Abstract: According to an embodiment, a row decoder to perform row decoding by using, as row soft input information, a row received word read as soft determination information from a non-volatile memory and to calculate row extrinsic information and a column decoder to perform column decoding by using column soft input information, which is a result of adding of the row extrinsic information to a column received word read as soft determination information from the non-volatile memory, and to calculate column extrinsic information are included. The row decoder includes a first decoder for first decoding, a second decoder for second decoding a decoding method of which is different from that of the first decoding, and a selection unit to select a decoded result based on accuracy of a decoded result of the first decoding and that of a decoded result of the second decoding and to calculate the row extrinsic information.

Abstract: An embodiment includes: a first decoder configured to calculate first distance information indicating a squared Euclidean distance between a first decoded word obtained by decoding a first received word read from a nonvolatile memory and the first received word, calculate a decoding success rate based on the first distance information, and calculate a first extrinsic value vector based on the first decoding success rate; and a second decoder configured to decode a result obtained by adding a second received word read from the nonvolatile memory to the rearranged set of the first extrinsic values corresponding to the second codeword, calculate second distance information based on a second decoded word obtained by the decoding, calculate a decoding success rate based on the second distance information, and calculate a second extrinsic value based on the second decoding success rate.

Abstract: According to one embodiment, an encoding apparatus includes an input unit and a generation unit. The input unit inputs a data symbol sequence containing q(N?J) symbols (q, J, and N are integers, N>J). The generation unit generates a codeword containing qN symbols by adding a parity symbol sequence containing qJ symbols to the data symbol sequence. The codeword satisfies parity check equations of a parity check matrix of qJ rows×qN columns. A first submatrix of qJ rows×qJ columns that corresponds to the parity symbol sequence in the parity check matrix includes a second submatrix. The second submatrix includes a first identity matrix of qL rows×qL columns (L is an integer, J>L) and a first non-zero matrix of q(J?L) rows×qL columns.

Abstract: According to one embodiment, a decoder includes a control unit and a decoding unit. The control unit determines a window size applied to a first target frame to be a first value and determines a window size applied to a second target frame different from the first target frame to be a second value different from the first value. The decoding unit carries out windowed decoding of a spatially coupled code on the first target frame with the window size set to the first value and carries out windowed decoding of a spatially coupled code on the second target frame with the window size set to the second value.

Abstract: A semiconductor memory device includes a semiconductor memory unit which stores LDPC encoded data, and a decoding unit which decodes the encoded data, wherein the decoding unit performs serial decoding using the posterior likelihood ratio as it is for a column element likelihood ratio when the absolute value of the posterior likelihood ratio is not smaller than a threshold and using the column element likelihood ratio as it is for the posterior likelihood ratio when the absolute value of the column element likelihood ratio is not smaller than the threshold, and if the decoding does not succeed even after a predetermined first cycle count of iterative processing is performed or if the number of syndrome errors becomes smaller than a predetermined first syndrome error count, the decoding unit shrinks the absolute values of at least some of posterior likelihood ratios and resets all prior likelihood ratios to “0.

Abstract: According to embodiments, an error correction decoder carrying out iterative decoding for coded data based on LDPC code. The decoder comprises a generation unit and an inversion, control unit. The generation unit is configured to generate an inversion node list listing variable nodes connected to check nodes not satisfying a parity check when a code word cannot be obtained after carrying out the iterative decoding a first number of iterations. The inversion control unit is configured to choose a variable node which is a target for inversion from among the variable nodes listed in the inversion node list, and to carry out inversion processing which includes updating an input likelihood of the variable node which is the target for inversion temporarily by inverting a sign of an a posteriori likelihood of the variable node which is the target for inversion.

Abstract: According to one embodiment, a decoder includes a control unit and a decoding unit. The control unit determines a window size applied to a first target frame to be a first value and determines a window size applied to a second target frame different from the first target frame to be a second value different from the first value. The decoding unit carries out windowed decoding of a spatially coupled code on the first target frame with the window size set to the first value and carries out windowed decoding of a spatially coupled code on the second target frame with the window size set to the second value.

Abstract: According to one embodiment, an encoding apparatus includes an input unit and a generation unit. The input unit inputs a data symbol sequence containing q(N?J) symbols (q, J, and N are integers, N>J). The generation unit generates a codeword containing qN symbols by adding a parity symbol sequence containing qJ symbols to the data symbol sequence. The codeword satisfies parity check equations of a parity check matrix of qJ rows×qN columns. A first submatrix of qJ rows×qJ columns that corresponds to the parity symbol sequence in the parity check matrix includes a second submatrix. The second submatrix includes a first identity matrix of qL rows×qL columns (L is an integer, J>L) and a first non-zero matrix of q(J?L) rows×qL columns.

Abstract: A semiconductor memory device includes a semiconductor memory unit which stores LDPC encoded data, and a decoding unit which decodes the encoded data, wherein the decoding unit performs serial decoding using the posterior likelihood ratio as it is for a column element likelihood ratio when the absolute value of the posterior likelihood ratio is not smaller than a threshold and using the column element likelihood ratio as it is for the posterior likelihood ratio when the absolute value of the column element likelihood ratio is not smaller than the threshold, and if the decoding does not succeed even after a predetermined first cycle count of iterative processing is performed or if the number of syndrome errors becomes smaller than a predetermined first syndrome error count, the decoding unit shrinks the absolute values of at least some of posterior likelihood ratios and resets all prior likelihood ratios to “0.

Abstract: According to one embodiment, a signal processing device comprises a first waveform equalizer, a second waveform equalizer, a first Viterbi decoder, a second Viterbi decoder. The first and the second waveform equalizers equalize a waveform of the input signal according to first and second partial response characteristics and output first and second partial response signals. The first and second Viterbi decoders decode the first and the second partial response signals by means of Viterbi decoding process. The input signal is reproduced based on an output of the first Viterbi decoder and an output of the second Viterbi decoder.

Abstract: According to an embodiment, an encoder has a storage and a generator. The storage stores information indicative of a generator matrix corresponding to a partial parity check matrix in a rank-deficient parity check matrix including a lower triangular matrix and one or more cyclic matrices or zero matrices, the partial parity check matrix including rows different from rows of the lower triangular matrix. The generator carries out semi-systematic coding using the generator matrix to generate a portion of code word. The generator matrix has a cyclic matrix portion with one or more cyclic matrices and a non-cyclic matrix portion with rows number of which is equal to a degree of rank deficiency in the partial parity check matrix.

Abstract: According to embodiments, an error correction decoder carrying out iterative decoding for coded data based on LDPC code. The decoder comprises a generation unit and an inversion, control unit. The generation unit is configured to generate an inversion node list listing variable nodes connected to check nodes not satisfying a parity check when a code word cannot be obtained after carrying out the iterative decoding a first number of iterations. The inversion control unit is configured to choose a variable node which is a target for inversion from among the variable nodes listed in the inversion node list, and to carry out inversion processing which includes updating an input likelihood of the variable node which is the target for inversion temporarily by inverting a sign of an a posteriori likelihood of the variable node which is the target for inversion.

Abstract: According to an embodiment, an error correction decoder carries out iterative decoding for data coded using an irregular LDPC code. The decoder includes a likelihood control unit. The likelihood control unit is configured to carry out weighting using first extrinsic value weights when a first condition including a condition that a code word cannot be obtained even when number of times the iterative decoding has been carried out is greater than a first iterative times, in order to increase absolute value of a extrinsic value from a check node not satisfying a parity check to a variable node, wherein the first extrinsic value weights are equal to each other or become larger in descending order of column weights of the variable nodes, and a maximum of the first extrinsic value weights is not equal to a minimum of the first extrinsic value weights.

Abstract: According to one embodiment, a signal processing device comprises a first waveform equalizer, a second waveform equalizer, a first Viterbi decoder, a second Viterbi decoder. The first and the second waveform equalizers equalize a waveform of the input signal according to first and second partial response characteristics and output first and second partial response signals. The first and second Viterbi decoders decode the first and the second partial response signals by means of Viterbi decoding process. The input signal is reproduced based on an output of the first Viterbi decoder and an output of the second Viterbi decoder.