# US 10,374,639 B2 · Adaptive bit-flipping decoder based on dynamic error information

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- Number: US 10,374,639 B2
- Document ID: US10374639B2
- Status: Granted
- Kind: B2
- Application number: 15/896,440
- Filed: 2018-02-14
- Published: 2018-06-21
- Granted: 2019-08-06
- Earliest claimed: 2016-12-06
- Assignees: Western Digital Technologies, Inc.
- Applicants: Western Digital Technologies, Inc.
- Inventors: Alexander Bazarsky; Eran Sharon; Omer Fainzilber; Ran Zamir
- Web page: https://patentgrep.com/patent/US10374639B2

## CPC

- H03M 13/3715: {Adaptation to the number of estimated errors or to the channel state}
- G06F 16/9017: {using directory or table look-up (use of a directory or look-up table in file systems G06F16/13)}
- H03M 13/1108: {Hard decision decoding, e.g. bit flipping, modified or weighted bit flipping}
- H03M 13/3723: {using means or methods for the initialisation of the decoder}
- H03M 13/43: Majority logic or threshold decoding
- H03M 13/6325: {Error control coding in combination with demodulation}
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A device includes a comparator configured to select a first threshold in response to a value of a variable node indicating a first logical value and to select a second threshold in response to the value of the variable node indicating a second logical value. The device also includes a variable node update circuit configured to adjust the value of the variable node in response to a number of unsatisfied check nodes associated with the variable node satisfying the selected threshold.

## Claims

### Claim 1

A device comprising:
a comparator configured to select a first threshold in response to a value of a variable node indicating a first logical value and to select a second threshold in response to the value of the variable node indicating a second logical value; and
a variable node update circuit configured to adjust the value of the variable node in response to a number of unsatisfied check nodes associated with the variable node satisfying the selected threshold.

### Claim 2 (depends on 1)

The device of claim 1. further comprising:
a memory; and
a bit-flipping error correction code (ECC) decoder configured to perform a bitflipping decoding operation on a representation of a codeword read from the memory, the bit-flipping ECC decoder comprising:
the comparator; and
the variable node update circuit.

### Claim 3 (depends on 2)

The device of claim 2, further comprising syndrome circuitry configured to determine, for each particular variable node of a plurality of variable nodes, a number of unsatisfied check nodes associated with the particular variable node.

### Claim 4 (depends on 1)

The device of claim 1, further comprising error detection circuitry configured to determine, based on one or more codewords read from a memory, a first count of erroneous bits having the first logical value and a second count of erroneous bits having the second logical value, wherein the comparator is further configured to select the first threshold based further on a first error rate based at least in part on the first count and to select the second threshold based further on a second error rate based at least in part on the second count.

### Claim 5 (depends on 4)

The device of claim 4, wherein the error detection circuitry is further configured to determine, based on the one or more codewords, a third count of unreliable correct bits having the first logical value and a fourth count of unreliable correct bits having the second logical value, wherein the comparator is further configured to select the first threshold based further on the third count and to select the second threshold based further on the fourth count.

### Claim 6 (depends on 1)

The device of claim 1, further comprising:
a first set of thresholds associated with the first logical value; and
a second set of thresholds associated with the second logical value.

### Claim 7 (depends on 6)

The device of claim 6, wherein the comparator is further configured to:
select the first set of thresholds or the second set of thresholds based on the value of the variable node; and
retrieve the selected threshold from the selected set of thresholds.

### Claim 8 (depends on 7)

The device of claim 7, wherein the comparator is further configured to perform a look-up operation to retrieve the selected threshold from the selected set of thresholds based on a count of cycles of a decoder clock.

### Claim 9 (depends on 6)

The device of claim 6, further comprising:
a third set of thresholds associated with the first logical value; and
a fourth set of thresholds associated with the second logical value.

### Claim 10 (depends on 9)

The device of claim 9, wherein the comparator is further configured to:
select the first set of thresholds, the second set of thresholds, the third set of thresholds, or the fourth set of thresholds based on the value of the variable node-and further based on a reliability indicator associated with the value; and
retrieve the selected threshold from the selected set of thresholds.

### Claim 11 (depends on 10)

The device of claim 10, wherein:
the value of the variable node-corresponds to a hard bit value; and
the reliability indicator corresponds to a soft bit value.

### Claim 12

A method comprising:
selecting, at a bit-flipping decoder:
a first threshold in response to a value of a variable node indicating a first logical value; or
a second threshold in response to the value of the variable node indicating a second logical value; and
adjusting the value of the variable node in response to a number of unsatisfied check nodes associated with the variable node satisfying the selected threshold.

### Claim 13 (depends on 12)

The method of claim 12, further comprising:
determining one or more bit counts based on one or more codewords read from a memory, the one or more bit counts including a first count of erroneous bits having the first logical value and a second count of erroneous bits having the second logical value;
selecting a first set of thresholds or a second set of thresholds based on the value of the variable node, the first set of thresholds associated with the first logical value and the first count, and the second set of thresholds associated with the second logical value and the second count; and
retrieving the selected threshold from the selected set of thresholds.

### Claim 14 (depends on 13)

The method of claim 13, further comprising performing a look-up operation to retrieve the selected threshold from the selected set of thresholds based on a count of decoding clock cycles of the bit-flipping decoder.

### Claim 15 (depends on 12)

The method of claim 12, further comprising:
selecting a first set of thresholds, a second set of thresholds, a third set of thresholds, or a fourth set of thresholds based on the value of the variable node and based on a reliability indicator associated with the value of the variable node,
wherein:
the first set of thresholds and the third set of thresholds are associated with the first logical value, and
the second set of thresholds and the fourth set of thresholds are associated with the second logical value; and
retrieving the selected threshold from the selected set of thresholds.

### Claim 16 (depends on 15)

The method of claim 15, wherein:
the first set of thresholds and the second set of thresholds are further associated with a first reliability value; and
the third set of thresholds and the fourth set of thresholds are further associated with a second reliability value.

### Claim 17 (depends on 16)

The method of claim 16, wherein:
the first set of thresholds is selected based further on a first bit error rate associated with bits having the first logical value and the first reliability value;
the second set of thresholds is selected based further on a second bit error rate associated with bits having the second logical value and the first reliability value;
the third set of thresholds is selected based further on a third bit error rate associated with bits having the first logical value and the second reliability value; and
the fourth set of thresholds is selected based further on a fourth bit error rate associated with bits having the second logical value and the second reliability value.

### Claim 18

An apparatus comprising:
means for selecting a first threshold in response to a value of a variable node indicating a first logical value and for selecting a second threshold in response to the value of the variable node indicating a second logical value; and
means for adjusting the value of the variable node in response to a number of unsatisfied check nodes associated with the variable node satisfying the selected threshold.

### Claim 19 (depends on 18)

The apparatus of claim 18, further comprising:
means for storing a representation of a codeword; and
means for performing a bit-flipping decoding operation on the representation of the codeword read from the means for storing, the means for performing the bit-flipping decoding operation comprising:
the means for selecting; and
the means for adjusting.

### Claim 20 (depends on 19)

The apparatus of claim 19, further comprising means for determining a number of unsatisfied check nodes associated with each variable node of a plurality of variable nodes, the plurality of variable nodes corresponding to bits of the representation of the codeword.