CN107370554A - Decoding method and decoder for low density parity check code - Google Patents

Abstract

A decoding method and decoder for low density parity check code is used to decode the correct code word from the input signal according to the preset low density parity check matrix. The method includes performing a plurality of decoding attempts within a predetermined number of decoding attempts according to the low density parity check matrix, the plurality of decoding attempts including at least a first decoding attempt using a first decoding schedule and a second decoding attempt using a second decoding schedule. The second decoding attempt is contiguous with the first decoding attempt. The first decoding schedule is a group that is not included in the second decoding schedule.

Description

Decoding method and decoder for low-density parity-check code

technical field

The present invention relates to a decoding method and decoder for low density parity check codes, and in particular to a decoding method and decoder for low density parity check codes with variable decoding schedule.

Background technique

In 1962, the low-density parity-check code (LDPC code) was proposed by Gallager, and it was proved that its error correction capability was very close to the theoretical maximum, the Shannon Limit, but there was no specific implementation method.

In recent years, in the research and development of wireless communication, in response to the needs of modern technology, the decoding method of the low density parity check code has been considered again. The demands of modern technology are, for example, those of video, which require the transmission of large amounts of data. Based on the large increase of transmission data, data signals are transmitted in parallel to facilitate the wireless communication device to receive data quickly and correctly. As for the mobile wireless communication device, it is more beneficial to lock the mobile wireless communication device when communicating in fast movement (for example, in a train). In addition, the parallel transmission of data signals can also be applied to optical transport, such as the application in ultra-high-speed serial optical transport network (ultra-high-speed serial optical transport network). With the technical evolution of integrated circuits, the specific implementation of low-density parity-check codes has gradually become feasible, and has become the channel coding standard of various advanced communication systems.

However, when decoding the LDPC code, it is mainly based on iterative belief propagation (BP) according to the encoding method of the LDPC matrix, and various decoding methods have also been proposed. However, in the traditional way, in multiple iterations of decoding attempts, the decoding schedule generally adopts the element order of the low-density parity check matrix, which is regarded as a decoding schedule.

Although the decoding method of this fixed decoding schedule can be implemented simply and directly, in terms of decoding efficiency, the improvement of decoding efficiency is a factor that needs to be considered in technology research and development.

Contents of the invention

The present invention provides a decoding method and a decoder for low-density parity-check codes, which are used to effectively decode an input signal to a correct codeword (codeword) according to a predetermined low-density parity-check matrix, and accelerate the convergence speed of iterative operations.

A decoding method of a low-density parity-check code of the present invention is used for decoding an input signal to a correct codeword according to a predetermined low-density parity-check matrix. The method includes performing multiple decoding attempts within a predetermined number of decoding attempts according to the low-density parity-check matrix, the multiple decoding attempts at least including the first decoding attempt using the first decoding schedule, and using the second decoding schedule the second decoding attempt. The second decoding attempt is adjacent to the first decoding attempt. The first decoding schedule is a group, which is not included in the second decoding schedule.

A low-density parity-check code decoder of the present invention is used to decode an input signal into a correct code word according to a predetermined low-density parity-check matrix, comprising: a decoding unit configured to convert the input signal according to a predetermined The low-density parity-check matrix solves the correct codeword, wherein according to the low-density parity-check matrix, multiple decoding attempts are performed within a predetermined number of decoding attempts, and the multiple decoding attempts include at least using the first decoding schedule and a second decoding attempt using a second decoding schedule, wherein the second decoding attempt is adjacent to the first decoding attempt, the first decoding schedule not included in the second decoding schedule; and A decoding schedule estimation unit is configured to generate and store a plurality of different decoding schedules according to the LDPC matrix, so that the decoding unit can obtain the first decoding schedule and the second decoding sequence.

In an embodiment of the present invention, in the above-mentioned decoding method and decoder for LDPC codes, the first decoding schedule is one of a layered reliability propagation order and a vertical reliability propagation order, and the first decoding schedule is Two-decoding scheduling is the other of the layered reliability propagation order and the vertical reliability propagation order.

In an embodiment of the present invention, in the decoding method and decoder of the above-mentioned low-density parity-check code, the first decoding schedule and the second decoding schedule are layered reliability propagation order, but the second decoding The scheduled code rate is lower than the code rate of the first decoding schedule.

In an embodiment of the present invention, in the decoding method and decoder of the above-mentioned low-density parity-check code, the first decoding schedule and the second decoding schedule are vertical reliability propagation order, but the second decoding The scheduled code rate is lower than the code rate of the first decoding schedule.

In an embodiment of the present invention, in the decoding method and decoder of the above-mentioned low-density parity-check code, the first decoding schedule and the second decoding schedule are based on maximum mutual information increase (maximum mutual information increase, M ² I ² ) Algorithms, according to different sequences determined by different parameter conditions.

In an embodiment of the present invention, in the decoding method and decoder of the above-mentioned low-density parity-check code, both the first decoding attempt and the second decoding attempt will reset the initial value of the codeword, or the subsequent The second decoding attempt uses the result of the first decoding attempt as an initial value.

In an embodiment of the present invention, in the decoding method and decoder for the LDPC code, the code rate of the second decoding attempt is lower than the code rate of the first decoding attempt.

In an embodiment of the present invention, in the above-mentioned decoding method and decoder for low density parity check codes, the first decoding schedule and the second decoding schedule are randomly arranged.

Based on the above, the decoding process of a rate-compatible LDPC code can include multiple decoding attempts, including two adjacent decoding attempts using different decoding schedules to obtain faster convergence speed, or higher throughput within the same iteration limit.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail with reference to the accompanying drawings.

Description of drawings

FIG. 1 is a schematic diagram illustrating a low density parity check matrix according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing connections between check nodes and variable nodes according to the low density parity check matrix in FIG. 1 .

FIG. 3 is a schematic diagram of a general planning of an LDPC matrix according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of the decoding schedule of M ² I ² adopted in LDPC decoding and the mechanism of each reset according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of an incremental decoding scheduling mechanism for M ² I ² decoding scheduling adopted in LDPC decoding according to an embodiment of the present invention.

FIG. 6 is a schematic flow chart of a decoding method for an LDPC code according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of an architecture of a decoder of an LDPC code according to an embodiment of the present invention.

【Symbol Description】

100: decoder

102: decoding unit

104: decoding scheduling estimation unit

106: storage unit

H: Low Density Parity Check Matrix

S100, S102: steps

detailed description

The present invention is aimed at the decoding method and decoder of the low-density parity-check code, and proposes that when decoding the codeword (codeword), it includes at least two decoding operations before and after two iterations, and uses different decoding schedules, so as to be more effective in the follow-up In the iterative decoding operation, it can more effectively use part of the information that has been solved and accumulated in the previous decoding operation, speed up the convergence speed of the iterative code operation, or obtain a higher throughput within the same iteration limit (throughput).

The present invention proposes a decoding scheduling plan to improve decoding efficiency, but the determined decoding scheduling is not limited to a specific decoding method operated at the backend. That is, for example, under the premise of a given decoding schedule, any applicable known decoding mechanism may be used for decoding, which may include hardware and/or software operations. That is, the decoding method of LDPC itself can adopt traditional existing technologies, or even technologies developed in the future. However, the present invention provides a plan for determining the decoding schedule it needs when decoding.

A number of examples are presented below to illustrate the present invention, but the present invention is not limited to the examples given.

FIG. 1 is a schematic diagram illustrating a low density parity check matrix according to an embodiment of the present invention. Referring to FIG. 1 , the low density parity check code is constructed based on a parity check matrix with sparse matrix properties. For (n, k) LDPC codes, every k bits of data are coded using n bits of codewords. The following is an example of a parity check matrix H used by a (9,6) LDPC code, as shown in FIG. 1 . Among the elements in this H matrix, the number of array elements with "1" is far less than the number of array elements with "0". This is the nature of the sparse matrix, which is the origin of the low density.

FIG. 2 is a schematic diagram showing connections between check nodes and variable nodes according to the low density parity check matrix in FIG. 1 . Referring to FIG. 2 , the decoding of the LDPC code can be represented as a bipartite graph. The bipartite graph is constructed according to the above-mentioned parity check matrix H, where the columns of H correspond to check nodes (check nodes, C), and the rows of H correspond to bit nodes (bit nodes). Called variable node (variable node). There is a connection relationship determined by the matrix H between the check node and the variable node, which is also called an edge, which is determined by the element 1 in the matrix H.

That is, among the numerical values of a column (column) in the matrix H, the array element with "1" represents that there is a connection with the variable node corresponding to the n variable nodes, and the array element with "0" represents that there is no connection. Taking Figures 1 and 2 as examples, the value of the first row (row) is [100100100] describing the connection relationship between the first check node and the variable node, so the 0th check node is connected to the 0th, 3rd, and 6th variable nodes are connected. Matrix H represents the encoding method adopted.

In wireless transmission, codewords of multiple bits are encoded and transmitted as analog signals, so the received signal is noisy, and therefore it is necessary to correctly decode the codewords to obtain correct codeword data. According to the multiplication rules of the matrix, when the matrix H is multiplied by the transposed matrix of the code word, the "0" matrix of kx1 can be obtained, and the content of the code word is considered to be correct data.

In the LDPC decoding process, according to the connection relationship and the received signal of the relative variable node, multiple iterations are performed according to the decoding schedule. The connection relationship basically includes the information (check to variable (C2V) message) transmitted from the check node to the variable node, and the information (variable to check (V2C) message) transmitted from the variable node to the check node. For example, in multiple A state of convergence is reached after the iterative operation to obtain the codeword. How to decode the codewords according to the decoding schedule and the encoding relationship of the matrix H is a known technology, and will not be described in detail, and the present invention is not limited to the application of a specific decoding mechanism.

The present invention includes proposing the planning of the decoding schedule required for LDPC decoding. Regarding the features proposed by the present invention, from a broader perspective, the decoding process of the low-density parity-check code can include multiple decodings. Attempts, including adjacent two decoding attempts, use different decoding schedules to obtain faster convergence speed, or within the same iteration limit, to obtain higher throughput.

The decoding methods adopted in the present invention include, for example, traditional layered belief propagation (LBP) operations or vertical shuffled belief propagation (SBP) operations. FIG. 3 is a schematic diagram of a general planning of an LDPC matrix according to an embodiment of the present invention. In the matrix H, for example, r1 to r6 represent the sequence of a column, and c1 to c8 represent the sequence of a row. The reliability propagation method is to divide the parity check matrix H into multiple layers. Decoded messages are delivered in layer order. Each layer can contain one or more rows. That is, the LBP transmits the decoded information according to the order of the rows in the parity check matrix. The Vertical Reliability Propagation (SBP) transmits the decoded information in the order of the columns in the parity check matrix.

For a matrix H, according to the size of the code rate (code rate) R, the matrix H will be divided into multiple sub-matrices corresponding to different code rates, for example, the corresponding code rates R1, R2, and R3 are divided into three sub-matrices H1, H2 , H3. Regarding the definition of the code rate, for a matrix H(n, k) that encodes k bits with n bits, the code rate value of this matrix is k/n.

An example of an LDPC matrix H of a rate-compatible LDPC code is shown in FIG. 3 . The code rates of H1, H2, and H3 are R1, R2, and R3 respectively, and R1>R2>R3. H3 contains 8 columns and 6 rows, H1 contains 4 columns and 2 rows. If LBP scheduling is used, the decoding schedule when solving H1 can be {r1, r2, r1, r2...}, and the decoding schedule when solving H3 can be {r1, r2, r3, r4, r5, r6, r1, r2...}, repeated for multiple iterations. If the SBP scheduling is used, the decoding schedule when solving H1 can be {c1, c2, c3, c4, c1, c2...}, and the decoding schedule when solving H3 can be {c1, c2, c3, c4, c5, c6, c7, c8, c1, c2...}, repeat the same for multiple iterations.

During decoding, generally, a sub-matrix with a higher code rate, such as matrix H1, is used first. If the data of the matrix H1 cannot be solved, a matrix with a lower code rate will be used. Generally speaking, if the noise of the signal is low, it means that the data it carries can be easily identified, so using the matrix H1 with a high code rate is enough to decode the codeword, but multiple iterative operations are still necessary. According to the traditional method, each decoding attempt (decoding attempt) will use the same schedule. For example, the first decoding attempt to decode a schedule using LBP, each subsequent decoding attempt will also use LBP.

However, the present invention proposes that in different decoding attempts, different decoding schedules may be employed. For example, when solving H1, the decoding order is {r1, r2, r1, r2...} of LBP, while when solving H3, the order of switching and using SBP can be {c1, c2, c3, c4, c5, c6, c7, c8, c1, c2...}. In other words, multiple decoding attempts are performed within a predetermined number of decoding attempts according to the LDPC matrix. The multiple decoding attempts include at least a first decoding attempt using a first decoding schedule, and a second decoding attempt using a second decoding schedule, wherein the second decoding attempt is adjacent to the first decoding attempt, and the first decoding The schedule is not included in the second decoding schedule.

However, the decoding attempts of the present invention are not limited to reducing code rates. For example, it is also possible to change the decoding schedule between adjacent iterative operations at the same code rate. To further illustrate with another embodiment, the change of the decoding order is not limited to the switching between LBP and SBP. If the order of solving layers in LBP is changed, for example, because {r1, r2, r3, r4, r1, r2...} is used to solve H2, then the traditional way to solve H3 is expected to be {r1, r2, r3, r4, r5, r6, r1, r2...}. However, according to the method of the present invention, for example, the scheduling is changed to {r3, r2, r1, r4, r6, r5, r3, r2...}, which is also the method of changing the decoding order in accordance with the present invention.

Described from a broader embodiment, the decoding process of a rate-compatible LDPC may include multiple decoding attempts. Each decoding attempt may use a specific decoding schedule. For example, S1, S2,...Sk may respectively represent the decoding schedule used for the first, second...kth decoding attempt. For example, when using LBP, what is included in Sk is the sequence of rows in the parity check matrix. For example, in the example of FIG. 3 , S1={r1, r2}, S2={r1, r2, r3, r4}. And if SBP is adopted, then S1={c1, c2, c3, c4}. In the traditional decoding process, usually the previous decoding scheduling sequence will be included in the next decoding sequence, such as when using LBP to solve the embodiment of Figure 3, S2={S1, r3, r4}, where S1 represents {r1, r2}. In a more general representation, the traditional decoding schedule can be written as S(k-1)∈Sk. However, the method proposed by the present invention does not include the previous decoding scheduling order in the next decoding scheduling, that is,

An embodiment of the decoding schedule of the present invention can be changed randomly under the same concept. However, the decision on the decoding schedule can also use other estimation mechanisms to find a better decoding schedule. For example, the variable decoding scheduling method published by the inventors "H.-C.Lee and Y.-L.Ueng, "IncrementalDecoding Schedules for Puncture-based Rate-compatible LDPC codes," accepted by IEEE VTC2016-Spring", where each The order used for the decoding attempts is given by the literature "H.-C.Lee and Y.-L.Ueng, "LDPC decoding scheduling for faster convergence and lower error floor," IEEE Trans. on Commun., vol.62, no. 9, pp.3104-3113, Sept.2014" proposed using the maximum mutual information increase (maximum mutual information increase, M ² I ² ) algorithm design. This method is also consistent with the aforementioned the rules. For the details of the maximum mutual information increase (M ² I ² ) algorithm, reference may be made to the description in the literature, which will not be detailed here.

However, it should be noted here that in the M ² I ² algorithm, the signal-to-noise ratio (S/N ratio, SNR) is a control parameter, which can change the estimated different decoding schedules. The signal-to-noise ratio is, for example, the signal-to-noise ratio provided by the channel environment. For the S1 decoding attempt, it is E _s1 /N ₀ , where E _s1 is energy and N ₀ is noise.

In addition, in different decoding attempts, if different code rates are used, the condition of the signal-to-noise ratio (SNR) will naturally change. Under the operation of M ² I ² , different decoding schedules will naturally be generated, which will not be included in the previous estimation The decoding schedule, consistent with the present invention technical characteristics.

Further simulation results show that the method used to decode the rate-compatible LDPC can significantly increase the throughput within a limited number of iterations. In each decoding attempt, the M ² I ² algorithm can be used to design the decoding scheduling order, but other design methods can also be used, and even random arrangements can be used. if only All are within the broad scope to be protected by the present invention.

Therefore, the present invention tries to use different decoding sequences for the two consecutive decodings. This feature can be achieved in many ways, for example, if the k-th decoding sequence is denoted by Sk, then For another example, when using LBP, what Sk contains is the sequence of rows in the parity check matrix used for the kth decoding attempt. For another example, when using the SBP method, what Sk contains is the sequence of columns in the parity check matrix used for the kth decoding attempt. For another example, the design method of the order of decoding is not limited, and can also be selected randomly. For example, the result of M ² I ² algorithm design, as long as It is included in the scope of protection of this proposal. For another example, it can be combined with incremental decoding schedules (Incremental Decoding Schedules) to obtain more efficient decoding schedules.

FIG. 4 is a schematic diagram of the decoding schedule of M ² I ² adopted in LDPC decoding and the mechanism of each reset according to an embodiment of the present invention. Referring to FIG. 4 , three decoding attempts S1 , S2 , S3 constructed by the M ² I ² algorithm according to the code rates R1 , R2 , R3 . For each code rate R1, R2, R3, the initial data will be reset first. Therefore, each code rate is restarted, so the estimation of the three decoding attempts S1 , S2 , S3 is performed independently without correlation. That is, each operation starts with the initial state reset to zero. This embodiment will be more time-consuming.

FIG. 5 is a schematic diagram of an incremental decoding scheduling mechanism for M ² I ² decoding scheduling adopted in LDPC decoding according to an embodiment of the present invention. Referring to FIG. 5 , three decoding attempts S1 , S2 , S3 constructed by the M ² I ² algorithm according to the code rates R1 , R2 , R3 . In this embodiment, for example, for the operation of the code rate R2 and R3, although the result may not be able to obtain an effective decoding schedule for the current code rate, the data obtained by the operation of this code rate will be retained for the following A code rate estimate is used as initial data. Taking the intermediate situation as an example, the decoding attempt S1 is estimated with the code rate R1. Since its convergence value is less than 1, successful decoding cannot be achieved, and the code rate R2 is used for estimation. At this time, although the result of the decoding attempt S1 cannot be effectively decoded, the result of the operation will be used as the initial condition by the decoding attempt S2, so the convergence rate will be accelerated. The differences in effects between FIG. 4 and FIG. 5 are also described in detail in the aforementioned documents, and will not be described in detail here.

FIG. 6 is a schematic flow chart of a decoding method for an LDPC code according to an embodiment of the present invention. Referring to FIG. 6 , according to the above description of the present invention, a decoding method of an LDPC code includes step S100 of receiving an input signal of a code word encoded according to an LDPC matrix. Step S102 decodes the codeword according to the planned decoding schedule. According to the low-density parity check matrix, multiple decoding attempts are performed within a predetermined number of decoding attempts, and the multiple decoding attempts include at least the first decoding attempt using the first decoding schedule, and the second decoding attempt using the second decoding schedule In an attempt, wherein the second decoding attempt is adjacent to the first decoding attempt, the first decoding schedule is not included in the second decoding schedule.

FIG. 7 is a schematic diagram of an architecture of a decoder of an LDPC code according to an embodiment of the present invention. Referring to FIG. 7 , according to the above description of the present invention, a LDPC decoder 100 is used to decode the input codeword signal according to a predetermined LDPC matrix to obtain a correct codeword and then output the codeword. The decoder 100 includes: a decoding unit 102 configured to decode the input signal into a correct code word according to a predetermined low density parity check matrix H, wherein according to the low density parity check matrix, within a predetermined number of decoding attempts performing a plurality of decoding attempts, the plurality of decoding attempts including at least a first decoding attempt using a first decoding schedule and a second decoding attempt using a second decoding schedule, wherein the second decoding attempt is adjacent to the first decoding attempt For a decoding attempt, the first decoding schedule is not included in the second decoding schedule. A decoding schedule estimation unit 104 is configured to generate and store a plurality of different decoding schedules according to the LDPC matrix, so that the decoding unit can obtain the first decoding schedule and the second decoding sequence. A storage unit 106 is configured to store the decoding schedule planned by the decoding schedule estimation unit 104 for use by the decoding unit 102 in decoding.

The present invention proposes a decoding method and a decoder for low-density parity-check codes. During two consecutive decodings with odd inclusions, different decoding schedules will be tried for decoding to achieve more efficient decoding operations. As for the planning of the decoding schedule, for example, the M ² I ² method can be used for more efficient planning, but the present invention is not limited to using the M ² I ² operation to find different decoding schedules. As long as the decoding scheduling plan of the present invention has The relationship between , and the present invention does not limit which mechanism is used to find the decoding schedule.

Although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Those skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention The scope defined by the appended claims shall prevail.

Claims (16)

1. a kind of coding/decoding method of low density parity check code, to by input signal according to predetermined low close Degree parity matrix solves correct code word, including：

According to the low-density parity check (LDPC) matrix, repeatedly decoding is carried out in predetermined decoding number of attempt and is tasted Examination, the multiple decoding comprises at least in attempting to be attempted using the first decoding of the first decoding scheduling, and is made Attempted with the second decoding of the second decoding scheduling,

Wherein the second decoding trial is adjacent is connected in the first decoding trial, and first decoding scheduling does not wrap It is contained in second decoding scheduling.

2. the coding/decoding method of low density parity check code as claimed in claim 1, wherein first decoding Scheduling is one of them of laminar reliability order of propagation and rectilinear reliability order of propagation, second solution Code scheduling is the other in which of the laminar reliability order of propagation and rectilinear reliability order of propagation.

3. the coding/decoding method of low density parity check code as claimed in claim 1, wherein first decoding Scheduling and second decoding scheduling are all laminar reliability order of propagation, but the code of second decoding scheduling Rate is less than the code check of first decoding scheduling.

4. the coding/decoding method of low density parity check code as claimed in claim 1, wherein first decoding Scheduling and second decoding scheduling are all rectilinear reliability order of propagation, but second decoding scheduling Code check is less than the code check of first decoding scheduling.

5. the coding/decoding method of low density parity check code as claimed in claim 1, wherein first decoding Scheduling and second decoding scheduling are to increase (maximum mutual information according to maximum mutual information Increase, M2I2) algorithm, the different order determined according to different parameters condition.

6. the coding/decoding method of low density parity check code as claimed in claim 1, wherein first decoding Attempt and second decoding is attempted all reset the initial value of the code word, or follow-up second decoding is tasted The result that examination can use first decoding to attempt is initial value.

7. the coding/decoding method of low density parity check code as claimed in claim 1, wherein second decoding The code check of trial is lower than the first decoding trial code check.

8. the coding/decoding method of low density parity check code as claimed in claim 1, wherein first decoding Scheduling and second decoding scheduling are random arrangements.

9. a kind of decoder of low density parity check code, to by input signal according to predetermined low-density Parity matrix solves correct code word, including:

Decoding unit, it is configured to according to predetermined low-density parity check (LDPC) matrix solve input signal just True code word, wherein according to the low-density parity check (LDPC) matrix, carried out in predetermined decoding number of attempt Repeatedly decoding is attempted, and the multiple decoding comprises at least in attempting is tasted using the first decoding of the first decoding scheduling Examination, and attempted using the second decoding of the second decoding scheduling, adjacent continue is attempted in wherein second decoding Attempted in first decoding, first decoding scheduling is not included in second decoding scheduling；And

Decoding scheduling estimation unit, it is configured to be produced and stored more according to the low-density parity check (LDPC) matrix The different decoding scheduling of kind, so that the decoding unit obtains first decoding scheduling and second decoding scheduling.

10. the decoder of low density parity check code as claimed in claim 9, wherein first decoding are adjusted Degree is one of them of laminar reliability order of propagation and rectilinear reliability order of propagation, second decoding Scheduling is the other in which of the laminar reliability order of propagation and rectilinear reliability order of propagation.

11. the decoder of low density parity check code as claimed in claim 9, wherein first decoding are adjusted Degree and second decoding scheduling are all laminar reliability order of propagation, but the code check of second decoding scheduling Less than the code check of first decoding scheduling.

12. the decoder of low density parity check code as claimed in claim 9, wherein first decoding are adjusted Degree and second decoding scheduling are all rectilinear reliability order of propagation, but the code of second decoding scheduling Rate is less than the code check of first decoding scheduling.

13. the decoder of low density parity check code as claimed in claim 9, wherein first decoding are adjusted Degree and second decoding scheduling are to increase (maximum mutual information according to maximum mutual information Increase, M2I2) algorithm, the different order determined according to different parameters condition.

14. the decoder of low density parity check code as claimed in claim 9, wherein first decoding are tasted Examination and second decoding are attempted all reset the initial value of the code word, or follow-up second decoding is attempted The result that first decoding can be used to attempt is initial value.

15. the decoder of low density parity check code as claimed in claim 9, wherein second decoding are tasted The code check of examination is lower than the first decoding trial code check.

16. the decoder of low density parity check code as claimed in claim 9, wherein first decoding are adjusted Degree and second decoding scheduling are random arrangements.