TECHNICAL FIELD 
     The present invention relates to the field of communication technology, in particular to a code channel activation method, a code channel activation device, a computer program and a storage medium. 
     BACKGROUND 
     In a CDMA (Code-Division Multiple Access) wireless communication system, adjacent cells may have an identical carrier frequency point so as to save frequency resources and improve the throughput of the system. 
     In this system, because a current cell has the same carrier frequency as an adjacent cell, a signal of the adjacent cell may be introduced into the current cell when passing through a RF section of a terminal, and it will interfere with a useful signal of the current cell. At this time, it needs to perform code channel activation. 
     Taking a TD-SCDMA wireless communication system as an example, in an existing coherent demodulation wireless communication system, when a signal received by the terminal is mixed with an intra-frequency signal of the adjacent cell, both an interference code channel and a user code channel will be introduced into a detector for joint detection. When the total number of the code channels exceeds the capacity of the detector, it will perform code channel activation and discard some of the code channels, so as to ensure that the total number of the code channels does not exceed the capacity of the detector, thereby to perform matching filtering and equalizing. 
     However, currently the code channels are selected according to the power of the code channels, rather than the other features. As a result, some code channels with more information may be discarded, which results in performance loss of a receiver. 
     SUMMARY 
     An object of the present invention is to provide a code channel activation method, a code channel activation device, a computer program and a storage medium so as to solve the problem in the prior art that performance loss of a receiver will be caused when performing code channel activation. 
     In one aspect, the present invention provides a code channel activation method, comprising: 
     calculating correlation between interference code channels on which code channel activation is to be performed and a user code channel, and correlation between the user code channels, to obtain correlation results; and 
     performing code channel activation according to the correlation results, reserving the code channels of the first kind and discarding the code channels of the second kind; 
     wherein the code channels of the first kind including more information that the code channels of the second code channel. 
     In another aspect, the present invention further provides a code channel activation device, comprising: 
     a correlation calculation module, configured to calculate correlation between interference code channels on which code channel activation is to be performed and a user code channel and correlation between the user code channels; and 
     a code channel activation module configured to perform code channel activation according to the correlation results, reserve the code channels of the first kind and discard the code channels of the second kind, wherein the code channels of the first kind including more information than the code channels of the second kind. 
     According to the present invention, the code channel activation is performed according to the correlation between the code channels. As a result, it is able to reserve the code channels with more information, thereby to prevent the performance loss of the receiver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart of a code channel activation method according to a first embodiment of the present invention; 
         FIG. 2  is a schematic view showing a simulation result obtained according to an algorithm of the present invention; and 
         FIG. 3  is a schematic view showing a code channel activation device according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is described hereinafter in conjunction with the drawings. The first embodiment of the present invention provides a code channel activation method. In this embodiment, a TD-SCDMA system is taken as an example, and the basic method and device for it may also be used for all DS-CDMA systems. To facilitate the understanding, the parameters are given in Table 1. 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
             
               
                   
                 Communication system 
                 TD-SCDMA 
               
               
                   
                 Number of cells 
                 2 
               
               
                   
                 Midamble No. 
                 52, 97 
               
               
                   
                 Modulation mode 
                 QPSK 
               
               
                   
                 Spreading factor 
                 16  
               
               
                   
                 Kcell 
                 8 
               
               
                   
                 Number of Tx antennae 
                 1 
               
               
                   
                 Number of Rx antennae 
                 1 
               
               
                   
                 Number of code channels 
                 current cell: 2 
               
               
                   
                   
                 adjacent cell: 16 
               
               
                   
                 Code channel No. 
                 current cell: 1, 2 
               
               
                   
                   
                 adjacent cell: 1~16 
               
               
                   
                 Number of timeslots 
                 1 
               
               
                   
                   
               
             
          
         
       
     
     As shown in  FIG. 1 , the present invention provides a code channel activation method, comprising: 
     Step  101 : calculating correlation between a first interference code channel within a window and two user code channels, and correlation between the two user code channels; and 
     Step  102 : performing code channel activation according to the correlation results. 
     In Step  101 , the first interference code channel may be used as the interference code channel on which the code channel activation is to be performed, and so does a second interference code channel or the others. Of course, for a TD-SCDMA system, all the interference code channels in a window are used as the interference code channels on which the code channel activation is to be performed. In this embodiment, there are 8 windows. Two interference code channels are located within one window, e.g., the first and second interference code channels are located within the same window. 
     To facilitate the implementation, the correlation between all the code channels (including 16 interference code channels and 2 user code channels received by a terminal) and the 2 user code channels is generated at first. During the implementation, it needs to generate combined channel impulse responses for all the k (k=1, 2, . . . , 18) code channels. The combined channel impulse response for the k th  code channel is calculated by the equation: 
     
       
         
           
             
               
                 
                   
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     wherein b (k)  represents the combined channel impulse response of the k th  code channel in all the code channels consisting of the interference code channels and the user code channels received by the terminal, k is an integer and k=1, 2, . . . , N users +1, N users +2, . . . , CH v , N users  represents the number of user code channels, CH v  represents the total number of the code channels, c (k)  represents a spreading code corresponding to the k th  code channel, m (k)  represents a scrambling code corresponding to the k th  code channel, h (k)  represents the channel impulse response corresponding to the k th  code channel, .* represents a symbol for point multiplication,             represents a symbol for linear convolution, Q represents a spreading factor, and W represents a window length for the channel impulse response.
     The correlation between the 18 code channels and the 2 user code channels is calculated according to the generated combined channel impulse responses for the 18 code channels (including the user code channels and the interference code channels), so as to generate a correlation matrix. 
     The code channels are selected according to the calculated correlation between the 18 code channels and the 2 user code channels, and then the code channel activation is performed, so as to obtain a more accurate demodulation result. 
     In this embodiment, the correlation matrix is generated as follows, when the number of the code channels in the current cell is defined as N user =2 and the total number of the code channels is defined as CH v =18, the correlation Cor(i, k) between the i th  code channel in the N user  code channels and the k th  code channel in the CH v  code channels is calculated by the following equation:
 
Cor( i,k )=abs(sum( b   (i)   .*b   (k)* )),( i= 1,2, k= 1,2, . . . ,18)
 
wherein sum(.) represents the operation for finding a sum of all elements of a vector, abs(.) represents the operation for finding an absolute value, and b (i)  represents the combined channel impulse response for the i th  code channel in the user code channels.
 
     In this embodiment, the code channel activation is performed as follows, at first a sum AutoCorUser of the correlation between the 2 user code channels is calculated by the equation 
               AutoCorUser   =       (       ∑     j   =   1     2     ⁢           ⁢       ∑     i   =   1     2     ⁢           ⁢     Cor   ⁡     (     i   ,   j     )           )     ⁢           ⁢     (       j   =   1     ,   2     )         ,         
wherein Cor(i, j) represents the correlation between the i th  user code channel and the j th  user code channel in the user code channels.
 
     Then, the correlation between the code channels within the m th  (m=1, 2, . . . , 8) window and the 2 user code channels is calculated by the equation 
                 WinCor   ⁡     (   m   )       =       ∑     l   ∈     Win   m         ⁢           ⁢       ∑     i   =   1     2     ⁢           ⁢     Cor   ⁡     (     i   ,   l     )             ,         
wherein Cor(i,l) represents the correlation between the i th  code user in the user code channels and the l th  interference code channels in all the interference code channels.
 
     And then, a threshold α is set, and when the l th  (1=3, 4, . . . , 18) code channel is located within the m th  window, the code channel activation is performed according to the correlation by using the following equation: 
     
       
         
           
             
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     That is to say, if WinCor(m)/CodeNum(m)&gt;α*AutoCorUser/N user , the interference code channels within the m th  window win m  will be activated, and if WinCor(m)/CodeNum(m)&lt;=α*AutoCorUser/N user , the interference code channels within the m th  window Win m  will not be activated. CodeNum(m) represents the number of the interference code channels within the m th  window, wherein α&lt;1. 
     Of course, it is merely a preferred scheme for the TD-SCDMA system to perform the code channel activation according to the equation 
               b     (   l   )       =     {             b     (   l   )       ⁡     (     the   ⁢           ⁢     l   th     ⁢           ⁢   code   ⁢           ⁢   channel   ⁢           ⁢   is   ⁢           ⁢   activated     )                 WinCor   ⁡     (   m   )       /   2     &gt;     α   *     AutoCorUser   /   2                   0   ⁢           ⁢     (     the   ⁢           ⁢     l   th     ⁢           ⁢   code   ⁢           ⁢   channel   ⁢           ⁢   is   ⁢           ⁢   not   ⁢           ⁢   activated     )                   WinCor   ⁡     (   m   )       /   2     )     &lt;=     α   *     AutoCorUser   /   2                       
and for the other CDMA systems, the code channel activation will be performed according to
 
     
       
         
           
             
               
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                   users 
                 
               
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             &gt; 
             
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                 AutoCorUser 
                 / 
                 
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               and 
             
           
         
       
       
         
           
             
               
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                     user 
                   
                   . 
                 
               
             
           
         
       
     
     Different from the aforementioned scheme where WinCor(m) is used as a first calculation result obtained according to the correlation result Cor(i,l) between the 2 user code channels, 
               ∑     l   =   1       N   users       ⁢           ⁢     Cor   ⁡     (     i   ,   l     )             
is used herein as the first calculation result obtained according to the correlation result Cor(i,l) between the 2 user code channels. Also, whether or not the interference code channel is activated may be judged according to
 
                 ∑     l   =   1       N   users       ⁢           ⁢     Cor   ⁡     (     i   ,   l     )         &gt;     β   *   AutoCorUser   ⁢           ⁢   and                       ∑     l   =   1       N   users       ⁢           ⁢     Cor   ⁡     (     i   ,   l     )         &lt;=     β   *   AutoCorUser       ,         
wherein β is another threshold. Here, both AutoCorUser/N user  and AutoCorUser are a second calculation result obtained according to Cor(i, j). It can be seen that, a principle for judging whether or not the interference code channel is activated is that the interference code channel on which the code channel activation is to be performed will be activated when a ratio of the second calculation result to the first calculation result is greater than the threshold, and otherwise the interference code channel will not be activated.
 
     After the code channel activation is performed according to the correlation results, the code channels of the first kind will be reserved and the code channels of the second kind will be discarded. The code channels of the first kind include more information than the code channels of the second kind. 
     A traditional code channel activation algorithm may also be used in the method of the present invention, and the code channel activation may be performed according to the correlation results and the power of each code channel. For example, when WinCor(m)/CodeNum(m)&gt;α*AutoCorUser/N user  and the power of the interference code channel within the m th  window Win m , needs to be greater than the given power, the interference code channel within the m th  window Win m  will be activated. 
       FIG. 2  shows the simulation results under the above-mentioned simulation configurations and channel environments. According to a simulation result 10 obtained by the traditional algorithm and a simulation result 20 obtained by the algorithm of the present invention, it is found that the algorithm of the present invention is less complex, and can obtain better performance, especially in a worse interference environment. 
     As shown in  FIG. 3 , an embodiment of the present invention provides a code channel activation device, comprising: 
     a correlation calculation module  201 , configured to calculate correlation between interference code channels on which code channel activation is to be performed and a user code channel, and correlation between the user code channels, to obtain correlation results; and 
     a code channel activation module  202 , configured to perform code channel activation according to the correlation results, reserve the code channels of the first kind and discard the code channels of the second kind, wherein the code channels of the first kind including more information than the code channels of the second kind. 
     Further, the correlation calculation module  201  is specifically configured to generate combined channel impulse responses for the interference code channels on which the code channel activation is to be performed and combined channel impulse responses for the user code channels, and calculate the correlation between the interference code channels on which the code channel activation is to be performed and the user code channel and the correlation between the user code channels according to the generated combined channel impulse responses. 
     The code channel activation module  202  is specifically configured to obtain a first calculation result according to the correlation between the user code channels, and a second calculation result according to the correlation between the interference code channels on which the code channel activation is to be performed and the user code channel, activate the interference code channels when a ratio of the second calculation result to the first calculation result is greater than a threshold, and otherwise, not activate the interference code channel. 
     The correlation calculation module  201  is specifically configured to generate the combined channel impulse responses for the interference code channels on which the code channel activation is to be performed and the combined channel impulse responses for the user code channels by using the following equation: 
                     b     (   k   )       =       ⁢     (       b   1     (   k   )       ,     b   2     (   k   )       ,   …   ⁢           ,     b     Q   +   W   -   1       (   k   )         )                 =       ⁢       (         c     (   k   )       .     *     m     (   k   )         )     ⊗     h     (   k   )                     =       ⁢       (         (       c   1     (   k   )       ,     c   2     (   k   )       ,   …   ⁢           ,     c   Q     (   k   )         )     .     *     (       m   1     (   k   )       ,     m   2     (   k   )       ,   …   ⁢           ,     m   Q     (   k   )         )       )     ⊗                     ⁢     (       h   1     (   k   )       ,     h   2     (   k   )       ,   …   ⁢           ,     h   W     (   k   )         )                 
wherein b (k)  represents the combined channel impulse response of the k th  code channel in all the code channels consisting of the interference code channels and the user code channels received by the terminal, k is an integer and k=1, 2, . . . , N user +1, N users +2, CH v , N users  represents the number of user code channels, CH v  represents the total number of the code channels, c (k)  represents a spreading code corresponding to the k th  code channel, m (k)  represents a scrambling code corresponding to the k th  code channel, h (k)  represents the channel impulse response corresponding to the k th  code channel, .* represents a symbol for point multiplication,             represents a symbol for linear convolution, Q represents a spreading factor, and W represents a window length for the channel impulse response.

     Then, the correlation calculation module  201  is configured to calculate the correlation between the interference code channels on which the code channel activation is to be performed and the user code channel, and the correlation between the user code channels according to the generated combined channel impulse responses by using the following equation:
 
Cor( i,k )=abs(sum( b   (i)   .*b   (k) *)), i= 1,2 , . . . ,N   users ,
 
wherein Cor(i,k) represents the correlation between the i th  code channel in the user code channels and the k th  code channel in all the code channels, sum(.) represents the operation for finding a sum of all elements of a vector, abs(.) represents the operation for finding an absolute value, and b (i)  represents the combined channel impulse response for the i th  code channel in the user code channels.
 
     The code channel activation module  202  is specifically configured to calculate a sum AutoCorUser of the correlation between the user code channels by using the equation 
               AutoCorUser   =       (       ∑     j   =   1       N   users       ⁢           ⁢       ∑     i   =   1       N   users       ⁢           ⁢     Cor   ⁡     (     i   ,   j     )           )     ⁢           ⁢     (       j   =   1     ,   2   ,   …   ⁢           ,     N   users       )         ,         
and use AutoCorUser/N user  as a first calculation result, wherein Cor(i, j) represents the correlation between the i th  code channel and the j th  code channel in the user code channels.
 
     The code channel activation device further comprises a joint detection module  203  configured to perform joint detection on the activated code channels. 
     Further, the code channel activation module  202  is specifically configured to calculate the correlation WinCor(m) between the interference code channels within the m th  window Win m  and the user code channels by using the equation 
                 WinCor   ⁡     (   m   )       =       ∑     l   ∈     Win   m         ⁢           ⁢       ∑     i   =   1       N   users       ⁢           ⁢     Cor   ⁡     (     i   ,   l     )             ,         
use WinCor(m)/CodeNum(m) as a second calculation result, if WinCor(m)/CodeNum(m)&gt;α*AutoCorUser/N user , activate the interference code channels within the m th  window Win m , and if WinCor(m)/CodeNum(m)&lt;=α*AutoCorUser/N user , not activate the interference code channels within the m th  window Win m , wherein Cor(i, l) represents the correlation between the i th  code channel in the user code channels and the l th  code channel in all the interference code channels, CodeNum(m) represents the number of the interference code channels in the m th  window, and a represents a given threshold.
 
     Further, the code channel activation module  202  is specifically configured to perform the code channel activation according to the correlation results and the power of each code channel. 
     The above embodiments are merely for illustrative purpose, but shall not be construed as limiting the present invention. It should be noted that, a person skilled in the art may make further modifications or equivalent substitutions without departing from the spirit and principle of the present invention, and these modifications and substitutions shall also be considered as the scope of the present invention.
The present invention provides a code channel activation method, a code channel activation device, a computer program and a storage medium, so as to solve the problem in the prior art that performance loss of a receiver will be caused when performing code channel activation. The method comprises calculating correlation between interference code channels on which code channel activation is to be performed and a user code channel, and correlation between the user code channels, to obtain correlation results; and performing code channel activation according to the correlation results. According to the present invention, the code channel activation is performed according to the correlation between the code channels. As a result, it is able to reserve the code channels with more information, thereby to prevent the performance loss of the receiver.