Abstract:
An input signal data string I is temporarily stored in a register, and is input to an adder according to the instruction of a control unit. The control unit designates a ROM storing a check matrix H and obtains information about a position, in which 1 is stored in a specific column of the check matrix. The ROM instructs SEL 1#1  through #CW to select a value corresponding the position, in which the check matrix is 1 from values from reg(M) using a selector SELL and sends it to an adder. If the result of an addition is selected by a selector SEL 2  instructed to select it by the ROM, then it is input to the reg(M). If no addition has been applied, the value output from the reg(M) is input to the reg (M) again through the selector SEL 2.  This process is repeated until all the operations have finished.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a matrix operation processing device.  
           [0003]    2. Description of the Related Art  
           [0004]    Currently, many data processing devices, including personal computers, are commercialized and are put into practical use. In such data processing devices, data is stored or transferred after being encoded. In particular, if digital signals are received from a storage/reproduction medium, such as a magnetic disk, an optical disk, a magneto-optical disk and the like, or a network, and are decoded, an LDPC (low density parity check) code is sometimes used for error correction.  
           [0005]    In order to obtain a process result P using N bits of signal data string I and N×M bits of check matrix H, the matrix operation P=H*I T  is needed. For example, if the following equation holds true,  
               I   =     [       i   0     ,     i   1     ,   Λ   ,     i     N   -   1         ]       ,                P   =     [       p   0     ,     p   1     ,   Λ   ,     p     M   -   1         ]       ,               H   =     [           h   00           h   01         Λ         h       0      N     -   1               M       M       M       M             h     M   -   10             h     M   -   11           Λ         h     M   -     1      M     -   1             ]                                 
 
           [0006]    the process result P can be calculated as follows.  
               P   m     =       ∑     n   =   0       N   -   1              h   mn     *     i   n                 (   1   )                               
 
           [0007]    In this case, for example, a magnetic disk device being a typical storage/reproduction medium is provided with an error correction function. An LDPC code is one of possibly many codes used for such error correction. In this case, calculating this code requires such a matrix operation.  
           [0008]    A check matrix used for a parity calculation or an LDPC decoding contains only binary values (1s and 0s. In this case, equation (1) is as follows.  
               P   m     =       ∑     n   =       0   /     h   mn       =   1         N   -   1            i   n               (   2   )                               
 
           [0009]    [0009]FIG. 1 shows a conventional matrix operation circuit.  
           [0010]    In order to obtain the process result P by performing such a process, equation (2) must be calculated after the full data of the signal data string I are obtained.  
           [0011]    After all the full data of the signal data string I are stored in a register  40 , a selector SEL  42  selects items, the value of which is 1 in each row read from a ROM  14  and the like storing a matrix datum H, and an adder  46  adds the items. The result of the addition is stored in a register  43 . In this case, RW represents the maximum number of 1s in each row. By repeating this process M times, the process result P can be obtained. In this case, if the selector and adder are shared until the full data of P are obtained, the process runs in O(N+M) time and causes great delay, which is a problem. In this case, a storage register N with a large circuit scale and/or RW adders is also needed.  
           [0012]    [0012]FIG. 2 shows another conventional matrix operation circuit.  
           [0013]    In this conventional matrix operation circuit, after the full data of a signal data string I are stored in a register  44 , an adder  47  wired based on the matrix H calculates the full data of the process result P. The result is stored in a register  45  and is output. In this case, although only O(N) time is needed to obtain the full of data of P, the size of a storage register N and the circuit scale become large since RW×M adders are needed, which is another problem.  
         SUMMARY OF THE INVENTION  
         [0014]    It is an object of the present invention to provide a matrix operation processing device performing a high-speed matrix operation with a small circuit scale.  
           [0015]    The matrix operation processing device of the present invention comprises a storage unit storing the elements of a matrix; a register storing a value, all initially set all 0s, and sequentially storing the result of a sequentially performed operation; an adder adding an input data value to a value output from the register; an operation control unit inputting a necessary value in the register to the adder, based on the matrix element value and adding an input data value to the value from the register; and a loop-back unit appropriately selecting the output of the adder and the output of the register and storing them in the register again.  
           [0016]    According to the present invention, the number of adders and the circuit scale can be reduced compared to the conventional circuit. If only necessary information about a matrix is stored, memory capacity can also be reduced and a small high-speed matrix operation processing device can be realized. 
       
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 shows a conventional matrix operating circuit.  
         [0018]    [0018]FIG. 2 shows another conventional matrix operating circuit.  
         [0019]    [0019]FIG. 3 shows an example configuration of the matrix operation circuit according to the preferred embodiment of the present invention.  
         [0020]    [0020]FIG. 4 shows an example circuit representing the operation of the preferred embodiment of the present invention.  
         [0021]    [0021]FIG. 5 shows an example of the realized control unit according to the preferred embodiment of the present invention (No. 1).  
         [0022]    [0022]FIG. 6 shows an example of the realized control unit according to the preferred embodiment of the present invention (No. 2).  
         [0023]    [0023]FIG. 7 shows an example of the realized control unit according to the preferred embodiment of the present invention (No. 3).  
         [0024]    [0024]FIG. 8 shows an example of the realized control unit according to the preferred embodiment of the present invention (No. 4). 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    In the matrix operation P=H×I T , obtaining a process result P using N bits of a signal data string I and N×M bits of a check matrix H, process delay and circuit scale are reduced by performing necessary operations for each column of the check matrix H and accumulating the result for each row. In particular, in a check matrix for error correcting codes needed for coding, the number of the columns M of the check matrix is far smaller than the number of the rows N. Therefore, by calculating a plurality of pieces of data in each column in parallel and accumulating the result for each row, the number of adders and circuit scale can be reduced.  
         [0026]    The matrix operation processing device comprises a storage unit storing a process result P, such as a register or the like; a storage unit storing a check matrix H, such as a ROM or the like; a unit reading the check matrix H and process result P when an address counter or the like receives a signal data string I and controlling the storage; and an operation unit, such as an adder or the like. The device obtains column data, the input data which must be processed every time the device receives a signal data string I, from H, reads necessary items of a target process result P, multiplies the received data by the necessary items and writes the result back into the storage unit as the process result P. By repeating this process for all the full received data of the signal data string I, a process result P can be obtained.  
         [0027]    [0027]FIG. 3 shows an example configuration of a matrix operation circuit according to the preferred embodiment of the present invention.  
         [0028]    A control unit  10  controls the reception of a signal data string I and stores it in a storage unit reg  12 . The control unit  10  also obtains the position of a target process result P in the column from a storage unit  11  for a check matrix H, based on the position of the received data. A storage unit reg(M)  13  for the process result P is initialized to all 0s prior to data reception. The control unit  10  and storage unit  11  enable a data selector SEL  1  to select the target process result P and to add input data to the process result P. In this case, the number of adders in the column is the same as the maximum number CW of 1s. SEL  1  is a selector for M→CW and the number of the selectors is also CW. SEL  2  is a selector for (CW+1)→1 and the number of the selectors is M. The SEL  2  judges whether each result of the additions and data read from the reg(M)  13  is process data or original data, and writes them back into the reg(M)  13 .  
         [0029]    Specifically, in FIG. 3, one bit of the signal data string I is stored in the reg  12 , is read by the control unit  10  and is input to each adder. The control unit  10  detects the position of an element with value 1 in an appropriate column of the check matrix from a ROM  11 , a selector SELL corresponding to the position of the element with value 1 in the column of the check matrix selects a value output from the reg(M)  13 , from signals output from the reg(M)  13  and adds the value to the signal data string. The result of the addition is sent to a selector SEL 2 . The selector SEL 2  inputs a data value, to which addition has been applied in the adder, to the reg(M)  13 . As for a data value to which addition has not been applied, the selector SEL 2  inputs the value to the reg(M)  13  again. When the reception/operation of all the signal data strings I finish, the reg(M)  13  outputs output data P.  
         [0030]    Speaking more conceptually, it is determined to which column the element of an input signal data string I should be multiplied when the I is read, by obtaining the offset of the I. If an I is input, the column to be used of a check matrix is read and the operations using parallel columns are performed in parallel (In reality, since the elements of a check matrix are 0 and 1, the matrix element of which is 1, is input to an adder without performing any process). Then, the result of the operation is stored in the reg(M), and it is added horizontally every time an I is sequentially input. When all addition finishes, a parity row vector is obtained and the operation terminates.  
         [0031]    According to this device, data process running time is O(N). As for circuit scale, the respective number of adders and storage registers become CW and M, respectively.  
         [0032]    If the storage unit for a check matrix H stores the address of a position taking 1, (Cadd1, Cadd2, Cadd3) are stored in the first address of a ROM(H). In this case, Cadd represents the position of the n-th 1 in a column, and if the number of 1s is less than CW, the value is designated as 0.  
         [0033]    For example, if H(N=8, M=5) is as follows,  
       H   =     [         1       0       1       1       0       1       1       0           0       1       0       1       1       1       1       1           1       0       1       0       0       0       1       1           1       1       0       1       1       0       0       1           0       1       1       0       1       1       0       0         ]                           
 
         [0034]    data are stored as follows.  
                           TABLE 1                                   address   data                           0   (1, 2, 4)           1   (2, 4, 5)           2   (1, 3, 5)           3   (1, 2, 4)           4   (2, 4, 5)           5   (1, 2, 5)           6   (1, 2, 3)           7   (2, 3, 4)                      
 
         [0035]    In this case, each address can be represented by three bits (0˜5&lt;8). Therefore, if CW=3, 3×3=9 bits can be stored as one word.  
         [0036]    If the offset of an input data string I is 0, (1, 3, 4) is output. Each of three SEL 1   s  from the left end selects the M of 1, the M of 3 and the M of 4 from left to right. Then, each of the first, third and fourth SEL 2   s  from the left end selects a signal from each SEL 1 , and each of the other SEL 2   s  selects a signal from M.  
         [0037]    The respective realized control of SEL  1  and SEL  2  are shown below. If it is assumed that SELL is a selector for M→1 and a control signal represents m (integer), the SELL selects/outputs the m-th data. In this case, if every three bits from the MSB of the output from the ROM can be designated as a control signal m, the control of the SELL can be realized.  
         [0038]    If it is assumed that SEL 2  is a selector for 4(CW+M)→1 and control signals select as follows,  
         [0039]    0→M; 1→SEL 1 # 1 ; 2→SEL 1 # 2  and 4→SEL 1 #CW  
         [0040]    the control of the SEL 2  can be realized by inputting the output from the ROM to the data multiplexer decoder shown in Table 2 and designating the output of each decoder as control signals, as shown in Table 2.  
                           TABLE 2                                   input   output data                           0   0 (00000b)           1   1 (00001b)           2   2 (00010b)           3   4 (00100b)           4   8 (01000b)           5   16 (10000b)                       
 
         [0041]    [0041]FIG. 4 shows an example of the circuit representing the operation of the preferred embodiment of the present invention.  
         [0042]    Control signals are output from a ROM (H)  1  and are input to each of selectors SEL 1 # 1  through SEL 1 #CW and each of multiplexer decoders DEC 3 - 1  through  3 - n . Signals obtained by decoding the control signals from the ROM (H)  1  to the selection signals of a selector SEL 2  are output from the multiplexer decoder DEC 3 - 1  through  3 - n . The SEL 2  is controlled by signals from these multiplexer decoders DEC 3 - 1  through  3 - n.    
         [0043]    An example of how to generate a reading address for a matrix H  
         [0044]    [0044]FIGS. 5 through 8 show examples of the realized control unit according to the preferred embodiment of the present invention.  
         [0045]    First, if at the top of an input data string I, data_start is as shown in FIG. 5 and during the valid time period of the data I, data_enable is as shown in FIG. 5, a control unit can be implemented by using a counter  22  with count enable (count up by 1) and clear (all 0 by 1). In the case of the matrix described above, a three-bit counter (0˜7) can function as the control unit.  
         [0046]    As shown in FIG. 5, an M storage register can be realized by selecting output SEL 2  if data_enable is 1, and storing it in an FF  21 . If it is 0, the M storage register can be realized by selecting data using a selector  20  and storing the data in a FF  21 .  
         [0047]    In this case, data_enable can also be discontinuous, as shown in FIG. 6. If data I is input in descending order, the control unit can be realized by storing H in reverse order.  
         [0048]    In FIG. 6, the control unit can be realized by replacing the counter with a down-counter with a loading function and loading a value N−1 by data_start, down-counting the data by data_enable.  
         [0049]    If data I is input in a pre-defined order, the control unit can be realized by storing H in that pre-defined order.  
         [0050]    If input data I is interleaved, the control unit can be realized by storing H in that order.  
         [0051]    The control unit can also be realized by the configuration shown in FIG. 7. In this case, n is an interleave interval. If n=2, the input order of the example described above (0˜7) becomes 0, 2, 4, 6, 1, 3, 5 and 7.  
         [0052]    A REG  33  is an FF storing addresses. When data_enable is 1, selectors  31  and  32  select data in the lower parts of selectors  31  and  32 , respectively. A comparator  34  compares the count enable of a counter  30  and input to the port in the upper parts of the selectors  31  or  32 .  
         [0053]    The operations are as follows:  
         [0054]    1. “0” is loaded into all REGs by data_start, and 1 is loaded into the counter  30  by clear.  
         [0055]    2. A value obtained by adding n to the value of the REG  33  can be loaded (set) by data_enable.  
         [0056]    3. It is tested whether REG&gt;N−1. If it holds true, the process proceeds to step 4. If it does not hold true, the flow returns step 2.  
         [0057]    4. The flow returns to step 1 by data_start. Otherwise, by data_enable, a counter value is set in the REG  33 . By CE, the counter  30  is incremented by one and the flow returns to step 2.  
         [0058]    If in this configuration, n=1, data in ascending order without interleave are obtained.  
         [0059]    In the configuration shown in FIG. 8, the operations are as follows, and data interleaved and in reverse order can be obtained.  
         [0060]    1. N− 1  is loaded into the REG  33  by data_start, and N−2 is loaded into the counter  30  by clear.  
         [0061]    2. A value obtained by subtracting n from the value of the REG  33  is loaded (set) by data_enable.  
         [0062]    3. It is tested whether REG=0. If it holds true, the flow proceeds to step 4. If it does not hold true, the flow returns to step 2.  
         [0063]    4. The flow returns to step 1 by data_start. Otherwise, by data_enable, a counter value is set in the REG  33 . By CE, the counter  30  is decremented by one, and the flow returns to step 2.  
         [0064]    In the preferred embodiment described above, comparison is made in one example of the check matrix for LDPC codes. In this case, if N=4352, M=256 and RW=51, in the preferred embodiment, the capacity of a storage memory becomes M/N=1/4 compared with that in the prior art. The number of adders becomes CW/RW=3/51 compared with that in the configuration shown in FIG. 1, and becomes CW/RW×M=3/13056 compared with that in the configuration shown in FIG. 2.  
         [0065]    In the device of the preferred embodiment, the process is performed for each column. Thus, the process can be performed regardless of the order in which the N bits of a signal data string I are received. By processing data for each column, the processing of N bits of a signal data string I can be started from an arbitrary position.  
         [0066]    Furthermore, in the preferred embodiment, a check matrix H can be stored by storing only the address of an item to be processed. Therefore, the circuit scale of the storage unit can be reduced.  
         [0067]    If the entire matrix is stored, capacity for M bits×N addresses is needed. However, if only its addresses are stored, only capacity for log 2 (M)bits×CW is needed.  
         [0068]    Furthermore, by storing the order in which the signal data string I is received using a matrix storage unit a processing device that can handle any receiving order can be realized.  
         [0069]    Furthermore, as described above, when a signal data string I is received in reverse order, there is no need to modify the circuit if only the addresses of the matrix are stored in reverse order.  
         [0070]    In the device described above, by storing the order in which the signal data string I is received using control data provided for a matrix storage unit, a processing device regardless of receiving order can be realized.  
         [0071]    For example, by organizing order in which addresses are received into a table using registers, dynamic modification to adapt to order in which data are received becomes possible.  
         [0072]    In the preferred embodiments described above, although the number of selectors with a fairly small circuit scale increases, the number of adders with a fairly large circuit scale decreases. Therefore, as a whole, circuit scale can be reduced.  
         [0073]    Since the ROM only stores the position of the is in a check matrix, there is no need for the ROM to store all the matrix elements. Therefore, memory capacity can be reduced. In particular, in the case of an LDPC code, since the number of 1s is fairly small, memory capacity can be effectively reduced.  
         [0074]    In the description of the preferred embodiments given above, although it is assumed that the signal value of an input data string I is a binary bit string, the present invention is not limited to this. Even when the signal value is composed of real numbers, the present invention is similarly applicable.  
         [0075]    For the details of an LDPC code and its coding, see the following references. Tadashi Wadayama, “Low-Density Parity Check Codes and a Decoding Method thereof”, Proceedings of the Magnetic Recording Study Group, December 2001, &lt;http://vega.c.oka-pu.ac.jp/˜wadayama/welcome_j.htm 1&gt; 
         [0076]    (1) Tadashi Wadayama, “An Extension of Gallager Ensemble Of Low-Density Parity Check Codes”, IEICE Trans. Fundamentals, Vol.E85-A, No.1, January 2002  
         [0077]    According to the present invention, the delay and circuit scale of a matrix operation circuit can be reduced.