Kabushiki Kaisha Toshiba

Toshiba Memory Corporation

Kioxia Corporation

Amr Ismail

Magnus Stig Torsten Sandell

Filippo Tosato

A method for storing input data in a flash memory. The method comprising generating a codeword by encoding the input data with an error correcting code and generating a shaped codeword by applying a shaping function to at least a part of the codeword. The shaping function comprising logically inverting every n-th occurrence of a bit associated with a high-charge storage state in the part of the codeword. The method further comprising writing the shaped codeword to the flash memory, generating an estimated shaped codeword by reading the flash memory, generating soft decision information for the estimated shaped codeword, and retrieving the input data by decoding the soft decision information using an error correcting code soft decoder.

Endurance modulation for flash storage

A method of soft decoding received signals. The method comprising defining quantisation intervals for a signal value range, determining a number of bits in each quantisation interval that are connected to unsatisfied constraints, providing, the number of bits in each quantisation interval that are connected to unsatisfied constraints, as an input to a trained model, wherein the trained model has been trained to cover an operational range of a device for soft decoding of signals, determining, using the trained model, a log likelihood ratio for each quantisation interval, and performing soft decoding using the log likelihood ratios.

LLR estimation for soft decoding

A method of generating soft decision detection parameters for a plurality of received signals. The method comprises defining a hard decision boundary and a plurality of quantisation intervals wherein each quantisation interval extends from the hard decision boundary by an interval distance, selecting a log likelihood value from a set of log likelihood values for each received signal based on the quantisation interval in which the received signal is detected, performing a soft decoding using a plurality of log likelihood values, adjusting the set of log likelihood values based on a result of the soft decoding, determining an error probability for a quantisation interval, comparing the error probability against a target error probability and adjusting the interval distance in order to obtain the target error probability.

Method and device for generating soft decision detection parameters

A method of storing a number of data values in a plurality of flash memory cells wherein each flash memory cell has a plurality of storage states and each data value is selected from a set of possible data values. The method comprises programming the number of data values to the plurality of flash memory cells using a mapping which uniquely associates each combination of storage states for the plurality of flash memory cells with a concatenated data value from a set of concatenated data values wherein the set of concatenated data values comprises a concatenated data value for every combination of possible data values for the number of data values, the concatenated data value has a position for each data value in the number of data values and the mapping is such that between adjacent storage states all but one data values are identical and each position in the concatenated data value changes the data value it represents between the same storage states on each flash memory cell.

Multi-cell modulation for flash memory

A method of decoding data stored in non-volatile memory in which each memory cell stores data by adopting one of a plurality of storage states. The method comprises using a threshold for determining a physical property of the memory cells to distinguish between at least two storage states, reading a data codeword from a plurality of the memory cells using the threshold and determining a bit error rate for the data codeword read using the threshold, repeatedly modifying said threshold and re-reading said data codeword using said modified threshold and determining a modified bit error rate for the data codeword read using the modified threshold, selecting the one of the modified thresholds for which the mutual information content between the stored data input and the read data is maximised based on the bit error rate for the data codeword read using the threshold and the bit error rate for the data codeword read using the modified threshold, determining a log likelihood ratio of a quantisation interval bounded by the threshold and the selected threshold generating soft decoded data by performing soft decoding of the data using said log likelihood ratio and outputting the soft decoding data.

Dynamic detection for flash memory

A method of soft decoding received signals. The method comprises defining quantisation intervals for a signal value range, determining a number of bits detected in each quantisation interval, a number of bits in each quantisation interval that are connected to unsatisfied constraints and a probability that the error correction code is unsatisfied, determining an overall bit error rate based on the probability that the error correction code is unsatisfied, determining a log likelihood ratio for each quantisation interval based on the overall bit error rate, the number of bits detected in each quantisation interval and the number of bits in each quantisation interval that are connected to unsatisfied constraints and performing soft decoding using the log likelihood ratios.

Soft decoding for flash memory

There is provided a device and method for demodulating a pulse amplitude modulated, hereinafter referred to as PAM, signal. The device comprises memory storing a set of boundaries of regions in which the log likelihood ratio, hereinafter referred to as LLR, for each bit to be determined is represented by a linear function of the received signal, along with the properties of the linear function for each bit for each region; and a controller. The controller is configured to: receive a PAM signal to be demodulated; determine which region the signal falls within; for each bit to be determined, retrieve the properties of the linear function for the LLR for the bit within the determined region and determine, from this linear function, the LLR value for the bit; and demodulate the signal based on the determined LLR values.

Demodulation of nonuniform QAM signals

A device for use in demodulating modulated signals by determining a value for a log likelihood ratio. The device has a storage device to store executable instructions and a processor to execute the instructions stored on the memory device. The processor is configured to, when executing the instructions: receive a modulated signal which is to be demodulated using a constellation diagram comprising a plurality of constellation points which are identified by binary reflected Gray-labelled codes; identify, for a bit of the Gray-labelled codes, a closest complementary constellation point to the signal when considering the signal as a point on a representation of one-dimension of the constellation diagram; identify a hard decision point, wherein the hard decision point is the closest constellation point to the signal when considering the signal as a point on a representation of one-dimension of a constellation diagram; and a complementary constellation point is a constellation point which has a different value for the bit compared to the hard decision point; and determine a value for a log likelihood ratio using the hard decision point and the closest complementary constellation point. Some devices identify a closest complementary constellation point to the signal, a second closest complementary constellation point to the signal, a hard decision point and an auxiliary hard decision point and determine a value for a log likelihood ratio using the hard decision point, an auxiliary hard decision point, the closest complementary constellation point and the second closest complementary constellation point.

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Bristol, United Kingdom

Amr Ismail