IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0158263
(2011-06-10)
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등록번호 |
US-8689083
(2014-04-01)
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발명자
/ 주소 |
- Nguyen, Thuy V.
- Nosratinia, Aria
- Divsalar, Dariush
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출원인 / 주소 |
- California Institute of Technology
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
2 인용 특허 :
8 |
초록
▼
Digital communication coding methods resulting in rate-compatible low density parity-check (LDPC) codes built from protographs. Described digital coding methods start with a desired code rate and a selection of the numbers of variable nodes and check nodes to be used in the protograph. Constraints a
Digital communication coding methods resulting in rate-compatible low density parity-check (LDPC) codes built from protographs. Described digital coding methods start with a desired code rate and a selection of the numbers of variable nodes and check nodes to be used in the protograph. Constraints are set to satisfy a linear minimum distance growth property for the protograph. All possible edges in the graph are searched for the minimum iterative decoding threshold and the protograph with the lowest iterative decoding threshold is selected. Protographs designed in this manner are used in decode and forward relay channels.
대표청구항
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1. A digital communication coding method, comprising: selecting a desired rate to be implemented by a low-density parity-check (LDPC) code represented by a protograph;selecting a number of variable nodes and a number of check nodes to be implemented in the protograph;selecting constraints for the pr
1. A digital communication coding method, comprising: selecting a desired rate to be implemented by a low-density parity-check (LDPC) code represented by a protograph;selecting a number of variable nodes and a number of check nodes to be implemented in the protograph;selecting constraints for the protograph;searching for all possible edges in the protograph to create computed permutations of the protograph;computing an iterative decoding threshold for each computed permutation of the protograph; andselecting the computed permutation of the protograph with a lowest computed iterative decoding threshold to implement the LDPC code. 2. The method according to claim 1, wherein selecting constraints for the protograph comprises selecting contracts for the protograph to satisfy a linear minimum distance property. 3. The method according to claim 1, wherein at least one variable node comprises a punctured node. 4. The method according to claim 1, wherein selecting a desired rate comprises selecting a rate of 1/2 and selecting a number of variable nodes comprises selecting 7 variable nodes and selecting a number of check nodes comprises selecting 4 check nodes and wherein the protograph is represented by a proto-matrix having four rows and seven columns and selecting constraints comprises: constraining a first column of the proto-matrix to have a degree of 1;constraining a second column of the proto-matrix to have a degree of 2;constraining a third column of the proto-matrix to be punctured; andconstructing a submatrix within the proto-matrix, wherein the submatrix comprises columns two through seven and rows two through four of the proto-matrix, wherein two or fewer columns in the submatrix have a degree of two and all columns in the submatrix not having a degree of two have a degree of three or greater and the maximum number of parallel edges represented in the third column of the submatrix is three and the maximum number of parallel edges represented in the remaining columns of the submatrix is two. 5. The method according to claim 4, wherein the selected computed permutation of the protograph comprises the following proto-matrix: H1/2′=(1000020010131110112221020002)4×7. 6. The method according to claim 1, wherein selecting a desired rate comprises selecting a higher rate based on a lower rate code implemented in a lower rate protograph having four check nodes and represented by a lower rate parity check matrix and selecting constraints for the protograph comprises constructing a higher rate parity check matrix for the selected higher rate, wherein the higher rate parity check matrix comprises the lower rate parity check matrix extended with three additional columns, wherein a first row of the three additional columns comprises edges for a check node that connects to a degree-1 variable node and rows two through four of the three additional columns comprise a subgraph, wherein sums of each column of the three additional columns within the subgraph are three or higher. 7. The method according to claim 6, wherein the edges in the subgraph are limited to two parallel edges or fewer. 8. The method according to claim 1, wherein selecting a desired rate comprises selecting a higher rate code based on a lower rate code implemented in a lower rate protograph represented by a lower rate parity check matrix and wherein selecting constraints comprises constructing a higher rate parity check matrix for the selected higher rate, wherein the higher rate parity check matrix comprises the lower rate parity check matrix extended with additional columns and wherein searching for all possible edges in the protograph comprises searching the higher rate parity check matrix and the LDPC code has a higher rate than the lower rate code. 9. The method according to claim 8, wherein in a channel having one relay, the higher rate code is selected for transmission from a source to the one relay and a destination, and wherein the lower rate code is received at the destination, and wherein codeword symbols that appear in the lower rate code but not in the higher rate code are provided by the relay to the destination. 10. A digital communication coding method for embedded rate-compatible LDPC codes, the method comprising: selecting a higher rate code represented by a higher rate parity check matrix with a higher rate row dimension and a higher rate column dimension;constructing a protograph represented by a lower rate parity matrix, wherein the lower rate parity matrix is created by extending the higher rate parity matrix by an equal number of added columns and added rows, wherein the added columns and added rows form three submatrices within the lower rate parity matrix, a first submatrix of the three submatrices having a location within the lower rate parity matrix defined by the added columns and the higher rate row dimension, a second submatrix of the three submatrices having a location within the lower rate submatrix defined by the added rows and a lower rate column dimension, and a third submatrix of the three submatrices having a location defined by the added columns and added rows, and wherein the first submatrix is a zero submatrix;constraining edges in the second and third submatrix to maintain linear growth of minimum distance;searching for all possible edges in the proto graph to create computed permutations of the protograph;computing an iterative decoding threshold for each computed permutation of the protograph; andselecting the computed permutation of the protograph with a lowest computed iterative decoding threshold to implement an LDPC code. 11. The method of claim 10, wherein the second submatrix comprises the following edges: edges in a first column of the second submatrix are set equal to zero;edges in a third column of the second submatrix comprise edges connecting to a highest degree variable node in the higher rate parity matrix; and,edges in all other columns of the second submatrix comprise edges connecting to all other variable nodes in the higher rate parity matrix except a degree-1 node, and wherein the third submatrix comprises a lower triangular matrix and the third submatrix comprises the following edges: edges at the main diagonal of the third submatrix are set equal to one;edges above the main diagonal of the third submatrix are set equal to zero; andedges below the main diagonal comprise edges that connect new variable nodes to new check nodes provided by the added rows and the added columns. 12. The method of claim 10, wherein edges in a third column of the second submatrix are set equal to 1 or 2, edges in all other columns of the second submatrix are set equal to 0 or 1 and edges below the main diagonal of the third submatrix are set equal to 0 or 1. 13. A digital communication coding method for rate-compatible LDPC codes comprising: selecting a first rate code represented by a first rate parity check matrix;constructing a second rate parity check matrix by extending the first rate parity check matrix by one or more rows or one or more columns or one or more rows and columns;selecting constraints for a protograph resulting from the second rate parity check matrix;searching for all possible edges in the protograph to create computed permutations of the protograph;computing an iterative decoding threshold for each computed permutation of the protograph; andselecting the computed permutation of the protograph with a lowest computed iterative decoding threshold to implement an LDPC code, wherein the LDPC code comprises a code at a second rate. 14. The method according to claim 13, wherein selecting constraints comprises for a protograph resulting from the second rate parity check matrix comprises selecting constraints for the protograph to satisfy a linear minimum distance property. 15. The method according to claim 13, wherein the first code comprises a high rate code and wherein constructing a second rate parity check matrix comprises constructing the second rate parity check matrix by extending the first rate parity check matrix by one or more added rows and wherein the LDPC code comprises a code at a lower rate than the high rate code. 16. The method according to claim 15, wherein selecting constraints comprises for a protograph resulting from the second rate parity check matrix comprises selecting constraints for the protograph to satisfy a linear minimum distance property. 17. The method according to claim 13, wherein the first rate code comprises a low rate code and wherein constructing a second rate parity check matrix comprises constructing the second rate parity matrix by extending the first rate parity matrix by one or more added columns and wherein the LDPC code comprises a code at a higher rate than the low rate code. 18. The method according to claim 17, wherein selecting constraints comprises for a protograph resulting from the second rate parity check matrix comprises selecting constraints for the protograph to satisfy a linear minimum distance property. 19. The method according to claim 15, wherein in a channel having one relay, the high rate code comprises a high rate codeword and wherein the high rate code is selected for initial transmission from a source to the relay and a destination, and wherein the LDPC code comprises a low rate codeword received at the destination and wherein codeword symbols that appear in the low rate codeword but not in the high rate codeword are provided by the relay to the destination. 20. The method according to claim 15, wherein in a channel with multiple relays, the high rate code is selected for initial transmission from a source to the multiple relays and a destination, and wherein each relay produces and transmits codeword symbols corresponding to a difference between its received codeword and a next lower-rate codeword, and the destination receives and decodes a lowest-rate codeword. 21. A method for transmission within a half-duplex relay channel having at least one relay, the method comprising: selecting a first LPDC code with a rate necessary to support transmission of source data from a source to a destination, wherein the first LDPC code comprising a first LDPC codeword is represented by a first protograph;adding one or more second protograph variable nodes to the first protograph to create a second protograph, wherein the second protograph has a linear distance property and the second protograph implements a second LDPC code comprising a second LDPC codeword;transmitting data from the source with the source data encoded with the second LDPC code;receiving data coded with the second LDPC code at a relay;decoding the data received at the relay to extract the second LDPC codeword;selecting a subset of the one or more second protograph variable nodes of the second LDPC code and adding one or more relay variable and check nodes to the selected subset of the one or more second protograph variable nodes to create a third LDPC code comprising a third LDPC codeword;encoding a combination of selected one or more second protograph variable nodes and one or more relay variable and check nodes with a fourth LDPC code comprising a fourth LDPC codeword;transmitting from the relay the combination of selected one or more second protograph variable nodes and one or more relay variable and check nodes coded with the fourth LPDC code to the destination;decoding data received at the destination to extract the combination of selected one or more second protograph variable nodes and one or more relay variable and check nodes coded with the fourth LDPC code;decoding a subset of the data received at the destination that constitutes the third LDPC codeword to extract a subset of the second LDPC codeword that excludes the first LDPC codeword;decoding a remaining part of data received at the destination with the first LDPC code to extract the first LDPC codeword; andextracting the source data from the extracted subset of the second LDPC codeword at the destination. 22. The method according to claim 21, wherein the first LDPC code comprises a rate-1/2 code. 23. A method for transmission within a half-duplex relay channel having at least one relay, the method comprising: selecting a first LPDC code with a rate necessary to support transmission of source data from a source to a relay, wherein the first LDPC code is represented by a first protograph;adding one or more check nodes and adding one or more variable nodes to the first protograph to create a second protograph, wherein the second protograph has a linear distance property and the second protograph implements a second LDPC code, wherein the added one or more variable nodes correspond to the second LDPC code;transmitting first data from the source, wherein the first data comprises the source data encoded with the first LDPC code;receiving the first data coded with the first LDPC code at the relay;decoding the first data received at the relay to extract the source data coded with the first LDPC code;computing at the relay the added one or more variable nodes corresponding to the second LDPC code to provide computed one or more variable nodes;encoding the computed one or more variable nodes with a third LDPC code;transmitting second data comprising the computed one or more variable nodes coded with the third LDPC code to a destination and transmitting encoded source data to the destination;decoding the second data received at the destination to extract the computed one or more variable nodes; anddecoding the encoded source data received at the destination using the computed one or more variable nodes to extract the source data from the encoded source data received at the destination. 24. The method according to claim 23, wherein the first LDPC code comprises a rate-1/2 code. 25. A method for transmission within a half-duplex relay channel having two or more relays, the method comprising: selecting a first LPDC code with a rate necessary to support transmission of source data from a source to a first relay, wherein the first LDPC code is represented by a first protograph;adding one or more check and variable nodes to the first protograph to create a second protograph, wherein the second protograph has a linear distance property and the second protograph implements a second LDPC code;adding one or more check and variable nodes to the second protograph to create a third protograph, wherein the third protograph has a linear distance property and the third protograph implements a third LDPC code;transmitting first data from the source with the source data encoded with the first LDPC code;receiving the first data coded with the first LDPC code at a first relay;decoding the first data received at the first relay to extract the source data coded with the first LDPC code;computing at the first relay, one or more added first relay variable nodes to produce a first LDPC codeword;encoding the one or more added first relay variable nodes with a fourth LDPC code;transmitting second data comprising the one or more added first relay variable nodes coded with the fourth LPDC code to a second relay and transmitting additional data contained the first LDPC codeword;decoding the second data received at the second relay to extract the one or more added first relay variable nodes coded with the fourth LDPC code;decoding the additional data received at the second relay using the extracted one or more added first relay variable nodes to extract the first LDPC codeword from the additional data received at the second relay;computing at the second relay, one or more added second relay variable nodes to produce a second LDPC codeword;encoding the one or more added second relay variable nodes with the third LDPC code;transmitting the third LDPC code from the second relay to a destination;decoding the third LDPC code at the destination to extract the one or more added second relay variable nodes;decoding the fourth LDPC code at the destination to extract the one or more added first relay variable nodes; anddecoding a destination message using the one or more added first relay variable nodes and the one or more added second relay variable nodes to extract the source data. 26. The method according to claim 25, wherein the first LDPC code comprises a rate-0.75 code. 27. The method according to claim 25, wherein the half-duplex relay channel comprises at least three relays and each subsequent relay after the first relay and the second relay computes additional variable nodes to form additional LDPC codewords.
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