JP2013207396A - Decoding device, decoding method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technology which reduces the amount of arithmetic operations in min-sum decoding.SOLUTION: A min-sum processing unit 46 executes a min-sum algorithm on input data and thereby alternately executes check node processing to update an external value ratio on the basis of a prior value ratio and variable node processing to update a prior value ratio on the basis of an external value ratio. An identification unit 60 identifies the minimum value of prior value ratio in terms of absolute value among the prior value ratios subject to check node processing for each of the external value ratios to be updated. An update unit 64 updates, by using the minimum value, one or more of the external value ratios for which the minimum value identified by the identification unit 60 is larger than their threshold values, or sets one or more of the external value ratios for which the minimum value identified by the identification unit 60 is smaller than their threshold values to a predetermined value.

Description

  The present invention relates to a decoding technique, and more particularly, to a decoding device, a decoding method, and a program for decoding data encoded by LDPC.

  In recent years, LDPC (Low Density Parity Check Code) has attracted attention as an error correction code having strong error correction capability even in a low S / N transmission path, and is applied in many fields. In LDPC, data is encoded by an encoding matrix generated on the transmission side based on a sparse check matrix. Here, a sparse check matrix is a matrix having 1 or 0 elements and a small number of 1s. On the other hand, on the receiving side, data decoding and parity check are performed based on the check matrix. In particular, decoding performance is improved by iterative decoding using the BP (Belief Propagation) method or the like.

  In this decoding, a check node process for decoding in the row direction of the check matrix and a variable node process for decoding in the column direction are repeatedly executed. As one of the check node processes, sum-product decoding using a Gallager function or a hyperbolic function is known. In sum-product decoding, a channel value obtained from a variance value of transmission channel noise is used as a prior value. A decoding method that simplifies sum-product decoding is min-sum decoding. In min-sum decoding, check node processing can be performed by simple processing such as comparison operation and sum operation without using a complicated function. Furthermore, since min-sum decoding does not require a channel value, it is widely used for simplifying and speeding up the processing. In order to reduce the circuit scale of min-sum decoding, it has been proposed to use the minimum value of the prior value ratio in each row of the parity check matrix and the next smallest value (for example, see Patent Document 1).

JP 2005-269535 A

  The process of deriving the minimum value of the prior value ratio in each row of the check matrix is realized by a very simple circuit. In order to derive the next smallest value, after deriving the minimum value, it is necessary to search for the minimum value again, or to have two memories, and to replace the memory while comparing both values and input values. And the circuit becomes complicated. For this reason, it is required to reduce the amount of calculation in min-sum decoding.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for reducing the amount of calculation in min-sum decoding.

  In order to solve the above problems, a decoding apparatus according to an aspect of the present invention performs an min-sum algorithm on data that has been subjected to LDPC encoding, thereby calculating an external value ratio based on a priori value ratio. A decoding unit that alternately executes check node processing to be updated and variable node processing to update the prior value ratio based on the external value ratio is provided. For each external value ratio to be updated, the decoding unit specifies the minimum value of the absolute value of the prior value ratio among the prior value ratios to be subjected to the check node processing, and specified by the specific unit For external value ratios where the minimum value is greater than the threshold value, update the external value ratio using the minimum value, and for external value ratios where the minimum value specified in the specific part is less than or equal to the threshold value And an updating unit that sets a predetermined value to the external value ratio.

  According to this aspect, since the predetermined value is set as the external value ratio with respect to the external value ratio whose minimum value is equal to or less than the threshold value, it is omitted to update the external value ratio using the minimum value. The amount of computation in min-sum decoding can be reduced.

  The specifying unit may specify the minimum value for each of the external value ratios before starting the check node process. In this case, since the minimum value is specified before the check node process is started, the specification can be performed collectively.

  The update unit may set the predetermined value set to the external value ratio to zero. In this case, a decrease in error correction capability can be suppressed. The updating unit may set the threshold value to zero. In this case, the error correction capability does not decrease.

  Another aspect of the present invention is a decoding method. This method performs check node processing for updating an external value ratio based on an a priori value ratio by executing a min-sum algorithm on LDPC-encoded data, and an external value ratio. And a step of alternately executing variable node processing for updating the priori value ratio. The steps to be executed include, for each of the external value ratios to be updated, a step of specifying the absolute value of the absolute value of the prior value ratio among the prior value ratios to be subjected to the check node processing, and the specified minimum value being For external value ratios that are greater than the threshold value, update the external value ratio using the minimum value.For external value ratios that have a specified minimum value that is less than or equal to the threshold value, set the external value ratio to the external value ratio. Setting to a value ratio.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, the amount of computation in min-sum decoding can be reduced.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. It is a figure which shows the test matrix used in the LDPC encoding part of FIG. It is a figure which shows the structure of the decoding part of FIG. It is a figure which shows the Tanner graph which represented typically the operation | movement of the decoding part of FIG. It is a figure which shows the outline | summary of the external value ratio update operation | movement in the decoding part of FIG. It is a figure which shows the outline | summary of the prior value ratio update operation | movement in the decoding part of FIG. It is a flowchart which shows the decoding procedure by the decoding part of FIG. It is a flowchart which shows another decoding procedure by the decoding part of FIG. It is a flowchart which shows the initialization procedure by the decoding part of FIG.

  Before describing the present invention specifically, an outline will be given first. Embodiments of the present invention include a transmission apparatus that performs LDPC encoding, and reception that repeatedly performs decoding on data encoded in the transmission apparatus (hereinafter referred to as “encoded data”) based on a check matrix. The present invention relates to a communication system including an apparatus. In particular, the receiving device executes a min-sum algorithm. The min-sun algorithm includes check node processing and variable node processing, but check node processing is more complicated than variable node processing. Therefore, it is desirable to simplify the min-sum algorithm process by simplifying the check node process. In order to cope with this, the communication system according to the present embodiment executes the following processing.

  The check node processing in the min-sum algorithm uses the minimum value of the absolute value other than the node whose external value ratio should be updated and the total product of the signs out of the prior value ratios output from the variable node processing. The value ratio is updated. Before starting the check node processing for the check matrix, the receiving device sets the minimum value of the absolute value of the prior value ratio from the prior value ratios to be checked for each of the external value ratios to be updated. Identify. Furthermore, the receiving device derives the total product of the codes of the prior value ratio. The receiving apparatus updates the external value ratio by using the sum of the minimum value and the sign for the external value ratio in which the specified minimum value is larger than the threshold value. That is, normal check node processing is executed. On the other hand, the receiving apparatus sets the external value ratio to zero with respect to the external value ratio whose specified minimum value is equal to or less than the threshold value. As a result, the update of the external value ratio using the minimum value and the total product of the codes is not executed.

  FIG. 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. The communication system 100 includes a transmission device 10 and a reception device 12. The transmission apparatus 10 includes an information data generation unit 20, an LDPC encoding unit 22, and a modulation unit 24. The receiving device 12 includes a demodulator 26, a decoder 28, and an information data output unit 30.

  The information data generation unit 20 acquires data to be transmitted and generates information data. The acquired data may be used as information data as it is. The information data generation unit 20 outputs the information data to the LDPC encoding unit 22. Information data is input to the LDPC encoding unit 22 from the information data generation unit 20. The LDPC encoding unit 22 adds a parity (hereinafter referred to as “LDPC parity”) based on a parity check matrix in LDPC to information data. Information data to which the LDPC parity is added corresponds to the encoded data described above. The LDPC encoding unit 22 outputs the encoded data to the modulation unit 24. FIG. 2 shows a parity check matrix used in the LDPC encoding unit 22. The check matrix Hmn is a matrix of m rows and n columns. Here, in order to clarify the explanation, it is assumed that the check matrix Hmn has 4 rows and 8 columns, but is not limited thereto. Returning to FIG.

  The modulation data is input to the modulation unit 24 from the LDPC encoding unit 22. The modulation unit 24 modulates the encoded data. As a modulation method, PSK (Phase Shift Keying), FSK (Frequency Shift Keying), or the like is used. The modulation unit 24 transmits the modulated encoded data as a modulation signal. The demodulator 26 receives the modulated signal from the modulator 24 via a communication path, for example, a wireless transmission path. The demodulator 26 demodulates the modulated signal. Since a known technique may be used for demodulation, the description is omitted here. The demodulator 26 outputs a demodulation result (hereinafter referred to as “demodulated data”) to the decoder 28.

The demodulated data from the demodulator 26 is input to the decoder 28. The decoding unit 28 repeatedly performs decoding processing using a parity check matrix in LDCP on the demodulated data. As the decoding process, for example, a min-sum algorithm is executed. The min-sum algorithm is executed in the following procedure.
1. Initialization: The prior value ratio is initialized and the maximum number of decoding iterations is set.
2. Check node processing: The external value ratio is updated in the row direction of the check matrix.
3. Variable node processing: The priori value ratio is updated in the column direction of the check matrix.
4). Calculate temporary estimated words.

  The decoding unit 28 outputs the decoding result (hereinafter referred to as “decoded data”) to the information data output unit 30. The information data output unit 30 receives the decoded data from the decoding unit 28. The information data output unit 30 generates information data based on the decoded data. The decoded data may be used as information data as it is. The information data output unit 30 includes an outer code decoding unit, and may decode an outer code such as a CRC, for example.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it can be realized by a program loaded in the memory, but here it is realized by their cooperation. Draw functional blocks. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 3 shows the configuration of the decoding unit 28. The decoding unit 28 includes a frame configuration unit 40, a control unit 42, a data storage unit 44, a min-sum processing unit 46, and a decoding result calculation unit 48. The min-sum processing unit 46 includes a check node processing unit 56 and a variable node processing unit 58, and the check node processing unit 56 includes a specifying unit 60 and an updating unit 64.

  Demodulated data from a demodulator 26 (not shown) is input to the frame configuration unit 40. The demodulated data can be said to be data that has been subjected to LDPC encoding via a communication channel. The frame configuration unit 40 detects a frame synchronization signal included in the demodulated data. The frame configuration unit 40 specifies a unit of a frame formed by the demodulated data based on the frame synchronization signal. For example, when the frame synchronization signal is arranged at the head portion of the frame and the frame period has a fixed length, the frame configuration unit 40 identifies the fixed-length period as a frame after detecting the frame synchronization signal. The unit of LDPC encoding may be a frame. The frame configuration unit 40 causes the data storage unit 44 to store the demodulated data collected in units of frames. The data storage unit 44 temporarily stores the demodulated signal in units of frames.

  The demodulated data from the data storage unit 44 is input to the min-sum processing unit 46. The min-sum processing unit 46 executes a min-sum algorithm on the demodulated data. In the min-sum algorithm, the check node processing unit 56 and the variable node processing unit 58 are executed alternately. FIG. 4 is a Tanner graph schematically showing the operation of the decoding unit 28. In the Tanner graph, b1 to b8 are called variable nodes, and c1 to c4 are called check nodes. Here, the number of variable nodes is n, and bn is the nth variable node. The number of check nodes is m, and cm is the mth check node. As message initialization, data y1 to y8 stored in the data storage unit 44 of FIG. 3 are input to variable nodes b1 to b8 at the beginning of iterative decoding. Returning to FIG.

  The check node processing unit 56 initializes the prior value ratio β at the beginning of iterative decoding. Here, the demodulated data stored in the data storage unit 44 is used as it is. Next, the check node processing unit 56 obtains a minimum value min | βmn ′ | of the absolute value of the prior value ratio. The check node processing unit 56 updates the external value ratio αmn from cm to bm with the variable node connected to the check node. The calculation of αmn is performed as follows for all pairs (m, n) satisfying the check matrix Hmn = 1.

αmn = a (Πsign (βmn ′)) · min | βmn ′ | (1)
Here, n ′ is A (m) \ n: A (m) is a variable node set connected to the check node m, and \ n indicates a difference set not including n. Further, sign represents a signature function, and min | βmn ′ | represents selection of the absolute minimum value. Here, a is a normalization constant. FIG. 5 shows an outline of the external value ratio update operation in the decoding unit 28. The external value ratio α11 is derived from β11 ′. That is, the check node processing unit 56 updates the external value ratio based on the prior value ratio. Returning to FIG. The minimum value min | βmn ′ | of the absolute value of the prior value ratio is derived for each iteration.

The variable node processing unit 58 updates the prior value ratio βmn from bn to cm between αmn and the check node connected to the variable node. The calculation of βmn is performed as follows for all pairs (m, n) satisfying the check matrix Hmn = 1.
βmn = Σαm′n + λn (2)
Here, λn is equal to the input data yn. The input data yn corresponds to demodulated data from the demodulator 26. M ′ is B (n) \ m: B (n) is a check node set connected to the variable node n, and \ m is a difference set not including m. FIG. 6 shows an outline of the prior value ratio update operation in the decoding unit 28. The prior value ratio β11 is derived from α1′1. That is, the variable node processing unit 58 updates the prior value ratio based on the external value ratio. Returning to FIG.

  The decoding result calculation unit 48 calculates a temporary estimated word after the processing in the check node processing unit 56 and the processing in the variable node processing unit 58 are repeated a predetermined number of times. Note that the decoding result calculation unit 48 may calculate a temporary estimated word even if the result of the parity check is correct even before being repeated a predetermined number of times. The decoding result calculation unit 48 outputs the temporary estimated word as a decoding result. The control unit 42 controls the operation timing of the min-sum processing unit 46.

  The expression (1) of the check node processing unit 56 repeats the calculation according to the number of 1s in each row of the check matrix, and the expression (2) of the variable node processing unit 58 repeats the calculation according to the number of 1s in each column. That is, in the check node process, as shown in the equation (1), the m-th row of the parity check matrix updates the nth (column index is n) external value ratio αmn whose element is 1, and the variable node process Updates the prior value ratio βmn as shown in equation (2). As for the check node process, simplifying the calculation corresponds to simply executing Expression (1), and simplification of Expression (1) is required to increase the processing speed of LDPC decoding. Below, simplification of Formula (1) is demonstrated.

  The specifying unit 60 executes initialization in the check node process. There are two types of initialization: (1) initialization before iterative decoding and (2) initialization of processing in units of rows. (1) As initialization before iterative decoding, the specifying unit 60 sets the data y1 to y8 stored in the data storage unit 44 of FIG. 3 to the prior value ratio βmn as described above.

  (2) The initialization of the processing in units of rows corresponds to the processing until the check node processing of each row in the LDPC coding check matrix is started. The identifying unit 60 identifies, for each external value ratio to be updated, the minimum value βmin of the absolute value of the prior value ratio among the prior value ratios βmn subject to the check node process. At that time, the column index Nmin including the minimum value βmin is also specified. The specifying unit 60 stores the minimum absolute value βmin of the prior value ratio and the column index Nmin in the data storage unit 44 of FIG. Furthermore, the specifying unit 60 derives a total product SIGNtmp of codes of the prior value ratio βmn included in the row to be processed. The specifying unit 60 also stores the total product SIGNtmp of the code in the data storage unit 44.

  Here, the case where the initialization is executed for the first line will be specifically described. At that time, as shown in FIG. 4, the check node is C1. Hereinafter, as an example, it is assumed that β11 = −3, β12 = 4, β13 = −1, and β14 = 2. The specifying unit 60 specifies “1” as the minimum absolute value βmin of the prior value ratio, and specifies “3” as the corresponding column index Nmin. Further, the specifying unit 60 derives “minus (+)” as the total product SIGNtmp of the code. In the third column, since the column index is 3, it is equal to Nmin. Therefore, the specifying unit 60 also specifies the minimum value βmin2 of the absolute value of the prior value ratio excluding β13. Note that βmin2 can be said to be the minimum value of βmn with respect to α13 and the like. Here, the minimum value βmin2 is “2”. The specifying unit 60 also stores the minimum value βmin2 in the data storage unit 44 of FIG. The minimum value βmin2 may be specified not by the specifying unit 60 but by the updating unit 64 described later.

  As a result, βmin, Nmin, SIGNtmp, and βmin2 are stored in the data storage unit 44. Furthermore, the data storage unit 44 stores the threshold value βsh in advance. For example, the threshold value βsh is set to “1”. The specifying unit 60 compares βmin and the threshold value βsh and stores the result in the data storage unit 44. The specifying unit 60 may compare βmin2 with the threshold value βsh and store the result in the data storage unit 44.

  The update unit 64 executes check node processing while referring to the contents stored in the data storage unit 44. That is, external value ratios α11, α12, α13, and α14 are derived. The updating unit 64 updates the external value ratio using the minimum value βmin or βmin2 with respect to the external value ratio at which the minimum value βmin or βmin2 specified by the specifying unit 60 becomes larger than the threshold value βsh. This corresponds to the calculation of the expression (1), which corresponds to the multiplication of the absolute minimum value, the total product of the codes, and the sign of the prior value ratio. On the other hand, the updating unit 64 sets a predetermined value as the external value ratio with respect to the external value ratio in which the minimum value βmin or βmin2 specified by the specifying unit 60 is equal to or less than the threshold value βsh. Here, the update unit 64 fixes the predetermined value to zero. This means that the external value ratio is set to “0” without performing the multiplication of the minimum absolute value shown in the equation (1), the total product of the codes, and the sign of the prior value ratio. It corresponds to.

  Based on the above example, the above processing will be specifically described. Since the column index of “α11” is “1”, which is different from Nmin = 3, according to the equation (1), α11 is set to βmin = 1, the code total product SIGNtmp “+” and the code “ The value is multiplied by “−”. However, since βmin is a value equal to or less than the threshold value βsh = 1, the updating unit 64 does not need to update α11 according to Expression (1), and sets α11 = 0. Next, the column index of “α12” is “2”, which is different from Nmin = 3. Therefore, similarly to “α11”, since βmin is a value equal to or less than the threshold value βsh = 1, the updating unit 64 does not need to update α12 according to Expression (1), and sets α12 = 0.

  Next, since the column index of “α13” is “3” and equal to Nmin, the absolute value βmin2 = 2 of the prior value ratio excluding β13 is compared with the threshold value βsh, not βmin. . Here, since βmin2 is not a value equal to or less than the threshold value βsh = 1, the update unit 64 multiplies the sign total product SIGNtmp “+” and the sign “−” of β13, “−”, and βmin2 Based on = 2, α13 = −2 is derived. Since the column index of “α14” is “4” and is different from Nmin = 3, “α14” is set to “0” similarly to “α11” and “α12”. Thus, the update unit 64 derives α11, α12, α13, and α14 as 0, 0, −2, and 0, respectively.

  As described above, the check node processing for the first row of the parity check matrix ends. Following this, a check node process on the second line may be executed, or a variable node process using the external value ratio α updated by the check node process on the first line may be executed. The check node process is executed m times for the row of the check matrix, and the variable node process is executed n times for the column value of the check matrix, thereby completing one iteration of decoding.

  Since the error correction capability decreases as the threshold value βsh is increased, the check node processing calculation is performed by setting an appropriate βsh value that is within the allowable range of the error correction capability. The amount can be reduced. Here, the appropriate βsh is determined by computer simulation or the like, for example. Further, when βsh = 0 is set, the error correction capability does not decrease.

  αmn is multiplied by a constant smaller than 1 (normalization constant a) to perform normalized min-sum decoding. In this case, the external value ratio having the minimum value βmin being equal to or less than the threshold value βsh does not need to be multiplied by the normalization constant a and is processed as αmn = 0. As a result, the effect of reducing the amount of computation of the check node process is greater with respect to normalized min-sum decoding.

  The operation of the communication system 100 configured as above will be described. FIG. 7 is a flowchart showing a decoding procedure by the decoding unit 28. The identifying unit 60 initializes the prior value ratio β (S10). If it is the head of the line (Y in S12), the specifying unit 60 executes an initialization process (S14), and returns to Step 12. As initialization, the minimum value βmin of the absolute value of βmn is detected, the column index Nmin of βmin is detected, the total product SIGNtmp of the code of the message βmn is detected, and the minimum value βmin and the threshold value βsh are compared. Note that for the case where the column index is Nmin, the absolute minimum value βmin2 of βmn whose column index is other than Nmin may also be detected, and βmin2 may be compared with the threshold value βsh.

  If it is not the head of the row (N in S12), if the column index is not Nmin (N in S16), the comparison result between the minimum value βmin and the threshold value βsh is read, and if βmin is equal to or less than βsh (Y in S18), The update unit 64 updates as αmn = 0 (S20). If βmin is larger than βsh (N in S18), the updating unit 64 calculates and updates αmn using βmin (S22). When the column index to be processed is Nmin (Y in S16), the minimum value βmin2 of the absolute value of βmn other than the column index to be processed is detected (S24). If this process is performed in step 14, step 24 may be omitted. If βmin2 is equal to or smaller than βsh (Y in S26), the update unit 64 updates αmn = 0 (S28). If βmin2 is larger than βsh (N in S26), the updating unit 64 calculates and updates αmn using βmin2 (S30).

  If one line is not completed (N in S32), the process returns to Step 12. If one line is finished (Y in S32) and the last line is not finished (N in S34), the process returns to Step 12. If the last line ends (Y in S34), the variable node processing unit 58 executes variable node processing (S36).

  FIG. 8 is a flowchart showing another decoding procedure by the decoding unit 28. This corresponds to a case where variable node processing is executed for each row processing. The identifying unit 60 initializes the prior value ratio β (S50). If it is the head of the line (Y in S52), the specifying unit 60 executes an initialization process (S54), and returns to Step 52. If it is not the beginning of the row (N in S52), if the column index is not Nmin (N in S56), the comparison result between the minimum value βmin and the threshold value βsh is read, and if βmin is equal to or less than βsh (Y in S58), The update unit 64 updates as αmn = 0 (S60). If βmin is larger than βsh (N in S58), the updating unit 64 calculates and updates αmn using βmin (S62).

  When the column index to be processed is Nmin (Y in S56), the minimum value βmin2 of the absolute value of βmn other than the column index to be processed is detected (S64). If this processing is performed in step 54, step 64 may be omitted. If βmin2 is equal to or less than βsh (Y in S66), the update unit 64 updates αmn = 0 (S68). If βmin2 is larger than βsh (N in S66), the updating unit 64 calculates and updates αmn using βmin2 (S70).

  If one line is not completed (N in S72), the process returns to step 52. If one line ends (Y in S72), the variable node processing unit 58 executes variable node processing (S74). If the last line has not ended (N in S76), the process returns to step 52. If the last line ends (Y in S76), the process ends.

  FIG. 9 is a flowchart showing an initialization procedure by the decoding unit 28. This corresponds to the processing in step 14 of FIG. 7 and step 54 of FIG. The specifying unit 60 initializes the total product SIGNtmp of βmn to “1 (+)” (S100), and initializes the minimum value βmin of the absolute value of βmn to a sufficiently large value “FFFFh” (S102). When βmn is negative (Y in S104), the identifying unit 60 multiplies the total product SIGNtmp by −1 (S106). If βmn is not negative (N in S104), step 106 is skipped. The identifying unit 60 obtains the absolute value | βmn | of βmn (S108).

  When the absolute value | βmn | is smaller than βmin (Y in S110), the specifying unit 60 holds the absolute value as the minimum value βmin (S112) and holds the column index as Nmin (S114). When the absolute value | βmn | is not smaller than βmin (N in S110), Step 112 and Step 114 are skipped. If the column index is not the last column (N in S116), the process returns to step 104. If the column index is the last column (Y in S116), the minimum value βmin and the threshold value βsh are compared, and a result indicating whether the minimum value βmin is equal to or less than the threshold value βsh is held (S118), and an initialization process is performed. Is terminated.

  According to the embodiment of the present invention, since the predetermined value is set as the external value ratio with respect to the external value ratio in which the absolute value of the prior value ratio is equal to or less than the threshold value, the minimum value is used. Updating the external value ratio can be omitted. In addition, since the update of the external value ratio using the minimum value is omitted, the amount of calculation in min-sum decoding can be reduced. Moreover, since the predetermined value is set to zero, deterioration of quality can be suppressed. In addition, since the minimum value is specified before the check node process is started, the specification can be performed collectively. In addition, since the identification can be executed collectively, the processing can be executed efficiently. Also, by starting the check node processing of each row, the total product of the sign of the prior value ratio included in the processing target row is derived, and the total product is used to derive each external value ratio. When deriving the external value ratio, the calculation of the total product of the codes can be omitted. Further, since the calculation of the total product of the codes is omitted when deriving each external value ratio, the amount of calculation can be reduced.

  Further, at the beginning of each line, the comparison result of the minimum value βmin of the message, the line index Nmin that is the position, the total product SIGNtmp, the minimum value βmin and the threshold value βsh is derived, and the minimum value βmin is the threshold. In the case of a message that is equal to or less than the value βsh, the message is set as αmn = 0 without performing the process of calculating the message αmn by multiplying the minimum absolute value, the sum of negative signs, and the sign of the message. Can be updated.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, since the communication system 100 is premised on a wireless communication system, the transmission device 10 and the reception device 12 are included in the wireless communication device. However, the present invention is not limited to this. For example, the communication system 100 may be based on a wired communication system. At that time, the transmission device 10 and the reception device 12 are included in the wired communication device. According to this modification, the present invention can be applied to various devices.

  DESCRIPTION OF SYMBOLS 10 Transmitter, 12 Receiver, 20 Information data generation part, 22 LDPC encoding part, 24 Modulation part, 26 Demodulation part, 28 Decoding part, 30 Information data output part, 40 Frame structure part, 42 Control part, 44 Data storage Unit, 46 min-sum processing unit, 48 decoding result calculation unit, 56 check node processing unit, 58 variable node processing unit, 60 specifying unit, 64 updating unit, 100 communication system.

Claims (5)

Check node processing for updating the external value ratio based on the prior value ratio by executing the min-sum algorithm on the data subjected to LDPC encoding, and the prior value ratio based on the external value ratio. A decoding unit that alternately executes variable node processing to be updated,
The decoding unit
For each of the external value ratios to be updated, a specific unit that specifies the minimum value of the absolute value of the prior value ratio among the prior value ratios to be subjected to the check node processing,
The external value ratio is updated using the minimum value for the external value ratio at which the minimum value specified in the specifying unit is larger than the threshold value, and the minimum value specified in the specifying unit is less than or equal to the threshold value. An update unit that sets a predetermined value to the external value ratio for a certain external value ratio;
A decoding apparatus comprising:   The decoding device according to claim 1, wherein the specifying unit specifies a minimum value for each of the external value ratios before starting the check node process.   The decoding apparatus according to claim 1, wherein the update unit sets a predetermined value to zero. Check node processing for updating the external value ratio based on the prior value ratio by executing the min-sum algorithm on the data subjected to LDPC encoding, and the prior value ratio based on the external value ratio. Comprising alternately executing variable node processing to be updated,
The performing step includes:
For each of the external value ratios to be updated, the step of identifying the minimum value of the absolute value of the prior value ratio among the prior value ratios subject to check node processing;
For external value ratios where the specified minimum value is greater than the threshold value, update the external value ratio using the minimum value, and for external value ratios where the specified minimum value is less than or equal to the threshold value, Setting a predetermined value to an external value ratio;
A decoding method comprising: Check node processing for updating the external value ratio based on the prior value ratio by executing the min-sum algorithm on the data subjected to LDPC encoding, and the prior value ratio based on the external value ratio. Comprising alternately executing variable node processing to be updated,
In the performing step,
For each of the external value ratios to be updated, the step of identifying the minimum value of the absolute value of the prior value ratio among the prior value ratios subject to check node processing;
For external value ratios where the specified minimum value is greater than the threshold value, update the external value ratio using the minimum value, and for external value ratios where the specified minimum value is less than or equal to the threshold value, A program for causing a computer to execute a step of setting a predetermined value to an external value ratio.

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