Patent Publication Number: US-2002009128-A1

Title: Receiving apparatus

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates to a receiving apparatus for signals simultaneously transmitted from a plurality antennas in a CDMA (code division multiple access) wireless mobile telephone system, for example.  
       [0003] 2. Description of Related Art  
       [0004] In case of effecting data communication through a wireless system, for example, of which characteristics of the propagation path cannot be estimated, it is normally employed to transmit predetermined known data (hereinafter called pilot signals) in addition to information data to be transmitted, such that, in the receiver side, pilot signals are used to estimate propagation paths and demodulate the information data. This method is widely used in wireless mobile telephone systems, and its standardization is progressed by ITU (International Telecommunication Union) toward its use as the next-generation wireless mobile telephone system. Its applications to IMT-2000 or W-CDMA (wideband-code division multiple access) mobile systems are expected.  
       [0005] In systems using pilot signals for estimation of propagation paths, it is necessary upon receipt to perform procedures of  
       [0006] (a) despreading pilot signals;  
       [0007] (b) filtering the pilot signals to remove noise components;  
       [0008] (c) multiplying a complex conjugate to obtain an estimated value of the transmission path; and  
       [0009] (d) demodulating the received data by using the estimated value obtained.  
       [0010] Further, in the next-generation mobile communication system, it is expected that the transmission antenna diversity technique for transmitting data from a plurality of antennas is employed to improve the reception characteristics.  
       [0011] If transmission antenna diversity is employed, propagation path characteristics of different propagation paths from respective antennas have to be estimated. Therefore, pilot signals for estimation of respective propagation paths are sent from individual antennas for individual outputs. Thus, on the part of a receiver, it is necessary to separate each pilot signal of each propagation path from other received pilot signals to actually estimate the characteristics of each propagation path.  
       [0012] As reviewed above, systems configured to estimate transmission paths by using pilot signals need procedures such as despread of pilot signals, filtering of the pilot signals, calculation of estimated values of the transmission paths, and so forth. Additionally, when they use antenna diversity, they need the procedure of separating each pilot signal. They therefore involve the problem that the circuit scale inevitably increases.  
       OBJECT AND SUMMARY OF THE INVENTION  
       [0013] It is therefore an object of the invention to provide a receiving apparatus that can simplifies procedures of dispreading pilot signals, separating each of received pilot signals through different propagation paths, filtering the pilot signals, estimating characteristics of individual propagation paths and demodulating data, in the case where characteristics of different propagation paths used to transmit signals from different antennas should be estimated in transmission antenna diversity configured to transmit data from a plurality of antennas, and thereby facilitates the size of the circuit.  
       [0014] According to the first aspect of the invention, there is provided a receiving apparatus in a system configured to take procedures of:  
       [0015] on the part of a transmitter, coding data signals into a first series and a second series and spreading each series with data spread codes;  
       [0016] spreading two pilot signals individually for the first series and the second series into pilot signal spread codes for individual first and second series;  
       [0017] combining the spread data signal of the first series and the spread pilot signal of the first series, and transmitting them from a first antenna;  
       [0018] combining the spread data signal of the second series and the spread pilot signal of the second series, and transmitting them from a second antenna;  
       [0019] on the part of a receiver, despreading the received data signals with data spread codes;  
       [0020] despreading the received pilot signals with the pilot spread codes, and separating components of first series pilot signal and components of the second series pilot signal from a despread output of the pilot signal;  
       [0021] obtaining an estimation value of the property of the first series and an estimation value of the property of the second series from components of the first series pilot signal and the second series pilot signal; and  
       [0022] demodulating the despread data signals by using the estimated value of the property of the first series and the estimated value of the property of the second series, comprising:  
       [0023] data despread means for executing despread of the received data signals;  
       [0024] pilot signal despread means for executing despread of the received pilot signals;  
       [0025] pilot separation means using orthogonality between the first series pilot signal and the second series pilot signal to separate components of the first series pilot signal and components of the second series pilot signal from outputs of the pilot signal despread means and to obtain an estimated value of the property of the first series and an estimated value of the property of the second series from the components of the first series pilot signal and the components of the second series pilot signal; and  
       [0026] data demodulating means using the estimated value of the property of the first series and the estimated of the property of the second series obtained by the pilot separation means to demodulate the despread data signals,  
       [0027] the pilot separation means being configured to separate the components of the first series pilot signal and components of the second pilot signal component by using pilot signals of patterns having the number of symbol L where L is the number of symbols per which the first series pilot signal and the second series pilot signal intersect orthogonally.  
       [0028] According to the second aspect of the invention, there is provided a receiving apparatus in a system configured to take procedures of:  
       [0029] on the part of a transmitter, coding data signals into a first series and a second series and spreading each series with data spread codes;  
       [0030] spreading two pilot signals individually for the first series and the second series into pilot signal spread codes for individual first and second series;  
       [0031] combining the spread data signal of the first series and the spread pilot signal of the first series, and transmitting them from a first antenna;  
       [0032] combining the spread data signal of the second series and the spread pilot signal of the second series, and transmitting them from a second antenna;  
       [0033] on the part of a receiver, despreading the received data signals with data spread codes;  
       [0034] despreading the received pilot signals with the pilot spread codes, and separating components of first series pilot signal and components of the second series pilot signal from a despread output of the pilot signal;  
       [0035] obtaining an estimation value of the property of the first series and an estimation value of the property of the second series from components of the first series pilot signal and the second series pilot signal; and  
       [0036] demodulating the despread data signals by using the estimated value of the property of the first series and the estimated value of the property of the second series, comprising:  
       [0037] data spread means for executing despread of the received data signals;  
       [0038] pilot signal despread means for executing despread of the received pilot signals, separating components of first series pilot signal and components of the second series pilot signal from a despread output of the pilot signal, and obtaining an estimation value of the property of the first series and an estimation value of the property of the second series from components of the first series pilot signal and the second series pilot signal; and  
       [0039] data demodulating means using the estimated value of the property of the first series and the estimated of the property of the second series obtained by the pilot separation means to demodulate the despread data signals,  
       [0040] the pilot signal despread means being configured to execute despread of the pilot signals and separate the components of the first series pilot signal and the components of the second pilot signal from each other by multiplying a pilot signal spread code having the length L times the spread code length and accumulating multiplication outputs in the amount of the length L times the spread code length where L is the number of symbols per which the first series pilot signal and the second series pilot signal intersect orthogonally.  
       [0041] The pilot signal P 1  and the pilot signal P 2  orthogonally intersect per every two symbols. Further, the pilot signal P 1  and the pilot signal P 2  are related to orthogonally intersect not only per every two symbols but also per every four symbols, every eight symbols, every 16 symbols, and so on.  
       [0042] By utilizing that the pilot signal P 1  and the pilot signal P 2  orthogonally intersect per every four symbols, every eight symbols, an so forth, the pilot signal P 1  and the pilot signal P 2  can be separated by addition or subtraction of data of L symbols (four symbols, eight symbols, and so on) which will intersect orthogonally. This results in being equivalent to averaging the pilot signal P 1  and the pilot signal P 2  separated per every two symbols, and separation and filtering of pilot signals can be executed simultaneously.  
       [0043] Upon despreading pilot signals, if the despread is performed in (Mx2) chips instead of M chips, then it is possible to perform processing equivalent to addition or subtraction of consecutive two symbols obtained by despread, and therefore, despread and separation of pilot signals can be executed simultaneously. Further, if despread is performed in (MxL) chips, then despread of pilot signals, separation of pilot signals and filtering can be effected simultaneously.  
       [0044] The above, and other, objects, features and advantage of the present invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0045]FIG. 1 is a block diagram used for explanation of a basic system using pilot signals;  
     [0046]FIG. 2 is a schematic diagram used for explanation of QPSK mapping;  
     [0047]FIG. 3 is a block diagram used for explanation of a data spread section;  
     [0048]FIG. 4 is a block diagram used for explanation of a pilot signal spread section;  
     [0049]FIG. 5 is a block diagram used for explanation of a data despread section;  
     [0050]FIG. 6 is a block diagram used for explanation of a pilot despread section;  
     [0051]FIG. 7 is a block diagram of a filter;  
     [0052]FIG. 8 is a block diagram used for explanation of antenna diversity;  
     [0053]FIG. 9 is a block diagram used for explanation of a basic system using pilot signals in case of antenna diversity;  
     [0054]FIG. 10 is a block diagram used for explanation of a receiver in a basic system using pilot signals in case of antenna diversity;  
     [0055]FIG. 11 is a schematic diagram used for explanation of separation of pilot signals in a basic system using pilot signals in case of antenna diversity;  
     [0056]FIG. 12 is a block diagram used for explanation of a first embodiment of the invention;  
     [0057]FIG. 13 is a block diagram used for explanation of a pilot separation section in the first embodiment of the invention;  
     [0058]FIG. 14 is a schematic diagram used for explanation of a pilot separation section in the first embodiment of the invention;  
     [0059]FIG. 15 is a block diagram used for explanation of a second embodiment of the invention;  
     [0060]FIG. 16 is a block diagram used for explanation of a pilot despread section in the second embodiment of the invention; and  
     [0061]FIG. 17 is a schematic diagram used for explanation of a pilot despread section in the second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0062] Explained below are embodiments of the invention with reference to the drawings. The invention is suitable for application to systems configured to estimate characteristics of propagation paths by using pilot signals. First explained is a system configured to estimate propagation paths by using such pilot signals.  
     [0063] (1) Wireless System Using Pilot Signals  
     [0064]FIG. 1 shows a basic structure of a wireless system using pilot signals. In FIG. 1, reference numeral  1  denotes a transmitter-side apparatus, and  2  denotes a receiver-side apparatus. The transmitter-side apparatus  1  is typically a base station of a wireless mobile telephone system, and the receiver-side apparatus  2  is typically a portable terminal.  
     [0065] In FIG. 1, the transmitter  1  includes a QPSK (Quadrature Phase Shift Keying) map section  11 , data spread section  12 , pilot spread section  13 , synthesizing section  14  and transmission antenna  15 .  
     [0066] Transmission data is supplied to an input terminal  16 . The transmission data is binary data that takes 1 or −1. The transmission data is supplied to the QPSK map section  11 . The QPSK map section  11  maps the input data into data on the I axis and data on the Q axis.  
     [0067] Data symbols mapped by the QPSK map section  11  are supplied to data spread section  12 . In the data spread section  12 , transmission data is spectrally spread with a data spread code. Output of the data spread section  12  is supplied to the synthesizing section  14 .  
     [0068] A pilot signal is supplied to the input terminal  17 . The pilot signal is supplied to the pilot spread section  13 . In the pilot spread section  13 , the pilot signal is spectrally spread with a pilot spread signal.  
     [0069] In the synthesizing section  14 , the transmission data spread with the data spread code and the pilot signal spread with the pilot signal spread code are combined. Output of the combining section  14  is output from the antenna  15 .  
     [0070] In the transmitter  1  shown in FIG. 1, input data from the input terminal  16  is mapped by the QPSK map section  11  on a complex plane in the manner shown in FIG. 2. That is, the first introduced bit is mapped on the I axis whereas the next introduced data is mapped on the Q axis.  
     [0071] Output of the QPSK map section  11  is supplied to the data spread section  12  and spectrally spread by the data spread section  12 . The data spread section  12  is configured to spectrally diffuse input data D[n] by multiplying it by data spread code Cd[m] as shown in FIG. 3. The data spread code Cd[m] is a M-chip code.  
     [0072] From the data spread section  12 , a signal spectrally spread from the input data D[n] by the data spread code Cd[m] 
     D[n]×Cd[m] 
     [0073] is output.  
     [0074] The pilot signal from the input terminal  17  is supplied to the pilot spread section  13 , and spectrally spread there. The pilot signal is a ((1+j)/{square root}2) QPSK symbol. The pilot signal is spectrally spread by the pilot spread section  13 .  
     [0075] The pilot spread section  13  is configured to execute spectral spread by multiplying the input pilot signal P[n] by the pilot spread code Cp[m] in a multiplier  32  as shown in FIG. 4. The pilot spread code Cp[m] is a M-chip code.  
     [0076] The data spread code Cd[m] and the pilot spread code Cp[m] intersect orthogonally with each other, and satisfy  
           ∑     m   =   0       M   -   1              Cp        [   m   ]       ×     Cd        [   m   ]           =   0                 
 
     [0077] From the pilot spread section  13 , the signal spectrally spread from the input pilot signal P[n] by the pilot spread code Cp[m] 
     P[n]×Cp[m] 
     [0078] is output.  
     [0079] Thus, from the transmitter  1 , the transmission data, which is mapped on a complex plane and spectrally spread with the data spread code, and the pilot signal, which is the ((1+j)/{square root}2) QPSK symbol and spectrally spread with the pilot signal spread code, are sent out simultaneously.  
     [0080] The signal transmitted from the transmitter  1  reaches the receiver  2  through a propagation path  3 . The signal from the transmitter  1  is received by the receiver  2 .  
     [0081] The receiver  2  includes a reception antenna  21 , data despread section  22 , pilot despread section  23 , propagation path estimation section  24 ,phase correction section  25  and a judge section  26 .  
     [0082] The signal received at the reception antenna  21  is supplied to the data despread section  22  and the pilot signal despread section  23 . In the data despread section  22 , despread of the data signal is executed. Output of the data despread section  22  is supplied to the phase correction section  25 .  
     [0083] In the pilot signal despread section  23 , the pilot signal undergoes despread. Output of the pilot spread section is supplied to the propagation path estimation section  24 .  
     [0084] The propagation estimation section  24  is configured to obtain a propagation path estimation value by multiplying the received pilot signal output from the pilot despread section  23  by its complex conjugate. The received pilot signal contains noise components due to phasing, or the like. For the purpose of removing such noise components, the propagation estimation section  24  executes filtering of the pilot signal.  
     [0085] Output of the phase correction section  25  is supplied to the judge section  16 . In the judge section  26 , opposite mapping is executed in accordance with the QPSK mapping. As a result, the QPSK signal is demodulated to binary data. The demodulated data is output from the output terminal  27 .  
     [0086] In the receiving apparatus  2  shown in FIG. 1, the data despread section  22  uses a spread code similar to the spread code used for data spread upon transmission to oppositely spread data.  
     [0087]FIG. 5 shows configuration of the data despread section  22 . As already explained, from the transmitter  1 , the signal spectrally spread from the data D[n] with the data spread code Cd[m], namely, 
     D[n]×Cd[m] 
     [0088] and the signal spectrally spread from the pilot signal P[n] with the pilot spread code Cp[m], namely, 
     P[n]×Cp[m] 
     [0089] are output simultaneously.  
     [0090] The signal from the transmitter  1  reaches the receiver  2  through the propagation path  3 . Therefore, if the property of the propagation path  3  is α, the signal received at the receiver  2  is 
     α×(D[n]×Cd[m]+P[n]×Cp[m]) 
     [0091] This received signal (α×(D[n]×Cd[m]+P[n]×Cp[m])) and the data spread code Cd[m] are multiplied in the multiplier  34 , and outputs of the multiplier  34  are accumulated in an accumulator  35 . From the accumulator  35 ,  
           ∑   m     M   -   1            α   ×     (         D        [   n   ]       ×     Cd        [   m   ]         +       P        [   n   ]       ×     Cp        [   m   ]           )          xCd        [   m   ]           =     a   ×   M   ×     D        [   n   ]                       
 
     [0092] is obtained as the data spread output.  
     [0093] The pilot despread section  23  uses a spread code similar to the spread code used for spread of the pilot signal upon transmission to despread the pilot signal.  
     [0094]FIG. 6 shows configuration of the pilot despread section  23 . If the property of the propagation path  3  is a, then the signal received at the receiver  2  is 
     α×(D[n]×Cd[m]+P[n]×Cp[m]) 
     [0095] This received signal (α×(D[n]×Cd[m]+P[n]×Cp[m])) and the pilot spread code Cp[m] are multiplied in the multiplier  37 , and outputs of the multiplier  37  are accumulated in an accumulator  38 . From the accumulator  38 ,  
           ∑   m     M   -   1            α   ×     (         D        [   n   ]       ×     Cd        [   m   ]         +       P        [   n   ]       ×     Cp        [   m   ]           )          xCd        [   m   ]           =     a   ×   M   ×     D        [   n   ]                       
 
     [0096] is obtained.  
     [0097] The property a of the propagation path  3  contains noise components due to influences of fading, or the like. When using “noise” to express such noise components at the output of the data despread section  22  and at the output of the pilot despread section  23 , output at the data despread section  22 , r_d[n], and output at the pilot despread section  23 , r_p[n] are 
       r   —   d[n]=α×M×D[n]+ noise 
       r   —   p[n]=α×M×P[n]+ noise 
     [0098] where M=spread code length  
     [0099] For the purpose of removing such noise components, the propagation path estimation section  24  executes filtering. This filtering can be realized by using, for example, a FIR low-pass-filter as shown in FIG. 7.  
     [0100] As shown in FIG. 7, the FIR low-pass-filter includes delay elements  41  through  44 , multipliers  51  through  55 , and adder  56 . An input signal is supplied to the input terminal  57 , and tap outputs are obtained from between respective stages of serially connected delay elements. These tap outputs are multiplied by a coefficient in the multipliers  51  through  55  and supplied to the adder  56 . A filtering output is obtained from the output of the adder  56 . The filtering output is output from the output terminal  58 .  
     [0101] In the propagation path estimation section  24 , a complex conjugate P[n]* of the pilot signal the filtered is multiplied on the pilot signal LPF (r_o[n]). As a result, a propagation path estimation value is obtained as follows.  
                     α   ^     =         P        [   n   ]       *     ×     LPF        (     r                 _                   p        [   n   ]         )                     =         P        [   n   ]       *     ×     (       α   ×   M   ×     P        [   n   ]         +   N     )                   =       α   ×   M     +   N                   EQUATION  7                       
 
     [0102] where LPF()indicates passing through the filter, and N is noise components after filtering.  
     [0103] This propagation path estimation value is supplied to the phase correction section  25 . In the phase correction section  25 , the propagation path property contained in the data despread section  22  is removed by using the propagation path estimation value.  
                       data              [   n   ]     =                  (       α   ×     d        [   n   ]         +   noise     )     ×       α   ^     *                   =                  M   ×   α   ×     α   *     ×     d        [   n   ]         +     M   ×     α   *     ×                                noise   +     α   ×     d        [   n   ]       ×   N     +     noise   ×   N                   ≅                A   ×   M   ×     d        [   n   ]                      
            where                 A     =     α   ×     α   *                 EQUATION  8                       
 
     [0104] In this manner, the propagation path property contained in the output of the data despread section  22  is removed in the phase correction section  25  based on the propagation path estimation value from the propagation path estimation section  24 . Output of the phase correction section  25  is supplied to the judge section  26 , oppositely mapped there in accordance with the QPSK mapping, and demodulated into binary data. The demodulated data is output from the output terminal  27 .  
     [0105] (2) Wireless System Using Antenna Diversity  
     [0106] Next explained is a system using antenna diversity. FIG. 8 shows configuration of a wireless communication system in case of using two transmission antennas. The wireless communication system includes a transmitter  61 , receiver  62  and propagation paths  63 ,  64 .  
     [0107] In FIG. 8, a signal from the transmitter  61  is transmitted from two antennas  65 ,  66 . The signal from the antenna  65  is transmitted through the propagation path  63  and received at the antenna  67  of the receiver  62 . The signal from the antenna  66  is transmitted through the propagation path  64  and received at the antenna  67  of the receiver  62 .  
     [0108]FIG. 9 shows configuration of the transmitter  61 . The transmitter  61  includes a QPSK map section  70 , data coding section  71 , pilot spread sections  72 ,  73 , data spread sections  74 ,  75 , synthesizing sections  76 ,  77 , and transmission antennas  65 ,  66 .  
     [0109] The input terminal  81  is supplied with transmission data. The transmission data is binary data that takes 1 or −1. The QPSK map section  70  maps the transmission on the I axis and the Q axis. The data symbol mapped by the QPSK map section  70  is supplied to the coding section  71 .  
     [0110] The coding section  71  is configured to change the QPSK-mapped complex data symbol into orthogonal codes.  
     [0111] Output of the coding section  71  is supplied to the data spread sections  74 ,  75 . The transmission data is spectrally spread in the data spread sections  74 ,  75  by using a data spread code.  
     [0112] Output of the data spread section  74  is supplied to the synthesizing section  76 . Output of the data spread section  75  is supplied to the synthesizing section  77 .  
     [0113] The input terminals  82 ,  83  are supplied with pilot signals. The pilot signal supplied to the input terminal  82  and that supplied to the input terminal  83  intersect orthogonally per every two symbols.  
     [0114] The pilot signal from the input terminal  82  is supplied to the pilot spread section  72 . The pilot signal from the input terminal  83  is supplied to the pilot spread section  73 .  
     [0115] The pilot spread section  72  spectrally spread the one of the pilot signals by using one of pilot spread codes. The pilot spread section  73  spectrally spread the other pilot signal by using the other pilot spread code. One and the other of the pilot signals intersect orthogonally per every two symbols.  
     [0116] Output of the pilot spread section  72  is supplied to the synthesizing section  76 . Output of the pilot spread section  73  is supplied to the synthesizing section  77 .  
     [0117] The synthesizing section  76  combines the transmission data, having been coded by the coding section  71  and spread by the data spread section  74  with the data spread code, and the pilot signal, having been spread by the pilot spread section  72  with the pilot signal spread code. The combined output of the synthesizing section  76  is output from the antenna  65 .  
     [0118] The synthesizing section  77  combines the transmission data, having been coded by the coding section  71  and spread by the data spread section  75  with the data spread code, and the pilot signal, having been spread by the pilot spread section  73  with the pilot signal spread code. The combined output of the synthesizing section  77  is output from the antenna  66 .  
     [0119]FIG. 10 shows configuration of the receiver  62 . As shown in FIG. 8, the signals transmitted from the antennas  65 ,  66  of the transmitter  61  reach the receiver  62  through the propagation paths  63 ,  64 , and the receiver  62  receives the signals from the transmitter  61 .  
     [0120] In FIG. 10, the receiver  62  includes a reception antenna  90 , pilot despread section  91 , data despread section  92 , pilot separation section  93 , propagation path estimation section  94 , data demodulating section  95 , and judge section  96 .  
     [0121] The signal received at the reception antenna  90  is supplied to the data despread section  92  and pilot despread section  91 . The data despread section  92  despreads the data signal. Output of the data despread section  92  is supplied to the data demodulating section  95 .  
     [0122] The pilot signal despread section  91  despreads the pilot signal. Output of the pilot despread section  91  is supplied to the pilot separation section  93 . In the pilot separation section  93 , the received signal of the pilot signal sent through the propagation path  63  and the received signal of the pilot signal sent through the propagation path  64  are separated.  
     [0123] Output of the pilot separation section  93  is supplied to the propagation path estimation section  94 , and their complex conjugates are multiplied to form respective propagation path estimation values. The estimation value of the propagation path  63  and that of the propagation path  64  are supplied to the data demodulating section  95 .  
     [0124] In the data demodulating section  95 , transmission data symbols are demodulated by using the estimation values obtained in the propagation path estimation section  94 .  
     [0125] Output of the data demodulating section  95  is supplied to the judge section  96 . The judge section  96  executes opposite mapping in conformity with the QPSK mapping. As a result, the QPSK signal is demodulated into binary data. The demodulated data is output from the output terminal  97 .  
     [0126] In the transmitter  61  shown in FIG. 9, the coding section  71  changes QPSK-mapped complex data symbols into orthogonal codes by each symbol.  
     [0127] That is, when input symbols are D[m] and D[m+1], the coding section  71  issues outputs 
     D[m], D[m+1] 
     [0128] to the data spread section  74 , and issues outputs 
     −D[m+1]*, D[m]* 
     [0129] to the data spread section  75 .  
     [0130] In the receiver  62  shown in FIG. 10, data is despread in the data despread section  92  with the data spread code. Output from the data despread section  92  becomes 
       r   —   d[n]=α×d[n]+β×d[n+ 1]*+noise 
     [0131] under influences of the property a of the propagation path  63  from the antenna  65  and the property β of the propagation path  64  from the antenna  66 .  
     [0132] The pilot signal supplied to the input terminal  82  and the pilot signal supplied to the input terminal  83  intersect orthogonally per every two symbols. That is, if the pilot signal supplied to the input terminal  82  is P 1  and the pilot signal supplied to the input terminal  83  is P 2 , they satisfy  
         Corr        [   n   ]       =         ∑     i   =   0     I            P1        [     n   +   i     ]       *       +   noise                   
 
     [0133] In the receiver  62  shown in FIG. 10, the pilot signal is despread by the pilot despread section  91  by using the pilot signal spread code. Output from the pilot despread section  91  becomes 
       r   —   p[n]=α× P1[ n]+β× P2[ n ]+noise 
     [0134] under influences of the property a of the propagation path  63  from the antenna  65  and the property β of the propagation path  64  from the antenna  66 .  
     [0135] The pilot signal P 1  and the pilot signal P 2  intersect orthogonally per every two symbols. Therefore, relation of the pilot signal from the antenna  65  and the pilot signal from the antenna  66  form a pattern as shown in FIG. 11.  
     [0136] Using the pattern as shown in FIG. 11, the pilot separation section  93  separates components of the pilot signals sent through the propagation paths  63 ,  64  from the respective antennas  65 ,  66 , as shown below. 
       r   —   p[n]=α× P1[ n]+β× P2[ n ]+noise 
     =P1[ n]× (α+β)+noise 
       r   —   p[n+ 1]=α×P1[ n+ 1]+β×P2[ n+ 1]+noise 
     =P1[ n]× (α−β)+noise 
     Pr 1=(   r   —   p[n]+r   —   p[n+ 1])=α×P1[ n]+ noise 
     Pr 2=(   r   —   p[n]−r   —   p[n+ 1])=β×P2[ n]+ noise 
     [0137] That is, using that the pilot signals P 1  and P 2  intersect orthogonally per every two symbols, the pilot separation section  93  separates the pilot signal Pr 1  through the propagation path  63  from the antenna  65  by adding data of consecutive two symbols in the despread output of the pilot signal output from the pilot despread section  91 , and separates the pilot signal Pr 2  through the propagation path  64  from the antenna  66  by subtraction of data of consecutive two symbols.  
     [0138] The propagation path estimation section  94  filters the received pilot signal Pr 1  and Pr 2 , individually and separately, to remove noise components by fading, or the like, and multiplies their respective complex conjugates to thereby form propagation path estimation values, respectively.  
     [0139] The data demodulating section  95  uses the data output from the data despread section  92 , namely, 
       r   —   d[n]=α×d[n]+β×d{n+ 1]*+noise 
       r   —   d[n+ 1]=α× d[n+ 1]+β× d[n]*+ noise 
     [0140] and uses the propagation path estimation values made by the propagation path estimation section  94 , and thereby demodulates transmission data symbols as shown below.  
     EQUATION 14  
       {circumflex over (D)}[n]={circumflex over (α)}*×r   —   d[n]+{circumflex over (β)}×r   —   d[n+ 1]* 
       {circumflex over (D)}[n+ 1]={circumflex over (α)}× r   —   d[n+ 1]*−{circumflex over (β)}*× r   —   d[n]   
     [0141] (3) Example of Simultaneous Separation and Filtering of Pilot Signals  
     [0142] In the receiver  62  shown in FIG. 10, the pilot separation section  93  separates the pilot signal Pr 1  by adding data of consecutive two symbols in the despread output of the pilot signal output from the pilot despread section  91 , and separates the pilot signal Pr 2  by subtraction of data of consecutive two symbols. Then, the propagation path estimation section  94  make individual propagation path estimation values by filtering the received pilot signal Pr 1  and Pr 2  independently and multiplying their complex conjugates individually.  
     [0143]FIG. 12 shows a receiver to which the invention is applied. This example is used in antenna diversity systems, similarly to the receiver  62  shown in FIG. 10. In this example, however, a single pilot separation section  103  executes separation of pilot signals, filtering thereof and creation of propagation path estimation values.  
     [0144] In FIG. 12, the receiver  111  includes a reception antenna  100 , pilot despread section  101 , data despread section  102 , pilot separation section  103 , data demodulating section  105 , and judge section  106 .  
     [0145] The pilot despread section  101 , data despread section  102 , data demodulating section  105  and data judge section  106  have substantially the same configurations as those of the pilot despread section  91 , data despread section  92 , data demodulating section  95  and data judge portion  96  in FIG. 10.  
     [0146] As shown in FIG. 13, the pilot separation section  103  includes delay elements  201  through  209 , multipliers  211  through  218 , multipliers  221  through  228 , adders  230 ,  231 , and multipliers  240 ,  241 .  
     [0147] A signal from the input terminal  200  is supplied to the delay elements  201  through  206 , serially connected, and tap outputs are obtained from between respective delay elements  201  through  209 . The tap outputs are supplied to the multipliers  211  through  218  and multipliers  221  through  228 .  
     [0148] The multipliers  211  through  218  are supplied with coefficients a 0  through a 7 . The multipliers  221  through  228  are supplied with coefficients b 0  through b 7 .  
     [0149] Outputs of the multipliers  211  through  218  are supplied to the adder  230 . Output of the adder  230  is supplied to the multiplier  240 . The multiplier  240  is also supplied with a complex conjugate of the pilot signal P 1 . Output of the multiplier  240  is released from the output terminal  250 .  
     [0150] Outputs of the multipliers  221  through  228  are supplied to the adder  231 . Output of the adder  231  is supplied to the multiplier  241 . The multiplier is also supplied with a complex conjugate of the pilot signal P 2 . Output of the multiplier  241  is released from the output terminal  251 .  
     [0151] Here is remarked that the pilot signal P 1  and the pilot signal P 2  intersect orthogonally not only per every two symbols but also per every four symbols or every eight symbols. That is, as already explained, the pilot signal P 1  and the pilot signal P 2  intersects per every two symbols, and the pattern of pilot signal from two antennas is as shown in FIG. 11.  
     [0152] It will be appreciated from FIG. 11 that such pilot signals P 1  and P 2  are related to intersect orthogonally not only per every two symbols, but also per every L symbols (four symbols, eight symbols, 16 symbols, and so forth).  
     [0153] As already explained, by using that the pilot signal P 1  and the pilot signal P 2  intersect orthogonally per every two symbols, the pilot signal P 1  and the pilot signal P 2  can be separated by addition and subtraction of consecutive two symbol data.  
     [0154] If it is used that the pilot signal P 1  and the pilot signal P 2  intersect orthogonally per every four symbols, the pilot signal P 1  and the pilot signal P 2  can be separated by addition or subtraction of consecutive four symbol data.  
     [0155] Similarly, if it is used that the pilot signal P 1  and the pilot signal P 2  intersect orthogonally per every eight symbols, the pilot signal P 1  and the pilot signal P 2  can be separated by addition or subtraction of consecutive four symbol data.  
     [0156] In the case where the pilot signal P 1  and the pilot signal P 2  are separated by addition or subtraction of consecutive four symbol data, using that they intersect orthogonally per every four symbols, it results in being equivalent to averaging of every two symbol data of the pilot signals P 1  and P 2  separated per every two symbols.  
     [0157] That is, in the case where the pilot signal P 1  and the pilot signal P 2  are separated by addition or subtraction of consecutive four symbol data, using that the pilot signal P 1  and the pilot signal P 2  intersects orthogonally per every four symbols, it results in being equivalent to the pilot signal P 1  and the pilot signal P 2  being separated and filtered.  
     [0158] Further, in the case where the pilot signal P 1  and the pilot signal P 2  are separated by addition or subtraction of consecutive eight symbol data, using that the pilot signal P 1  and the pilot signal P 2  intersects orthogonally per every eight symbols, it results in being equivalent to the pilot signal P 1  and the pilot signal P 2  being separated and filtered more strictly.  
     [0159] The pilot separation section  103  shown in FIG. 13 can be switched among separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of two consecutive symbol data, separation of the pilot signal P 1  and the pilot signal P 2  by addition of subtraction of four consecutive symbol data and separation of the pilot signal P 1  and the pilot signal P 2  by addition of subtraction of eight consecutive symbol data, depending on the manner of applying the coefficients a 0  through a 7  and the coefficients b 0  through b 7  that are applied to the multipliers  211  through  218  and the multipliers  221  through  228 .  
     [0160] That is, in the pilot separation section  103  shown in FIG. 13, when the coefficients a 0  through a 7  and the coefficients b 0  through b 7  are determined as 
     [a0, a1, a2, a3, a4, a5, a6, a7]=(1, 1, 0, 0, 0, 0, 0, 0] 
     [b0, b1, b2, b3, b4, b5, b6, b7]=[1, −1, 0, 0, 0, 0, 0, 0] 
     [0161] the pilot signal P 1  and the pilot signal P 2  are separated by addition or subtraction of two symbol patterns. In this case, although the pilot signals P 1  and P 2  are separated, filtering is not performed.  
     [0162] When the coefficients a 0  through a 7  and the coefficients b 0  through b 7  are determined as 
     [a0, a1, a2, a3, a4, a5, a6, a7]=[1, 1, 1, 1, 0, 0, 0, 0] 
     [b0, b1, b2, b3, b4, b5, b6, b7]=[−1, 1, −1, 1, 0, 0, 0, 0] 
     [0163] the pilot signal P 1  and the pilot signal P 2  are separated by addition or subtraction of four symbol patterns. In this case, the pilot signals P 1  and P 2  are separated, and filtering is performed simultaneously.  
     [0164] When the coefficients a 0  through a 7  and the coefficients b 0  through b 7  are determined as 
     [a0, a1, a2, a3, a4, a5, a6, a7]=[1, 1, 1, 1, 1, 1, 1, 1] 
     [b0, b1, b2, b3, b4, b5, b6, b7]=[−1, 1, −1, 1, −1, 1, −1, 1] 
     [0165] the pilot signal P 1  and the pilot signal P 2  are separated by addition or subtraction of eight symbol patterns. In this case, the pilot signals P 1  and P 2  are separated, and stricter filtering is performed simultaneously.  
     [0166] The separated pilot signals P 1  and P 2  are output from the adders  230 ,  231 . Outputs of the adders  230 ,  231  are supplied to the multipliers  240 ,  241 . The multipliers  240 ,  241  multiply complex conjugates on the pilot signals P 1 , P 2 , respectively. As a result, path estimation values are obtained. The path estimation values are output from the output terminals  250 ,  251 .  
     [0167] In the pilot separation section  103  shown in FIG. 13, it is possible to preset, as shown in FIG. 14, separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of two symbol patterns, separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of four symbol patterns and separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of eight symbol patterns, depending upon the manner of applying the coefficients a 2  through a 7  and the coefficients b 0  through b 7 .  
     [0168] In case of separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of four symbol patterns, separation and filtering of the pilot signals occur simultaneously, and in case of separation of the pilot signal aP 1  and the pilot signal P 2  by addition or subtraction of eight symbol patterns, separation of more strict filtering of the pilot signals occur simultaneously. Therefore, later filtering is not necessary.  
     [0169] Properties may be switched depending upon the noise level to perform separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of two symbol patterns when the noise is little, perform separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of four symbol patterns when the noise is more but still little, and perform separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of two symbol patterns when the noise is large.  
     [0170] The example of FIG. 13 is configured to perform separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of two symbol patterns, separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of four symbol patterns, and separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of eight symbol patterns. However, the number of taps of the delay elements may be increased to enable separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of 16 symbol patterns, separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of 32 symbol patterns, or even more, as well.  
     [0171] (4) Example of Simultaneous Despread, Separation and Filtering of Pilot Signals  
     [0172] In the foregoing examples, upon despread of pilot signals on the part of a receiver, the received signal and the pilot signal spread code are multiplied to accumulate data of M chips (M is the spread code length). In this case, data is despread, one symbol by one symbol.  
     [0173] In this example, despread is performed by for example (Mx2) chips instead of in M chips. Thereby, despread of pilot signals and separation of pilot signals can be executed simultaneously.  
     [0174]FIG. 15 shows a received of this type. In FIG. 15, the receiving apparatus  311  includes a reception antenna  320 , pilot despread section  321 , data despread section  322 , data demodulating section  325 , and judge section  326 .  
     [0175] The data demodulating section  325  and data judge section  326  have substantially the same configurations as those of the data demodulating section  95  and data judge portion  96  in FIG. 10.  
     [0176] As shown in FIG. 16, the pilot despread section  321  includes code generators  331 A,  331 B, code generators  332 A,  332 B, multipliers  333 ,  334 , accumulators  335 ,  336 , and pilot component removers  337 ,  338 .  
     [0177] The code generators  331 A,  331 B generate pilot signal spread codes Cp[m]. The code generators  332 A,  332 B generate pilot signal spread codes Cp[m] and −Cp[m]. Although the code generators  331 A,  331 B, and the code generators  332 A,  332 B are illustrated separately for the purpose of explaining execution of despread by (Mx2) chips, the concept can be realized with a single code generator.  
     [0178] The accumulators  335 ,  336  accumulate (Mx2) chips of outputs from the multipliers  333 ,  334 .  
     [0179] A received signal from the antenna  32  is supplied to the input terminal  341 . This signal is supplied to the multiplier  333  and further to the multiplier  334 . The multiplier  333  multiplies the M-chip received signal by the spread code Cp[m], and multiplies the next M-chip received signal by the spread code Cp[m]. Outputs of the multiplier  333  are supplied to the accumulator  335 , and the accumulator  335  accumulates (Mx2) chips of outputs from the multipliers  333 .  
     [0180] The multiplier  334  multiplies the M-chip received signal by the spread code Cp[m], and multiplies the next M-chip received signal by the spread code −Cp[m]. Outputs of the multipliers  334  are supplied to the accumulator, and the accumulator  336  accumulates (Mx2) chip of outputs from the multiplier  334 .  
     [0181] In this manner, the multiplier  333  is supplied with the codes, [Cp[m], Cp[m]], having the code length of (Mx2) chips, such that the codes and the input signal rp[m] are multiplied and accumulated up to the (Mx2) chips in the accumulator  335 . Therefore, the following output is obtained from the accumulator  335 .  
                     acc                 _                 1     =                  ∑     m   =   0         2      xM     -   1              rp        [   m   ]       ×     C        [   m   ]                       =                    ∑     m   =   0       M   -   1              rp        [   m   ]       ×     Cp        [   m   ]           +                                ∑     m   =   0       M   -   1              rp        [     m   +   M     ]       ×     Cp        [   m   ]                       =                  ∑     m   =   0       M   -   1              (       α   ×   P   ×     Cp        [   m   ]         +     β   ×   P   ×     Cp        [   m   ]           )     ×                                  Cp        [   m   ]       +       ∑     m   =   0       M   -   1            (       α   ×   P   ×     Cp        [   m   ]         -   β   -     P   ×                                        Cp        [   m   ]       )     ×     Cp        [   m   ]                   =                  2   ×   α   ×   P   ×   M     +   noise                   EQUATION  15                       
 
     [0182] On the other hand, the multiplier  334  is supplied with the codes, [Cp[m], −Cp[m]], having the code length of (Mx2) chips, such that the codes and the input signal rp[m] are multiplied and accumulated up to the (Mx2) chips in the accumulator  336 . Therefore, the following output is obtained from the accumulator  336 .  
                     acc                 _      2     =                  ∑     m   =   0         2      xM     -   1              rp        [   m   ]       ×     C        [   m   ]                       =                    ∑     m   =   0       M   -   1              rp        [   m   ]       ×     Cp        [   m   ]           -                                ∑     m   =   0       M   -   1              rp        [     m   +   M     ]       ×     Cp        [   m   ]                       =                  ∑     m   =   0       M   -   1            (       α   ×   P   ×     Cp        [   m   ]         +     β   ×   P   ×     Cp        [   m   ]         +                                    noise              )     ×     Cp        [   m   ]         -       ∑     m   =   0       M   -   1            (       α   ×   P   ×     Cp        [   m   ]         -                                    β   -     P   ×     Cp        [   m   ]         +   noise     )     ×     Cp        [   m   ]                   =                  2   ×   α   ×   P   ×   M     +   noise                   EQUATION  16                       
 
     [0183] Further, by multiplying complex conjugates in the pilot component removers  367 ,  338 , the following propagation properties can be obtained from respective antennas.  
     EQUATION 17  
     {circumflex over (α)}=acc — 1× P*= 2×α× M+ noise 
     {circumflex over (β)}=acc — 2× P*= 2×β× M+ noise 
     [0184] By executing despread by (Mx2) chips in this manner, processing equivalent to addition or subtraction of two consecutive symbols obtained by despread, and despread and separation of pilot signals can be achieved simultaneously.  
     [0185] Additionally, although the above example executes despread by (Mx2) chips, since the pilot signal P 1  and the pilot signal P 2  intersect orthogonally not only per every two symbols, but also per every four symbols or every eight symbols, despread may be made by (Mx4) chips as shown in FIG. 17. In this manner, also filtering for removal of noise can be achieved simultaneously.  
     [0186] More specifically, in case the code length is L, it can be expressed as follows. 
     {circumflex over (α)}= L×α×M+ noise 
     {circumflex over (β)}= L×β×M+ noise 
     [0187] The signal-to-noise ratio at that time is (L/2) times that of the case where the pilot code length is 2, because the signal components are L/2 times. Therefore, when the value of L is increased, filtering is for removal of noise is not required, and the transmission path estimation section can be omitted.  
     [0188] The length of the code used for despread can be changed simply by changing outputs of the code generators  331 A,  331 B,  332 A and  332 B and numbers of accumulation of the accumulators  335  and  336 . Therefore, the code length may be switched depending on the required level of noise removal, among L=8 in case of requiring strict noise removal, L=2 in case of requiring no noise removal, and so on.  
     [0189] The pilot signal P 1  and the pilot signal P 2  intersect orthogonally per every two symbols. Further, the pilot signal P 1  and the pilot signal P 2  are related to intersect orthogonally not only per every two symbols, but also per every four symbols, every eight symbols, every 16 symbols, or even more.  
     [0190] In the present invention, by using that the pilot signal P 1  and the pilot signal P 2  intersect orthogonally per every four symbols or every eight symbols, the pilot signal P 1  and the pilot signal P 2  can be separated by addition or subtraction of four or eight consecutive symbol data. It results in being equivalent to averaging the pilot signals P 1  and P 2  separated per every two symbols, and separation of the pilot signals and filtering can be achieved simultaneously.  
     [0191] Filtering properties can be switched depending upon the noise level so as to select separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of two symbol patterns when the noise is little, select separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of four symbol patterns when the noise is more but still little, and select separation of the pilot signal P 1  and the pilot signal P 2  by addition or subtraction of two symbol patterns when the noise is large.  
     [0192] Further, in the present invention, by employing (Mx2) chips, instead of M chips, upon spreading the pilot signals, processing equivalent to addition or subtraction of consecutive two symbols obtained by despread can be achieved, and despread and separation of pilot signals can be effected simultaneously.  
     [0193] Furthermore, if despread is executed by (MxL) chips, despread of pilot signals, separation of pilot signals and filtering can be achieved simultaneously. Additionally, depending upon the noise level, filtering properties can be switched by changing the magnitude of L.  
     [0194] Having described a specific preferred embodiment of the present invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to that precise embodiment, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or the spirit of the invention as defined in the appended claims.