WO2013069887A1 - Procédé de génération de matrice de contrôle de parité adaptée à la qualité de liaison de canal et procédé et appareil de codage de code de contrôle de parité à faible densité l'utilisant - Google Patents

Procédé de génération de matrice de contrôle de parité adaptée à la qualité de liaison de canal et procédé et appareil de codage de code de contrôle de parité à faible densité l'utilisant Download PDF

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WO2013069887A1
WO2013069887A1 PCT/KR2012/007732 KR2012007732W WO2013069887A1 WO 2013069887 A1 WO2013069887 A1 WO 2013069887A1 KR 2012007732 W KR2012007732 W KR 2012007732W WO 2013069887 A1 WO2013069887 A1 WO 2013069887A1
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parity check
channel link
link quality
quality
criterion
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PCT/KR2012/007732
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English (en)
Korean (ko)
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김상효
장민
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성균관대학교 산학협력단
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Publication of WO2013069887A1 publication Critical patent/WO2013069887A1/fr

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
    • H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
    • H03M13/11—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits using multiple parity bits
    • H03M13/1102—Codes on graphs and decoding on graphs, e.g. low-density parity check [LDPC] codes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
    • H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
    • H03M13/11—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits using multiple parity bits

Definitions

  • the present invention relates to a low-density parity-check (LDPC) code, and more particularly, to design a suitable LDPC code according to the characteristics of the technology to which the LDPC code is applied and the link state
  • the present invention relates to a method of performing error correction encoding and an apparatus for performing the same.
  • Low-density parity-check (LDPC) codes have good performance close to Shannon channel capacity, which is a theoretical communication limit. Due to the excellent performance, various standard technologies such as IEEE 802.16m mobile WiMAX and IEEE 802.11 Wi-Fi adopt LDPC codes as error correction codes.
  • Each LDPC code is defined by a parity-check matrix, and the parity check matrix may be represented by a bipartite graph called a Tanner graph for visual and intuitive understanding.
  • the bipartite graph includes a variable node set, a check node set, and a set of edges connecting elements of the variable node set and the check node set to each other.
  • the variable node corresponds one-to-one with bits of a codeword that is a coded result
  • the check node corresponds to a parity-check equation indicating an algebraic relationship between the bits of the codeword.
  • 1 is an example of a parity check matrix of a binary LDPC code consisting of four rows and eight columns. Referring to FIG. 1, since the parity check matrix of the LDPC code has eight columns, a codeword having a length of eight is generated.
  • FIG. 2 is a Tanner graph corresponding to the parity check matrix of the LDPC code of FIG. 1.
  • the Tanner graph of FIG. 2 shows eight variable nodes v1 201, v2 202, v3 203, v4 204, v5 205, v6 206, v7 207, and v8 ( 208 and four test nodes c1 211, c2 212, c3 213, c4 214 and connecting lines connecting them.
  • the connection line of the Tanner graph is connected according to the parity check matrix of FIG. 1. If the value of the element h ij of the i th row and the j th column of the parity check matrix is not 0, the j th variable node and the i th check node are It is connected by connecting line.
  • the parity check matrix and Tanner graph of an LDPC code as shown in FIGS. 1 and 2 are characterized by basic elements including the length and code rate of a codeword.
  • the length N of the codeword is the number of columns of the parity check matrix, and the number of variable nodes in a Tanner graph.
  • the code rate R represents the ratio of the number of columns and the number of rows in the parity check matrix, and the ratio of the number N of variable nodes and the number M of check nodes in a Tanner graph.
  • the code rate is calculated by the following equation.
  • the degree of a variable node and an inspection node represents the number of connection lines connected to each node.
  • the order of the variable node is the number of nonzero elements present in the corresponding column array in the parity check matrix
  • the order of the check node is the number of nonzero elements present in the corresponding row array in the parity check matrix.
  • the orders of) are 2, 2, 2, 2, 3, 3, 3, and 4 in order
  • the order of test nodes c1 211, c2 212, c3 213, and c4 214 is 6 in order. , 5, 5 and 5.
  • the node perspective degree distribution of each of the variable node and the check node of the LDPC code is an index indicating a probabilistic distribution of orders of nodes in the LDPC code.
  • ⁇ i represents the ratio of the number of variable nodes of order i to the number N of all variable nodes
  • ⁇ j represents the ratio of the number of inspection nodes of degree j and the number M of all inspection nodes.
  • the order distribution of the LDPC code does not represent all the features of the LDPC code. That is, even if they have the same order distribution, different LDPC codes may be generated according to the actual connection configuration. However, LDPC codes with the same order distribution have the same asymptotic performance.
  • the asymptotic performance of the LDPC code is the error correction capability of the LDPC code under the assumption that there is no cycle in the corresponding Tanner graph, that is, the length of the codeword is infinite. As described above, a process of calculating asymptotic performance using the order distribution of the LDPC code is called density evolution.
  • a general optimization process of LDPC codes is to find an order distribution with good asymptotic performance at a given code rate.
  • the order distribution is obtained by changing the order distribution to obtain asymptotic performance through density evolution, and among these, select an order distribution having excellent asymptotic performance.
  • this optimization process is performed under the assumption of asymptotic performance, i.e., the length of codeword is infinite, the performance tendency is similar in LDPC code with finite length of codeword. That is, an LDPC code of finite length with an order distribution of good asymptotic performance is generally superior to an LDPC code of equal length with an order distribution of poor asymptotic performance.
  • the asymptotic performance of LDPC codes with the same order distribution is all the same.
  • the actual performance of LDPC codes having the same order distribution may vary. That is, in the case of the LDPC code having a finite length, even if they have the same order distribution, the performance may vary depending on the actual connection configuration. Therefore, it is important to design an LDPC code having excellent performance that is suitable for the characteristics and requirements of a system which intends to use the LDPC code even among LDPC codes having the same order distribution in the actual LDPC code design.
  • a first object of the present invention for overcoming the above disadvantages is to provide a method of designing a parity check matrix of an LDPC code having optimal performance according to the characteristics of a communication system in which an LDPC code is to be used and the quality of a channel link. .
  • a method of generating a parity check matrix of a Low Density Parity Check (LDPC) code according to an embodiment of the present invention for achieving the first object of the present invention is that of the communication system using the LDPC code
  • the connection order set condition may be set so that the number of different connection order sets of the check nodes is greater than a preset connection order set number criteria when the channel link quality is worse than a preset quality criterion.
  • the number of different connection order sets of the check nodes may be set to be smaller than a preset connection order set number criterion.
  • the connectivity condition may be set so that the distribution value of the connectivity of the check nodes is greater than a preset connectivity dispersion value criterion when the channel link quality is worse than a preset quality criterion.
  • the dispersion value of the connectivity of the check nodes may be set to be smaller than the preset connectivity dispersion value criterion.
  • the channel link quality may be determined based on a bit energy to noise ratio (Eb / No).
  • the quality criterion of the LDPC code is that the frame error rate curve of the LDPC code belongs to a waterfall region when the channel link quality is poorer than the quality criterion, and the channel link quality is superior to the quality criterion.
  • the frame error rate curve may be characterized as belonging to an error-floor region.
  • a method of receiving information data and a set of connection orders of inspection nodes (generating a parity check matrix of a predetermined number of LDPC codes having different connected-degree set conditions, or connectivity conditions, selecting one parity check matrix from the generated predetermined number of parity check matrices; And encoding the information data based on the selected parity check matrix to generate a codeword.
  • the selecting of the parity check matrix may include measuring channel link quality of a communication system in which the LDPC code is used and having an error correction capability of the predetermined number of parity check matrices based on the channel link quality. And selecting an excellent parity check matrix.
  • the measuring of the channel link quality may include estimating the channel link quality based on a stochastic characteristic of the channel link quality, which may include a signal-to-noise ratio (SNR). Can be.
  • the selecting of the parity check matrix may include selecting a number of sets of different connection order sets among the predetermined number of parity check matrices when the channel link quality is worse than a preset quality criterion.
  • a parity check matrix may be selected that is larger than a set number criterion, and when the channel link quality is superior to a preset quality criterion, the number of different connection order sets of the check nodes among the generated predetermined number of parity check matrices is preset.
  • the selecting of the parity check matrix may include: when the channel link quality is worse than a preset quality criterion, a variance value of the connectivity set by the variance value of the connectivity of the check nodes among the generated predetermined number of parity check matrices.
  • a parity check matrix larger than a reference may be selected, and if the channel link quality is superior to a preset quality criterion, the variance value of the connectivity of the check nodes among the generated predetermined number of parity check matrices is preset.
  • the parity check matrix smaller than the reference may be selected.
  • the quality criterion is that the frame error rate curve of the LDPC code belongs to a waterfall region when the channel link quality is poorer than the quality criterion, and the frame error rate of the LDPC code when the channel link quality is superior to the quality criterion.
  • the curve may be characterized as belonging to an error-floor region.
  • a low density parity check (LDPC) encoding apparatus for achieving the third object of the present invention includes an input unit for receiving information data and a set of connection order of check nodes.
  • a parity check matrix generator for generating a parity check matrix of a predetermined number of LDPC codes having at least one of a connected-degree set condition and a connectivity condition, and a parity of one of the generated number of parity check matrices;
  • a control unit for selecting a parity check matrix, and an encoding unit for generating a codeword by encoding the information data based on the selected parity check matrix.
  • the encoding apparatus may further include a measuring unit measuring a channel link quality of a communication system in which the LDPC code is used, wherein the controller is configured to correct an error in a predetermined number of parity check matrices based on the channel link quality.
  • the best parity check matrix may be selected.
  • the measurement unit may estimate the channel link quality based on a stochastic characteristic of the channel link quality, which may include a signal-to-noise ratio (SNR).
  • SNR signal-to-noise ratio
  • the controller may be further configured to determine that the number of different connection order sets of the check nodes is greater than the predetermined number of connection order sets based on the predetermined number of parity check matrices when the channel link quality is worse than a preset quality criterion.
  • a check matrix can be selected, and if the channel link quality is superior to a predetermined quality criterion, the number of different connection order sets of the check nodes among the generated predetermined number of parity check matrices is greater than the preset connection order set number criteria. You can choose a smaller parity check matrix.
  • the control unit may further include a parity check matrix having a variance value of the connectivity of the check nodes greater than a preset variance criterion of the predetermined number of parity check matrices when the channel link quality is worse than a preset quality criterion.
  • the parity check matrix of the generated number of parity check matrix is smaller than the dispersion value of the connectivity of the preset connection node of the predetermined number of parity check matrix Can be selected.
  • the quality criterion is that the frame error rate curve of the LDPC code belongs to a waterfall region when the channel link quality is poorer than the quality criterion, and the frame error rate of the LDPC code when the channel link quality is superior to the quality criterion.
  • the curve may be characterized as belonging to an error-floor region.
  • a connected order set means a set of orders of a variable node connected to a check node.
  • a parity check matrix can be generated in accordance with the characteristics of a communication system using an LDPC code in consideration of the diversity and distribution of connectivity, meaning -degree set) and order sum. Further, in performing error correction encoding in a communication and compression system using an LDPC code, a parity check matrix may be selected according to the quality of a channel link through which information encoded with an LDPC code is transmitted.
  • the fall / error-floor conflict can be adjusted in the error correction coding using the LDPC code.
  • using a single LDPC code solves the problem of having relatively poor error correction ability as the channel link quality changes, and uses error correction coding that always has an optimal error correction capability regardless of the channel link quality. Can be done.
  • 1 is an exemplary diagram of a parity check matrix of an LDPC code having a length of a codeword of 8 and a code rate of 1/2.
  • FIG. 2 is an exemplary diagram of a Tanner graph corresponding to the example of the parity check matrix of FIG. 1.
  • FIG. 3 is an illustration of a circular ring in a Tanner graph of an LDPC code.
  • FIG. 4 is an exemplary diagram of a Tanner graph of an LDPC code under design and an extended tree rooted at an arbitrary variable node corresponding to the Tanner graph.
  • 5 is a frame error rate curve graph of an LDPC code having different downpour / error-floor conflict performance.
  • FIG. 6 is an exemplary diagram of a set of connection orders of test nodes in a Tanner graph.
  • FIG. 7 is an exemplary diagram of connectivity of test nodes in a Tanner graph.
  • FIG. 8 is a connectivity distribution diagram of a first LDPC code having 129 different sets of connection orders.
  • FIG. 9 is a connectivity distribution diagram of a second LDPC code having 2021 sets of different link orders.
  • 10 is a connectivity distribution diagram of a third LDPC code having 2446 different order sets.
  • FIG. 11 is a frame error rate curve graph of the first LDPC code, the second LDPC code, and the third LDPC code of FIGS. 8, 9, and 10.
  • FIG. 12 is a frame error rate curve graph of a channel quality adaptive LDPC encoding / decoding method according to an embodiment of the present invention.
  • FIG. 13 is a flowchart of a method of generating a parity check matrix of an LDPC code according to an embodiment of the present invention.
  • 15 is a flowchart of a method of encoding an LDPC code according to an embodiment of the present invention.
  • 16 is a block diagram of an apparatus for encoding an LDPC code, according to an embodiment of the present invention.
  • first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.
  • the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.
  • the design of the LDPC code is based on design factors.
  • the length N and code rate R of the codeword are determined according to the characteristics of the communication system in which the LDPC code is to be used, and a degree distribution having excellent asymptotic performance at the determined code rate is selected. Based on these design elements, an important point in designing a practically usable LDPC code, that is, a finite length LDPC code, is to generate a short cycle of minimum length.
  • a circular ring is a set of connecting lines that start from one node and then through other nodes to its own node.
  • FIG. 2 is an exemplary diagram of a Tanner graph corresponding to the example of the parity check matrix of FIG. 1
  • FIG. 3 is an exemplary diagram of a circular ring in the Tanner graph of FIG. 2.
  • a connection line connected from the variable node v1 301 to the variable node v1 301 through the test node c1 311, the variable node v5 305, and the test node c2 312 is again connected to a circular loop ( 320).
  • the length of the purified ring is the number of connecting lines constituting the circulation ring, and the length of the circulation ring 320 of FIG. 3 is four.
  • the LDPC code has an error correction capability that is exponentially improved as the quality of the channel link is improved.
  • the error-floor phenomenon is a phenomenon in which the error correction capability is not significantly improved compared to the degree of improvement in the quality of the channel link. . Stopping sets and trapping sets, which are extended concepts of circular loops, also affect the error-floor behavior of LDPC codes.
  • stop sets and trap sets including circular loops, are necessarily generated. Therefore, it is important to reduce the size of the stop set and trap set including the circular loop in the designed LDPC code in designing the LDPC code based on the given design elements such as code length, code rate and order distribution.
  • PEG progressive-edge-growth
  • variable node v1 411, v2 412, v3 413, and v4 414 connect connection lines of a predetermined order to the test node. It is a state.
  • the variable node v5 415 connects one connection line to the inspection node c1 421, and it is time to determine which inspection node to connect the second connection line to.
  • the goal of the design is to maximize the length of the loop that is created by placing new connections.
  • variable node v5 415 constructs a spreading tree for looking at the distance of each variable node and the check node from itself.
  • the test node farthest from the variable node v5 415 is c3 423. Therefore, if the new connection line is connected between the variable nodes v5 415 and c3 423, the size of the circular ring formed by the new connection line is maximized. This process is inevitably performed in the design process of the LDPC code.
  • FIG. 5 is a frame error rate curve graph of an LDPC code having different downpour / error-floor conflict performance. That is, a diagram showing a frame error rate (FER) curve graph indicating the performance of two LDPC codes having the same order distribution but different connection configurations.
  • FER frame error rate
  • the horizontal axis 501 is a bit energy-to-noise ratio indicating the quality of the channel link. The larger the value, the better the quality of the channel link, and the smaller the value, the worse the quality of the channel link.
  • the vertical axis 502 represents the average probability of restoration failure when the LDPC code is used in the quality of each channel link. The smaller the value, the better the performance of the LDPC code. The higher the quality of the channel link, the lower the average probability of restoration failure when the LDPC code is used. The worse the quality of the channel link, the higher the average probability of restoration failure when the LDPC code is used.
  • the performance graph of the LDPC code is largely divided into a waterfall region 510 and an error-floor region 520.
  • the downpour area 510 is an area where the slope of the error rate curve increases rapidly as the quality of the channel link improves in a range where the quality of the channel link is relatively poor.
  • the error-floor area 520 is an area where the slope of the error rate curve is drastically lower than that of the downfall area in a range where the quality of the channel link is relatively good.
  • Drop / error-floor conflicts between finite length LDPC codes with different order distributions can be controlled by varying the ratio of order-2 variable nodes. However, the factors causing the fall / error-floor conflict between LDPC codes having the same order distribution have not yet been identified.
  • the LDPC code can be designed according to the characteristics of the communication system using the LDPC code and the quality of the channel link.
  • the order distribution of LDPC codes is optimized through asymptotic performance analysis using density evolution under a given code rate of LDPC codes, and then suitable drop / error-according to the characteristics and requirements of the communication system and the quality of the channel link. Designing LDPC codes with floor conflict features can improve the overall performance of the system.
  • the average reliability of the link can be improved by using an LDPC code having better performance in the downfall region 510.
  • the channel link quality between the transmitter and the receiver is generally good, the average reliability of the link can be improved by using an LDPC code having excellent performance in the error-floor region 520.
  • the method of designing an LDPC code provides a method of designing an LDPC code when a length, a code rate, and an order distribution of a codeword are given.
  • the LDPC code design method according to an embodiment of the present invention provides a design method of the LDPC code having a suitable performance according to the characteristics of the communication system even if the same codeword length, code rate, and order distribution.
  • FIG. 6 is an exemplary diagram of a set of connection orders of test nodes in a Tanner graph. That is, a diagram showing an example of a connected-degree set in an extension tree drawn with one test node as a root in an arbitrary Tanner graph.
  • a connection order set of one test node is a set of orders of variable nodes connected to the test node and one connection line.
  • the number of variable nodes connected to the test node c1 601 as one connection line is v1 611, v2 612, v3 613, and v4 614.
  • the order of this variable node is v1 611 is 2, v2 612 is 3, v3 613 is 3 and v4 614 is 4, respectively.
  • the connection order set of the check node c1 601 is ⁇ 2, 3, 3, 4 ⁇ .
  • FIG. 7 is an exemplary diagram of connectivity of test nodes in a Tanner graph. That is, an example of connectivity is shown in an extension tree drawn with one test node as a root in a Tanner graph as shown in FIG. 6.
  • the connectivity of a test node in a Tanner graph of an LDPC code is a sum of subtracting 1 from orders of variable nodes connected to the test node and one connection line.
  • four variable nodes are connected to the test node c1 701 with one connection line, that is, v1 711, v2 712, v3 713, and v4 714.
  • connectivity is the number of test nodes 703 located at depth 2 when drawing an extension tree rooted at test node c1 701 under the premise that there are no circular rings of length 4.
  • LDPC code design method in designing an LDPC code when a length, a code rate, and an order distribution of a codeword are given, the connection order set and connectivity of a check node, which have not been previously considered, are considered. .
  • LDPC code according to an embodiment of the present invention even if the same codeword length, the same code rate and the same or similar order distribution according to the fall / error-floor conflict according to the diversity of the connection order set of the test node and the variance of the connectivity This has an adjusted performance.
  • connection order set of each test node constituting the Tanner graph of the LDPC code is uniform or the variance of the connectivity is small, the performance in the error-floor region is excellent, but the performance in the falling water region is poor.
  • the connection order set of check nodes constituting the Tanner graph of the LDPC code is ⁇ 2, 3, 3, 4 ⁇ and the connectivity is all equal to 12, or ii) the connection order of some check nodes.
  • the set is ⁇ 2, 3, 3, 4 ⁇ , the connectivity is 12, and the connection order set of the test nodes other than some of the check nodes is ⁇ 2, 2, 3, 4 ⁇ , and the connectivity is 11 per check node.
  • the connection order set and connectivity are somewhat different, but generally similar, they have good performance in the error-floor domain.
  • connection order set of each check node constituting the Tanner graph of the LDPC code is varied or the dispersion of connectivity is large, the performance in the error-floor region is poor, but the performance is excellent in the downpour region.
  • a check order set of some check nodes is ⁇ 2, 2, 2, 2 ⁇ , and has a connectivity of 8, and other check nodes other than the check nodes. If the connection order set of these is ⁇ 4, 4, 4, 4 ⁇ , and the connectivity is 16, if the connection order set is varied for each test node constituting the Tanner graph and the distribution of connectivity is large, it has excellent performance in the falling water region. .
  • FIG. 8 is a connectivity distribution diagram of a first LDPC code having 129 different connection order sets
  • FIG. 9 is a connectivity distribution diagram of a second LDPC code having 2021 different connection order sets
  • FIG. 10 is a 2446 different connection order set.
  • the first to third LDPC codes have the same length of the codeword, the same code rate, the same variable node order distribution, and the same check node order distribution.
  • the connection order set and the connectivity distribution of the check nodes of the first to third LDPC codes are different from each other. Table 1 below shows the number of different connection order sets appearing in the first to third LDPC codes.
  • the connectivity is widely spread in the order of the first LDPC code, the second LDPC code, and the third LDPC code.
  • 11 is a diagram illustrating a frame error rate curve of each of the first to third LDPC codes.
  • the third LDPC code has the best performance in the falling water region, and the second LDPC code shows the best performance, and the first LDPC code shows the poor performance. That is, the LDPC code having various connection order sets of check nodes, that is, a large number of different connection order sets, has a better performance in a falling water region.
  • the first LDPC code has the best performance
  • the second LDPC code has the best performance
  • the third LDPC code has the worst performance. That is, the LDPC code having a relatively uniform connection order set of the check node, that is, a small number of different connection order sets, has better performance in the error-floor region.
  • a fall / error-floor conflict is adjusted in consideration of the connection order set and the connectivity of the test node.
  • FIG. 12 is a frame error rate curve graph of a channel quality adaptive LDPC encoding / decoding method according to an embodiment of the present invention. That is, it is a graph illustrating a frame error rate curve of a communication device that selects an LDPC code having an optimal fall / error-floor conflict performance based on a stochastic characteristic on channel link quality.
  • the encoder of the LDPC code selects and encodes an LDPC code having excellent fall / error-floor conflict performance in the channel link quality in a situation where the quality of the channel link is known.
  • SNR signal-to-noise ratio
  • the LDPC coder according to the present invention has the same or similar codeword length, code rate, and order distribution, and has a different number of connected order set distributions and connectivity distributions, thereby showing different drop / error-floor conflict performance.
  • An LDPC code to be used for encoding is selected within the LDPC code group based on a stochastic characteristic on the quality of channel link using the group.
  • an encoder of a communication device using an LDPC code has three LDPC code groups having different falling / error-floor conflict performances.
  • the LDPC code group may include first to third LDPC codes of FIGS. 8 to 10.
  • error correction such as a frame error rate curve 1201 Have the ability.
  • overall performance improvement can be expected in data transmission throughput and final error rate of the communication system. That is, by adaptively selecting the LDPC code without being affected by the change in channel link quality, it always has an optimal error correction capability.
  • FIG. 13 is a flowchart of a parity check matrix generation method of an LDPC code according to an embodiment of the present invention
  • FIG. 14 is a detailed flowchart of a condition determination step of FIG. 13.
  • a method of generating a parity check matrix of a low density parity check (LDPC) code is based on a channel link quality of a communication system using the LDPC code.
  • a condition setting step (S1310) of determining at least one of a connected-degree set condition and a connectivity condition of the check nodes based on the parity based on at least one of the determined connection order set condition and the connectivity condition A check matrix may be generated (S1320).
  • connection of check nodes to generate a parity check matrix of the LDPC code having the best error correction capability in the communication system Use order aggregation conditions, or connectivity conditions.
  • the condition setting step (S1310) includes determining a communication system to which the LDPC code is applied (S1410), and the average quality of the channel link of the determined communication system is higher than a predetermined quality criterion. Determining whether it is excellent (S1420), if the quality of the channel link is superior to a predetermined quality standard, as a result of the determination, minimizing the number of different connection order sets by uniformizing the connection order sets (S1430), Minimizing the variance of connectivity when the quality of the channel link is better than the preset quality criterion (S1440); when the quality of the channel link is worse than the predetermined quality criterion, varying the connection order set to diversify the different connection order Maximizing the number of sets (S1450); and maximizing the connectivity variance value if the quality of the channel links is worse than the preset quality criteria. It may include (S1450).
  • the communication system is determined and the average channel link quality of the determined communication system is determined. For example, it is determined whether the quality of the channel link between the transmitter and the receiver included in the communication system is generally low, or whether the quality of the channel link between the transmitter and the receiver is generally good.
  • the average quality of the determined channel link is compared with a predetermined quality criterion, and a connection order set or condition of connectivity is determined based on the comparison result.
  • the error rate curve of the LDPC code is divided into the downfall area 510 and the error-floor area 520 by the quality of the channel link, and the dispersion of the connectivity of the test nodes is large or the connection order set is high.
  • the channel link quality may be determined based on a bit energy-to-noise ratio (Eb / No), and is represented on the horizontal axis 501 of the graph of FIG. 5.
  • the preset quality criterion 540 includes a frame error rate curve of the LDPC code belonging to a waterfall region 510, and the quality criterion 540.
  • the frame error rate curve of the LDPC code may belong to an error-floor region 520.
  • the quality criterion 540 is compared with the quality of the channel link to determine whether the quality of the channel link is superior to the quality criterion 540 (S1420).
  • the connection order set condition is that if the channel link quality is worse than a preset quality criterion 540, the number of connection order sets of the test nodes is set to be larger than a preset connection order set criterion. If the channel link quality is superior to a preset quality criterion 540, the number of different connection order sets of the check nodes is less than the preset number of different connection order sets. It is possible to set the connection order set to be uniform (S1430). The preset different sets of connection order sets may be used to find and use different sets of connection order sets having similar error correction capability in the falling water region or the error-floor region through simulation.
  • the connectivity condition may be set such that when the channel link quality is worse than a preset quality criterion 540, the variance value of the connectivity of the test nodes is greater than a preset connectivity variance criterion (S1460). If the link quality is superior to the preset quality criterion 540, the distribution value of the connectivity of the check nodes may be set to be smaller than the preset connectivity dispersion value criterion (S1440).
  • the predetermined connectivity variance criterion may be used to find and use different connection order sets having similar error correction capability in the falling water region or the error-floor region through simulation.
  • the quality of the channel link can vary depending on the situation, so that using the parity check matrix of the first LDPC code has excellent error correction capability in the error-floor region when the quality of the channel link is good.
  • it has poor error correction capability in the falling down region, and using the parity check matrix of the second LDPC code has poor error correction capability in the error-floor region when the quality of the channel link is excellent.
  • a situation with excellent error correction capability may occur in the downpour area when the channel link quality is poor. Accordingly, there is a need for an LDPC code encoding method that selects a parity check matrix of an LDPC code adaptively to the quality of a channel link and always has an optimal error correction capability.
  • 15 is a flowchart of a method of encoding an LDPC code according to an embodiment of the present invention.
  • a method of encoding a low density parity check (LDPC) code includes inputting information data (S1501) and connecting order sets of check nodes. generating a parity check matrix of a predetermined number of LDPC codes different from at least one of a degree set condition and a connectivity condition (S1502), and selecting one parity check matrix from the generated number of parity check matrices And a step S1505 of generating a codeword by encoding the information data based on the selected parity check matrix.
  • S1501 information data
  • S1502 degree set condition and a connectivity condition
  • the step of selecting the parity check matrix may include measuring channel link quality of a communication system in which the LDPC code is used (S1503), and generating the predetermined number of parity check matrices based on the channel link quality.
  • the method may include selecting one parity check matrix having the best error correction capability (S1504).
  • Information data including information to be transmitted through a channel link of the communication system is input (S1501), and a predetermined number of parity check matrices are generated to encode the information data (S1502).
  • the parity check matrix of the LDPC code may generate a predetermined number of parity check matrices having different connection order aggregation conditions or connectivity conditions for adaptively selecting the quality of the channel link.
  • a parity check matrix of three LDPC codes is generated, and as described through Table 1, the parity check matrix of the first LDPC code has the number of 129 different connection order sets, and the parity of the second LDPC code.
  • the parity check matrix may have the number of 2021 different connection order sets, and the parity check matrix of the third LDPC code may have the number of 2445 different connection order sets.
  • the connectivity variance of the parity check matrices of the LDPC code is the smallest when the parity check matrix of the first LDPC code is used, and the parity check matrix of the second LDPC code and the third LDPC code.
  • the parity check matrix grows in order.
  • measuring the channel link quality may include estimating the channel link quality based on a stochastic characteristic of the channel link quality, which may include a signal-to-noise ratio (SNR). It can be characterized.
  • one of the generated parity check matrices having the best error correction capability is selected (S1504).
  • a frame error rate curve can be obtained for encoding using a parity matrix of each LDPC code through simulation.
  • the parity check matrix having the best error correction capability may be selected with reference to the frame error rate curve based on the measured or estimated channel link quality. For example, referring to FIG. 11, when the quality of the measured or estimated channel link is 1.0, the smallest frame error rate is shown when the parity check matrix of the second LDPC code is used (1120). The parity check matrix can be selected.
  • the selection criterion of the parity check matrix may use any criterion including not only the quality of the channel link described above but also the characteristics, state and type of the channel link.
  • a quality criterion may be set in advance, and one of the generated predetermined number of parity check matrices may be selected based on a result of comparing the quality criterion with the quality of the measured or estimated channel link.
  • the number of different connection order sets of the check nodes among the generated predetermined number of parity check matrices is larger than the preset connection order set number criterion.
  • a parity check matrix is selected, and if the measured or estimated channel link quality is superior to a preset quality criterion, the number of sets of different connection order sets of the check nodes among the generated predetermined number of parity check matrices is preset A parity check matrix may be selected that is smaller than the set number criterion.
  • the parity check of the generated variance of the connectivity of the test nodes is greater than the predetermined variance criterion of the connectivity among the predetermined number of parity check matrices.
  • the variance value of the connectivity of the check nodes among the generated predetermined number of parity check matrices is greater than the preset variance criterion of the connectivity. You can select a small parity check matrix.
  • the quality criterion of the LDPC code is that the frame error rate curve of the LDPC code belongs to a waterfall region when the channel link quality is poorer than the quality criterion, and the channel link quality is superior to the quality criterion.
  • the frame error rate curve may be characterized as belonging to an error-floor region.
  • the quality criterion 1140 may be set, and the number of different connection order sets may be set to 1000. Therefore, when the quality of the channel link exceeds 1.05, the parity check matrix of the first LDPC code having the number of 129 different connection order sets less than 1000, which is based on the preset number of connection order sets, is selected, and the quality of the channel link is selected. If less than 1.05, it is possible to select a parity check matrix of the third LDPC code having the number of 2446 different connection order sets greater than 1000, which is a preset number of connection order sets.
  • a plurality of quality standards may be set like the first quality standard and the second quality standard, and the interval may be set using the plurality of quality criteria to select a parity check matrix corresponding to each quality interval.
  • a codeword may be generated by encoding the information data based on the selected parity check matrix (S1505).
  • the codeword generation method may use a conventional LDPC code encoding method.
  • a frame error rate curve 1201 having an optimal error correction capability can be obtained. That is, by selecting the parity check matrix adaptively to the quality of the channel link, it is possible to solve the fall / error-floor conflict and obtain the encoding result of the LDPC code having the optimal error correction capability.
  • 16 is a block diagram of an apparatus for encoding an LDPC code, according to an embodiment of the present invention.
  • the LDPC code encoding apparatus includes an input unit 1610 for inputting information data, a connected-degree set condition of test nodes, or connectivity.
  • Parity check matrix generator 1620 for generating a parity check matrix of a predetermined number of LDPC codes having different conditions; a measurer 1630 for measuring channel link quality of a communication system in which the LDPC code is used;
  • a controller 1640 for selecting one parity check matrix having the best error correction capability among the generated predetermined number of parity check matrices based on quality, and encoding the information data based on the selected parity check matrix.
  • the encoder 1650 to generate and the communicator 1660 to transmit the generated codeword to the decoding apparatus through a channel link.
  • the measurement unit 1630 may estimate the channel link quality based on a stochastic characteristic of the channel link quality, which may include a signal-to-noise ratio (SNR).
  • SNR signal-to-noise ratio
  • the controller 1640 may have a larger number of sets of different connection order sets of the check nodes among the generated predetermined number of parity check matrices. If a parity check matrix is selected and the channel link quality is superior to a preset quality criterion, the number of different connection order sets of the check nodes among the generated predetermined number of parity check matrices is greater than the preset connection order set number criterion. You can choose a smaller parity check matrix.
  • the controller 1640 may have a variance value of the connectivity of the check nodes greater than a predetermined variance criterion of the connectivity among the predetermined number of parity check matrices.
  • a parity check matrix is selected, and if the channel link quality is superior to a preset quality criterion, the variance value of the connectivity of the check nodes among the generated predetermined number of parity check matrices is smaller than the preset variance criterion of connectivity. You can select a check matrix.
  • the quality criterion is that the frame error rate curve of the LDPC code belongs to a waterfall region when the channel link quality is poorer than the quality criterion, and the frame error rate of the LDPC code when the channel link quality is superior to the quality criterion.
  • the curve may be characterized as belonging to an error-floor region.
  • a detailed operation method of the encoding apparatus of the LDPC code according to the embodiment of the present invention is the same as the description of the encoding method of the LDPC code according to the embodiment of the present invention described above.
  • controller 1650 encoder

Abstract

La présente invention concerne une conception d'un code de contrôle de parité à faible densité (LDPC), qui est utilisé dans divers environnements de communication comprenant une transmission de données et une compression de données, et concerne un procédé et un appareil pour concevoir un code LDPC approprié en fonction de caractéristiques et d'exigences d'une technologie appliquée utilisant le code LDPC et de la qualité d'une liaison de canal et l'utiliser pour un codage/décodage à correction d'erreur. Le procédé pour concevoir le code LDPC, selon la présente invention, est caractérisé par la considération d'un ensemble de degré de connexion, d'une diversité de connectivités et d'une distribution de nœuds variables qui sont connectés à un nœud de contrôle sur un graphe de Tanner, qui affiche visuellement une matrice de contrôle de parité du code LDPC.
PCT/KR2012/007732 2011-11-09 2012-09-26 Procédé de génération de matrice de contrôle de parité adaptée à la qualité de liaison de canal et procédé et appareil de codage de code de contrôle de parité à faible densité l'utilisant WO2013069887A1 (fr)

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CN104639178A (zh) * 2015-03-06 2015-05-20 中山大学 一种基于ldpc码的动态列更新译码方法
WO2016140514A1 (fr) * 2015-03-02 2016-09-09 Samsung Electronics Co., Ltd. Émetteur et son procédé de segmentation
CN107317587A (zh) * 2016-04-27 2017-11-03 王晋良 低密度奇偶检查码的编解码方法

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WO2016140514A1 (fr) * 2015-03-02 2016-09-09 Samsung Electronics Co., Ltd. Émetteur et son procédé de segmentation
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CN107317587B (zh) * 2016-04-27 2020-08-28 王晋良 低密度奇偶检查码的编解码方法

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