
                     
                     
                       δ 
                       g 
                     
                   
                 
               
               
                 
                   [ 
                   61 
                   ] 
                 
               
             
             
               
                 
                   
                     
                       δ 
                       ~ 
                     
                     g 
                   
                   = 
                   
                     
                       
                         
                           δ 
                           g 
                         
                         · 
                         
                           δ 
                           g 
                         
                       
                       - 
                       
                         δ 
                         b 
                       
                     
                     
                       δ 
                       g 
                     
                   
                 
               
               
                 
                   [ 
                   62 
                   ] 
                 
               
             
           
         
       
     
         [0104]    Alternative devices for the interference suppression and space time decoding blocks of  FIGS. 10A and 10B  are shown in  FIGS. 11A and 11B . Apparatus  1110  of  FIG. 11A  comprises a weight generation block  1120  and first and second multipliers  1122  and  1124 . Apparatus  1140  of  FIG. 11B  comprises a weight generation block  1150  and first and second multipliers  1152  and  1154 . While similar in overall configuration, the two devices have very different numbers of inputs. Apparatus  1110  receives 4 input signals r, 4 signals each for the channel information H and G and the signal to noise ration. Apparatus  1140  receives 4L input signals, 4L signals each for H and G and the signal to noise ration. One apparatus  1110  is used in the receiver of  FIG. 9B  for each finger while only one apparatus  1140  is used in the receiver of  FIG. 9C . 
         [0105]    In apparatus  1110 , the correlation matrix R can be determined from the channel information and the signal to noise ratio by 
         [0000]    
       
         
           
             
               
                 
                   
                     R 
                     
                       l 
                        
                       
                           
                       
                        
                       4 
                        
                       x 
                        
                       
                           
                       
                        
                       4 
                     
                   
                   = 
                   
                     
                       A 
                       1 
                     
                      
                     
                       A 
                       1 
                     
                     * 
                     
                       
                         + 
                         
                           1 
                           
                             Γ 
                             1 
                           
                         
                       
                       · 
                       I 
                     
                   
                 
               
               
                 
                   [ 
                   63 
                   ] 
                 
               
             
           
         
       
     
         [0000]    To obtain estimates of the signal pairs c=c 1 , c 2  and s=s 1 , s 2  for each finger, we need to find a set of weights 
         [0000]        W   c,l4×2   =R   l   −1   ·H   l    [64] 
         [0000]    
       
      
       W 
       s,l4×2 
       =R 
       l 
       −1 
       ·G 
       l  
      
     
         [0000]    such that 
         [0000]        W*   c,l   ·r   l   =c+ñ   c,l    [65] 
         [0000]        W*   c,l   ·r   l   =c+ñ   c,l    [65] 
         [0106]    As indicated, the weights are obtained by determining the correlation matrix, inverting it and multiplying it by the channel information H or G. 
         [0107]    The estimates are obtained by multiplying the weights at multipliers  1122  and  1124  with the received signals. Thereafter, the estimates are combined at combiners  948   a  and  948   b  of the receiver of  FIG. 9B  and forwarded to tentative decision blocks  952   a ,  952   b  where an estimate of the received signals is made by a minimum mean square error computation. 
         [0108]    Apparatus  1140  processes the signals in the same fashion but uses much larger matrices encompassing all the signals supplied to the interference suppression and space time decoding block. In particular, the correction matrix R has the size 4L×4L where L is the number of fingers and the weighting matrices have the size 4L×2. 
         [0109]    As will be apparent to those skilled in the art, numerous modifications may be made to the above invention with the spirit and scope of the invention.

Technology Category: h