LDPC (Low Density Parity Check) coded modulation symbol decoding using non-Gray code maps for improved performance
First Claim
1. A decoder that is operable to perform symbol decoding of an LDPC-BICM (Low Density Parity Check-Bit Interleaved Coded Modulation) signal that includes at least one symbol that is mapped using a non-Gray code mapping, the decoder comprising:
- a check node update functional block that calculates a plurality of forward metrics and a plurality of backward metrics that correspond to symbol of a plurality of symbols of the LDPC-BICM signal;
wherein the check node update functional block uses the plurality of forward metrics and the plurality of backward metrics that correspond to each symbol of the plurality of symbols of the LDPC-BICM signal to update a plurality of edge messages that corresponds to a plurality of edges that communicatively couple a plurality of symbol nodes to a plurality of check nodes within an LDPC coded modulation bipartite graph that corresponds to an LDPC code;
a symbol sequence estimate and symbol node update functional block that computes a plurality of possible soft symbol estimates for each symbol of the plurality of symbols of the LDPC-BICM signal;
wherein the symbol sequence estimate and symbol node update functional block updates the plurality of edges using the plurality of possible soft symbol estimates;
wherein the check node update functional block and the symbol sequence estimate and symbol node update functional block cooperatively perform iterative decoding of the plurality of symbols of the LDPC-BICM signal; and
wherein, during a last iterative decoding iteration, the symbol sequence estimate and symbol node update functional block makes a best estimate for each symbol of the plurality of symbols of the LDPC-BICM signal using that symbol'"'"'s corresponding plurality of possible soft symbol estimates.
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Abstract
LDPC (Low Density Parity Check) coded modulation symbol decoding using non-Gray code maps for improved performance. Symbol decoding is supported by appropriately modifying an LDPC tripartite graph to eliminate the bit nodes thereby generating an LDPC bipartite graph (such that symbol nodes are appropriately mapped directly to check nodes thereby obviating the bit nodes). The edges that communicatively couple the symbol nodes to the check nodes are labeled appropriately to support symbol decoding of the LDPC coded modulation signal. In addition, the LDPC coded modulation symbol decoding can be employed to decode a signal that has been encoded using LDPC-BICM (Low Density Parity Check-Bit Interleaved Coded Modulation) encoding with non-Gray code mapping. By using the non-Gray code mapping, a performance improvement over such a system using only Gray code mapping may be achieved.
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Citations
30 Claims
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1. A decoder that is operable to perform symbol decoding of an LDPC-BICM (Low Density Parity Check-Bit Interleaved Coded Modulation) signal that includes at least one symbol that is mapped using a non-Gray code mapping, the decoder comprising:
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a check node update functional block that calculates a plurality of forward metrics and a plurality of backward metrics that correspond to symbol of a plurality of symbols of the LDPC-BICM signal; wherein the check node update functional block uses the plurality of forward metrics and the plurality of backward metrics that correspond to each symbol of the plurality of symbols of the LDPC-BICM signal to update a plurality of edge messages that corresponds to a plurality of edges that communicatively couple a plurality of symbol nodes to a plurality of check nodes within an LDPC coded modulation bipartite graph that corresponds to an LDPC code; a symbol sequence estimate and symbol node update functional block that computes a plurality of possible soft symbol estimates for each symbol of the plurality of symbols of the LDPC-BICM signal; wherein the symbol sequence estimate and symbol node update functional block updates the plurality of edges using the plurality of possible soft symbol estimates; wherein the check node update functional block and the symbol sequence estimate and symbol node update functional block cooperatively perform iterative decoding of the plurality of symbols of the LDPC-BICM signal; and wherein, during a last iterative decoding iteration, the symbol sequence estimate and symbol node update functional block makes a best estimate for each symbol of the plurality of symbols of the LDPC-BICM signal using that symbol'"'"'s corresponding plurality of possible soft symbol estimates. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A decoder that is operable to perform symbol decoding of an LDPC-BICM (Low Density Parity Check-Bit Interleaved Coded Modulation) signal that includes at least one symbol that is mapped using a non-Gray code mapping, the decoder comprising:
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a check node update functional block that is operable to update a plurality of edge messages that corresponds to a plurality of edges that communicatively couple a plurality of symbol nodes to a plurality of check nodes within an LDPC (Low Density Parity Check) coded modulation bipartite graph that corresponds to an LDPC code; and a symbol sequence estimate and symbol node update functional block that is operable to employ the updated plurality of edge messages when making a best estimate of a symbol of the LDPC-BICM signal. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A decoding method that performs symbol decoding of an LDPC-BICM (Low Density Parity Check-Bit Interleaved Coded Modulation) signal that includes at least one symbol that is mapped using a non-Gray code mapping, the method comprising:
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receiving a symbol block, that includes a plurality of symbols, of the LDPC-BICM signal; mapping the plurality of symbols according to at least one modulation that corresponds to the plurality of symbols thereby generating a plurality of mapped symbols, wherein the at least one modulation includes a constellation and mapping; making initial estimates of each mapped symbol of the plurality of mapped symbols; calculating initial conditions of a plurality of forward metrics and a plurality of backward metrics that correspond to at least one symbol of the plurality of mapped symbols; beginning with the initial conditions of the plurality of forward metrics and the plurality of backward metrics that correspond to the at least one symbol of the plurality of mapped symbols, calculating a plurality of forward metrics and a plurality of backward metrics that correspond to each mapped symbol of the plurality of mapped symbols; updating a plurality of edge messages, that corresponds to a plurality of edges that communicatively couple a plurality of symbol nodes to a plurality of check nodes within an LDPC coded modulation bipartite graph that corresponds to an LDPC code, using the plurality of forward metrics and the plurality of backward metrics that correspond to each mapped symbol of the plurality of mapped symbols; computing a plurality of soft symbol estimates for each mapped symbol of the plurality of mapped symbols; updating each edge message of the plurality of edges messages using the corresponding plurality of soft symbol estimates for each mapped symbol of the plurality of mapped symbols; performing iterative decoding of the plurality of mapped symbols; and during a last iterative decoding iteration, estimating each mapped symbol of the plurality of mapped symbols using that mapped symbol'"'"'s corresponding plurality of soft symbol estimates thereby generating best estimates of each symbol of the plurality of symbols of the LDPC-BICM signal. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. A decoding method that performs symbol decoding of an LDPC-BICM (Low Density Parity Check-Bit Interleaved Coded Modulation) signal that includes at least one symbol that is mapped using a non-Gray code mapping, the method comprising:
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calculating a plurality of forward metrics and a plurality of backward metrics that correspond to each mapped symbol of a plurality of mapped symbols that is mapped from a plurality of symbols of the LDPC-BICM signal; updating a plurality of edge messages, that corresponds to a plurality of edges that communicatively couple a plurality of symbol nodes to a plurality of check nodes within an LDPC bipartite graph that corresponds to an LDPC code, using the plurality of forward metrics and the plurality of backward metrics that correspond to each mapped symbol of the plurality of mapped symbols; computing a plurality of soft symbol estimates for each mapped symbol of the plurality of mapped symbols; updating each edge message of the plurality of edges messages using the corresponding plurality of soft symbol estimates for each mapped symbol of the plurality of mapped symbols; performing iterative decoding of the plurality of mapped symbols; and during a last iterative decoding iteration, estimating each mapped symbol of the plurality of mapped symbols using that mapped symbol'"'"'s corresponding plurality of soft symbol estimates thereby generating best estimates of each symbol of the plurality of symbols of the LDPC-BICM signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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Specification