The present invention relates to a decoding apparatus and a decoding method for realizing the decoding of LDPC codes, in which, while the circuit scale is suppressed, the operating frequency can be suppressed within a sufficiently feasible range, and control of memory access can be performed easily, and to a program therefor. A check matrix of LDPC codes is formed by a combination of a (P×P) unit matrix, a matrix in which one to several 1s of the unit matrix are substituted with 0, a matrix in which they are cyclically shifted, a matrix, which is the sum of two or more of them, and a (P×P) 0-matrix. A check node calculator 313 simultaneously performs p check node calculations. A variable node calculator 319 simultaneously performs p variable node calculations.
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40. A non-transitory computer readable medium having a program for causing a computer to perform a decoding method for use with a decoding apparatus for decoding low density Parity check (“LDPC”) codes, said method comprising:
a first computation step, performed by the computer, of simultaneously performing p check node computations for decoding said LDPC codes;
a second computation step, performed by the computer, of simultaneously performing p variable node computations for decoding said LDPC codes; and
a message storage step, performed by the computer, for simultaneously reading and writing message data corresponding to p edges, the message data being obtained as a result of said p check node computations or said p variable node computations;
wherein the message storage step stores message data corresponding to the edges, the message data being read during the check node computation in such a manner that the sub-matrices of the check matrix are packed closer in a predetermined direction excluding the zero matrix.
0. 62. A method for decoding low density parity check (LDPC) codes, the LDPC codes being represented by a check matrix, which is composed of a plurality of sub-matrices, the sub-matrices including a (P×P) unit matrix, a quasi-unit matrix, a shift matrix, a sum matrix, and a (P×P) zero matrix, wherein the quasi-unit matrix is a unit matrix having one or more 1s being substituted with 0, the shift matrix is a unit matrix or a quasi-unit matrix which is cyclically shifted, the sum matrix is the sum of two or more of the unit matrix, the quasi-unit matrix, and the shift matrix, the method comprising using a decoding apparatus to perform:
decoding the LDPC codes by simultaneously performing p check node computations;
decoding the LDPC codes by simultaneously performing p variable node computations;
storing message data corresponding to p edges of the sub-matrices, the message data being obtained from the p check node computations or from the p variable node computations; and
reading the message data during the p check node computations in a manner that the sub-matrices of the check matrix are packed closer in a predetermined direction excluding the zero matrix.
0. 63. A non-transitory computer readable medium having a program for causing a computer apparatus to perform a method for decoding low density parity check (LDPC) codes, the LDPC codes being represented by a check matrix, which is composed of a plurality of sub-matrices, the sub-matrices including a (P×P) unit matrix, a quasi-unit matrix, a shift matrix, a sum matrix, and a (P×P) zero matrix, wherein the quasi-unit matrix is a unit matrix having one or more 1s being substituted with 0, the shift matrix is a unit matrix or a quasi-unit matrix which is cyclically shifted, the sum matrix is the sum of two or more of the unit matrix, the quasi-unit matrix, and the shift matrix, the method comprising:
decoding the LDPC codes by simultaneously performing p check node computations using the computer;
decoding the LDPC codes by simultaneously performing p variable node computations using the computer;
storing message data corresponding to p edges of the sub-matrices, the message data being obtained from the p check node computations or from the p variable node computations; and
reading the message data during the p check node computations in a manner that the sub-matrices of the check matrix are packed closer in a predetermined direction excluding the zero matrix.
0. 41. An apparatus for decoding low density parity check (LDPC) codes, the LDPC codes being represented by a check matrix, which is composed of a plurality of sub-matrices, the sub-matrices including a (P×P) unit matrix, a quasi-unit matrix, a shift matrix, a sum matrix, and a (P×P) zero matrix, wherein the quasi-unit matrix is a unit matrix having one or more 1s being substituted with 0, the shift matrix is a unit matrix or a quasi-unit matrix which is cyclically shifted, the sum matrix is the sum of two or more of the unit matrix, the quasi-unit matrix, and the shift matrix, the apparatus comprising:
a check node calculation section for simultaneously performing p check node computations for decoding the LDPC codes;
a variable node calculation section for simultaneously performing p variable node computations for decoding the LDPC codes; and
a message storage unit for storing message data corresponding to p edges of the sub-matrices, the message data being obtained from the p check node computations or from the p variable node computations;
wherein the message storage unit reads the message data during the p check node computations in a manner that the sub-matrices of the check matrix are packed closer in a predetermined direction excluding the zero matrix.
1. A decoding apparatus for decoding low density Parity check (“LDPC”) codes, the LDPC codes being represented by a check matrix, which is composed of a plurality of sub-matrices, the sub-matrices including a (P×P) unit matrix, a quasi-unit matrix, a shift matrix, a sum matrix, and a (P×P) zero matrix, wherein the quasi-unit matrix is a unit matrix having one or more 1s being substituted with 0, the shift matrix is a unit matrix or a quasi-unit matrix which is cyclically shifted, the sum matrix is the sum of two or more of said unit matrix, said quasi-unit matrix, and said shift matrix, the decoding apparatus comprising:
first computation means for simultaneously performing p check node computations for decoding said LDPC codes;
second computation means for simultaneously performing p variable node computations for decoding said LDPC codes; and
message storage means for simultaneously reading and writing message data corresponding to p edges, the message data being obtained as a result of said p check node computations or said p variable node computations;
wherein said message storage means stores message data corresponding to the edges, the message data being read during the check node computation in such a manner that the sub-matrices of the check matrix are packed closer in a predetermined direction excluding the zero matrix.
39. A decoding method for use with a decoding apparatus for decoding low density Parity check (“LDPC”) codes, the LDPC codes being represented by a check matrix, which is composed of a plurality of sub-matrices, the sub-matrices including a (P×P) unit matrix, a quasi-unit matrix, a shift matrix, a sum matrix, and a (P×P) zero matrix, wherein the quasi-unit matrix is a unit matrix having one or more 1s being substituted with 0, the shift matrix is a unit matrix or a quasi-unit matrix which is cyclically shifted, the sum matrix is the sum of two or more of said unit matrix, said quasi-unit matrix, and said shift matrix, the decoding method comprising:
a first computation step of simultaneously performing p check node computations for decoding said LDPC codes;
a second computation step of simultaneously performing p variable node computations for decoding said LDPC codes; and
a message storage step of simultaneously reading and writing message data corresponding to p edges, the message data being obtained as a result of said p check node computations or said p variable node computations;
wherein the message storage step stores message data corresponding to the edges, the message data being read during the check node computation in such a manner that the sub-matrices of the check matrix are packed closer in a predetermined direction excluding the zero matrix.
2. The decoding apparatus according to
said first computation means has p check node calculators for performing check node computations; and
said second computation means has p variable node calculators for performing variable node computations.
3. The decoding apparatus according to
the sub-matrices of the check matrix are packed closer in the row direction.
4. The decoding apparatus according to
the sub-matrices of the check matrix are packed closer in the column direction.
5. The decoding apparatus according to
said message storage means stores, at the same address, messages corresponding to p edges belonging to a unit matrix whose weight is 1, a quasi-unit matrix, or a shift matrix, when the sub-matrices, whose weight is 2 or more from among the sub-matrices representing said check matrix, are represented in the form of the sum of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix.
6. The decoding apparatus according to
said message storage means comprises number-of-rows/p FIFOs and number-of-columns/p FIFOs; and
said number-of-rows/p FIFOs and said number-of-columns/p FIFOs each have a number of words corresponding to the weight of the row and the weight of the column of said check matrix, respectively.
7. The decoding apparatus according to
said message storage means comprises a Random Access Memory (“RAM”); and
said RAM stores said message data in the read-out sequence in such a manner as to be packed closer and reads said message data in the storage position sequence.
8. The decoding apparatus according to
received information storage means for storing received information of LDPC codes and for simultaneously reading p pieces of said received information.
9. The decoding apparatus according to
said received information storage means stores said received information in such a manner that the received information can be read in the sequence necessary for said variable node computation.
10. The decoding apparatus according to
rearranging means for rearranging messages obtained as a result of said p check node computations or said p variable node computations.
11. The decoding apparatus according to
said rearranging means comprises a barrel shifter.
12. The decoding apparatus according to
said first computation means and said second computation means determine messages corresponding to p edges.
13. The decoding apparatus according to
said first computation means performs some of said p check node computations and said p variable node computations; and
said second computation means performs some of the others of said p variable node computations.
14. The decoding apparatus according to
said first computation means comprises p calculators for performing some of said p check node computations and said p variable node computations; and
said second computation means comprises p calculators for performing some of the others of said p variable node computations.
15. The decoding apparatus according to
first decoding in-progress result storage means for simultaneously reading and writing first decoding in-progress results corresponding to p edges, which are obtained by said first computation means by performing some of said p check node computations and said p variable node computations.
16. The decoding apparatus according to
said first decoding in-progress result storage means stores said first decoding in-progress results corresponding to the edge, which are read when some of the others of said p variable node computations are performed, in such a manner that 1s of the check matrix are packed closer in the row direction.
17. The decoding apparatus according to
said first decoding in-progress result storage means are two single-port Random Access Memories (“RAMs”).
18. The decoding apparatus according to
said two single-port RAMs alternately store said first decoding in-progress results in units of said first decoding in-progress results corresponding to edges of p rows of said check matrix.
19. The decoding apparatus according to
said two single-port RAMs each read said first decoding in-progress results stored at the same address, where said decoding in-progress results were previously stored.
20. The decoding apparatus according to
said first decoding in-progress result storage means stores, at the same address, said first decoding in-progress results corresponding to p edges belonging to a unit matrix whose weight is 1, a quasi-unit matrix, or a shift matrix when the sub-matrices, whose weight is 2 or more from among the sub-matrices representing said check matrix, are represented in the form of the sum of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix.
21. The decoding apparatus according to
second decoding in-progress result storage means for simultaneously reading and writing said second decoding in-progress results corresponding to p edges, which are obtained by said second computation means by performing some of the others of said p variable node computations.
22. The decoding apparatus according to
received information storage means for storing received information of LDPC codes and simultaneously reading said p pieces of received information.
23. The decoding apparatus according to
said received information storage means stores said received information in such a manner that said received information can be read in the sequence necessary for some of the others of said p variable node computations.
24. The decoding apparatus according to
rearranging means for rearranging first decoding in-progress results obtained by said first computation means by performing some of said p check node computations and said p variable node computations, or second decoding in-progress results obtained by said second computation means by performing some of the others of said p variable node computations.
25. The decoding apparatus according to
said rearranging means comprises a barrel shifter.
26. The decoding apparatus according to
said first computation means performs some of said p check node computations; and
said second computation means performs some of the others of said p check node computations, and said p variable node computations.
27. The decoding apparatus according to
said first computation means comprises p calculators for performing some of said p check node computations; and
said second computation means comprises p calculators for performing some of the others of said p check node computations, and said p variable node computations.
28. The decoding apparatus according to
first decoding in-progress result storage means for simultaneously reading and writing first decoding in-progress results corresponding to p edges, which are obtained by said first computation means by performing some of said p check node computations.
29. The decoding apparatus according to
second decoding in-progress result storage means for simultaneously reading and writing second decoding in-progress results corresponding to p edges, which are obtained by said second computation means by performing some of the others of said p check node computations, and said p variable node computations.
30. The decoding apparatus according to
said second decoding in-progress result storage means stores said second decoding in-progress results corresponding to edges, which are read when some of the others of said p check node computations; and
said p variable node computations are performed, in such a manner that 1s of the check matrix are packed closer in the column direction.
31. The decoding apparatus according to
said second decoding in-progress result storage means are two single-port Random Access Memories (“RAMs”).
32. The decoding apparatus according to
said single-port RAMs alternately store said second decoding in-progress results in units of said second decoding in-progress results corresponding to p edges of said check matrix.
33. The decoding apparatus according to
said two single-port RAMs each read said second decoding in-progress results stored at the same address, where said decoding in-progress results were previously stored.
34. The decoding apparatus according to
said second decoding in-progress result storage means stores, at the same address, said second decoding in-progress results corresponding to p edges belonging to a unit matrix whose weight is 1, a quasi-unit matrix, or a shift matrix when the sub-matrices whose weight is 2 or more from among the sub-matrices representing said check matrix are represented in the form of the sum of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix.
35. The decoding apparatus according to
received information storage means for storing received information of LDPC codes and for simultaneously reading said p pieces of received information.
36. The decoding apparatus according to
said received information storage means stores said received information in such a manner that said received information can be read in the sequence necessary for some of the others of said p check node computations, and said p variable node computations.
37. The decoding apparatus according to
rearranging means for rearranging first decoding in-progress results obtained by said first computation means by performing some of said p check node computations, or second decoding in-progress results obtained by said second computation means by performing some of the others of said p check node computations, and said p variable node computations.
38. The decoding apparatus according to
said rearranging means comprises a barrel shifter.
0. 42. The apparatus of claim 41, wherein the check node calculation section includes a plurality of check node calculators for performing the p check node computations, and the variable node calculation section includes a plurality of variable node calculators for performing the p variable node computations.
0. 43. The apparatus of claim 41, wherein the sub-matrices of the check matrix are packed closer in a row direction.
0. 44. The apparatus of claim 41, wherein the sub-matrices of the check matrix are packed closer in a column direction.
0. 45. The apparatus of claim 41, wherein, when a sub-matrix has a weight of 2 or more, which is formed by summing two or more of the unit matrix, the quasi-unit matrix, and the shift matrix, the storage unit stores the message data corresponding to the p edges of the unit matrix, the quasi-unit matrix, or the shift matrix at the same address.
0. 46. The apparatus of claim 41, wherein the storage unit comprises a random access memory (RAM), wherein the RAM stores the message data in a read-out sequence in such a manner as to be packed closer, and reads the message data in a storage position sequence.
0. 47. The apparatus of claim 41, further comprising a received information storage unit for storing received information of the LDPC codes and for simultaneously reading pieces of the received information.
0. 48. The apparatus of claim 47, wherein the received information storage unit stores the received information in a such manner that the received information is readable in a sequence necessary for the p variable node computations.
0. 49. The apparatus of claim 41, further comprising a rearranging unit for rearranging the message data obtained from the p check node computations or the p variable node computations.
0. 50. The apparatus of claim 49, wherein the rearranging unit comprises a barrel shifter.
0. 51. The apparatus of claim 41, wherein the check node calculation section and the variable node calculation section determine the message data corresponding to the edges.
0. 52. The apparatus of claim 41, wherein the check node calculation section performs the p check node computations and some of the p variable node computations, and the variable node calculation section performs some of the other p variable node computations.
0. 53. The apparatus of claim 52, wherein the check node calculation section comprises a plurality of first calculators for performing the p check node computations and some of the p variable node computations, and the variable node calculation section comprises a plurality of second calculators for performing some of the other p variable node computations.
0. 54. The apparatus of claim 52, further comprising a first decoding in-progress result storage unit for simultaneously reading and writing first decoding in-progress results corresponding to the edges obtained from the check node calculation section by performing the p check node computations and some of the p variable node computations.
0. 55. The apparatus of claim 52, further comprising a second decoding in-progress result storage unit for simultaneously reading and writing second decoding in-progress results corresponding to the edges obtained from the variable node calculation section by performing some of the other p variable node computations.
0. 56. The apparatus of claim 52, further comprising a rearranging unit for rearranging first decoding in-progress results obtained from the check node calculation section by performing the p check node computations and some of the p variable node computations, or rearranging second decoding in-progress results obtained from the variable node calculation section by performing some of the other p variable node computations.
0. 57. The apparatus of claim 41, wherein the check node calculation section performs some of the p check node computations, and the variable node calculation section performs the p variable node computations and some of the other p check node computations.
0. 58. The apparatus of claim 57, wherein the check node calculation section comprises a plurality of first calculators for performing some of the p check node computations, and the variable node calculation section comprises a plurality of second calculators for performing the p variable node computations and some of the other p check node computations.
0. 59. The apparatus of claim 57, further comprising a first decoding in-progress result storage unit for simultaneously reading and writing first decoding in-progress results corresponding to the edges obtained from the check node calculation section by performing some of the p check node computations.
0. 60. The apparatus of claim 57, further comprising a second decoding in-progress result storage unit for simultaneously reading and writing second decoding in-progress results corresponding to the edges obtained from the variable node calculation section by performing the p variable node computations and some of the other p check node computations.
0. 61. The apparatus of claim 57, further comprising a rearranging unit for rearranging first decoding in-progress results obtained from check node calculation section by performing some of the p check node computations, or rearranging second decoding in-progress results obtained from the variable node calculation section by performing the p variable node computations and some of the other p check node computations.
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The present invention relates to a decoding apparatus, a decoding method, and a program. More particularly, the present invention relates to a decoding apparatus and a decoding method for decoding codes on which coding is performed using low density parity check codes (LDPC codes), and to a program therefor.
In recent years, research in, for example, communication fields such as mobile communication and deep space communication, and broadcasting fields such as terrestrial-wave or satellite digital broadcasts has progressed remarkably. Along with this situation, research on coding theories for making error correction coding and decoding efficient has been actively carried out.
As a theoretical limit of code performance, the Shannon limit implied by the so-called Shannon's (C. E. Shannon) channel coding theorem is known. Research on coding theories has been carried out for the purpose of developing codes exhibiting performance near this Shannon limit. In recent years, as a coding method exhibiting performance near the Shannon limit, for example, techniques for what is commonly called “turbo coding”, such as parallel concatenated convolutional codes (PCCC) and serially concatenated convolutional codes (SCCC), have been developed. Furthermore, whereas this turbo coding has been developed, low density parity check codes (hereinafter referred to as “LDPC codes”), which is a coding method that has been known for a long time, have attracted attention.
LDPC codes were proposed first in R. G. Gallager, “Low Density Parity Check Codes”, Cambridge, Mass.: M. I. T. Press, 1963. Thereafter, LDPC codes reattracted attention in D. J. C. MacKay, “Good error correcting codes based on very sparse matrices”, submitted to IEEE Trans. Inf. Theory, IT-45, pp. 399-431, 1999, and M. G. Luby, M. Mitzenmacher, M. A. Shokrollahi and D. A. Spielman, “Analysis of low density codes and improved designs using irregular graphs”, in Proceedings of ACM Symposium on Theory of Computing, pp. 249-258, 1998.
It is beginning to be known from this recent research that, for the LDPC codes, as the code length increases, performance close to the Shannon limit can be obtained, similarly to turbo coding. Furthermore, since the LDPC codes have the property that the minimum length is proportional to the code length, they have the advantages that the block error probability characteristics are good, and a so-called error floor phenomenon, which is observed in decoding characteristics of turbo coding, hardly occurs.
Such LDPC codes will now be described in detail below. The LDPC codes are linear codes and do not always need to be two-dimensional, but here, a description is given assuming that the LDPC codes are two-dimensional.
The greatest features of the LDPC codes are that the parity check matrix that defines the LDPC codes are sparse. Here, a sparse matrix is formed in such a manner that the number of 1s in the elements of the matrix is very small. If the sparse check matrix is denoted as H, examples thereof include a check matrix in which, as shown in
As described above, the LDPC codes defined by the check matrix H in which the Hamming weight of each row and each column is fixed are called “regular LDPC codes”. On the other hand, the LDPC codes defined by a check matrix H in which the Hamming weight of each row and each column is not fixed are called “irregular LDPC codes”.
Coding by such LDPC codes is realized by generating a generation matrix G on the basis of the check matrix H and by generating a code word by multiplying this generation matrix G by a two-dimensional information message. More specifically, a coding apparatus for performing coding by LDPC codes computes a generation matrix G in which the equation GHT=0 holds with a transpose matrix HT of the check matrix H. Here, when the generation matrix G is a k×n matrix, the coding apparatus multiplies the generation matrix G by a k-bit information message (vector u), and generates an n-bit codeword c (=uG). The codeword generated by this coding apparatus is transmitted with the code bit whose value is “0” being mapped to “+1” and the code bit whose value is “1” being mapped to “−1”, and is received at the reception side via a predetermined communication channel.
On the other hand, decoding of the LDPC codes can be performed by a message passing algorithm by belief propagation on a so-called Tanner graph, which is formed of a variable node (also called a message node) and a check node; this message passing algorithm was proposed by Gallager and is known as “probabilistic decoding”. Hereafter, the variable nodes and the check nodes are also referred to simply as nodes where appropriate.
However, in probabilistic decoding, since messages exchanged between nodes are real-number values, in order to find an analytical solution, it is necessary to trace the probability distribution of the message that takes a continuous value. This necessitates analysis involving a large degree of difficulty. Accordingly, Gallager has proposed an algorithm A or an algorithm B as an algorithm for decoding LDPC codes.
In general, decoding of the LDPC codes is performed in accordance with the procedure shown in
In the decoding of the LDPC codes, initially, as shown in
Here, dv and dc in equations (1) and (2) are parameters respectively that indicate the number of 1s in the vertical direction (in the row direction) and in the horizontal direction (in the column direction) of the check matrix H and that can be selected as desired. For example, in the case of a (3, 6) code, dv=3 and dc=6.
In the computation of each of equations (1) and (2), since the message input from an edge from which a message is to be output is not used as a parameter for a sum or product computation, the range of the sum or product computation is from 1 to dv−1 or 1 to dc−1. In practice, the computation shown in equation (2) is performed by creating in advance a table of a function R(v1, v2), shown in equation (3), that is defined by one output with respect to two inputs v1 and v2 and by using this table continuously (recursively), as shown in equation (4).
x=2 tan h−1{ tan h(v1/2)tan h(v2/2)}=R(v1, v2) (3)
uj=R(v1, R(v2, R(v3, . . . R(vd
In step S12, furthermore, the variable k is incremented by 1, and the process then proceeds to step S13. In step S13, it is determined whether or not the variable k is greater than or equal to a predetermined number N of iterative decodings. When it is determined in step S13 that the variable k is not greater than or equal to N, the process returns to step S12, and the identical processing is performed again.
When it is determined in step S13 that the variable k is greater than or equal to N, the process proceeds to step S14, where the message v serving as the decoded result, which is finally output as a result of performing the computation shown in equation (5), is determined and output. This completes the decoding process of the LDPC codes.
Here, unlike the computation of equation (1), the computation of equation (5) is performed using the input messages from all the edges connected to the variable nodes.
In such LDPC code decoding, for example, in the case of (3, 6) code, as shown in
Furthermore, in recent years, research on an implementation method of the decoding of LDPC codes has been carried out. Before describing the implementation method, the decoding of LDPC codes is described in a schematic form.
In the sum product algorithm, which is a method of decoding LDPC codes, the computation of the variable node and the computation of the check node are repeatedly performed.
In the variable node, as shown in
Before describing the check node computation, equation (2) is rewritten as shown in equation (6) by using the equation a×b=exp{ln(|a|)+ln(|b|)}× sign (a)×sign (b), where sign (x) is 1 when x≧0 and is −1 when x<0.
Furthermore, in the case of x≧0, when the definition φ(x)=ln(tan h(x/2)) is made, since φ−1(x)=2 tan h−1(e−x), equation (6) can be written as equation (7).
In the check node, as shown in
The function φ(x) can also be expressed as φ(x)=ln((ex+1)/(ex−1)) and when x>0, φ(x)=φ−1(x). When the functions φ(x) and φ−1(x) are implemented as hardware, there are cases in which they are implemented using an LUT (Look-Up Table), and both of them are the same LUT.
When the sum product algorithm is implemented as hardware, it is necessary to repeatedly perform the variable node computation expressed by equation (1) and the check node computation expressed by equation (7) with an appropriate circuit scale and at an appropriate operating frequency.
As an example of the implementation of the decoding apparatus, a description is given first of an implementation method in a case where decoding is performed by simply performing the computation of each node one-by-one in sequence (full serial decoding).
It is assumed here that, for example, codes (a coding rate of ⅔, and a code length of 90) represented by a 30 (rows)×90 (columns) check matrix of
In the decoding apparatus of
More specifically, the decoding apparatus of
In the decoding apparatus of
The memory 100 for edges stores messages D100 supplied from the variable node calculator 103 of the decoding apparatus (not shown) at a previous stage in the order in which the check node calculator 101 at a subsequent stage reads them. Then, at the phase of the check node calculation, the memory 100 for edges supplies, to the check node calculator 101, the messages D100 as a message output D101 in the order in which they are stored.
Based on the control signal D106 supplied from the control section 105, the check node calculator 101 performs a computation in accordance with equation (7) by using the message D101 supplied from the memory 100 for edges, and supplies a message D102 determined by that computation to the memory 102 for edges at a subsequent stage.
The memory 102 for edges stores the messages D102 supplied from the check node calculator 101 at a previous stage in the order in which the variable node calculator 103 at a subsequent stage reads them. Then, at the phase of the variable node calculation, the memory 102 for edges supplies the message D102 as a message D103 to the variable node calculator 103 in the order in which they are stored.
Furthermore, a control signal D107 is supplied to the variable node calculator 103 from the control section 105, and received data D104 is supplied thereto from the memory 104 for reception. Based on a control signal D107, the variable node calculator 103 performs a computation in accordance with equation (1) by using the message D103 supplied from the memory 100 for edges and the received data D104 supplied from the memory 100 for reception, and supplies a message D105 obtained as a result of the computation to the memory 100 for edges, of the decoding apparatus (not shown) at a subsequent stage.
In the memory 104 for reception, received data (LDPC codes) that are converted into LDPC codes are stored. The control section 105 supplies a control signal D106 for controlling a variable node computation and a control signal D107 for controlling a check node computation to the check node calculator 101 and the variable node calculator 103, respectively. The control section 105 supplies the control signal D106 to the check node calculator 101 when the messages of all the edges are stored in the memory 100 for edges, and the control section 105 supplies the control signal D107 to the variable node calculator 103 when the messages of all the edges are stored in the memory 102 for edges.
In
Based on, for example, a 1-bit control signal D106 supplied from the control section 105, the check node calculator 101 of
More specifically, in the check node calculator 101, 6-bit messages D101 (messages vi) from the variable node, corresponding to each column of the check matrix, are read one-by-one, the absolute value D122 (|vi|), which is the lower-order bits thereof, is supplied to the LUT 121, and a sign bit D121, which is the highest bit thereof, is supplied to an EXOR circuit 129 and an FIFO (First In First Out) memory 133, respectively. Furthermore, the control signal D106 is supplied to the check node calculator 101 from the control section 105, and the control signal D106 is supplied to a selector 124 and a selector 131.
The LUT 121 reads a 5-bit computation result D123 (φ(|vi|)) such that the computation of φ(|vi|) in equation (7) is performed on the absolute value D122 (|vi|), and supplies it to an adder 122 and an FIFO memory 127.
The adder 122 integrates the computation results D123 by adding together the computation results D123 (φ(|vi|)) and a 9-bit value D124 stored in a register 123, and stores the 9-bit integration value obtained thereby in the register 123 again. When the computation results for the absolute values D122 (|vi|) of the messages D101 from all the edges over one row of the check matrix are integrated, the register 123 is reset.
When the messages D101 over one row of the check matrix are read one-by-one and the integrated value such that the computation results D123 for one row is stored in the register 123, the control signal D106 supplied from the control section 105 changes from 0 to 1. For example, when the row weight is “9”, the control signal D106 is “0” at the first to eighth clocks, and is “1” at the ninth clock.
When the control signal D106 is “1”, the selector 124 selects the value stored in the register 123, that is, the 9-bit value D124 (Σφ(|vi|) from i=1 to i=dc) such that φ(|vi|) determined from the messages D101 (messages vi) from all the edges over one row of the check matrix, and outputs the value as a value D125 to a register 125, whereby it is stored. The register 125 supplies the stored value D125 as a 9-bit value D126 to the selector 124 and the adder 126. When the control signal D106 is “0”, the selector 124 selects the value D126 supplied from the register 125, and outputs the value to the selector 124, whereby it is stored again. That is, until φ(|vi|) determined from the messages D101 (messages vi) from all the edges over one row of the check matrix are integrated, the register 125 supplies the previously integrated φ(|vi|) to the selector 124 and the adder 126.
On the other hand, the FIFO memory 127 delays the computation results D123 (φ(|(|vi|)) output by the LUT 121 until a new value D126 (Σφ(|vi|) from i=1 to i=dc) is output from the register 125, and supplies them as a 5-bit value D127 to a subtractor 126. The subtractor 126 subtracts, from the value D126 supplied from the register 125, the value D127 supplied from the FIFO memory 127, and supplies the subtracted result as a 5-bit subtracted value D128 to the LUT 128. That is, the subtractor 126 subtracts φ(|vi|) determined from the messages D101 (messages vi) from the edge to be determined, from the integrated value of φ(|vi|) determined from the messages D101 (messages vi) from all the edges over one row of the check matrix, and supplies the subtracted value (Σφ(|vi|) from i=1 to i=dc−1) as a subtracted value D128 to the LUT 128.
The LUT 128 outputs the 5-bit computation results D129 (φ−1(Σφ(|vi|))) such that the computation of φ−1(Σφ(|vi|)) in equation (7) is performed on the subtracted value D128 (Σφ(|vi|) from i=1 to i=dc−1).
In parallel with the above processing, the EXOR circuit 129 performs a multiplication of sign bits by computing the exclusive OR of a 1-bit value D131 stored in a register 130 and the sign bit D121, and stores the 1-bit multiplication result D130 in the register 130 again. When the sign bits D121 of the messages D101 from all the edges over one row of the check matrix are multiplied, the register 130 is reset.
When the multiplied results D130 (Πsign (vi) from i=1 to dc) such that the sign bits D121 of the messages D101 from all the edges over one row of the check matrix are multiplied are stored, the control signal D106 supplied from the control section 105 changes from “0” to “1”.
When the control signal D106 is “1”, the selector 131 selects the value stored in the register 130, that is, the value D131 (Πsign (vi) from i=1 to i=dc) such that the sign bits D121 of the messages D101 from all the edges over one row of the check matrix are multiplied, and outputs the value as a 1-bit value D133 to a register 132, whereby it is stored. The register 132 supplies the stored value D132 as a 1-bit value D132 to the selector 131 and the EXOR circuit 134. When the control signal D106 is “0”, the selector 131 selects a value D133 supplied from the register 132, and outputs the value to the register 132, whereby it is stored again. That is, until the sign bits D121 of the messages D101 (messages vi) from all the edges over one row of the check matrix are multiplied, the register 132 supplies the value stored at the previous time to the selector 131 and the EXOR circuit 134.
On the other hand, the FIFO memory 133 delays the sign bits D121 until a new value D133 (Πsign (vi) from i=1 to i=dc) is supplied from the register 132 to the EXOR circuit 134, and supplies the result as a 1-bit value D134 to the EXOR circuit 134. The EXOR circuit 134 divides the value D133 by the value D134 by computing the exclusive OR of the value D133 supplied from the register 132 and the value D134 supplied from the FIFO memory 133, and outputs a 1-bit divided result as a divided value D135. That is, the EXOR circuit 134 divides the multiplication value of the sign bits D121 (sign (|vi|)) of the messages D101 from all the edges over one row of the check matrix by the sign bits D121 (sign (|vi|)) of the messages D101 from the edge to be determined, and outputs the divided value (Πsign (|vi|) from i=1 to i=dc−1) as a divided value D135.
In the check node calculator 101, a total of six bits such that the 5-bit computation result D129 output from the LUT 128 is the lower-order 5 bits and the 1-bit divided value D135 output from the EXOR circuit 134 is the highest-order bit is output as a message D102 (message uj).
As described above, in the check node calculator 101, the computation of equation (7) is performed, and a message uj is determined.
Since the maximum of the row weight of the check matrix of
In
Based on, for example, a 1-bit control signal D107 supplied from the control section 105, the variable node calculator 103 of
More specifically, in the variable node calculator 103, 6-bit messages D103 (messages uj) from the check node corresponding to each row of the check matrix is read one-by-one, and the messages D103 are supplied to the adder 151 and the FIFO memory 155. Furthermore, in the variable node calculator 103, 6-bit received data D104 are read one-by-one from the memory 104 for reception, and is supplied to the adder 156. Furthermore, a control signal D107 is supplied to the variable node calculator 103 from the control section 105, and the control signal D107 is supplied to a selector 153.
The adder 151 integrates the messages D103 by adding together the messages D103 (messages uj) and a 9-bit value D151 stored in the register 152, and stores the 9-bit integrated value in the register 152 again. When the message D103 from all the edges over one row of the check matrix are integrated, the register 152 is reset.
When the messages D103 from all the edges over one row of the check matrix are read one-by-one, and the value such that the messages D103 for one column are integrated is stored in the register 152, the control signal D107 supplied from the control section 105 changes from “0” to “1”. For example, when the column weight is “5”, the control signal D107 is “0” at the first clock up to the fourth clock and is “0” at the fifth clock.
When the control signal D107 is “1”, the selector 153 selects the value stored in the register 152, that is, a 9-bit value D151 (Σuj from j=1 to dv) such that the messages D103 (messages uj) from all the edges over one row of the check matrix are integrated, and outputs the value to the register 154, whereby it is stored. The register 154 supplies the stored value D151 as a 9-bit value D152 to the selector 153 and the adder-subtractor 156. When the control signal D107 is “0”, the selector 153 selects a value D152 supplied from the register 154, and outputs the value to a register 154, whereby it is stored again. That is, until the messages D103 (messages uj) from all the edges over one row of the check matrix are integrated, the register 154 supplies the previously integrated value to the selector 153 and the adder-subtractor 156.
On the other hand, the FIFO memory 155 delays the message D103 from the check node until a new value D152 (Σuj from j=1 to dv) is output from the register 154, and supplies it as a 6-bit value D153 to the adder-subtractor 156. The adder-subtractor 156 subtracts the value D153 supplied from the FIFO memory 155, from the value D152 supplied from the register 154. That is, the adder-subtractor 156 subtracts the message uj from the edge to be determined, from the integrated value of the messages D103 (messages uj) from all the edges over one row of the check matrix, and determines the subtracted value (Σuj from j=1 to dv−1). Furthermore, the adder-subtractor 156 adds the received data D104 supplied from the memory 104 for reception to the subtracted value (Σuj from j=1 to dv1), and outputs the 6-bit value obtained thereby as a message D105 (message vi).
As described above, in the variable node calculator 103, the computation of equation (1) is performed, and the message vi is determined.
Since the maximum of the column weight of the check matrix of
In the decoding apparatus of
Although not shown, in the decoding apparatus of
When LDPC codes are decoded by repeatedly using the decoding apparatus of
Therefore, for performing one decoding using the check matrix having 269 edges of
Furthermore, in a case where, for example, 50 decoding apparatuses of
Next, a description is given of the implementation method of the decoding apparatus in a case where decoding is performed by simultaneously performing computations of all the nodes (full parallel decoding).
This implementation method is described in, for example, C. Howland and A. Blanksby, “Parallel Decoding Architectures for Low Density Parity Check Codes”, Symposium on Circuits and Systems, 2001.
The decoding apparatus of
In the decoding apparatus of
The memory 206 for edges simultaneously stores all the messages D2061 to D20690 from the variable node calculators 2041 to 20490 at a previous stage, reads the messages D2061 to D20690 as messages D2071 to D20790 at the next clock (the timing of the next clock), and supplies them as messages D200 (D2001 to D20090) to the edge interchange device 200 at the subsequent stage. The edge interchange device 200 rearranges (interchanges) the order of the messages D2001 to D20090 supplied from the memory 206 for edges in accordance with the check matrix of
The check node calculators 2011 to 20130 perform a computation in accordance with equation (7) by using the messages D2011 to D20130 supplied from the edge interchange device 200, and supplies the messages D2021 to D20230 obtained as a result of the computation to the memory 202 for edges.
The memory 202 for edges simultaneously stores all the messages D2021 to D20230 supplied from the check node calculators 2011 to 20130 at the previous stage, and at the next time, supplies all the messages D2021 to D20230, as messages D2031 to D20330, to the edge interchange device 203 at the subsequent stage.
The edge interchange device 203 rearranges the order of the messages D2031 to D20330 supplied from the memory 202 for edges in accordance with the check matrix of
The variable node calculators 2041 to 20490 perform a computation in accordance with equation (1) by using the messages D2041 to D20490 supplied from the edge interchange device 203 and the received data D2051 to D20590 supplied from the memory 205 for reception, and supplies messages D2061 to D20690 obtained as a result of the computation to the memory 206 for edges at the subsequent stage.
In the check node calculator 201m of
More specifically, in the check node calculator 201m of
The LUTs 2211 to 2219 read 5-bit computation results D2241 to D2249 (φ(|vi|)) such that the computation of φ(|vi|) in equation (7) is performed, respectively, on the absolute values D2221 to D2229 (|vi|), respectively, and supplies them to the respective subtractors 2231 to 2239. The LUTs 2211 to 2219 supply the computation results D2241 to D2249 (φ(|vi|)) to an adder 222.
The adder 222 computes the total sum of the values of the computation results D2241 to D2249 (φ(|vi|)) (the total sum of the computation results for one row), and supplies the 9-bit computation results D225 (Σφ(|vi|) from i=1 to 9) to the subtractors 2231 to 2239. The subtractors 2231 to 2239 subtract the computation results D2241 to D2249 (φ(|vi|)) from the computation results D225, respectively, and supply the 5-bit subtracted value D2271 to D2279 to the LUTs 2241 to 2249. That is, the subtractors 2231 to 2239 subtract φ(|vi|) determined from the message vi from the edge to be determined, from the integrated value of φ(|vi|) determined from the message vi from all the edges, and supply the subtracted values D2271 to D2279 (Σφ(|vi|) from i=1 to 8) to the LUTs 2241 to 2249, respectively. The LUTs 2241 to 2249 read the 5-bit computation results D2281 to D2289 such that the computation of φ−1 (Σφ(|vi|)) in equation (7) is performed on the subtracted values D2271 to D2279, and outputs them.
On the other hand, the EXOR circuit 225 performs a multiplication of the sign bits D2231 to D2239 by computing the exclusive OR of all the sign bits D2231 to D2239, and supplies a 1-bit multiplication value D226 (multiplication value of the sign bits for one row (Πsign (vi) from i=1 to 9)) to the respective EXOR circuit 2261 to 2269. By computing the exclusive OR of the multiplication value D226 and the sign bits D2231 to D2239, respectively, the EXOR circuits 2261 to 2269 determine 1-bit divided values D2291 to D2299 (Πsign (vi) from i=1 to 8) such that the multiplication value D226 is divided by the sign bits D2231 to D2239, respectively, and output them.
In the check node calculator 201m, a total of six bits such that the 5-bit computation results D2281 to D2289 output from the LUTs 2241 to 2249 are each made to be the five lower-order bits and the divided values D2291 to D2299 output from the EXOR circuits 2261 to 2269 are each made to be the highest-order bit is output as messages D2301 to D2309 obtained as a result of the check node computation.
In the manner described above, in the check node calculator 201m, the computation of equation (7) is performed, and the message uj is determined.
In
In the check node calculator 201m of
In the variable node calculators 204p of
More specifically, in the variable node calculators 204p of
The adder 251 integrates all the messages D2511 to D2515 (messages uj), and supplies a 9-bit integrated value D252 (the total sum value of messages for one column (Σuj from j=1 to 5)) to the adders-subtractors 2521 to 2525. The adders-subtractors 2521 to 2525 subtract the messages D2511 to D2515 (messages uj) from the added value D252, respectively. That is, the adders-subtractors 2521 to 2525 subtract the messages D2511 to D2515 (messages uj) from the edge to be determined, from the integrated value D252 of the messages uj from all the edges, respectively, and determine the subtracted value (Σuj from j=1 to 4).
Furthermore, the adders-subtractors 2521 to 2525 add the received data D271 (u0i) to the subtracted value (Σuj from j=1 to 4), and output 6-bit added values D2531 to D2535 as the results of the variable node computations.
In the manner described above, in the variable node calculator 204p, the computation of equation (1) is performed, and the message vi is determined.
In
In the variable node calculators 204p of
Although not shown, also, in the decoding apparatus of
According to the decoding apparatus of
When decoding is performed by repeatedly using the decoding apparatus of
However, in the decoding apparatus of
In addition to the decoding apparatus of
Furthermore, a method of implementation by approximating the sum product algorithm has also been proposed. However, in this method, the deterioration of performance is caused to occur. For implementing the sum product algorithm as hardware, there are, as described above, a method in which computations of messages corresponding to the edges (a check node computation and a bit node computation) are serially performed one-by-one, a method in which all the computations of messages are performed in parallel (full parallel), and a method in which the computations of messages are performed in units of several computations in parallel (parallel).
However, in the method in which computations of messages corresponding to the edges are performed one-by-one, a high operating frequency is required. Accordingly, as a method for increasing throughput, a method for arranging the apparatus in a pipeline structure is known. In this case, the circuit scale, in particular, (the capacity of) the memory, increases.
In the method in which all the computations of messages are performed in parallel, the circuit scale for logic increases, and the dependence on codes is high.
In the method in which the computations of messages are performed in units of several computations in parallel, control of memory access is difficult.
The present invention has been made in view of such circumstances. An object of the present invention is to suppress the operating frequency to a sufficiently realizable range while suppressing the circuit scale for both logic and memory, and to be capable of easily controlling memory access.
The decoding apparatus of the present invention, when using as a sub-matrix, a (P×P) unit matrix, a quasi-unit matrix in which one or more 1s, which are elements of the unit matrix, are substituted with 0, a shift matrix in which the unit matrix or the quasi-unit matrix is cyclically shifted, a sum matrix, which is the sum of two or more of the unit matrix, the quasi-unit matrix, and the shift matrix, or a (P×P) 0-matrix, a check matrix of the LDPC codes is represented by a combination of a plurality of the sub-matrices, includes: first computation means for simultaneously performing p check node computations for decoding the LDPC codes; and second computation means for simultaneously performing p variable node computations for decoding the LDPC codes.
The first computation means may have p check node calculators for performing check node computations, and the second computation means may have p variable node calculators for performing variable node computations.
The decoding apparatus may further include message storage means for simultaneously reading and writing message data corresponding to p edges, which is obtained as a result of the p check node computations or the p variable node computations.
The message storage means may store message data corresponding to the edges, which is read during the check node computation in such a manner that 1s of the check matrix are packed closer in the row direction.
The message storage means may store message data corresponding to edges, which is read during the variable node computations in such a manner that 1s of the check matrix are packed closer in the column direction.
The message storage means may store, at the same address, messages corresponding to p edges belonging to a unit matrix whose weight is 1, a quasi-unit matrix, or a shift matrix when the sub-matrices whose weight is 2 or more from among the sub-matrices representing the check matrix are represented in the form of the sum of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix.
The message storage means may include number-of-rows/p FIFOs and number-of-columns/p FIFOs, and the number-of-rows/p FIFOs and the number-of-columns/p FIFOs each have a number of words corresponding to the row weight and the column weight of the check matrix, respectively.
The message storage means may include a RAM (Random Access Memory), and the RAM may store the message data in the read-out sequence in such a manner as to be packed closer and reads the message data in the storage position sequence.
The decoding apparatus may further include received information storage means for storing received information of LDPC codes and for simultaneously reading p pieces of the received information.
The received information storage means may store the received information in such a manner that the received information can be read in the sequence necessary for the variable node computation.
The decoding apparatus may further include rearranging means for rearranging messages obtained as a result of the p check node computations or the p variable node computations.
The rearranging means may include a barrel shifter.
The first computation means and the second computation means may determine messages corresponding to p edges.
The first computation means may perform some of the p check node computations and the p variable node computations, and the second computation means may perform some of the others of the p variable node computations.
The first computation means may include p calculators for performing some of the p check node computations and the p variable node computations, and the second computation means may include p calculators for performing some of the others of the p variable node computations.
The decoding apparatus may further include first decoding in-progress result storage means for simultaneously reading and writing first decoding in-progress results corresponding to p edges, which are obtained by the first computation means by performing some of the p check node computations and the p variable node computations.
The first decoding in-progress result storage means may store the first decoding in-progress results corresponding to the edges, which are read when some of the others of the p variable node computations are performed, in such a manner that 1s of the check matrix are packed closer in the row direction.
The first decoding in-progress result storage means may be two single-port RAMs (Random Access Memories).
The two single-port RAMs may alternately store the first decoding in-progress results in units of p of the first decoding in-progress results.
The two single-port RAMs (Random Access Memories) each may read the first decoding in-progress results stored at the same address.
The first decoding in-progress result storage means may store, at the same address, the first decoding in-progress results corresponding to p edges belonging to a unit matrix whose weight is 1, a quasi-unit matrix, or a shift matrix when the sub-matrices whose weight is 2 or more from among the sub-matrices representing the check matrix are represented in the form of the sum of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix.
The decoding apparatus may further include second decoding in-progress result storage means for simultaneously reading and writing the second decoding in-progress results corresponding to p edges, which are obtained by the second computation means by performing some of the others of the p variable node computations.
The decoding apparatus may further include received information storage means for storing received information of LDPC codes and simultaneously reading p pieces of the received information.
The received information storage means may store the received information in such a manner that the received information can be read in the sequence necessary for some of the others of the p variable node computations.
The decoding apparatus may further include rearranging means for rearranging first decoding in-progress results obtained by the first computation means by performing some of the p check node computations and the p variable node computations, or second decoding in-progress results obtained by the second computation means by performing some of the others of the p variable node computations.
The rearranging means may include a barrel shifter.
The first computation means may perform some of the p check node computations, and the second computation means may perform some of the others of the p check node computations, and the p variable node computations.
The first computation means may include p calculators for performing some of the p check node computations, and the second computation means may include p calculators for performing some of the others of the p check node computations, and the p variable node computations.
The decoding apparatus may further include first decoding in-progress result storage means for simultaneously reading and writing first decoding in-progress results corresponding to p edges, which are obtained by the first computation means by performing some of the p check node computations.
The decoding apparatus may further include second decoding in-progress result storage means for simultaneously reading and writing second decoding in-progress results corresponding to p edges, which are obtained by the second computation means by performing some of the others of the p check node computations, and the p variable node computations.
The second decoding in-progress result storage means may store the second decoding in-progress results corresponding to edges, which are read when some of the others of the p check node computations, and the p variable node computations are performed, in such a manner that 1s of the check matrix are packed closer in the column direction.
The second decoding in-progress result storage means may be two single-port RAMs (Random Access Memories).
The two single-port RAMs may alternately store the second decoding in-progress results in units of p of the second decoding in-progress results.
The two single-port RAMs (Random Access Memories) each may read the second decoding in-progress results stored at the same address.
The second decoding in-progress result storage means may store, at the same address, the second decoding in-progress results corresponding to p edges belonging to a unit matrix whose weight is 1, a quasi-unit matrix, or a shift matrix when the sub-matrices whose weight is 2 or more from among the sub-matrices representing the check matrix are represented in the form of the sum of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix.
The decoding apparatus may further include received information storage means for storing received information of LDPC codes and for simultaneously reading p pieces of the received information.
In the decoding apparatus according to claim 36, the received information storage means may store the received information in such a manner that the received information can be read in the sequence necessary for some of the others of the p check node computations, and the p variable node computations.
The decoding apparatus may further include rearranging means for rearranging first decoding in-progress results obtained by the first computation means by performing some of the p check node computations, or second decoding in-progress results obtained by the second computation means by performing some of the others of the p check node computations, and the p variable node computations.
The rearranging means may include a barrel shifter.
The decoding method of the present invention, when using as a sub-matrix, a (P×P) unit matrix, a quasi-unit matrix in which one or more 1s, which are elements of the unit matrix, are substituted with 0, a shift matrix in which the unit matrix or the quasi-unit matrix is cyclically shifted, a sum matrix, which is the sum of two or more of the unit matrix, the quasi-unit matrix, and the shift matrix, or a (P×P) 0-matrix, a check matrix of LDPC codes is represented by a combination of a plurality of the sub-matrices, includes a first computation step of simultaneously performing p check node computations for decoding the LDPC codes; and a second computation step of simultaneously performing p variable node computations for decoding the LDPC codes.
The program of the present invention includes a first computation step of simultaneously performing p check node computations for decoding LDPC codes; and a second computation step of simultaneously performing p variable node computations for decoding the LDPC codes.
In the present invention, when using as a sub-matrix, a (P×P) unit matrix, a quasi-unit matrix in which one or more 1s, which are elements of the unit matrix, are substituted with 0, a shift matrix in which the unit matrix or the quasi-unit matrix is cyclically shifted, a sum matrix, which is the sum of two or more of the unit matrix, the quasi-unit matrix, and the shift matrix, or a (P×P) 0-matrix, a check matrix of the LDPC codes is represented by a combination of a plurality of the sub-matrices, p check node computations for decoding the LDPC codes are simultaneously performed, and p variable node computations for decoding the LDPC codes are simultaneously performed.
Specific embodiments to which the present invention is applied will be described below in detail with reference to the drawings.
In
It may be said that the check matrix of
A decoding apparatus 300 of
Before describing in detail each section of the decoding apparatus 300, the method of storing data in the edge data storage memories 311 and 316 will be described first.
The edge data storage memory 311 includes six FIFOs 3111 to 3116, the number being such that 30, the number of rows, of the check matrix is divided by 5, the number of rows. The FIFO 311y (y=1, 2, . . . , 6) is formed in such a manner that messages corresponding to five edges, which is the number of the rows and the columns of the sub-matrix, can be read or written simultaneously. The length (the number of stages) thereof is 9, which is the maximum number of 1s (Hamming weight) in the row direction of the check matrix.
In the FIFO 3111, the data corresponding to the positions of 1s from the first row up to the fifth row of the check matrix of
In the FIFO 3112, the data corresponding to the positions of 1s from the sixth row up to the tenth row of the check matrix of
More specifically, for the sub-matrix whose weight is 2 or more, the data (the message corresponding to the edges belonging to the unit matrix, the sum matrix, or the shift matrix) corresponding to the positions of 1s of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix, when the sub-matrix is represented in the form of the sum of two or more of the (P×P) unit matrix whose weight is 1, the quasi-unit matrix in which one or more 1s, which are elements of the unit matrix, are substituted with 0, and the shift matrix in which the unit matrix or the quasi-unit matrix is cyclically shifted, is stored at the same address (the same FIFOs among the FIFOs 3111 to 3116).
Hereafter, for the third to the ninth elements, the data is stored in such a manner as to correspond to the check matrix. The number of the elements of the FIFO 3112 is 9 for all the rows.
For the FIFOs 3113 to 3116, similarly, data is stored in such a manner as to correspond to the check matrix, and the length of each of the FIFOs 3113 to 3116 is 9.
The memory 316 for storing edge data is formed of 18 FIFOs 3161 to 31618, the number being such that 90, the number of rows of the check matrix, is divided by 5, the number of the rows of the sub-matrix. The FIFO 316x (x=1, 2, . . . , 18) is formed in such a manner that messages corresponding to five edges, the number being the number of the rows and the number of the columns of the sub-matrix, can be read or written simultaneously.
In the FIFO 3161, data corresponding to the positions of 1s from the first column up to the fifth column of the check matrix of
More specifically, for the sub-matrix whose weight is 2 or more, data (messages corresponding to the edges belonging to the unit matrix, the quasi-unit matrix, or the shift matrix) corresponding to the position of 1s of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix when the sub-matrix is represented in the form of the sum of two or more of the (P×P) unit matrix whose weight is 1, the quasi-unit matrix in which is, which are elements of the unit matrix, are substituted with 0, and the shift matrix in which the unit matrix or the quasi-unit matrix is cyclically shifted, is stored at the same address (the same FIFO from among the FIFOs 3161 to 31618).
Hereafter, for the fourth and fifth elements, also, data is stored in such a manner as to correspond to the check matrix. The number of elements (the number of stages) of the FIFO 3161 is 5, which is the maximum number of 1s (Hamming weight) in the row direction from the first column up to the fifth column of the check matrix.
Also, for the FIFOs 3162 and 3163, similarly, data is stored in such a manner as to correspond to the check matrix, and each of the length (the number of stages) thereof is 5. Also, for the FIFOs 3164 to 31612, similarly, data is stored in such a manner as to correspond to the check matrix, and each of the lengths thereof is 3. Also, for the FIFOs 31613 to 31618, similarly, data is stored in such a manner as to correspond to the check matrix, and each of the lengths thereof is 2. However, since the first element of the FIFO 31618 corresponds to (1, 86) to (5, 90) of the check matrix, and there are no is in the fifth column ((1, 90) to (5, 90) of the check matrix), data is not stored.
A description will now be given below in detail of the operation of each section of the decoding apparatus 300 of
The edge data storage memory 311 includes six FIFOs 3111 to 3116. In the FIFOs 3111 to 3116 of the edge data storage memory 311, five messages D319 are collectively supplied from the switch 310 in sequence, and the FIFOs 3111 to 3116 collectively store the five messages D319 in sequence (simultaneously). Furthermore, when data is to be read, the edge data storage memory 311 sequentially reads the five messages (data) D3111 from the FIFO 3111, and supplies them to the selector 312 at the subsequent stage. After the reading of the messages D3111 from the FIFO 3111 is completed, the edge data storage memory 311 also sequentially reads messages D3111 to D3116 from the FIFOs 3112 to 3116, respectively, and supplies them to the selector 312.
A selection signal D321 indicating the selection of the FIFO from which message data is read (the FIFO from which data has been read currently) from among the FIFOs 3111 to 3116 is supplied to the selector 312 from the control section 321, and also, five messages (data) D3111 to D3116 are supplied to the selector 312 from the edge data storage memory 311. The selector 312 selects the FIFO from which data has been read currently from among the FIFOs 3111 to 3116 in accordance with a selection signal D321, and supplies the five pieces of message data supplied from the selected FIFO, as messages D312, to the check node calculation section 313.
The check node calculation section 313 includes five check node calculators 3131 to 3135. Five messages D312 are supplied to the check node calculation section 313 via the selector 312, and the messages D312 are supplied individually to each of the check node calculators 3131 to 3135. Furthermore, a control signal D322 is supplied to the check node calculator 313 from the control section 321, and the control signal D322 is supplied to the check node calculators 3131 to 3135. The check node calculators 3131 to 3135 simultaneously perform computations in accordance with equation (7) by using the messages D312, and determine messages D313 corresponding to five edges as a result of the computations. The check node calculation section 313 supplies the five messages D313 obtained as a result of the computations by the check node calculators 3131 to 3135 to the cyclic shift circuit 314.
A control signal D322 supplied from the control section 321 to the check node calculator 313 corresponds to the control signal D106 of
The five messages D313 calculated in the check node calculation section 313 are supplied to the cyclic shift circuit 314. Also, a control signal D323 indicating information (matrix data) as to the fact that the edge corresponding to the message D313 is connected as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 314 from the control section 321. The cyclic shift circuit 314 cyclically shifts the five messages D313 on the basis of the control signal D323, and supplies the result as a message D314 to the switch 315.
A control signal D324 indicating information as to which column of the check matrix the five messages (data) D314 supplied from the cyclic shift circuit 314 belong to 1s supplied to the switch 315, and also the message D314 is supplied thereto from the cyclic shift circuit 314. Based on the control signal D324, the switch 315 selects the FIFO for storing the message D314 from among the FIFOs 3161 to 31618, and collectively supplies the five messages D314 in sequence.
An edge data storage memory 316 includes 18 FIFOs 3161 to 31618. The five messages D314 are collectively supplied in sequence (simultaneously) from the switch 315 to the FIFOs 3161 to 31618 of the edge data storage memory 316, and the FIFOs 3161 to 31618 collectively store the five messages D314 in sequence. Furthermore, when the data is to be read, the memory 316 for storing edge data sequentially reads five messages D3151 from the FIFO 3161 and supplies them to the selector 317 at the subsequent stage. After the reading of the data from the FIFO 3161 is completed, the memory 316 for storing edge data sequentially reads the messages D3152 to D31318 also from the FIFOs 3161 to 31618 and supplies them to the selector 317.
A selection signal D325 indicating the selection of the FIFO for reading message data (the FIFO from which data has been read currently) from among the FIFOs 3161 to 31618 is supplied from the control section 321 to the selector 317, and also, message data D3151 to D31318 are supplied thereto from the edge data storage memory 316. Based on the selection signal D325, the selector 317 selects the FIFO from which data has been read currently from among the FIFOs 3161 to 31618, and supplies the five pieces of the message data supplied from the selected FIFO, as messages D316, to the variable node calculation section 319 and the above-described block (not shown) for performing the computation of equation (5).
On the other hand, the memory 318 for received data has calculated the reception LLR (log likelihood ratio) from the received information through the communication channel.
Five pieces of the calculated reception LLR are supplied collectively (simultaneously) as received data D317 (LDPC codes) to the variable node calculation section 319 and the block (not shown) for receiving the computation of equation (5). The memory 318 for received data reads the received data D317 in the sequence necessary for the variable node computation of the variable node calculation section 319.
The variable node calculation section 319 includes five variable node calculator 3191 to 3195. Five messages D316 are supplied to the variable node calculation section 319 via the selector 317, and the messages D316 are supplied individually to each of the variable node calculators 3191 to 3195. Furthermore, the five pieces of the received data D317 are supplied to the variable node calculation section 319 from the memory 318 for received data, and the pieces of the received data D317 are supplied individually to each of the variable node calculators 3191 to 3195. Furthermore, a control signal D326 is supplied from the control section 321 to the variable node calculation section 319, and the control signal D326 is supplied to the variable node calculators 3191 to 3195.
The variable node calculators 3191 to 3195 perform computations in accordance with equation (1) by using the messages D316 and the received data D317, and determine messages D318 corresponding to five edges as a result of the computations. The variable node calculation section 319 supplies the five messages D318 obtained as a result of the variable node calculators 3191 to 3195 to the cyclic shift circuit 320.
Here, the control signal D326 supplied from a control section 521 to the variable node calculation section 319 corresponds to the control signal D107 of
Five messages D318 are supplied to the cyclic shift circuit 320 from the variable node calculation section 319. Also, a control signal D327 indicating information (matrix data) as to the fact that the edge corresponding to the message D318 is connected as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 320 from the control section 321. Based on the control signal D327, the cyclic shift circuit 320 performs a cyclic shifting of rearranging the messages D327, and supplies the results as messages D319 to the switch 310.
The control section 321 supplies a selection signal D320 to the switch 310 and supplies a selection signal D321 to the selector 312 in order to control them, respectively. The control section 321 supplies a control signal D322 to the check node calculation section 313, supplies a control signal D323 to the cyclic shift circuit 314, and supplies a control signal D324 to the switch 315 in order to control them, respectively. Furthermore, the control section 321 supplies a selection signal D325 to the selector 317, supplies a control signal D326 to the variable node calculation section 319, and supplies a control signal D327 to the cyclic shift circuit 320 in order to control them, respectively.
As a result of the above operation being circulated once, one decoding of the LDPC codes can be performed. After the decoding apparatus 300 of
For the portions in which edge data (messages corresponding to the edges) lacks, during the storage in the memory (when data is stored in the edge data storage memories 311 and 316), no message is stored. During node computation (during the check node computation at the check node calculation section 313 and during the variable node computation at the variable node calculation section 319), no computation is performed.
In step S31, the variable node calculation section 319 performs a variable node computation.
More specifically, five messages D316 (messages uj) are supplied to the variable node calculation section 319 via the selector 317. That is, the edge data storage memory 316 sequentially reads the five messages D3161 stored in step S39 (to be described later) from the FIFO 3161, and thereafter, sequentially reads messages D3162 to D31618 also from the FIFOs 3162 to 31618, and supplies them to the selector 317.
A selection signal D307 indicating the selection of the FIFO (the FIFO from which data has been read currently) from which message (data) is to be read from among the FIFOs 3161 to 31618 is supplied to the selector 317 from the control section 321, and also, message data D3161 to D31618 are supplied to the selector 317 from the edge data storage memory 316. Based on the selection signal D307, the selector 317 selects the FIFO from which data has been read currently from among the FIFOs 3161 to 31618, and supplies the five pieces of the message data supplied from the selected FIFO, as the messages D316, to the variable node calculation section 319.
When a check node computation has not yet been performed on the received data D309 supplied from the memory 306 and a message D304 is not stored in the edge data storage memory 316, the variable node calculation section 319 sets the message uj to an initial value used for a variable node computation.
The five pieces of the received data D309 (received value u0i) are supplied to the variable node calculation section 319 from the memory 318 for received data, and the pieces of the received data D309 are supplied individually to each of the variable node calculators 3191 to 3195. Furthermore, a control signal D315 is supplied to the variable node calculation section 319 from the control section 321, and the control signal D315 is supplied to the variable node calculators 3191 to 3195.
Based on the control signal D315, the variable node calculators 3191 to 3195 simultaneously perform computations in accordance with equation (1) by using the messages D316 and the received data D309, and determine five messages D319 as a result of the computations.
That is, the control signal D315 supplied to the variable node calculation section 319 by the control section 321 corresponds to the control signal D107 described with reference to
After the processing of step S31, the process proceeds to step S32, where the variable node calculation section 319 supplies the five messages D319 (messages vi) obtained as a result of the variable node computations of the variable node calculators 3191 to 3195 to the cyclic shift circuit 320. The process then proceeds to step S33.
In step S33, the cyclic shift circuit 320 cyclically shifts (rearranges) the five messages D318 supplied from the variable node calculation section 319.
More specifically, a message D318 is supplied to the cyclic shift circuit 320 from the variable node calculation section 319. Also, a control signal D327 indicating information (matrix data) as to the fact that the edge corresponding to the message D318 is connected as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 320 from the control section 321. Based on the control signal D327, the cyclic shift circuit 320 cyclically shifts five messages D327, and supplies the results as the message sD319 to the switch 310.
After the processing of step S33, the process proceeds to step S34, where the switch 310 supplies the five messages D319 supplied from the cyclic shift circuit 320 to the edge data storage memory 311.
More specifically, a message (data) D304 is supplied to the switch 310 from the cyclic shift circuit 320, and also, a control signal D312 indicating information as to which row of the check matrix the message D304 belongs to 1s supplied to the switch 310. Based on the control signal D312, the switch 310 selects the FIFO for storing the messages D304 from among the FIFO 3001 to 3006, and sequentially supplies the five pieces of the message data D304 collectively in the selected FIFO.
Then, the FIFO 3001 to 30018 of the edge data storage memory 311 collectively store the five pieces of the message data D304 supplied from the switch 310 in sequence.
After the processing of step S34, the process proceeds to step S35, where the control section 321 determines whether or not the messages of the total number of edges have been computed by the variable node calculation section 319. When it is determined that the messages of the total number of edges have not been computed, the process returns to step S31, and the above-described processing is performed again.
On the other hand, when it is determined in step S35 that the variable node calculation section 319 has computed the messages of the total number of edges, the process proceeds to step S36, where the check node calculation section 313 performs a check node computation.
More specifically, five message D302 are supplied to the check node calculation section 313 via the selector 312. That is, the edge data storage memory 311 sequentially reads, from the FIFO 3111, five messages D3111 (messages vi) stored in step S34, and thereafter, sequentially reads the message data D3112 to D3116 also from the FIFOs 3112 to 3116, and supplies it to the selector 312.
A selection signal D321 indicating the selection of the FIFO for reading message data (the FIFO from which data has been read currently) from among the FIFOs 3111 to 3116 is supplied to the selector 312 from the control section 321, and also, message data D3111 to D3116 is supplied to the selector 312 from the edge data storage memory 311. Based on the selection signal D321, the selector 301 selects the FIFO from which data has been read currently, and supplies five pieces of the message data supplied from the selected FIFO, as messages D311, to the check node calculation section 313.
Furthermore, a control signal D322 is supplied to the check node calculation section 313 from the control section 321. Based on the control signal D322, the check node calculators 3131 to 3135 of the check node calculation section 313 simultaneously perform check node computations in accordance with equation (7) by using the messages D302, and determine five messages D303 (messages uj) as a result of the computations.
More specifically, the control signal D322 supplied to the check node calculation section 313 by the control section 321 corresponds to the control signal D106 in
After the processing of step S37, the process proceeds to step S38, where the check node calculation section 313 outputs five messages D313 obtained as a result of the check node computation to the cyclic shift circuit 314. The process then proceeds to step S38.
In step S38, the cyclic shift circuit 314 cyclically shifts the five messages D313 supplied from the check node calculation section 313.
More specifically, the messages D313 are supplied to the cyclic shift circuit 314 from the check node calculation section 313. Also, a control signal D314 indicating information (matrix data) as to the fact that the edge corresponding to the message D313 is connected as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 314 from the control section 321. Based on the control signal D314, the cyclic shift circuit 314 cyclically shifts the five messages D313, and supplies the results as the messages D304 to the switch 315.
After the processing of step S38, the process proceeds to step S39, where the switch 315 stores the five messages D304 supplied from the cyclic shift circuit 314 in the edge data storage memory 316.
More specifically, the five messages (data) D304 are supplied from the cyclic shift circuit 314 to the switch 316, and also, a control signal D324 indicating information as to which row of the check matrix the messages (data) D304 belong to 1s supplied to the switch 316 from the cyclic shift circuit 314. Based on the control signal D324, the switch 316 selects the FIFO for storing the message D304 from among the FIFOs 3161 to 31618 of the edge data storage memory 316, and collectively supplies the five pieces of the message data D304 to the selected FIFO in sequence.
Then, the FIFOs 3161 to 31618 of the edge data storage memory 316 collectively store the five pieces of the message data D304 supplied from the switch 316 in sequence.
After the processing of step S39, the process proceeds to step S40, where the control section 321 determines whether or not the messages of the total number of the edges have been computed by the check node calculation section 313. When it is determined that the messages of the total number of the edges have not been computed, the process returns to step S36, and the above-described processing is performed again.
On the other hand, when the control section 321 determines in step S40 that the messages of the total number of the edges have been computed by the check node calculation section 313, the processing is completed.
When the decoding apparatus 300 repeatedly performs the decoding process of
In the above description, although an FIFO is used to store edge data (although the edge data storage memory 311 and 316 are formed by FIFOs, a RAM may be used instead of the FIFO. In that case, for the RAM, a bit width at which p pieces of edge information (messages corresponding to edges) can be simultaneously read, and the total-number-of-edges/p words are required. For writing into the RAM, at which position the data to be written is read when it is read next is determined on the basis of the information of the check matrix, and the data is written at that position. For reading from the RAM, data is sequentially read from the beginning of the address. That is, in the RAM, the message data is stored in the sequence in which it is read in such a manner as to be packed closer, and the message data is read in the storage position sequence. If the RAM is used in place of the FIFO, the selectors 312 and 317 are not necessary.
When the physical bit width of the FIFO and the RAM is not sufficient, by providing the same control signal by using a plurality of RAMs, these can be logically assumed as one RAM.
In the decoding apparatus 300 of
Accordingly, in order to further reduce the circuit scale of the decoding apparatus, a decoding apparatus in which the capacity of the memory is reduced further when compared to the decoding apparatus 300 of
In a decoding apparatus 400 of
The decoding apparatus 400 includes a memory 410 for storing decoding in-progress results, a cyclic shift circuit 411, a calculation section 412 made up of five calculators 4121 to 4125, a memory 413 for storing decoding in-progress results, a cyclic shift circuit 414, a calculation section 415 made up of five calculators 4151 to 4155, a memory 416 for reception, and a control section 417.
A description will now be given, with reference to
In the decoding apparatus 400 of
More specifically, the calculator 412 k of
The calculator 412k of
Therefore, it is possible for the decoding apparatus 400 of
In the calculator 412k of
Next, a description is given of the computation performed by the calculator 412k and the computation performed by the calculator 415k by using equations.
More specifically, the calculation section 412 performs a first computation in accordance with equation (7) described above and equation (8) described below, and supplies the decoding in-progress results uj, which are the results of the first computation, to the memory 410 for storing decoding in-progress results, whereby they are stored. The calculation section 415 performs a second computation in accordance with equation (5) described above, and supplies the decoding in-progress results v, which are the results of the second computation, to the memory 410 for storing decoding in-progress results, whereby they are stored.
vi=v−udv (8)
udv of equation (8) represents the in-progress results (here, the check node computation results themselves) of the check node computation from the edge for which the message of the i-th column of the check matrix H is to be determined. That is, udv is the decoding in-progress results corresponding to the edge to be determined.
More specifically, the decoding in-progress results v obtained as a result of the second computation in accordance with equation (5) described above are such that the received value u0i and the decoding in-progress results uj of the check node computation from all the edges corresponding to 1s of each row of the i-th column of the check matrix H are multiplied together. The value vi used for equation (7) described above becomes such that the decoding in-progress results udv of the check node computation from the edges for which messages are to be determined from among the decoding in-progress results uj of the check node computation from the edges corresponding to 1s of each row, of the i-th column of the check matrix H, are subtracted from the decoding in-progress results v obtained as a result of the second computation in accordance with equation (5). That is, the computation of equation (1) for determining the value vi used for the computation of equation (7) is a computation in which the above-described equation (5) and equation (8) are combined.
Therefore, in the decoding apparatus 400, the first computation in accordance with equation (7) and equation (8) by the calculation section 412, and the second computation in accordance with equation (5) by the calculation section 415 are alternately performed, and the calculation section 415 outputs the result of the final second computation as the decoded results, making it possible to perform repeated decoding of LDPC codes.
Here, the first computation results in accordance with equation (7) and equation (8) are described as the decoding in-progress results uj, and these decoding in-progress results uj are equal to the check node computation results uj of equation (7).
Since v of equation (5), which is determined from the second computation, is such that the check node computation results uj from the edges from which messages are to be determined are added to the variable node computation results vi of equation (1), only one of v is determined with respect to one column (one variable node) of the check matrix H.
In the decoding apparatus 400, the calculation section 412 performs the first computation by using the decoding in-progress results v (the second decoding in-progress results) corresponding to the column of the check matrix H, which are the results of the second computation by the calculation section 415, and stores, in the memory 413 for storing decoding in-progress results, the decoding in-progress results uj (the first decoding in-progress results) of the check node computation from the edges of the messages (the messages output to each edge by each check node) of the edges corresponding to 1s of each row, of the i-th column of the check matrix H obtained as a result of the computation. Therefore, the capacity of the memory 413 for storing decoding in-progress results becomes a value such that, similarly to the number of 1s (the total number of edges) of the check matrix and the number of quantization bits are multiplied together. On the other hand, the calculation section 415 performs a second computation by using the decoding in-progress results uj corresponding to 1s of each row, of the i-th column of the check matrix H, which are the results of the first computation by the calculation section 412 and the received value u0i, and stores the decoding in-progress results v corresponding to the i-th column obtained as a result of the computation in the memory 410 for storing decoding in-progress results. Therefore, the capacity necessary for the memory 410 for storing decoding in-progress results becomes a value such that the number of columns of the check matrix, which is smaller than the number of 1s of the check matrix, that is, the code length of the LDPC codes, and the number of quantization bits of the number of quantization bits are multiplied together.
Therefore, in the decoding apparatus 400 for decoding LDPC codes, in which is in the check matrix H are sparse, the capacity of the memory of the memory 410 for storing decoding in-progress results can be reduced when compared to the edge data storage memory 311 of
Furthermore, in the decoding apparatus 400, since the calculation section 415 performs a second computation in accordance with equation (5), the decoding apparatus 400 does not need to have the block (not shown) for performing the computation of equation (5) for computing the final decoded results in the decoding apparatus 300 of
A description will now be given in detail of the operation of each section of the decoding apparatus 400 of
Five decoding in-progress results D415 corresponding to five columns of the check matrix, which are the results of the second computation by the calculation section 415, are supplied to the memory 410 for storing decoding in-progress results from the calculation section 415. The memory 410 for storing decoding in-progress results stores the five decoding in-progress results D415 supplied from the calculation section 415 in sequence starting from the first address.
More specifically, at the first address of the memory 410 for storing decoding in-progress results, the decoding in-progress results v from the first column up to the fifth column from among the decoding in-progress results corresponding to the column of the check matrix are stored. Similarly, at the second address, the decoding in-progress results v from the sixth column up to the tenth column are stored, and at the third address, the decoding in-progress results from the 11th column up to the 15th column are stored. Hereafter, similarly, the decoding in-progress results v from the 16th column up to the 90th column are stored at the fourth address up to the 18th address in units of five results, and a total of 90 decoding in-progress results v are stored in the memory 410 for storing decoding in-progress results. Therefore, the number of words of the memory 410 for storing decoding in-progress results becomes 18 such that 90, the number of columns of the check matrix H (the code length of the LDPC codes) of
The memory 410 for storing decoding in-progress results simultaneously reads, from the decoding in-progress results D415 which have already been stored, five decoding in-progress results v, which are “1” in the corresponding row of the check matrix H, of the decoding in-progress results uj to be determined by the calculation section 412 at the subsequent stage, and supplies them as decoding in-progress results D410 to the cyclic shift circuit 411.
The memory 410 for storing decoding in-progress results is formed by, for example, a single-port RAM capable of simultaneously reading and writing five decoding in-progress results. Since, in the memory 410 for storing decoding in-progress results, the decoding in-progress results v corresponding to the column at which the computation is performed by the second computation of the calculation section 415 are stored, the amount of data stored in the memory 410 for storing decoding in-progress results, that is, the storage capacity necessary for the memory 410 for storing decoding in-progress results, is a multiplication value of the number of quantization bits of the decoding in-progress results and the number of columns of the check matrix H (the code length of the LDPC codes).
Five decoding in-progress results D410 are supplied to the cyclic shift circuit 411 from the memory 410 for storing decoding in-progress results. Also, a control signal D619 indicating information (matrix data) as to the fact that is of the check matrix, which corresponds to the decoding in-progress results D410, are arranged as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 411 from the control section 417. The cyclic shift circuit 611 performs a cyclic shifting of rearranging the five decoded results D410 on the basis of the control signal D619, and supplies the results as decoding in-progress results D411 to the calculation section 412.
The calculation section 412 includes five calculators 4121 to 4125. The five decoding in-progress results D411 (the second decoding in-progress results) v, which are obtained as a result of the second computation by the calculation section 415, are supplied to the calculation section 412 from the cyclic shift circuit 411. Also, the five decoding in-progress results D413 (the first decoding in-progress results) uj obtained previously as a result of the first computation by the calculators 4121 to 4125 are supplied to the calculation section 412 from the memory 413 for storing decoding in-progress results. The five decoding in-progress results D411 and the five decoding in-progress results D413 are supplied to each of the calculator 4121 to 4125. Furthermore, a control signal D419 is supplied to the calculation section 412 from the control section 417, and the control signal D419 is supplied to the calculators 4121 to 4125. The control signal D419 is a signal common to the five calculators 4121 to 4125.
The calculators 4121 to 4125 perform the first computation in accordance with equation (7) and equation (8) by using the decoding in-progress results D411 and the decoding in-progress results D413, and determine the decoding in-progress results D412 (vi). The calculation section 412 supplies the five decoding in-progress results D412 corresponding to five 1s of the check matrix, which are obtained as a result of the computations by the calculators 4121 to 4125, to the memory 413 for storing decoding in-progress results.
The memory 413 for storing decoding in-progress results is formed by, for example, two single-port RAMs capable of simultaneously reading and writing five decoding in-progress results. The five decoding in-progress results D412 are supplied to the memory 413 for storing decoding in-progress results from the calculation section 412, and also, a control signal D420 for controlling the reading and writing of the decoding in-progress results 413 is supplied to the memory 413 from the control section 417.
Based on the control signal D420, the memory 413 for storing decoding in-progress results collectively stores the five decoding in-progress results D412 supplied from the calculation section 412, and at the same time, reads the five decoding in-progress results D412, which have already been stored, and supplies them as decoding in-progress results D413 to the calculation section 412 and the cyclic shift circuit 414. That is, the memory 413 for storing decoding in-progress results simultaneously performs the reading of the decoding in-progress results D413 to be supplied to the calculation section 412 and the cyclic shift circuit 414 and the writing of the decoding in-progress results D412 supplied from the calculation section 412.
In the memory 413 for storing decoding in-progress results, the decoding in-progress results uj of the check node computation from the edges corresponding to 1s of each row, of the i-th column of the check matrix H, which are computed by the first computation of the calculation section 412, are stored. Therefore, the amount of data stored in the memory 413 for storing decoding in-progress results, that is, the storage capacity necessary for the memory 413 for storing decoding in-progress results, becomes the multiplication value of the number of the quantization bits of the decoding in-progress results and the number of 1s of the check matrix.
Five decoding in-progress results D413 (the decoding in-progress results uj) are supplied to the cyclic shift circuit 414 from the memory 413 for storing decoding in-progress results. Also, a control signal D421 indicating information (matrix data) as to the fact that 1s of the check matrix, which corresponds to the decoding in-progress results D413, are arranged as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 414 from the control section 417. The cyclic shift circuit 414 performs a cyclic shifting of rearranging the five decoding in-progress results D413 on the basis of the control signal D421, and supplies the results as decoding in-progress results D414 to the calculation section 415.
The calculation section 415 includes five calculators 4151 to 4155. Five decoding in-progress results D414 are supplied to the calculation section 415 from the cyclic shift circuit 414, and the decoding in-progress results D414 are supplied to the respective calculators 4151 to 4155. Furthermore, five pieces of received data D417 (LDPC codes) are supplied to the calculation section 415 from the memory 417 for reception, and the pieces of received data D417 are supplied to the respective calculators 4151 to 4155. Furthermore, a control signal D422 is supplied to the calculation section 417 from the control section 417, and the control signal D422 is supplied to the calculators 4151 to 4155. The control signal D422 is a signal common to the five calculators 4171 to 4175.
The calculators 4151 to 4155 each perform the second computation in accordance with equation (5) by using the decoding in-progress results D414 and the received data D417, and determine decoding in-progress results D415. The calculation section 415 supplies the five decoding in-progress results D415 (v) obtained as a result of the second computation by the calculators 4151 to 4155 to the memory 410 for storing decoding in-progress results. Furthermore, when the computation that is being performed currently is the final second computation, the calculation section 415 outputs the five decoding in-progress results D415, which are obtained as a result of the computation, as the final decoded results.
The memory 416 for reception stores, as received data D417, the reception LLR (log likelihood ratio), which is the 0-likeness value of the sign bit, which is calculated from the received value (the sign bit) received through the communication channel.
That is, at the first address of the memory 416 for reception, the received data D417 corresponding to the first column up to the fifth column of the check matrix from among the received data D417 corresponding to the column of the check matrix is stored. Then, at the second address, the received data D417 corresponding to the sixth column up to the tenth column of the check matrix is stored, and at the third address, the received data D417 corresponding to the 11th column up to the 16th column of the check matrix is stored. Hereafter, similarly, at the fourth address up to the 18th address, the received data D417 corresponding to the 17th column up to the 90th column is stored in units of five pieces of data.
Then, a memory 616 for reception reads the received data D417 which has already been stored in units of five pieces of data in the sequence necessary for the variable node computation, and supplies them to the calculation section 415.
The memory 416 for reception is formed by, for example, a single-port RAM capable of simultaneously reading and writing five pieces of received data. The amount of data stored in the memory 416 for reception, that is, the storage capacity necessary for the memory 315 for reception, is the multiplication value of the code length of the LDPC codes and the number of quantization bits of the received data. The number of words of the memory 416 for reception is 18, which is the value such that the code length of the LDPC codes, that is, 90, the number of columns of the check matrix, is divided by 5, the number of pieces of the received data D417 to be read simultaneously.
The control section 417 supplies a control signal D418 to the cyclic shift circuit 411 and supplies a control signal D419 to the calculation section 412 in order to control them, respectively. The control section 417 supplies a control signal D420 to the memory 413 for storing decoding in-progress results, supplies a control signal D421 to the cyclic shift circuit 414, and supplies a control signal D421 to the calculation section 415 so as to control them, respectively.
As a result of the data being circulated in the order of the memory 410 for storing decoding in-progress results, the cyclic shift circuit 411, the calculation section 412, the memory 413 for storing decoding in-progress results, the cyclic shift circuit 414, and the calculation section 415, the decoding apparatus 400 can perform one decoding. In the decoding apparatus 400, after decodings are performed repeatedly a predetermined number of times, the decoding in-progress results D415, which are the results of the second computation by the calculation section 415, are output as the final decoded results.
In
In
Based on the control signal D419 supplied from the control section 417, the calculator 4121 of
More specifically, one decoding in-progress result D411 from among the five 9-bit decoding in-progress results D411 (v) supplied from the cyclic shift circuit 411 is supplied to the calculator 4121. Also, one decoding in-progress result D413, which is the result of the computation by the calculation section 412 at the previous time, from among the five 6-bit decoding in-progress results D413(uj), which are the results of the computation by the calculation section 412 at the previous time, which are supplied from the memory 413 for storing decoding in-progress results, is supplied to the calculator 4121. The 9-bit decoding in-progress results D411 (v) and the 6-bit decoding in-progress results D413 (udv) are supplied to the subtractor 431. Furthermore, the control signal D419 is supplied to the calculator 4121 from the control section 417, and the control signal D419 is supplied to the selector 435 and the selector 442.
The subtractor 431 subtracts the 6-bit decoding in-progress result D413 (uj) from the 9-bit decoding in-progress result D411 (v), and outputs the 6-bit subtracted value D431. That is, the subtractor 431 performs a computation in accordance with equation (8), and outputs the subtracted value D431 (vi), which is the result of the computation.
A sign bit D432 (sign (vi)) indicating the positive or negative sign of the highest-order bit from among the 6-bit subtracted value D431 output from the subtractor 431 is supplied to the EXOR circuit 440, and the absolute value D433 (|vi|) of the five lower-order bits is supplied to the LUT 432.
The LUT 432 reads the 5-bit computation results D434 (φ(|vi|)) such that the computation of φ(vi) in equation (7) is performed on the absolute value D433 (|vi|), and supplies it to an adder 433 and an FIFO memory 438.
The adder 433 integrates the computation results D434 by adding together the computation results D434 (|vi(|vi|)) and the 9-bit value D435 stored in the register 434, and stores the 9-bit integrated value obtained as the result in the register 434 again. When the computation results for the absolute value D433 (|vi|) determined from the decoding in-progress results D411 corresponding to all the 1s over one row of the check matrix are integrated, the register 434 is reset.
When the decoding in-progress results D411 over one row of the check matrix are read one-by-one and the integrated value such that the computation results D434 for one row are integrated is stored in the register 434, the control signal D419 supplied from the control section 417 changes from 0 to 1. For example, when the row weight is “9”, the control signal D419 is “0” at the first to eighth clocks, and is “1” at the ninth clock.
When the control signal D419 is “1”, the selector 435 selects the value stored in the register 434, that is, the 9-bit value D435 (Σφ(|vi|)) from i=1 to i=dc) such that φ(|vi|) determined from the decoding in-progress results D411 (the decoding in-progress results v) corresponding to all the 1s over one row of the check matrix are integrated, and outputs the value as a value D436 to the register 436, whereby it is stored. The register 436 supplies the stored value D436 as a 9-bit value D437 to the selector 435 and the adder 437. When the control signal D419 is “0”, the selector 435 selects the value D437 supplied from the register 436, and outputs the value to the register 436, whereby it is stored again. That is, until φ(|vi|) determined from the decoding in-progress results D411 (the decoding in-progress results v) corresponding to all the 1s over one row of the check matrix are integrated, the register 436 supplies φ(|vi|) integrated at the previous time to the selector 435 and the adder 437.
On the other hand, the FIFO memory 438 delays the computation result D434 (φ(|vi|)) output by the LUT 432 until a new value D437 (Σφ(|vi|)) from i=1 to i=dc) is output from the register 436, and supplies it as a 5-bit value D438 to the subtractor 437. The subtractor 437 subtracts the value D438 supplied from the FIFO memory 438, from the value D437 supplied from the register 436, and supplies the subtracted result as a 5-bit subtracted value D439 to the LUT 439. That is, the subtractor 437 subtracts, from the integrated value of φ(|vi|) determined from the decoding in-progress results D411 (the decoding in-progress results v) corresponding to all the 1s over one row of the check matrix, the decoding in-progress results corresponding to the edges to be determined, that is, φ(|vi|) determined from the decoding in-progress results D411 (the decoding in-progress results v) corresponding to predetermined 1s of the check matrix, and supplies the subtracted value (Σφ(|vi|)) from (i=1 to i=dc−1) as a subtracted value D439 to the LUT 439.
The LUT 439 outputs the 5-bit computation result D440 (φ−1(Σφ(|vi|))) such that the computation of φ−1 (Σφ(|vi|)) in equation (7) is performed on the subtracted value D439 (Σφ(|vi|) from i=1 to i=dc−1).
In parallel with the above processing, the EXOR circuit 440 performs a multiplication of sign bits by computing the exclusive OR of a 1-bit value D442 stored in the register 441 and the sign bit D432, and stores a 1-bit multiplication result D441 in the register 441 again. When the sign bit D432 determined from the decoding in-progress results D411 corresponding to all the 1s over one row of the check matrix is multiplied, the register 441 is reset.
When the multiplication results D441 (Πsign (vi)) from i=1 to dc) such that the sign bit D432 determined from the decoding in-progress results D411 corresponding to all the 1s over one row of the check matrix are stored in the register 441 is multiplied, the control signal D419 supplied from the control section 417 changes from “0” to “1”.
When the control signal D419 is “1”, the selector 442 selects the value stored in the register 441, that is, the value D442 (Πsign (vi) from i=1 to i=dc) such that the sign bit D432 determined from the decoding in-progress results D411 corresponding to all the 1s over one row of the check matrix is multiplied, and outputs the value as a 1-bit value D443 to the register 443. The register 443 supplies the stored value D443 as a 1-bit value D444 to a selector 442 and an EXOR circuit 445. When the control signal D419 is “0”, the selector 442 selects a value D444 supplied from the register 443, and outputs the value to the register 443, whereby it is stored again. That is, until the sign bit D432 determined from the decoding in-progress results D411 (the decoding in-progress results v) corresponding to all the 1s over one row of the check matrix is multiplied, the register 443 supplies the value stored at the previous time to the selector 442 and the EXOR circuit 445.
On the other hand, the FIFO memory 444 delays the sign bit D432 until a new value D444 (Πsign (vi) from i=1 to i=dc) is supplied from the register 443 to the EXOR circuit 445, and supplies it as a 1-bit value D445 to the EXOR circuit 445. The EXOR circuit 445 divides the value D444 by the value D445 by computing the exclusive OR of the value D444 supplied from the register 443 and the value D445 supplied from the FIFO memory 444, and outputs the 1-bit divided result as a divided value D446. That is, the EXOR circuit 445 divides the multiplied value of the sign bit D432 (sign (vi)) determined from the decoding in-progress results D411 corresponding to all the 1s over one row of the check matrix by the sign bit D432 (sign (vi)) determined from the decoding in-progress results D411 corresponding to predetermined 1s of the check matrix, and outputs the divided value (Πsign (vi)) from i=1 to i=dc−1) as a divided value D446.
In the calculator 4121, a total of six bits, in which the 5-bit computation results D440 output from the LUT 439 are the five lower-order bits and the 1-bit divided value D446 output from the EXOR circuit 445 is the highest-order bit, is output as the decoding in-progress results D412 (the decoding in-progress results uj).
As described above, in the calculator 4121, the computations of equation (7) and equation (8) are performed, and the decoding in-progress result uj is determined.
Since the maximum of the row weight of the check matrix of
In
In
Based on the control signal D422 supplied from the control section 417, the calculator 4151 of
More specifically, in the calculator 4151, the 6-bit decoding in-progress results D414 (the decoding in-progress results uj) corresponding to 1s of each row of the check matrix are read one-by-one from the cyclic shift circuit 414, and the decoding in-progress results D414 are supplied to the adder 471. Furthermore, in the calculator 4151, the 6-bit received data D417 is read one-by-one from the memory 416 for reception, and is supplied to the adder 475. Furthermore, a control signal D422 is supplied to the calculator 4151 from the control section 417, and the control signal D422 is supplied to the selector 473.
The adder 471 integrates the decoding in-progress results D414 by adding together the decoding in-progress results D414 (the decoding in-progress results uj) and the 9-bit integrated value D471 stored in the register 472, and stores the 9-bit integrated value in the register 472 again. When the decoding in-progress results D414 corresponding to all the 1s over one row of the check matrix are integrated, the register 472 is reset.
When the decoding in-progress results D414 over one row of the check matrix are read one-by-one and the value such that the decoding in-progress results D414 for one row are integrated is stored in the register 472, the control signal D422 supplied from the control section 417 changes from “0” to “1”. For example, when the weight of the column is “5”, the control signal D422 is “0” at the first clock up to the fourth clock, and is “1” at the fifth clock.
When the control signal D422 is “1”, the selector 473 selects the value stored in the register 472, that is, a 9-bit value 471 (Σuj from j=1 to dv) such that the decoding in-progress results D414 (the decoding in-progress results uj) from all the edges over one row of the check matrix are integrated, and outputs the value to the register 474, whereby it is stored. The register 474 supplies the stored value D471 as a 9-bit value D472 to the selector 471 and the adder 475. When the control signal D422 is “0”, the selector 473 selects the value D472 supplied from the register 474, and outputs the value to the register 474, whereby it is stored again. That is, until the decoding in-progress results D414 (the decoding in-progress results uj) from all the edges over one row of the check matrix are integrated, the register 474 supplies the previously integrated value to the selector 473 and the adder 475.
The adder 475 adds together the 9-bit value D472 and the 6-bit received data D417 supplied from the memory 416 for reception, and outputs the 6-bit value obtained thereby as the decoding in-progress result D415 (the decoding in-progress results v).
As described above, in the calculator 4151, the computation of equation (5) is performed, and the decoding in-progress result v is determined.
Since the maximum of the weights of the columns of the check matrix of
The memory 413 for storing decoding in-progress results includes switches 501 and 504, and two RAMs 502 and 503 for storing decoding in-progress results, which are single-port RAMs.
Before describing in detail each section of the memory 413 for storing decoding in-progress results, the method of storing data in the RAMs 502 and 503 for storing decoding in-progress results will be described first.
The RAMs 502 and 503 for storing decoding in-progress results store the decoding in-progress results D412 that are obtained as a result of the first computation and that are supplied via a switch 501.
More specifically, at the first address up to the ninth address of the RAM 502 for storing decoding in-progress results, the decoding in-progress results D412 (D501) corresponding to 1s from the first row up to the fifth row of the check matrix H of
More specifically, when the j-th row and the i-th column is denoted as (j, i), at the first address of the RAM 502 for storing decoding in-progress results, data corresponding to 1s of the 5×5 unit matrix from (1, 1) to (5, 5), which is a sub-matrix of the check matrix of
At the 10th address up to the 18th address of the RAM 502 for storing decoding in-progress, data corresponding to 1s from the 11th row up to the 15th row of the check matrix of
More specifically, for the sub-matrix whose weight is 2 or more, data (the decoding in-progress results of the messages corresponding to the edges belonging to the unit matrix, the quasi-unit matrix, or the shift matrix) corresponding to the positions of 1s of the unit matrix whose weight is 1, the quasi-unit matrix, or the shift matrix when the sub-matrix is represented in the form of the sum of two or more of the (P×P) unit matrix whose weight is 1, the quasi-unit matrix in which one or more 1s, which are the elements of the unit matrix, are substituted with 0, and a shift matrix in which the unit matrix or the quasi-unit matrix is cyclically shifted is stored at the same address.
Similarly, at the 19th address up to the 27th address of the RAM 502 for storing decoding in-progress, data corresponding to 1s from the 21th row up to the 25th row is stored in such a manner as to correspond to the check matrix of
At the first address up to the ninth address of a RAM 503 for storing decoding in-progress results, decoding in-progress results D412 (D502) corresponding to 1s from the sixth row up to the 10th row of the check matrix H of
More specifically, at the first address of the RAM 503 for storing decoding in-progress results, data corresponding to 1s of the first shift matrix making up the sum matrix from (6, 1) to (10, 5) (the sum matrix, which is the sum of a first shift matrix in which the 5×5 unit matrix is cyclically shifted by one to the right and a second shift matrix in which the unit matrix is cyclically shifted by two to the right), which is a sub-matrix of the check matrix is stored. At the second address, data corresponding to 1s of the second shift matrix making up the sum matrix from (6, 1) to (10, 5), which is a sub-matrix of the check matrix, is stored. Hereafter, also, at the third address up to the ninth address, data is stored in such a manner as to correspond to the sub-matrix of the check matrix.
Similarly, at the 10th address up to the 18th address of the RAM 503 for storing decoding in-progress, data corresponding to 1s from the 16th row up to the 20th row of the check matrix of
In the manner described above, the number of words of the RAMs 502 and 503 for storing decoding in-progress results is 27. That is, the number of words becomes a value such that 9, which is the row weight of the check matrix, is multiplied by 30, the number of rows, the multiplied result (the number of 1s of the check matrix) is divided by 5, the number of decoding in-progress results D501, which are read simultaneously, and further, the result is divided by 2, the number of RAM 502 for storing decoding in-progress results possessed by the memory 413 for storing decoding in-progress results.
A description will now be given in detail of the operation of each section of the memory 413 for storing decoding in-progress results of
When the first computation is performed by the calculation section 412, the decoding in-progress results D412 (uj) obtained as a result of the first computation are supplied from the calculation section 412 to the memory 413 for storing decoding in-progress results, and the decoding in-progress results D412 are written at a predetermined address of one of the RAM 502 for storing decoding in-progress results and the RAM 503 for storing decoding in-progress results. At the same time, the decoding in-progress results D412 (uj) obtained as a result of the first computation by the calculation section 412 at the previous time is read from the other RAM, and are output to the calculation section 412. On the other hand, when the second computation is performed by the calculation section 415, the memory 413 for storing decoding in-progress results does not perform writing into the RAM 502 for storing decoding in-progress results or the RAM 503 for storing decoding in-progress results, reads the decoding in-progress results from a predetermined address of one of the RAMs, and supplies them to the cyclic shift circuit 414.
The five decoding in-progress results D412 are supplied from the calculation section 412 to the switch 501, and also, a control signal D4201 indicating the selection of one of the RAM 502 for storing decoding in-progress results and the RAM 503 for storing decoding in-progress results as a memory for writing the decoding in-progress results D412 is supplied to the switch 501 from the control section 417. Based on the control signal D4201, the switch 501 selects one of the RAM 502 for storing decoding in-progress results and the RAM 503 for storing decoding in-progress results, and supplies the five decoding in-progress results D412 to the selected RAM.
The five decoding in-progress results D412 are supplied as decoding in-progress results D501 to the RAM 502 for storing decoding in-progress results from the switch 501, and also, a control signal D4202 indicating the address is supplied thereto from the control section 417. The RAM 502 for storing decoding in-progress results reads the five decoding in-progress results D501 obtained as a result of the first computation by the calculation section 412 at the previous time, which are already stored at the address indicated by the control signal D4022, and supplies them as decoding in-progress results D503 to the switch 504. Furthermore, the RAM 502 for storing decoding in-progress results stores (writes) the five decoding in-progress results D501 supplied from the switch 501 at the address indicated by the control signal D4022.
The five decoding in-progress results D412 are supplied as decoding in-progress results D502 to the RAM 503 for storing decoding in-progress results from the switch 501, and also, a control signal D4203 indicating the address is supplied to the RAM 503 from the control section 417. The RAM 503 for storing decoding in-progress results reads the five decoding in-progress results D502 obtained as a result of the first computation by the calculation section 412 at the previous time, which have already been stored at the address indicated by the control signal D4203, and supplies them as decoding in-progress results D504 to the switch 504. Furthermore, the RAM 502 for storing decoding in-progress results stores (writes) the five decoding in-progress results D502 supplied from the switch 501 at the address indicated by the control signal D4203.
The decoding in-progress results D503 are supplied to the switch 504 from the RAM 502 for storing decoding in-progress results or the decoding in-progress results D504 are supplied to the switch 504 from the RAM 503 for storing decoding in-progress results. Furthermore, a control signal D4204 indicating the selection one of the RAM 502 for storing decoding in-progress results and the RAM 503 for storing decoding in-progress results is supplied to the switch 504 from the control section 417. Based on the control signal D4201, the switch 504 selects one of the RAM 502 for storing decoding in-progress results and the RAM 503 for storing decoding in-progress results, and supplies the five decoding in-progress results supplied from the selected RAM, as the five decoding in-progress results D413, to the calculation section 412 and the cyclic shift circuit 414.
In
In the memory 413 for storing decoding in-progress results, when the first computation is to be performed by the calculation section 412, based on the control signal D4202, the RAM 502 for storing decoding in-progress results reads nine times decoding in-progress results D501 corresponding to 1s from the first row up to the fifth row of the check matrix, which are stored at the same address, from among the decoding in-progress results D501 obtained as a result of the first computation by the calculation section 412 at the previous time, which are already stored, in units of five results, and supplies them to the calculation section 412 via the switch 504. That is, since the row weight of the check matrix H of
Next, based on the control signal D4203, the RAM 503 for storing decoding in-progress results reads continuously nine times the decoding in-progress results D502 corresponding to 1s from the sixth row to the 10th row, which are stored at the same address, from among the decoding in-progress results D502 obtained as a result of the first computation by the calculation section 412 at the previous time, which are already stored, in units of five results, and supplies them to the calculation section 412 via the switch 504. At the same time, the five decoding in-progress results D412 corresponding to 1s from the first row to the fifth row of the check matrix, which are obtained as a result of the first computation that is being performed currently by the calculation section 412 are supplied as the decoding in-progress results D501 to the RAM 502 for storing decoding in-progress results via the switch 501. Based on the control signal D4202, the RAM 502 for storing decoding in-progress results continuously stores nine times the decoding in-progress results D501 at the address at which the already read decoding in-progress results D503 are stored.
Thereafter, based on the control signal D4202, the RAM 502 for storing decoding in-progress results continuously reads nine times the decoding in-progress results D501 corresponding to 1s from the 11th row up to the 15th row of the check matrix, which are stored at the same address, from among the already stored decoding in-progress results D501 obtained as a result of the first computation by the calculation section 412 at the previous time, in units of five results, and supplies them to the calculation section 412 via the switch 504. At the same time, five decoding in-progress results D412 corresponding to 1s from the sixth row up to the 10th row of the check matrix, which are obtained as a result of the first computation that is being currently performed by the calculation section 412, are supplied as the decoding in-progress results D502 to the RAM 503 for storing decoding in-progress results via the switch 501. Based on the control signal D4203, the RAM 503 for storing decoding in-progress results continuously stores nine times the decoding in-progress results D502 at the address at which the already read decoding in-progress results D504, are stored.
Hereafter, similarly, until the decoding in-progress results corresponding to all the 1s of the check matrix, which are obtained as a result of the first computation by the calculation section 412, are stored in the RAM 502 for storing decoding in-progress results or the RAM 503 for storing decoding in-progress results, the RAM 502 for storing decoding in-progress results and the RAM 503 for storing decoding in-progress results alternately perform the reading or writing in units of nine times.
In the memory 413 for storing decoding in-progress results, when the second computation is performed by the calculation section 415, based on the control signal D4202, the already stored decoding in-progress results D503, which are obtained as a result of the first computation, from the RAM 502 for storing decoding in-progress results, or based on the control signal D4203, the already stored decoding in-progress results D504 obtained as a result of the first computation, are read from the RAM 503 for storing decoding in-progress results, and the read-out decoding in-progress results are supplied to the cyclic shift circuit 414 via the switch 504.
In step S50, the cyclic shift circuit 414 cyclically shifts the five decoding in-progress results D413 to be stored in step S56 (to be described later), which are supplied from the memory 413 for storing decoding in-progress results, and supplies them to the calculation section 415.
More specifically, five decoding in-progress results D413 are supplied to the cyclic shift circuit 414 from the memory 413 for storing decoding in-progress results, and also, a control signal D421 indicating information (matrix data) as to the fact that 1s of the check matrix, which corresponds to the decoding in-progress results D413, are arranged as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 414 from the control section 417. Based on the control signal D421, the cyclic shift circuit 414 cyclically shifts (rearranges) the five decoding in-progress results D413, and supplies the results as decoding in-progress results D414 to the calculation section 415.
When the first computation has not yet been performed on the received data D417 supplied to the memory 416 for reception and the decoding in-progress results D413 are not stored in the memory 413 for storing decoding in-progress results, the calculation section 415 sets the decoding in-progress results uj to an initial value.
In step S51, the calculation section 415 performs the second computation, and supplies the decoding in-progress results D415, which are the results of the computation, to the memory 410 for storing decoding in-progress results.
More specifically, in step S50, the five decoding in-progress results D414 are supplied to the calculation section 415 from the cyclic shift circuit 414, and also, five received data D417 are supplied to the calculation section 415 from the memory 416 for received data. The decoding in-progress results D415 and the received data D417 are supplied individually to each of the calculators 4151 to 4155 of the calculation section 415. Furthermore, a control signal D422 is supplied to the calculation section 415 from the control section 417, and the control signal D422 is supplied to the calculator 4151 to 4155.
Based on the control signal D422, the calculators 4151 to 4155 each perform a computation in accordance with equation (5) by using the decoding in-progress results D414 and the received data D417, and supply the decoding in-progress results D415 (v) corresponding to the column of the check matrix, which are obtained as a result of the computation, to the memory 410 for storing decoding in-progress results.
After the processing of step S51, the process proceeds to step S52, where the memory 410 for storing decoding in-progress results stores the decoding in-progress results D415 supplied from the calculation section 415 in step S51 at the same address, and the process then proceeds to step S53.
In step S53, the control section 417 determines whether or not all the decoding in-progress results D415 corresponding to the columns of the check matrix have been computed by the calculation section 415. When it is determined that all the decoding in-progress results D415 have not been computed, the process returns to step S50, and the above-described processing is performed again.
On the other hand, when the control section 417 determines in step S53 that all the decoding in-progress results D415 corresponding to the column of the check matrix have been computed by the calculation section 415, the process proceeds to step S54, where the cyclic shift circuit 411 cyclically shifts the decoding in-progress results D410 (v) supplied from the memory 410 for storing decoding in-progress results.
More specifically, five decoding in-progress results D410 are supplied to the cyclic shift circuit 411 from the memory 410 for storing decoding in-progress results. Also, a control signal D418 indicating information (matrix data) as to the fact that 1s of the check matrix, which corresponds to the decoding in-progress results D410, are arranged as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 411 from the control section 417. Based on the control signal D418, the cyclic shift circuit 411 cyclically shifts (rearranges) the five decoding in-progress results D410, and supplies them as the decoding in-progress results D411 to the calculation section 412.
After the processing of step S54, the process proceeds to step S55, where the calculation section 412 performs the first computation, and supplies the decoding in-progress results D412, which are the computation results, to the cyclic shift circuit 414.
More specifically, the five decoding in-progress results D411 (v) are supplied to the calculation section 412 from the cyclic shift circuit 411 in step S54. Also, the five decoding in-progress results D412 (D413) (uj) obtained as a result of the first computation by the calculation section 412 at the previous time, which are already stored in step S56 (to be described later), are supplied to the calculation section 412. The decoding in-progress results D411 and the decoding in-progress results D413 are supplied individually to each of the calculators 4121 to 4125 of the calculation section 412. Furthermore, a control signal D419 is supplied to the calculation section 412 from the control section 417, and the control signal D419 is supplied to the calculator 4121 to 4125.
Based on the control signal D419, the calculators 4121 to 4125 each perform computations in accordance with equation (7) and equation (8) by using the decoding in-progress results D411 and the decoding in-progress results D413, and supply the decoding in-progress results D412 (uj) obtained as a result of the computation to the memory 413 for storing decoding in-progress results.
After the processing of step S55, the process proceeds to step S56, where the memory 413 for storing decoding in-progress results stores at the same address the five decoding in-progress results D412 supplied from the calculation section 412 in step S55, and the process then proceeds to step S57.
In step S57, the control section 417 determines whether or not the decoding in-progress results D412 corresponding to all the 1s of the check matrix have been computed by the calculation section 412. When it is determined that all the 1s of the check matrix have not been computed, the process returns to step S54, and the above-described processing is performed again.
On the other hand, when the control section 417 determines in step S57 that the decoding in-progress results D412 corresponding to all the 1s have been computed by the calculation section 412, the processing is completed.
The decoding apparatus 400 repeatedly performs the decoding process of
In the above description, although the memory 413 for storing decoding in-progress results is formed from two single-port RAMs, it may be formed from three or more RAMs if reading and writing do not occur simultaneously from and to one RAM. When the physical bit width of the RAM is not sufficient, by providing the same control signal by using a plurality of RAMs, these can be logically assumed as one RAM.
For the portions in which edge data (messages corresponding to edges) lacks, during the storage in the memory (when data is stored in the memories 410 and 413 for storing decoding in-progress results), no message is stored, and during the computation (during the first computation at the calculation section 412 and during the second computation at the calculation section 415), no computation is performed.
In a decoding apparatus 600 of
The decoding apparatus 600 includes a memory 610 for storing decoding in-progress results, a cyclic shift circuit 611, a calculation section 612 made up of five calculators 6121 to 6125, a memory 613 for storing decoding in-progress results, a cyclic shift circuit 614, a calculation section 615 made up of five calculators 6151 to 6155, a memory 616 for reception, and a control section 617.
Referring to
In the decoding apparatus 600 of
More specifically, the calculator 612k of
On the other hand, the calculator 615k of
The calculator 612k of
Therefore, it is possible for the decoding apparatus 600 of
In the calculator 615k of
Next, by using equations, a description is given of the computations performed by the calculator 6121 to the calculator 6125 of the calculation section 612 and the computations performed by the calculator 6151 to the calculator 6155 of the calculation section 615.
The calculation section 612 performs a first computation in accordance with equation (9), and supplies the decoding in-progress results w, which are the results of the first computation, to the memory 613 for storing decoding in-progress results, whereby they are stored. The calculation section 615 performs the above-described equation (1) and the second computation in accordance with equations (10) and (11), and supplies decoding in-progress results vi′, which are the results of the second computation, to the memory 610 for storing decoding in-progress results, whereby they are stored.
uj=φ−1(|w|−|vi′|)×sign(vi′)×sign(w) (10)
vi′=φ(|vi|)×sign(vi) (11)
More specifically, the decoding in-progress results w obtained as a result of the first computation in accordance with equation (9) are such that the total sum of the absolute values |vi′| of the decoding in-progress results vi′ of the check node computation, corresponding to all the 1s of the j-th row of the check matrix H, which are obtained as a result of the second computation in accordance with equation (1), equation (10), and equation (11), and the sign bit sign (vi′) are multiplied together. Therefore, as shown in equation (10), uj obtained by the check node computation in accordance with equation (7) can be expressed by using a value such that the absolute value |vi′| of the decoding in-progress results vi′, corresponding to the edge to be determined, from among (a plurality of) decoding in-progress results vi′ corresponding to “1s” (edges) of each column, of the j-th row of the check matrix H, is subtracted from the absolute values |w| of the decoding in-progress results w, which are obtained as a result of the first computation in accordance with equation (9).
In the decoding apparatus 600, the first computation in accordance with the equation (9) by the calculation section 612, and the second computation in accordance with equation (1), equation (10), and equation (11) are alternately performed, and the calculation section 615 performs a computation in accordance with equation (5) by using the results of the final first computation, and outputs the computation results as the decoded results, thereby performing iterative decodings of LDPC codes.
More specifically, in the decoding apparatus 600, the calculation section 612 performs the first computation by using the decoding in-progress results vi′ corresponding to all the 1s of the j-th row of the check matrix H, which are the results of the second computation by the calculation section 615, and stores the decoding in-progress results w corresponding to each row of the check matrix, which are obtained as a result of the computation, in the memory 613 for storing decoding in-progress results. Therefore, the capacity of the memory 613 for storing decoding in-progress results becomes a value such that the number of rows of the check matrix, which is smaller than the number of “1s” of the check matrix, and the number of quantization bits of the decoding in-progress results w are multiplied together. The calculation section 615 performs the second computation by using the decoding in-progress results w corresponding to each row of the i-th column of the check matrix H, which are the results of the first computation by the calculation section 612, and the received value u0i, and stores the decoding in-progress results vi′ of the check node computation corresponding to 1s (edges) of the i-th column of the check matrix, which are obtained as a result of the computation, in the memory 610 for storing decoding in-progress results. Therefore, the capacity necessary for the memory 610 for storing decoding in-progress results becomes a value such that the number of 1s of the check matrix and the number of quantization bits of the decoding in-progress results vi′ are multiplied together similarly to the edge data storage memory 311 of
Therefore, in the decoding method 600, when compared to the edge data storage memory 311 of
The operation of each section of the decoding apparatus 600 of
Based on a control signal D618, the memory 610 for storing decoding in-progress results collectively stores the five decoding in-progress results D615 supplied from the calculation section 615, and at the same time, reads the five already stored decoding in-progress results D615, and supplies them as decoding in-progress results D610 to the cyclic shift circuit 611 and the calculation section 615. That is, the memory 610 for storing decoding in-progress results simultaneously performs the reading of the decoding in-progress results D610 to be supplied to the cyclic shift circuit 611 and the writing of the decoding in-progress results D615 supplied from the calculation section 615.
In the memory 610 for storing decoding in-progress results, the decoding in-progress results vi′ (the second decoding in-progress results) corresponding to 1s (edges) of the check matrix, which are computed by the second computation by the calculation section 615, are stored. Therefore, the amount of data stored in the memory 610 for storing decoding in-progress results, that is, the storage capacity required for the memory 610 for storing decoding in-progress results, becomes the multiplied value of the number of quantization bits of the decoding in-progress results and the number of 1s (the total number of the edges).
The memory 610 for storing decoding in-progress results includes, for example, two single-port RAMs capable of simultaneously reading and writing five decoding in-progress results. Five decoding in-progress results D615 are supplied to the memory 610 for storing decoding in-progress results from the calculation section 615, and also, a control signal D618 for controlling the reading and writing of the decoding in-progress results D615 is supplied to the memory 610 from the control section 617.
Five decoding in-progress results D610 are supplied to the cyclic shift circuit 611 from the memory 610 for storing decoding in-progress results. Also, a control signal D619 indicating information (matrix data) as to the fact that 1s of the check matrix, which corresponds to the decoding in-progress results D610, are arranged as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 611 from the control section 617. Based on the control signal D619, the cyclic shift circuit 611 performs a cyclic shifting of rearranging the five decoded results D610, and supplies the results as decoding in-progress results D611 to the calculation section 612.
The calculation section 612 includes five calculators 6121 to 6125. The five decoding in-progress results D611 (second decoding in-progress results) (vi′) are supplied to the calculation section 612 from the cyclic shift circuit 611, and the five decoding in-progress results D611 (the first decoding in-progress results) (w) are supplied to the calculators 6121 to 6125, respectively. A control signal D620 is supplied to the calculation section 612 from the control section 617, and the control signal D620 is supplied to the calculators 6121 to 6125. The control signal D620 is a signal common to the five calculators 6121 to 6125.
The calculators 6121 to 6125 each perform the first computation by using the decoding in-progress results D611 in accordance with equation (9) in order to determine decoding in-progress results D612 (w). The calculation section 612 supplies the five decoding in-progress results D612, which are obtained as a result of the computations by the calculators 6121 to 6125, to the memory 613 for storing decoding in-progress results.
The five decoding in-progress results D612 corresponding to the row of the check matrix, which are the results of the first computation by the calculation section 612, are supplied to the memory 613 for storing decoding in-progress results from the calculation section 612. The memory 613 for storing decoding in-progress results stores the five decoding in-progress results D612 supplied from the calculation section 612 in sequence starting from the first address.
More specifically, at the first address of the memory 613 for storing decoding in-progress results, the decoding in-progress results w from the first row up to the fifth row from among the decoding in-progress results corresponding to the row of the check matrix are stored. Similarly, at the second address, the decoding in-progress results w from the sixth row up to the 10th row are stored, and at the third address, the decoding in-progress results w from the 11th row up to the 15th row are stored. Hereafter, similarly, the decoding in-progress results w from the 16th row up to the 30th row are stored at the fourth address up to the sixth address in units of five results, and a total of 60 decoding in-progress results w are stored in the memory 613 for storing decoding in-progress results. Therefore, the number of words of the memory 610 for storing decoding in-progress results becomes 6 such that 30, the number of rows of the check matrix H of
The memory 613 for storing decoding in-progress results simultaneously reads five decoding in-progress results w, which are “1s” in the column of the check matrix H, to which the decoding in-progress results vi′ to be determined by the calculation section 615 correspond, from the five already stored decoding in-progress results D613, and supplies them as decoding in-progress results D613 to the cyclic shift circuit 614.
The memory 613 for storing decoding in-progress results includes, for example, a single-port RAM capable of simultaneously reading and writing five decoding in-progress results. Since the decoding in-progress results w corresponding to the row, which are computed by the first computation of the calculation section 612, are stored in the memory 613 for storing decoding in-progress results, the amount of data stored in the memory 613 for storing decoding in-progress results, that is, the storage capacity required for the memory 613 for storing decoding in-progress results, becomes the multiplied value of the number of quantization bits of the decoding in-progress results and the number of rows of the check matrix H.
The five decoding in-progress results D613 (the decoding in-progress results w) are supplied to the cyclic shift circuit 614 from the memory 613 for storing decoding in-progress results. Also, a control signal D621 indicating information (matrix data) as to the fact that 1s of the check matrix, which corresponds to the decoding in-progress results D613, are arranged as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 614 from the control section 617. Based on the control signal D621, the cyclic shift circuit 614 performs a cyclic shifting of rearranging the five decoding in-progress results D613, and supplies the results as the decoding in-progress results D614 to the calculation section 615.
The calculation section 615 includes five calculators 6151 to 6155. Five decoding in-progress results D614 (w) are supplied to the variable node calculation section 615 from the cyclic shift circuit 614, and also, five decoding in-progress results D610 (vi′) are supplied to the variable node calculation section 615 from the memory 610 for storing decoding in-progress results. The decoding in-progress results D614 and the decoding in-progress results D610 are supplied to each of the calculators 6151 to 6155. Five pieces of received data D617 are supplied to the calculation section 615 from the memory 617 for reception, and the pieces of received data D617 are supplied individually to each of the calculators 6151 to 6155. Furthermore, a control signal D622 is supplied to the calculation section 617 from the control section 617, and the control signal D622 is supplied to the calculators 6151 to 6155. The control signal D622 is a signal common to the five calculator 6171 to 6175.
The calculators 6151 to 6155 each perform the second computation in accordance with equation (1), equation (10), and equation (11) by using the decoding in-progress results D614 and D611, and the received data D617 (LDPC CODES) in order to determine five decoding in-progress results D615 (vi′) corresponding to 1s of each column of the check matrix. The calculation section 615 supplies the five decoding in-progress results D615, which are obtained as a result of the second computation by the calculators 6151 to 6155, to the memory 610 for storing decoding in-progress results.
The memory 616 for reception stores, as the received data D617, the reception LLR (log likelihood ratio) that is the 0-likeness value of the sign bit, which is calculated from the received value (sign bit) received through the communication channel.
More specifically, at the first address of the memory 616 for reception, the received data D617 corresponding to the first column up to the fifth column of the check matrix from among the received data D617 corresponding to the column of the check matrix is stored. At the second address, the received data D617 from the sixth column up to the 10th column of the check matrix is stored, and at the third address, the received data D617 from the 11th column up to the 16th of the check matrix is stored. Hereafter, similarly, at the fourth address up to the 18th address, the received data D617 corresponding to the 17th column up to the 90th column is stored in units of five pieces of the data.
Then, the memory 616 for reception simultaneously reads the already stored received data D617, in the sequence necessary for the second computation by the calculation section 615 in units of five pieces of the data, and supplies them to the calculation section 615.
The memory 616 for reception includes, for example, a single-port RAM. The amount of data stored in the memory 616 for reception, that is, the storage capacity necessary for the memory 616 for reception, is the multiplied value of the code length of the LDPC codes and the number of quantization bits of the received data. Furthermore, the number of words of the memory 616 for reception is 18 such that the code length of the LDPC codes, that is, 90, the number of columns of the check matrix, is divided by 5, the number of pieces of the received data D617, which are simultaneously read.
The control section 617 supplies the control signal D618 to the memory 610 for storing decoding in-progress results and supplies the control signal D619 to the cyclic shift circuit 611 in order to control them, respectively. Furthermore, the control section 617 supplies the control signal D620 to the calculation section 612 and supplies the control signal D621 to the cyclic shift circuit 614 in order to control them, respectively.
As a result of the data being circulated in the order of the memory 610 for storing decoding in-progress results, the cyclic shift circuit 611, the calculation section 612, the memory 613 for storing decoding in-progress results, the cyclic shift circuit 614, and the calculation section 615, the decoding apparatus 600 can perform one decoding. In the decoding apparatus 600, after decodings are performed repeatedly a predetermined number of times, the calculation section 615 performs a computation in accordance with equation (5), and the computation results are output as the final decoded results.
In
Furthermore, in
Based on the control signal D620 supplied from the control section 617, the calculator 6121 of
More specifically, one decoding in-progress result D611 from among the five 6-bit decoding in-progress results D611 (vi′) supplied from the cyclic shift circuit 611 is supplied to the calculator 6121, the sign bit D631, which is the highest-order bit, is supplied to the EXOR circuit 635, and the absolute value D632 (|vi′|), which is the five lower-order bits of the 6-bit decoding in-progress results D611 (vi′), are supplied to the adder 631. Furthermore, the control signal D620 is supplied to the calculator 6121 from the control section 617, and the control signal D620 is supplied to the selector 633 and the selector 637.
The adder 631 integrates the absolute values D632 (|vi′|) by adding together the absolute value D632 (|vi|) and the 9-bit value D633 stored in the register 632, and stores the 9-bit integrated value obtained as a result in the register 632 again. When the absolute values D632 (|vi|) determined from the decoding in-progress results D611 corresponding to all the 1s over one row of the check matrix are integrated, the register 632 is reset.
When the decoding in-progress results D611 over one row of the check matrix are read one-by-one and the integrated value such that the absolute values D632 for one row are integrated is stored in the register 632, the control signal D620 supplied from the control section 617 changes from 0 to 1. For example, when the row weight is “9”, the control signal D620 is “0” at the first to eighth clocks, and is “1” at the ninth clock.
When the control signal D620 is “1”, the register 632 selects the value stored in the selector 633, that is, a 9-bit value D633 (Σ|vi′| from i=1 to i=dc) such that the absolute values D632 (|vi′|)) of the decoding in-progress results D611 (the decoding in-progress results vi′) corresponding to all the 1s over one row of the check matrix are integrated, and outputs the value as a value D634 to the register 634, whereby it is stored. The register 634 supplies the stored value D634 as a 9-bit value D635 to the selector 633, and also, outputs it. When the control signal D620 is “0”, the selector 633 selects the value D635 supplied from the register 634, and outputs the value to the register 634, whereby it is stored again. That is, until the absolute values D632 (|vi′|) of the decoding in-progress results D611 (the decoding in-progress results vi′) corresponding to all the 1s over one row of the check matrix are integrated, the register 634 supplies the previously integrated |vi′| to the selector 633, and also, outputs it.
In parallel with the above processing, the EXOR circuit 635 performs a multiplication of the sign bits by computing the exclusive OR of a 1-bit value D637 stored in the register 636 and the sign bit D631, and stores the 1-bit multiplication result D636 in the register 636 again. When the sign bits D631 of the decoding in-progress results D611 corresponding to all the 1s over one row of the check matrix are multiplied, the register 636 is reset.
When the multiplication results D636 (Πsign (vi′) from i=1 to dc) such that the sign bits D631 determined from the decoding in-progress results D611 corresponding to all the 1s over one row of the check matrix are multiplied are stored in the register 636, the control signal D620 supplied from the control section 617 changes from “0” to “1”.
When the control signal D620 is “1”, the selector 637 selects the value stored in the register 636, that is, the value D637 (Πsign (vi′) from i=1 to i=dc) such that the sign bits D631 of the decoding in-progress results D611 corresponding to all the 1s over one row of the check matrix are multiplied, and outputs the value as a 1-bit value D638 to the register 638, whereby it is stored. The register 638 supplies the stored value D638 as a 1-bit value D639 to the selector 637, and outputs it. When the control signal D620 is “0”, the selector 637 selects the value D639 supplied from the register 638, and outputs the value to the register 638, whereby it is stored again. That is, until the sign bits D631 of the decoding in-progress results D611 (the decoding in-progress results vi′) corresponding to all the 1s over one row of the check matrix are multiplied, the register 638 supplies the previously stored value to the selector 637 and outputs it.
In the calculator 6121, a total of 10 bits, in which the 9-bit value D635 (Σ|vi′| from i=1 to i=dc) output from the register 634 is made to be the nine lower-order bits and the 1-bit value D639 (sign (vi′) output from the register 638 is made to be the highest-order bit, are output as the decoding in-progress results D612 (the decoding in-progress results w).
As described above, in the calculator 6121, the computation of equation (9) is performed, and the decoding in-progress result w is determined.
In
Furthermore, in
Based on the control signal D622 supplied from the control section 617, the calculator 6151 of
More specifically, in the calculator 6151, the 10-bit decoding in-progress results D614 (the decoding in-progress results w) corresponding to the row of the check matrix are read one-by-one from the cyclic shift circuit 614. The 6-bit decoding in-progress results D610 (the decoding in-progress results vi′) obtained previously as a result of the second computation by the calculation section 615 are read one-by-one from the memory 610 for storing decoding in-progress results. The sign bit D651 (sign (w)) of the highest-order bit of the decoding in-progress results D614 and the sign bit D653 (sign (uj)) of the highest-order bit of the decoding in-progress results D610 are supplied to the EXOR circuit 653. An absolute value D652 (|w|)) of the nine lower-order bits of the decoding in-progress results D614 and the sign bit D653 (|vi′|) of the nine lower-order bits of the decoding in-progress results D610 are supplied to a subtractor 651. Furthermore, in the calculator 6151, the pieces of the 6-bit received data D617 are read one-by-one from the memory 616 for reception, and are supplied to an adder 658. Furthermore, in the calculator 6151, the control signal D622 is supplied from the control section 617, and the control signal D622 is supplied to the selector 656.
The subtractor 651 subtracts the absolute value D654 from the absolute value D652, and supplies a 5-bit subtracted value D655 to an LUT 652. The LUT 652 outputs the 5-bit computation result D656 (φ−1(|w|−|vi′|)) such that the computation of φ−1 is performed on the subtracted value D655.
On the other hand, the EXOR circuit 653 multiplies together the sign bit D651 and the sign bit D653 by computing the exclusive OR of the sign bit D651 (sign (w)) and the sign bit D653 (sign (vi′)), and outputs a 1-bit multiplication result as a multiplied value D657. Then, a 6-bit value D658, in which the 5-bit computation results D656 supplied from the LUT 652 are made to be the five lower-order bits (φ−1(|w|−|vi′|)) and the 1-bit value D657 (sign (w)×sign (vi′)) supplied from the EXOR circuit 653 is made to be the highest-order bit, is supplied to an adder 654, and is also supplied to an FIFO memory 659.
In the manner described above, the computation in accordance with equation (10) is performed, and the 6-bit value D658 (uj), which is the result of the computation, is supplied to the adder 654 and is also supplied to the FIFO memory 659.
The adder 654 integrates the values D658 by adding together the 6-bit value D658 (uj) and the 9-bit value D659 stored in the register 655, and stores the 9-bit integrated value obtained as a result in the register 655 again. When the value D658 corresponding to all the 1s over one column of the check matrix are integrated, the register 655 is reset.
When the values D658 over one column of the check matrix are read one-by-one and the value such that the values D658 for one column are integrated is stored in the register 655, the control signal D622 supplied from the control section 617 changes from “0” to “1”. For example, when the column weight is “5”, the control signal D622 is “0” at the first to fourth clocks, and is “1” at the fifth clock.
When the control signal D622 is “1”, the selector 656 selects the value stored in the register 655, that is, a 9-bit value D659 (Σuj from j=1 to dv) such that the value D658 (uj) corresponding to 1s over one column of the check matrix are integrated, and outputs the value to the register 657, whereby it is stored. The register 657 supplies the stored value D659 as a 9-bit value D660 to a selector 471 and an adder 658. When the control signal D622 is “0”, the selector 656 selects the value D660 supplied from the register 657, and outputs the value to the register 657, whereby it is stored again. That is, until the values D658 (uj) corresponding to 1s over one column of the check matrix are integrated, the register 657 supplies the previously integrated value to the selector 656 and the adder 658.
The adder 658 adds together the 9-bit value D660 and the 6-bit received data D617 supplied from the memory 616 for reception, and supplies the 9-bit value D661 obtained as a result.
In the calculator 615, when the final computation is to be performed, the adder 658 outputs the 9-bit value D661 as the final decoded results. That is, the calculation section 615 performs a computation in accordance with equation (5).
On the other hand, until a new value D660 (Σuj from j=1 to j=dv) is output from the register 665, the FIFO memory 659 delays the 6-bit value D658 (uj), and supplies the value as a 6-bit value D662 to the subtractor 660. The subtractor 660 subtracts the 6-bit value D662 from the 9-bit value D660, and outputs the subtracted value D663. That is, the subtractor 660 subtracts the value corresponding to the edge to be determined, that is, the value D658 (uj) corresponding to predetermined 1s of the check matrix, from the integrated value of the values D658 corresponding to 1s over one column of the check matrix, and outputs the subtracted value (Σuj from i=1 to i=dc−1) as a 6-bit subtracted value D663.
In the manner described above, the computation in accordance with equation (1) is performed, and the 6-bit subtracted value D663 (vi), which is the result of the computation, is output. Then, the absolute value (|vi|) of the five lower-order bits of the 6-bit subtracted value D663 output from the subtractor 660 is supplied to the LUT 661, and the sign bit (sign (vi)) of the highest-order bit is output as a value D665.
The LUT 661 outputs the 5-bit computation results D666 (φ(|vi|)) such that the computation of φ is performed on the absolute value (|vi|). Then, the LUT 661 supplies, as decoding in-progress results (vi′), a total of six bits, in which the 5-bit computation result D666 (φ(|vi|)) output from the LUT 661 is made to be the five lower-order bits and the value D665 (sign (vi)) is made to be the highest-order bit, to the memory 610 for storing decoding in-progress results.
As described above, in the calculator 6151, the computations of equation (1), equation (10), and equation (11) are performed, and the decoding in-progress results vi′ are determined.
The maximum of the column weight of the check matrix of
The memory 610 for storing decoding in-progress results includes switches 701 and 704, and RAMs 702 and 703 for storing decoding in-progress results, which are two single-port RAMs.
Before each section of the memory 610 for storing decoding in-progress results is described in detail, the method for storing data in the RAMs 702 and 703 for storing decoding in-progress results will be described first.
The RAMs 702 and 703 for storing decoding in-progress results store the decoding in-progress results D615 that are obtained as a result of the first computation by the calculation section 612 and that are supplied via the switch 701.
More specifically, at the first address up to the fifth address of the RAM 702 for storing decoding in-progress results, the decoding in-progress results D615 (D701) corresponding to 1s from the 1st column up to the fifth column of the check matrix H of
More specifically, when the j-th row and the i-th column is denoted as (j, i), at the first address of the RAM 702 for storing decoding in-progress results, data corresponding to 1s of the 5×5 unit matrix from (1, 1) to (5, 5) of the check matrix of
At the sixth address up to the 10th address of the RAM 702 for storing decoding in-progress, data corresponding to 1s from the 11th column up to the 15th column of the check matrix of
Similarly, at the 10th address up to the 28th address of the RAM 702 for storing decoding in-progress, in such a manner as to correspond to the check matrix of
At the first address to the fifth address of the RAM 703 for storing decoding in-progress results, the decoding in-progress results D615 (D702) corresponding to 1s from the sixth column up to the 10th column of the check matrix H of
More specifically, at the first address of the RAM 703 for storing decoding in-progress results, data corresponding to 1s of the first shift matrix forming the sum matrix from (6, 1) to (10, 5) (the sum matrix, which is the sum of the first shift matrix in which the 5×5 unit matrix is cyclically shifted by one to the right, and the second shift matrix in which the unit matrix is cyclically shifted by two to the right), which is the sub-matrix of the check matrix, is stored. At the second address, data corresponding to 1s of the second shift matrix forming the sum matrix from (6, 1) to (10, 5), which is the sub-matrix of the check matrix, is stored. Hereafter, similarly, at the third address to the fifth address, also, data is stored in such a manner as to correspond to the sub-matrix of the check matrix.
Similarly, at the sixth address up to the second 6 address of the RAM 703 for storing decoding in-progress, data corresponding to 1s from the 16th column up to the 20th column of the check matrix of
As described above, the number of words of the RAM 702 for storing decoding in-progress results is 28, and the number of words RAM 703 for storing decoding in-progress results is 26.
In
In the memory 610 for storing decoding in-progress results, when the first computation by the calculation section 612 is to be performed, based on a control signal D7202 supplied from the control section 617, the already stored decoding in-progress results D703 obtained as a result of the second computation are read from the RAM 702 for storing decoding in-progress results, or based on the control signal D7203 supplied from the control section 617, the already stored decoding in-progress results D704 obtained as a result of the second computation are read from the RAM 703 for storing decoding in-progress results. The read decoding in-progress results are supplied to the cyclic shift circuit 614 via the switch 704.
When the second computation is to be performed by the calculation section 615, the decoding in-progress results D615 (vi′) obtained as a result of the second computation are supplied to the memory 610 for storing decoding in-progress results from the calculation section 615. At the same time when the decoding in-progress results D615 are written at a predetermined address of one of the RAM 702 for storing decoding in-progress results and the RAM 703 for storing decoding in-progress results, the decoding in-progress results D610 (vi′) obtained previously as a result of the second computation by the calculation section 615 are read from the other RAM, and are output to the calculation section 615 via the cyclic shift circuit 614.
The five decoding in-progress results D615 are supplied to the switch 701 from the calculation section 615, and also, a control signal D7201 indicating the selection one of the RAM 702 for storing decoding in-progress results and the RAM 703 for storing decoding in-progress results as a memory for writing the decoding in-progress results D615 is supplied to the switch 701. Based on the control signal D7201, the switch 701 selects one of the RAM 702 for storing decoding in-progress results and the RAM 703 for storing decoding in-progress results, and supplies the five decoding in-progress results D612 to the selected one of them.
The five decoding in-progress results D612 are supplied as decoding in-progress results D701 to the RAM 702 for storing decoding in-progress results from the switch 701, and also, a control signal D7022 indicating the address is supplied thereto from the control section 617. The RAM 702 for storing decoding in-progress results reads the five decoding in-progress results D701 obtained previously as a result of the second computation by the calculation section 615, which are already stored at the address indicated by the control signal D7202, and supplies them as the decoding in-progress results D703 to the switch 704. Furthermore, the RAM 702 for storing decoding in-progress results stores (writes) the five decoding in-progress results D702 supplied from the switch 701 at the address indicated by the control signal D7202.
The five decoding in-progress results D615 are supplied as decoding in-progress results D702 to the RAM 703 for storing decoding in-progress results from the switch 701, and also, a control signal D7203 indicating the address is supplied thereto from the control section 617. The RAM 703 for storing decoding in-progress results reads the five decoding in-progress results D702 obtained previously as a result of the second computation by the calculation section 615, which are already stored at the address indicated by the control signal D7203, and supplies them as decoding in-progress results D704 to the switch 704. Furthermore, the RAM 702 for storing decoding in-progress results stores (writes) the five decoding in-progress results D702 supplied from the switch 701 at the address indicated by the control signal D7203.
The decoding in-progress results D703 are supplied to the switch 704 from the RAM 702 for storing decoding in-progress results, or the decoding in-progress results D704 are supplied thereto from the RAM 703 for storing decoding in-progress results. Furthermore, a control signal D7204 indicating the selection of one of the RAM 702 for storing decoding in-progress results and the RAM 703 for storing decoding in-progress results is supplied thereto from the control section 617. Based on the control signal D7204, the switch 704 selects one of the RAM 702 for storing decoding in-progress results and the RAM 703 for storing decoding in-progress results, and supplies the five decoding in-progress results supplied from the selected RAM are supplied as the five decoding in-progress results D610 to the calculation section 615.
In the memory 610 for storing decoding in-progress results, when the second computation is to be performed by the calculation section 615, based on the control signal D7202, the RAM 702 for storing decoding in-progress results reads five times the decoding in-progress results D701 corresponding to 1s from the 1st column up to the fifth column of the check matrix, which are stored at the same address, from among the already stored decoding in-progress results D701 obtained previously as a result of the second computation by the calculation section 615 in units of five results, and supplies them to the calculation section 615 via the switch 704. That is, since the column weight of the check matrix H of
Next, based on the control signal D7203, the RAM 703 for storing decoding in-progress results continuously reads five times the five decoding in-progress results D702 corresponding to 1s from the sixth column to the 10th column of the check matrix, which are stored at the same address, from among the decoding in-progress results D702 obtained previously as a result of the second computation by the calculation section 615, which are already stored, and supplies them to the calculation section 615 via the switch 704 and the cyclic shift circuit 614. At the same time, the five decoding in-progress results D615 corresponding to 1s from the 1st column up to the fifth column of the check matrix obtained as a result of the second computation that is currently being performed by the calculation section 615 are supplied as the decoding in-progress results D701 to the RAM 702 for storing decoding in-progress results via the switch 701. Based on the control signal D7202, the RAM 702 for storing decoding in-progress results continuously stores five times the decoding in-progress results D701 at the address at which the already read decoding in-progress results D703 are stored.
Thereafter, based on the control signal D7202, the RAM 702 for storing decoding in-progress results continuously reads five times the decoding in-progress results D701 corresponding to 1s from the 11th column up to the 15th column of the check matrix, which are stored at the same address, from among the already stored decoding in-progress results D701 obtained previously as a result of the second computation by the calculation section 615 in units of five results, and supplies them to the calculation section 615 via the switch 704. At the same time, the five decoding in-progress results D612 corresponding to 1s from the sixth column up to the 10th column of the check matrix, which are obtained as a result of the second computation that is currently being performed by the calculation section 615, are supplied as the decoding in-progress results D702 to the RAM 703 for storing decoding in-progress results via the switch 701. Based on the control signal D7203, the RAM 703 for storing decoding in-progress results continuously stores five times the already read decoding in-progress results D702 at the address at which the decoding in-progress results D704 are stored.
Hereafter, similarly, until the decoding in-progress results corresponding to all the 1s, which are obtained as a result of the second computation by the calculation section 615, are stored in the RAM 702 for storing decoding in-progress results or the RAM 703 for storing decoding in-progress results, the RAM 702 for storing decoding in-progress results and the RAM 703 for storing decoding in-progress results alternately perform reading and writing of five times.
In step S70, the cyclic shift circuit 614 performs a cyclic shifting of rearranging the five decoding in-progress results D613 stored in step S76 (to be described later), which are supplied from the memory 613 for storing decoding in-progress results, and supplies them to the calculation section 615.
More specifically, the five decoding in-progress results D613 are supplied to the cyclic shift circuit 614 from the memory 613 for storing decoding in-progress results. Also, a control signal D621 indicating information (matrix data) as to the fact that 1s of the check matrix, which corresponds to the decoding in-progress results D613, are arranged as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 614 from the control section 617. Based on the control signal D621, the cyclic shift circuit 614 cyclically shifts (rearranges) the five decoding in-progress results D613, and supplies them as the decoding in-progress results D614 to the calculation section 615.
When the first computation has not been performed on the received data D617 supplied from the memory 616 for reception and the decoding in-progress results D612 have not been stored in the memory 613 for storing decoding in-progress results, the calculation section 615 sets the result to an initial value.
In step S71, the calculation section 615 performs the second computation, and supplies the decoding in-progress results D615, which are the results of the computation, to the memory 610 for storing decoding in-progress results.
More specifically, the five decoding in-progress results D614 are supplied to the calculation section 615 from the cyclic shift circuit 614 in step S70, and the previous decoding in-progress results D610 are supplied thereto from the memory 610 for storing decoding in-progress results in step S72 (to be described later). Five pieces of received data D617 are supplied from the memory 616 for received data, and the five decoding in-progress results D615 and D610, and the received data D617 are supplied individually to each of the calculators 6151 to 6155 of the calculation section 615. Furthermore, the control signal D622 is supplied to the calculation section 615 from the control section 617, and the control signal D622 is supplied to the calculators 6151 to 6155.
Based on the control signal D622, the calculators 6151 to 6155 each perform a computation in accordance with equation (1), equation (10), and equation (11) by using the decoding in-progress results D614 and D610 and the received data D617, and supply the decoding in-progress results D615 (vi′) corresponding to 1s of each column of the check matrix, which are obtained as a result of the computation, to the memory 610 for storing decoding in-progress results.
After the processing of step S71, the process proceeds to step S72, where the memory 610 for storing decoding in-progress results stores the decoding in-progress results D615 supplied from the calculation section 615 in step S71 at the same address, reads the already stored decoding in-progress results D615 (D610), and supplies them to the cyclic shift circuit 611 and the calculation section 615.
After the processing of step S72, the process proceeds to step S73, where the control section 617 determines whether or not all the decoding in-progress results D615 corresponding to 1s of each column of the check matrix have been computed by the calculation section 615. When the control section 617 determines that all the decoding in-progress results D615 have not been computed, the process returns to step S70, and the above-described processing is performed again.
On the other hand, when the control section 617 determines in step S73 that all the decoding in-progress results D615 have been computed by the calculation section 615, the process proceeds to step S74, where the cyclic shift circuit 611 cyclically shifts the decoding in-progress results D610 (vi′) supplied from the memory 610 for storing decoding in-progress results.
More specifically, the five decoding in-progress results D610 are supplied to the cyclic shift circuit 611 from the memory 610 for storing decoding in-progress results. Also, a control signal D619 indicating information (matrix data) as to the fact that 1s of the check matrix, which corresponds to the decoding in-progress results D610, are arranged as a result of how many times, for example, the unit matrix forming the basis in the check matrix is cyclically shifted, is supplied to the cyclic shift circuit 611 from the control section 617. Based on the control signal D619, the cyclic shift circuit 611 cyclically shifts (rearranges) the five decoding in-progress results D610, and supplies them as the decoding in-progress results D611 to the calculation section 612.
After the processing of step S74, the process proceeds to step S75, where the calculation section 612 performs the first computation, and supplies the decoding in-progress results D612, which are the results of the computation, to the cyclic shift circuit 614.
More specifically, the five decoding in-progress results D611 (vi′) are supplied to the calculation section 612 from the cyclic shift circuit 611 in step S74, and the decoding in-progress results D611 are supplied individually to each of the calculators 6121 to 6125 of the calculation section 612. Furthermore, the control signal D621 is supplied to the calculation section 612 from the control section 617, and the control signal D621 is supplied to the calculators 6121 to 6125.
Based on the control signal D619, the calculators 6121 to 6125 each perform a computation in accordance with equation (9) by using the decoding in-progress results D611, and supply the decoding in-progress results D612(w) corresponding to the row of the check matrix, which are obtained as a result of the computation, to the memory 613 for storing decoding in-progress results.
After the processing of step S75, the process proceeds to step S76, where the memory 613 for storing decoding in-progress results stores the decoding in-progress results D612 supplied from the calculation section 612 in step S75 at the same address, and the process then proceeds to step S77.
In step S77, the control section 617 determines whether or not the decoding in-progress results D612 corresponding to all the rows of the check matrix have been computed by the calculation section 612. When the control section 617 determines that all the decoding in-progress results have not been computed, the process returns to step S74, and the above-described processing is performed again.
On the other hand, when the control section 617 determines in step S77 that the decoding in-progress results D612 corresponding to all the rows have been computed by the calculation section 612, the processing is completed.
The decoding apparatus 600 repeatedly performs the decoding process of
In the above description, although the memory 610 for storing decoding in-progress results is formed from two single-port RAMs, it may be formed from three or more RAMs if reading and writing do not occur simultaneously from and to one RAM. When the physical bit width of the RAM is insufficient, by providing the same control signal by using a plurality of RAMs, these can be logically assumed as one RAM.
For the portions in which edge data (messages corresponding to edges) lacks, during the storage in the memory (when data is stored in the memories 610 and 613 for storing decoding in-progress results), no message is stored, and during the computation (during the first computation at the calculation section 612 and during the second computation at the calculation section 615), no computation is performed.
If a barrel shifter is used for the cyclic shift circuits 314 and 320 of
In the above-described case, for the sake of simplification of description, a case, in which p is 5, that is, the number of rows and the number of computation of the sub-matrix forming the check matrix is 5, is used as an example. The number of rows and the number of columns of the sub-matrix need not always to be 5, and can take a different value depending on the check matrix. For example, p may be 360 or 392.
Furthermore, in this embodiment, LDPC codes of a code length of 90 and a coding rate of ⅔ are used. However, the code length and the coding rate may be any value. For example, when the number of rows and the number of columns, p, of the sub-matrix is 5, if the total number of the edges is smaller than or equal to 5, LDPC codes of even any code length and coding rate can be decoded by using the decoding apparatus 300 of
Furthermore, the decoding apparatus for certain LDPC codes, which satisfy the conditions in which the number of rows and the number of columns, p, of the sub-matrix is a predetermined value, and the total number of the edges is smaller than or equal to a particular value, is able to decode LDPC codes of any desired coding rate at any desired code length, which satisfy the conditions.
When the check matrix is not a multiple of the number p of the rows and columns of the sub-matrix, the present invention may be applied by assuming the check matrix to be a multiple of p by assigning elements of all 0s to the outside of the fractions of the check matrix.
Next, the above-described series of processes can be performed by hardware, and it can also be performed by software. When the series of processes is performed by software, the program forming the software is installed into a general-purpose computer, etc.
Accordingly,
The program may be recorded in advance in a hard disk 905 and a ROM 903 serving as a recording medium incorporated in the computer.
Alternatively, the program can be temporarily or permanently stored (recorded) in a removable recording medium 911, such as a flexible disk, a CD-ROM (Compact Disc Read-Only Memory), an MO (Magneto optical) disk, a DVD (Digital Versatile Disc), a magnetic disk, or a semiconductor memory. Such a removable recording medium 911 can be provided as so-called packaged software.
In addition to being installed into a computer from the removable recording medium 911 such as that described above, programs can be transferred to the computer in a wireless manner from a download site via a man-made satellite for digital satellite broadcasting or can be transferred by wire to the computer via a network, such as a LAN (Local Area Network) or the Internet. In the computer, the programs that are transferred in such a manner can be received at a communication section 908, and can be installed into the hard disk 905 contained therein.
The computer incorporates a CPU (Central Processing Unit) 902. An input/output interface 910 is connected to the CPU 902 via a bus 901. When an instruction is input by a user by operating an input section 907 including a keyboard, a mouse, a microphone, etc., via the input/output interface 910, the CPU 902 executes the program stored in the ROM (Read Only Memory) 903 in accordance with that instruction. Alternatively, the CPU 902 loads, into the RAM (Random Access Memory) 904, the program stored in the hard disk 905, the program that is transferred from a satellite or a network, that is received by the communication section 908, and that is installed into the hard disk 905, or the program that is read from the removable recording medium 911 loaded to a drive 909 and is installed into the hard disk 905, and the CPU 902 executes the program. As a result, the CPU 902 performs processing in accordance with the above-described flowcharts or processing according to the above-described block diagrams. Then, for example, the CPU 902 outputs the processing result via the input/output interface 910 from an output section 906 including an LCD (Liquid-Crystal Display), a speaker, etc., transmits the processing result from the communication section 908, and further records it in the hard disk 905 as required.
In this specification, processing steps for writing the program for enabling the computer to perform various processing need not to be executed chronologically according to the orders written as flowcharts. Also, they may be executed concurrently or individually (for example, parallel processing or object-based processing).
The program may be processed by one computer or may be processed by a plurality of computers in a distributed manner. Furthermore, the program may be transferred to a distant computer and may be processed thereby.
For decoding LDPC codes having a check matrix that can be represented by a combination of a (P×P) unit matrix, a quasi-unit matrix in which one or more 1s, which are elements of the unit matrix, are substituted with 0, a shift matrix in which the unit matrix or the quasi-unit matrix is cyclically shifted, a sum matrix, which is the sum of two or more of the unit matrix, the quasi-unit matrix, and the shift matrix, and a (P×P) 0-matrix, an architecture for simultaneously performing p check node computations and p variable node computations is adopted. As a result, by simultaneously performing p node computations, the operating frequency can be suppressed within a feasible range. Thus, while a large number of iterative decodings can be performed, it is possible to prevent simultaneous access to different addresses from occurring during writing to and reading from the memory (FIFO and RAM).
When LDPC codes represented by the check matrix of
The decoding apparatus 400 of
For example, when the check matrix of the LDPC codes is the check matrix of
Furthermore, for example, when the check matrix of the LDPC codes is the check matrix of
In general, since the code length of the LDPC codes is as great as several thousands to several tens of thousands, the LDPC codes whose value of p has a size of several hundreds are used. In that case, the advantages of using the decoding apparatus according to the present invention increase.
Furthermore, since the decoding apparatus according to the present invention faithfully implements the sum product algorithm, decoding loss other than quantization of messages does not occur.
From the above viewpoints, by using the decoding apparatus according to the present invention, high-performance decoding becomes possible.
Yokokawa, Takashi, Iida, Yasuhiro, Miyauchi, Toshiyuki
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