Abstract:
Provided is a communication capacity evaluating apparatus whereby the communication capacity can be grasped and the necessity of changing the content of a dead spot measure after the placement of a relay apparatus can be eliminated. In the communication capacity evaluating apparatus, a system information analyzing unit ( 121 ) acquires, from a received signal, used-band information of the communication using a MIMO mode. An S/N calculating unit ( 122 ) analyzes the received signal to determine a signal-to-noise ratio. A channel estimating unit ( 123 ) analyzes the received signal to determine a channel matrix. A throughput limit calculating unit ( 124 ) calculates the limit value of the communication capacity on the basis of the used-band information, information about the number of transmission antennas of a base station ( 180 ), information about the number of reception antennas of a radio relay apparatus ( 100 ) stored in advance, the signal-to-noise ratio and the channel matrix. A display unit ( 133 ) displays the result of a comparison between the limit value and a desired value of communication capacity set in advance.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a communication capacity evaluating apparatus, a radio repeater apparatus, and a communication capacity evaluating method. More particularly, the present invention relates to a communication capacity evaluating apparatus, a radio repeater apparatus, and a communication capacity evaluating method, which learn communication capacity in a setting location of a radio repeater apparatus performing relay processing of communication using a multi-input multi-output (MIMO) scheme, 
       BACKGROUND ART 
       [0002]    Recently it has been required to set a repeater apparatus which enables communication using a MIMO scheme as countermeasures for blind zones in communication using a MIMO scheme which is one of next-generation communications. When setting the repeater apparatus, it is necessary to learn communication capacity (throughput) of communication using a. MIMO scheme in a setting location and set a repeater apparatus on condition that a certain amount of communication capacity can be secured. 
         [0003]    Also, conventionally, it is known to determine a state of communication using a MIMO scheme (see, for example, Patent Literature 1). Patent Literature 1 discloses a state index calculating section that calculates a state index showing a current communication state using all or part of transfer functions, and a communication state display section that changes display contents according to a value of a state index. 
       CITATION LIST 
     Patent Literature 
     PTL 1  
     Japanese Patent Application Laid-Open No.2006-211566 
     SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    However, with Patent Literature 1, it is not possible to calculate communication capacity from a communication state index calculated from only a transfer function, and. therefore there is a problem that communication capacity cannot be learnt. Also, with Patent Literature 1, a limit value of communication capacity cannot be known even when a communication state index is displayed, and there is a problem that cannot determine whether or not it is appropriate as a setting location of a repeater apparatus. Also, with Patent Literature 1, since it is not possible to determine whether or not it is appropriate as a setting location, therefore, there is a problem that the contents of countermeasures for blind zones need to be changed upon finding that a limit value of communication capacity does not satisfy a desired value after the setting of the repeater apparatus. 
         [0005]    It is therefore an object of the present invention to provide a communication capacity evaluating apparatus, a radio repeater apparatus, and a communication capacity evaluating method that can learn communication capacity and eliminate the need to change the contents of countermeasures for blind zones after the setting of a repeater apparatus. 
       Solution to Problem 
       [0006]    A communication capacity evaluating apparatus according to the present invention is a communication capacity evaluating apparatus that evaluates communication capacity of communication using a multiple-input and multiple-output scheme, and employs a configuration to include an acquiring section that acquires band information for use of communication using the multiple-input and multiple-output scheme from a received signal, and analyzes the received signal to calculate a signal-to-noise ratio and a channel matrix; a limit value calculating section that calculates a limit value of communication capacity based on the band information for use, the signal-to-noise ratio, the channel matrix, the number of transmitting antennas of a communication party, and the number of receiving antennas; and a display section that displays a comparison result between the limit value and a desired value of communication capacity set in advance. 
         [0007]    A radio repeater apparatus according to the present invention is a radio repeater apparatus that performs relay processing of communication using a multiple-input and multiple-output scheme, and that employs a configuration to include an acquiring section that acquires band information for use of communication using the multiple-input and multiple-output scheme from a received signal, and analyzes the received signal to calculate a signal-to-noise ratio and a channel matrix; a limit value calculating section that calculates a limit value of communication capacity based on the band information for use, the signal-to-noise ratio, the channel matrix, the number of transmitting antennas of a communication party, and the number of receiving antennas; and a display section that displays a comparison result between the limit value and a desired value of communication capacity set in advance. 
         [0008]    A communication capacity evaluating method according to the present invention is a method for evaluating communication capacity of communication using a multiple-input and multiple-output scheme, and employs the steps of acquiring band information for use of communication using the multiple-input and multiple-output scheme from. a received signal, and analyzing the received signal to calculate a signal-to-noise ratio and a channel matrix; calculating a limit value of communication capacity based on the band information for use, the signal-to-noise ratio, the channel matrix, the number of transmitting antennas of a communication party, and the number of receiving antennas; and displaying a comparison result between the limit value and a desired value of communication capacity set in advance. 
       Advantageous Effects of Invention 
       [0009]    According to the present invention, it is possible to learn communication capacity and eliminate the need to change the contents of countermeasures for blind zones after the setting of a repeater apparatus. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a block diagram showing the configuration of a radio repeater apparatus according to Embodiment 1 of the present invention; 
           [0011]      FIG. 2  illustrates a method of calculating a channel matrix between a base station and a radio repeater apparatus according to Embodiment 1 of the present invention; 
           [0012]      FIG. 3  is a block diagram showing the configuration of a radio repeater apparatus according to Embodiment 2 of the present invention; 
           [0013]      FIG. 4  illustrates a relationship between a limit value of communication capacity and an eigenvalue upon changing the eigenvalue in a case where the number of antennas according to Embodiment 2 of the present invention are two in transmission and reception; and 
           [0014]      FIG. 5  is a block diagram showing the configuration of a communication capacity evaluating apparatus according to Embodiment 3 of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    Now, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       Embodiment 1 
       [0016]      FIG. 1  is a block diagram showing the configuration of radio repeater apparatus  100  according to Embodiment 1 of the present invention. 
         [0017]    Radio repeater apparatus  100  mainly has repeater amplification apparatus  150 , communication capacity calculating section  160 , and display control section  170 . 
         [0018]    Repeater amplification apparatus  150  receives signals transmitted from base station  180  using a MIMO scheme, and amplifies and transmits the received signals to communication terminal apparatuses (not shown) or other repeater apparatuses (not shown). Also, in communication using a MIMO scheme, repeater amplification apparatus  150  receives and amplifies signals transmitted from communication terminal apparatuses (not shown) or other repeater apparatuses (not shown) using a MIMO scheme, and transmits the amplified signals to base station  180 . That is to say, repeater amplification apparatus  150  performs relay processing of signals in communication using a MIMO scheme. 
         [0019]    Communication capacity calculating section  160  calculates a limit value of communication capacity of signals in which repeater amplification. apparatus  150  receives from base station  180 , and outputs the calculated limit value to display control section  170 . 
         [0020]    Display control section  170  calculates a desired value of communication capacity based on a calculating result of a limit value of communication capacity input from communication capacity calculating section  160 , and performs control to display a comparison result between the limit value and the desired value. 
         [0021]    Next, a detailed configuration of repeater amplification apparatus  150  will be described with reference to  FIG. 1 . 
         [0022]    Repeater amplification apparatus  150  is mainly formed with first antenna  101 , second antenna  102 , filter  103 , filter  104 , demultiplexing section  105 , demultiplexing section  106 , amplifier  107 , amplifier  108 , amplifier  109 , amplifier  110 , filter  111 , filter  112 , third antenna  113 , and fourth antenna  114 . 
         [0023]    First antenna  101  receives signals transmitted from base station  180  and outputs the signals to filter  103 . Also, first antenna  101  transmits signals input from filter  103  to base station  180 . 
         [0024]    Second antenna  102  receives signals transmitted from base station  180  and outputs the signals to filter  104 , Also, second antenna  102  transmits signals input from filter  104  to base station  180 , Here, first antenna  101  and second antenna  102  are used for performing communication using a MIMO scheme. 
         [0025]    Filter  103  performs band limitation to signals input from first antenna  101  and outputs the signals to demultiplexing section  105 . Also, filter  103  performs band limitation to signals input from amplifier  108  and outputs the signals to first antenna  101 . 
         [0026]    Filter  104  performs band limitation to signals input from second antenna  102  and. outputs the signals to demultiplexing section  106 . Filter  104  performs band limitation to signals input from amplifier  110  and outputs the signals to second antenna  102 , 
         [0027]    Demultiplexing section  105  demultiplexes signals input from filter  103  and outputs the demultiplexed signals to amplifier  107 , system information analysis section  121 , S/N calculating section  122 , and channel estimation section  123 . 
         [0028]    Demultiplexing section  106  demultiplexes signals input from filter  104  and outputs the demultiplexed signals to amplifier  109 , system information analysis section  121 , S/N calculating section  122 , and channel estimation section  123 . 
         [0029]    Amplifier  107  amplifies signals input from demultiplexing section  105  and outputs the signals to filter  111 . 
         [0030]    Amplifier  108  amplifies signals input from filter  111  and outputs the signals to filter  103 . 
         [0031]    Amplifier  109  amplifies signals input from demultiplexing section  106  and outputs the signals to filter  112 , 
         [0032]    Amplifier  110  amplifies signals input from filter  112  and outputs the signals to filter  104 . 
         [0033]    Filter  111  performs band limitation to signals input from amplifier  107  and outputs the signals to third antenna  113 . Also, filter  111  performs band limitation to signals input from third antenna  113  and outputs the signals to amplifier  108 . 
         [0034]    Filter  112  performs band limitation to signals input from amplifier  109  and outputs the signals to fourth antenna  114 . Also, filter  112  performs band limitation to signals input from fourth antenna  114  and outputs the signals to amplifier  110 . 
         [0035]    Third antenna  113  transmits signals input from filter  111  to communication terminal apparatuses (not shown) or other repeater apparatuses (not shown). Also, third antenna  113  outputs signals received from communication terminal apparatuses (not shown) or other repeater apparatuses (not shown) to filter  111 . 
         [0036]    Fourth antenna  114  transmits signals input from filter  112  to communication terminal apparatuses (not shown) or other repeater apparatuses (not shown). Also, fourth antenna  114  outputs signals received from communication terminal apparatuses (not shown) or other repeater apparatuses (not shown) to filter  112 . 
         [0037]    Next, a detailed configuration of communication capacity calculating section  160  will be described with reference to  FIG. 1 . 
         [0038]    Communication capacity calculating section  160  is mainly formed with system information analysis section  121 , S/N calculating section  122 , channel estimation section  123 , and throughput limit calculating section  124 . System information analysis section  121 , S/N calculating section  122 , and channel estimation section  123  form an acquiring section that acquires band information for use, and acquires communication quality and a channel matrix. 
         [0039]    System information analysis section  121  analyzes signals input from demultiplexing section  105  and demultiplexing section  106 . System information analysis section  121  acquires band information for use (BW) in communication using a MIMO scheme and information about the number of transmitting antennas of base station  180 , Also, system information analysis section  121  outputs the acquired band information for use and information about the number of transmitting antennas to throughput limit calculating section  124 . 
         [0040]    SIN calculating section  122  analyzes known pilot signals input from demultiplexing section  105  and demultiplexing section  106  to calculate a S/N ratio (a signal-to-noise ratio). S/N calculating section  122  outputs the calculating result of the S/N ratio to throughput limit calculating section  124 . 
         [0041]    Channel estimation section  123  analyzes known pilot signals input from demultiplexing section  105  and demultiplexing section  106 , and estimates a channel matrix (a transfer function) between transmitting antennas of base station  180 , and first antenna  101  and second antenna  102 . Channel estimation section  123  outputs the estimation result of the channel matrix to throughput limit calculating section  124 . 
         [0042]    Throughput limit calculating section  124  calculates a limit value of communication capacity based on band information for use and information about the number of transmitting antennas, which are input from system information analysis section  121 , previously stored information about the number of receiving antennas of radio repeater apparatus  100 , a calculating result of a S/N ratio input from S/N calculating section  122 , and an estimation result of a channel matrix input from channel estimation section  123 . Throughput limit calculating section  124  outputs the calculating result of a limit value to comparing section  132 . Here, a method for calculating a throughput limit value will be described later. 
         [0043]    Next, a detailed configuration of display control section  170  will be described with reference to  FIG. 1 . 
         [0044]    Display control section  170  is mainly formed with throughput desired value setting section  131 , comparing section.  132 , and display section  133 . 
         [0045]    Throughput desired value setting section  131  sets a desired value and an allowable range in advance. Here, the above setting is performed by users (for example, telecommunication carriers). 
         [0046]    Comparing section  132  compares a limit value input from throughput limit calculating section  124  with a desired value input from throughput desired value setting section  131 , and outputs the comparison result to display section  133 . 
         [0047]    Display section  133  displays a comparison result input from comparing section  132 . Display section  133 , for example, can display a comparison result by the number of antenna bars according to a difference between a limit value and a desired value. Also, display section  133  can display a comparison result by color according to a difference between a limit value and a desired value. Upon the display of a comparison result by color, for example, it is possible to display all or part of a display screen in red in a case where a difference between a limit value and a desired value is equal to or greater than a threshold, and to display all or part of a display screen in green in a case where a difference between a limit value and a desired value is less than a threshold. The display of a comparison result can be performed by no means limited to the number of antenna bars and color, but performed by any method. 
         [0048]    Next, a method of calculating a limit value of communication capacity in radio repeater apparatus  100  will be described. According to the present embodiment, communication based on long term evolution (LTE) which is one of next-generation communication schemes will be described as an example. A communication scheme is not limited to LTE, but appropriately changeable. 
         [0049]    System information analysis section  121  demodulates a physical broadcast channel (PBCH) in a LTE downlink signal, acquires a master information block (MIB), and analyzes acquired MIB. System information analysis section  121  analyzes a MIB, and acquires band information for use in a system and information about the number of transmitting antennas, which are stored in the MIB, so that it is possible to learn bandwidth for use and the number of transmitting antennas. System information analysis section  121  can eliminate the need to acquire information about the number of transmitting antennas in a case where the number of transmitting antennas of radio repeater apparatus  100  is already known between base station  180  and radio repeater apparatus  100 . In this case, the number of transmitting antennas is previously stored in a memory (not shown) and the like, as with the information about the number of receiving antennas. 
         [0050]    Also, S/N calculating section  122  calculates a S/N ratio by analyzing known pilot signals embedded in received signals. For example, as shown in equation 1, S/N calculating section  122  calculates a difference between adjacent pilot signals to calculate an ensemble average of the calculated deference. By this means, S/N calculating section  122  can calculate noise component σ. 
         [0000]    
       
         
           
             
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
                      
                     1 
                   
                   ) 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     σ 
                     2 
                   
                   = 
                   
                     
                       1 
                       
                         N 
                         - 
                         1 
                       
                     
                      
                     
                       
                         ∑ 
                         
                           n 
                           = 
                           0 
                         
                         
                           N 
                           - 
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                        
                       
                         
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                               P 
                               
                                 N 
                                 + 
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                               n 
                             
                           
                            
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   1 
                   ] 
                 
               
             
           
         
       
     
         [0051]    Also, as shown. equation 2, S/N calculating section  122  adds adjacent pilot signals and calculates an ensemble average of the addition result. S/N calculating section  122  calculates signal component S by dividing an ensemble average of the addition result by noise component n calculated from equation 1. 
         [0000]    
       
         
           
             
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
                      
                     2 
                   
                   ) 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     S 
                     2 
                   
                   = 
                   
                     
                       
                         1 
                         
                           N 
                           - 
                           1 
                         
                       
                        
                       
                         
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                             n 
                             = 
                             0 
                           
                           
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                              
                             
                               
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                               + 
                               
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                                 n 
                               
                             
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                     - 
                     
                       σ 
                       2 
                     
                   
                 
               
               
                 
                   [ 
                   2 
                   ] 
                 
               
             
           
         
       
     
         [0052]    Also, S/N calculating section  122  calculates a S/N ratio by calculating a ratio between signal component S calculated from equation  2  and noise component calculated from equation 1. 
         [0053]    Also, channel estimation section  123  estimates a channel matrix (a transfer function) between a plurality of transmitting antennas of base station  180 , and first antenna  101  and second antenna  102  by analyzing known signals embedded in received signals. 
         [0054]    Also, a channel matrix between base station  180  and radio repeater apparatus  100  can be calculated by the following method in channel estimation section  123 .  FIG. 2  illustrates a method of calculating a channel matrix between base station  180  and radio repeater apparatus  100 . 
         [0055]    In the case of receiving signals transmitted from a plurality of antennas by a plurality of antennas, received signals arc represented by equation 3. 
         [0000]      [Equation 3] 
         [0000]      R=HS  (3)
 
         [0056]    Here, R: received signal 
         [0057]    S: transmission signal 
         [0058]    H: channel matrix (transfer function) 
         [0059]    Also, equation 3 can be represented by equation 4 according to  FIG. 2 . 
         [0000]    
       
         
           
             
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
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                     4 
                   
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                     [ 
                     
                       
                         
                           
                             
                               r 
                               1 
                             
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                               ( 
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                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
                               h 
                               31 
                             
                           
                           
                             
                               h 
                               32 
                             
                           
                         
                         
                           
                             
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                               41 
                             
                           
                           
                             
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                       ] 
                     
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                                 ( 
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                       ] 
                     
                   
                 
               
               
                 
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                   4 
                   ] 
                 
               
             
           
         
       
     
         [0060]    Here, a pilot signal is targeted for analysis, and therefore, it is possible to calculate channel matrix H by dividing a received signal by a pilot signal as in equation 5. 
         [0000]      [Equation 5] 
         [0000]      H=RS −1   (5)
 
         [0061]    Here, R: received signal 
         [0062]    S: transmission signal 
         [0063]    H: channel matrix (transfer function) 
         [0064]    Throughput limit calculating section  124  calculates a limit value of communication capacity based on a channel matrix calculated by the above-described method, band information for use, information about the number of transmitting antennas, information about the number of receiving antennas, and the S/N ratio calculating result. 
         [0065]    Specifically, throughput limit calculating section  124  calculates channel capacity (a throughput limit value) per unit frequency from equation 6. 
         [0000]    
       
         
           
             
               
                 
                   ( 
                   
                     Equation 
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                   ) 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         
                           C 
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                   [ 
                   6 
                   ] 
                 
               
             
           
         
       
     
         [0066]    Here, k: subcarrier index (total number N) 
         [0067]    I Nt : N 1 ×N t  identity matrix 
         [0068]    N rx : the number of receiving antenna 
         [0069]    N ts : the number of transmitting antenna 
         [0070]    H: N rs ×N is  channel matrix 
         [0071]    p: SNR per one antenna 
         [0072]    λ i(k) : i th eigenvalue of H H  (k)H(k) 
         [0073]    That is to say, throughput limit calculating section  124  calculates throughput using a matrix eigenvalue which can be calculated from a channel matrix. In the case of OFDM transmission, throughput limit calculating section  124  calculates throughput per subcarrier and calculates an average of all subcarriers using the calculated throughput, thereby calculating throughput limit value. 
         [0074]    Also, throughput limit calculating section  124  calculates a throughput limit value in transmission bandwidth by multiplying the throughput limit value calculated from equation 6 by bandwidth for use in the system. 
         [0075]    As described above, according to the present embodiment, it is possible to learn communication capacity, and eliminate the need to change the contents of countermeasures for blind zones after the setting of a repeater apparatus by determining whether or not a limit value of desired communication capacity is satisfied. 
       Embodiment 2 
       [0076]      FIG. 3  is a block diagram showing the configuration of radio repeater apparatus  300  according to Embodiment 2 of the present invention. 
         [0077]    In contrast to radio repeater apparatus  100  according to Embodiment 1 shown in  FIG. 1 , radio repeater apparatus  300  shown in  FIG. 3  has repeater amplification apparatus  350  instead of repeater amplification apparatus  150  and has communication capacity calculating section  360  instead of communication capacity calculating section  160 . Here, in  FIG. 3 , parts that are the same configuration as in  FIG. 1  will be assigned the same reference numerals as in  FIG. 1 . 
         [0078]    In communication using a MIMO scheme, repeater amplification apparatus  350  receives signals transmitted from base station  180 , amplifies the received signals, and transmits the amplified signals to communication terminal apparatuses (not shown) or other repeater apparatuses (not shown). That is to say, repeater amplification apparatus  350  performs relay processing of signals in communication using a MIMO scheme. Also, repeater amplification apparatus  350  sets a variable gain by control of communication capacity calculating section  360  and amplifies signals. 
         [0079]    Communication capacity calculating section  360  calculates a limit value of communication on capacity of signals in which repeater amplification apparatus  350  receives from base station  180 , and outputs the calculated limit value to display control section  170 . Also, communication capacity calculating section  360  adjusts a gain upon amplifying signals in repeater amplification apparatus  350 . 
         [0080]    Display control section  170  performs control to display a comparison result between a limit value and a desired value of communication capacity, based on a calculating result of communication capacity input from communication capacity calculating section  360 . 
         [0081]    Next, a detailed configuration of repeater amplification apparatus  350  will be described with reference to  FIG. 3 . 
         [0082]    Repeater amplification apparatus  350  is mainly formed with first antenna  301 , second antenna  302 , amplifier  303 , variable amplifier  304 , amplifier  305 , adder  306 , demultiplexing section  307 , demultiplexing section  308 , third antenna  309 , and fourth antenna  310 . Amplifier  303  and amplifier  305  form an amplification section that amplifies signals received from first antenna  301  and signals received from second antenna  302 . 
         [0083]    First antenna  301  receives signals transmitted from base station  180  and outputs the signals to amplifier  303  and variable amplifier  304 . 
         [0084]    Second antenna  302  receives signals transmitted from base station  180  and outputs the signals to amplifier  305 . 
         [0085]    Amplifier  303  amplifies signals input from first antenna  301  and outputs the signals to demultiplexing section  307 . 
         [0086]    Variable amplifier  304  sets a predetermined gain by control of throughput limit calculating section  321 . Also, variable amplifier  304  amplifies signals input from first antenna  301  by the set gain and outputs the amplified signals to adder  306 . That is to say, variable amplifier  304  amplifies signals by a variable gain. A Method of adjusting a gain in variable amplifier  304  will be described later, 
         [0087]    Amplifier  305  amplifies signals input from second antenna  302  and outputs the amplified signals to adder  306 . 
         [0088]    Adder  306  adds signals input from variable amplifier  304  and signals input from amplifier  305 , and outputs the added signals to demultiplexing section  308 . 
         [0089]    Demultiplexing section  307  demultiplexes signals input from amplifier  303  and outputs the demultiplexed signals to third, antenna  309 , system information, analysis section  121 , S/N calculating section  122 , and channel estimation section  123 . 
         [0090]    Demultiplexing section  308  demultiplexes signals input from adder  306  and outputs the demultiplexed signals to fourth antenna  310 , system information analysis section  121 , S/N calculating section  122 , and channel estimation section  123 . 
         [0091]    Third antenna  309  transmits signals input from demultiplexing section  307  to communication terminal apparatuses (not shown) or other repeater apparatuses (not shown). 
         [0092]    Fourth antenna  310  transmits signals input from demultiplexing section  308  to communication terminal apparatuses (not shown) or other repeater apparatuses (not shown). 
         [0093]    Next, a detailed configuration of communication capacity calculating section  360  will be described with reference to  FIG. 3 . 
         [0094]    In contrast to communication capacity calculating section  160  according to Embodiment 1 shown in  FIG. 1 , communication capacity calculating section  360  shown in  FIG. 3  has throughput limit calculating section  321  instead of throughput limit calculating section  124 . Here, in  FIG. 3 , parts that are the same configuration as in  FIG. 1  will be assigned the same reference numerals as in  FIG. 1  and therefore an explanation thereof will be omitted. 
         [0095]    Communication capacity calculating section  360  is mainly formed with system information analysis section  121 , S/N calculating section  122 , channel estimation section  123 , and throughput limit calculating section  321 . 
         [0096]    System information analysis section  121  analyzes signals input from demultiplexing section  307  and demultiplexing section  308 . System information analysis section  121  acquires band information for use in communication using a MIMO scheme and information about the number of transmitting antennas of base station  180 . Also, system information analysis section  121  outputs acquired band information for use and information about the number of transmitting antennas to throughput limit calculating section  321 . System information analysis section  121  can eliminate the need to acquire information about the number of transmitting antennas in a case where the number of transmitting antennas is already known between base station  180  and radio repeater apparatus  100 . In this case, the number of transmitting antennas is stored in a memory (not shown) and the like in advance, as with information about the number of receiving antennas of radio repeater apparatus  300 . 
         [0097]    S/N calculating section  122  analyzes known pilot signals input from demultiplexing section  307  and demultiplexing section  308  to calculate a S/N ratio (a signal-to-noise ratio). At this time, S/N calculating section  122  amplifies signals by a gain adjusted in throughput. limit calculating section  321 , and calculates a S/N ratio using the signals amplified in variable amplifier  304 . S/N calculating section  122  outputs the calculating result of the S/N ratio to throughput limit calculating section  321 . 
         [0098]    Channel estimation section  123  analyzes known pilot signals input from demultiplexing section  307  and demultiplexing section  308 , and estimates a channel matrix (a transfer function) between transmitting antennas of base station  180 , and first antenna  301  and second antenna  302 . Channel estimation section  123  outputs the estimation result of the channel matrix to throughput limit calculating section  321 . 
         [0099]    Throughput limit calculating section  321  calculates a limit value of communication capacity based on band information for use and information about the number of transmitting antennas, which are input from system information analysis section  121 , information about the number of receiving antennas of radio repeater apparatus  100 , a calculating result of the S/N ratio input from S/N calculating section  122 , and an estimation result of the channel matrix input from channel estimation section  123 . Also, throughput limit calculating section  321  adjusts a gain of variable amplifier  304  such that the calculated limit value is optimal. Also, throughput limit calculating section  321  outputs the calculating result of the limit value to comparing section  132 . Also, a method of calculating a throughput limit value is the same as in above Embodiment 1, and therefore an explanation thereof will be omitted. 
         [0100]    Comparing section  132  compares a limit value input from throughput limit calculating section  321  with a desired value input from throughput desired. value setting section  131 , and outputs the comparison result to display section  133 . 
         [0101]    Next, an operation of channel estimation section  123  and throughput limit calculating section  321  will be described. 
         [0102]    Throughput limit calculating section  321  can change a channel matrix to be estimated in channel estimation section  123 , by changing a gain of variable amplifier  304 . By this means, communication capacity can be improved. 
         [0103]    Specifically, the above equation 4 is represented by equation 7 by changing a gain of variable amplifier  304 . A of equation 7 is a fixed value (for example, users can set this value), and A′ and B are variables. When B=0, A=A′, equation 7 is the same as equation 4 in case of receiving signals by simply two antennas. From this state, it is possible to change a state of equation 4 by increasing B and decreasing A′ such that A′ is equal to output power of radio repeater apparatus  300 . A of Equation 7 may be determined, for example, based on path loss between base station  180  and radio repeater apparatus  300 . 
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         [0104]    Accordingly, channel estimation section  123  calculates a channel matrix from equation 7. 
         [0105]    That is to say, the change of a gain of variable amplifier  304  is equivalent to the operation of a channel matrix, and also equivalent to the change of an eigenvalue of equation 6. 
         [0106]      FIG. 4  illustrates a relationship between a limit value and eigenvalue of communication capacity in the case of changing eigenvalue λ 1  of equation 6, in a case where the number of antennas is two in transmission and reception. In  FIG. 4 , the vertical axis is a limit value of communication capacity and the horizontal axis is an eigenvalue. 
         [0107]    As shown in  FIG. 4 , throughput limit calculating section  321 , for example, adjusts a gain set in variable amplifier  304  such that a limit value of communication capacity is the highest, and acquires an effect to improve communication capacity. 
         [0108]    As described above, according to the present embodiment, in addition to the effect in the above-described Embodiment 1, since a cause to degrade a limit value of communication capacity is cancelled by varying a gain and correcting an eigenvalue, therefore, it is possible to prevent the decrease in communication capacity. 
         [0109]    In the present embodiment, although the radio repeater apparatus performs relay processing of only signals received from a base station, the present embodiment is not limited to this, but the radio repeater apparatus may perform relay processing of signals transmitted to the base station. In this case, as with  FIG. 1 , it is possible to demultiplex transmission signals and received signals by providing a band limitation filter immediately beneath an antenna. 
       Embodiment 3 
       [0110]      FIG. 5  is a block diagram showing the configuration of communication capacity evaluating apparatus  500  according to Embodiment 3 of the present invention. 
         [0111]    Communication capacity evaluating apparatus  500  is mainly formed with communication capacity calculating section  550  and display control section  560 . 
         [0112]    Communication capacity calculating section  550  calculates a limit value of communication capacity in a MIMO scheme using signals received from base station  180  and outputs the calculated signals to display control section  560 . 
         [0113]    Display control section  560  calculates a desired value of communication capacity based on a calculating result of a limit value of communication capacity input from communication capacity calculating section  550 , and performs control to display a comparison result between a limit value and a desired value. 
         [0114]    Next, a detailed configuration of communication capacity calculating section  550  will he described with reference to  FIG. 5 . 
         [0115]    Communication capacity calculating section  550  is mainly formed with first antenna  501 , second. antenna  502 , system information analysis section  503 , S/N calculating section  504 , channel estimation section  505 , and throughput limit calculating section  506 . System information analysis section  503 , S/N calculating section  504 , and channel estimation section  505  form an acquiring section that acquires band information for use and acquires communication quality and a channel matrix. 
         [0116]    First antenna  501  receives signals transmitted from base station  180  and outputs the signals to system information analysis section  503 , S/N calculating section  504 , and channel estimation. section  505 . 
         [0117]    Second antenna  502  receives signals transmitted from base station  180  and outputs the signals to system information analysis section  503 , S/N calculating section  504 , and channel estimation section  505 . 
         [0118]    System information analysis section  503  analyzes signals input from first antenna  501  and second antenna  502 . System information analysis section  503  acquires band information for use in communication using a MIMO scheme and information about the number of transmitting antennas of base station  180 . System information analysis section  503  outputs the acquired band information for use and information about the number of transmitting antennas to throughput limit calculating section  506 . System information analysis section  503  can eliminate the need to acquire information about the number of transmitting antennas in a case where the number of transmitting antennas is already known between base station  180  and communication capacity evaluating apparatus  500 . In this case, the number of transmitting antennas is stored in a memory (not shown) and the like in advance, as with information about the number of receiving antennas of communication capacity evaluating apparatus  500 . 
         [0119]    S/N calculating section  504  analyzes known pilot signals input from first antenna  501  and second antenna  502  to calculate a S/N ratio (a signal-to-noise ratio). S/N calculating section  504  outputs the calculating result of the S/N ratio to throughput limit calculating section  506 . 
         [0120]    Channel estimation section  505  analyzes known pilot signals input from first antenna  501  and second antenna  502 , and estimates a channel matrix (a transfer function) between transmitting antennas of base station  180 , and first antenna  501  and second antenna  502 . Channel estimation section  505  outputs the estimation result of the channel matrix to throughput calculating section  506 . 
         [0121]    Throughput limit calculating section  506  calculates a limit value of communication capacity based on band information for use and information about the number of transmitting antennas, which are input from system information analysis section  503 , information about the number of receiving antennas of communication capacity evaluating apparatus  500 , a calculating result of the S/N ratio input from S/N calculating section  504 , and an estimation result of the channel matrix input from channel estimation section  505 . Throughput limit calculating section  506  outputs the calculating result of a limit value to comparing section  512 . Also, a method of calculating a throughput limit value is the same as in above Embodiment 1, and therefore an explanation thereof will be omitted. 
         [0122]    Next, a detailed configuration of display control section  560  will be described with reference to  FIG. 5 . 
         [0123]    Display control section  560  is mainly formed with throughput desired value setting section  511  and comparing section  512 , and display section  513 . 
         [0124]    Throughput desired value setting section  511  sets a desired value and an allowable range in advance. 
         [0125]    Comparing section  512  compares a limit value input from throughput limit calculating section  506  with a desired value input from throughput desired value setting section  511 , and outputs the comparison result to display section  513 . 
         [0126]    Display section  513  displays a comparison result input from comparing section  512 . Display section  513 , for example, can display a comparison result by the number of antenna bars according to a difference between a limit value and a desired value. Also, display section  513  can display a comparison result by color according to a difference between a limit value and a desired value. Upon the display of a comparison result by color, for example, it is possible to display all or part of a display screen in red in a case where a difference between a limit value and a desired value is equal to or greater than a threshold, and to display all or part of a display screen in green in a case where a difference between a limit value and a desired value is less than a threshold. The display of a comparison result can be performed by no means limited to the number of antenna bars and color, but performed by any method. 
         [0127]    As described above, according to the present embodiment, it is possible to learn communication capacity, and eliminate the need to change the contents of countermeasures for blind zones after the setting of a repeater apparatus by determining whether or not a limit value of desired communication capacity is satisfied. Also, according to the present embodiment, since communication capacity is calculated by a communication capacity evaluating apparatus which is separately provided from a radio repeater apparatus, therefore, manufacturing cost of a radio repeater apparatus can be reduced compared to a case where a communication capacity evaluating apparatus is provided in a radio repeater apparatus. 
         [0128]    In the above Embodiment 1 to Embodiment 3, although each of the number of antennas of a base station, a radio repeater apparatus, and a communication capacity evaluating apparatus is two, the present invention is not limited to this, it is equally possible to set any number of antennas equal to or greater than three. 
         [0129]    The disclosures of Japanese Patent Application No. 2009-260222, filed on Nov. 13, 2009, including the specifications, drawings and abstracts, are incorporated herein by reference in their entirety. 
       INDUSTRIAL APPLICABILITY 
       [0130]    A communication capacity evaluating apparatus, a radio repeater apparatus, and a communication capacity evaluating method according to the present invention are particularly suitable for learning communication capacity in a setting location of a radio repeater apparatus which performs relay processing of communication using a MIMO scheme.