System and method for a message passing algorithm
First Claim
1. A method comprising:
- receiving, by a Message Passing Algorithm (MPA) processor, a sequence of samples representative of a received signal from a device;
receiving, or otherwise generating, one or more probabilities associated codewords of a codebook assigned to a data stream in the received signal, wherein each codeword in the codebook represents a different spreading sequence;
removing, in accordance with the one or more probabilities, at least one of the codewords from the codebook to obtain a pruned codebook, the pruned codebook excluding the at least one codeword;
processing, by the MPA processor, the sequence of samples according to the pruned codebook to generate soft decision values corresponding to the received signal; and
sending the soft decision values to a forward error correction (FEC) decoder for use in bit-level decoding of the received signal.
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Abstract
The complexity of sparse code multiple access (SCMA) decoding can be reduced by pruning codebooks to remove unlikely codewords prior to, or while, performing an iterative message passing algorithm (MPA). The pruned codebook is then used by to perform one or more iterations of MPA processing, thereby reducing the number codeword probabilities that are calculated for the corresponding SCMA layer. The pruned codebook also reduces the computational complexity of calculating codeword probabilities associated with other SCMA layers. The pruned codebook may be “reset” by reinserting the pruned codewords into the codebook after a final hard-decision for a given set of received samples is made, so that the pruning does not affect evaluation of the next set of samples.
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Citations
20 Claims
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1. A method comprising:
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receiving, by a Message Passing Algorithm (MPA) processor, a sequence of samples representative of a received signal from a device; receiving, or otherwise generating, one or more probabilities associated codewords of a codebook assigned to a data stream in the received signal, wherein each codeword in the codebook represents a different spreading sequence; removing, in accordance with the one or more probabilities, at least one of the codewords from the codebook to obtain a pruned codebook, the pruned codebook excluding the at least one codeword; processing, by the MPA processor, the sequence of samples according to the pruned codebook to generate soft decision values corresponding to the received signal; and sending the soft decision values to a forward error correction (FEC) decoder for use in bit-level decoding of the received signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A decoder comprising:
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a forward error correction (FEC) decoder; and a message passing algorithm (MPA) processor coupled to the FEC decoder, the MPA processor configured to receive a sequence of samples representative of a received signal from a device, to receive, or otherwise obtain, one or more probabilities associated codewords of a codebook assigned to a data stream in the received signal, to remove, in accordance with the one or more probabilities, at least one of the codewords from the codebook to obtain a pruned codebook, the pruned codebook excluding the at least one codeword, to process the sequence of samples according to the pruned codebook to generate soft decision values corresponding to the received signal, and to send the soft decision values to a forward error correction (FEC) decoder for use in bit-level decoding of the received signal, wherein each codeword in the codebook represents a different spreading sequence. - View Dependent Claims (19)
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20. A computer program product comprising a computer readable storage medium storing programming, the programming including instructions to:
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receive, at a Message Passing Algorithm (MPA) processor a sequence of samples representative of a received signal from a device; receive, or otherwise obtain, one or more probabilities associated codewords of a codebook assigned to a data stream in the received signal, wherein each codeword in the codebook represents a different spreading sequence; remove, in accordance with the one or more probabilities, at least one of the codewords from the codebook to obtain a pruned codebook, the pruned codebook excluding the at least one codeword; process, at the MPA processor, the sequence of samples according to the pruned codebook to generate soft decision values corresponding to the received signal; and send the soft decision values to a forward error correction (FEC) decoder for use in bit-level decoding of the received signal.
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Specification