Decoding system and method for electronic non-volatile computer storage apparatus

1. A method for providing an input log-likelihood ratio to a decoder of an electronic non-volatile computer storage apparatus, comprising:

estimating a raw bit error rate for a particular data unit;

calculating an input log-likelihood ratio based on a ratio of the estimated raw bit error rate (BER) to (1−BER); and

providing the calculated input log-likelihood ratio to a decoder of an electronic non-volatile computer storage apparatus for decoding data from that particular data unit.

2. The method of claim 1 , wherein the raw bit error rate is estimated by comparing converged data with channel observations for that particular data unit.

3. The method of claim 1 , wherein the input log-likelihood ratio is calculated as

log

⁢

BER

1

-

BER

.

4. The method of claim 3 , wherein the decoder passes

log

⁢

BER

1

-

BER

for 0 and passes

-

log

⁢

BER

1

-

BER

for 1.

5. The method of claim 1 , wherein the raw bit error rate is estimated for each data unit being decoded, wherein the data unit being one of: a line, a page and a block.

6. The method of claim 1 , wherein the decoder is a belief-propagation decoder.

7. A method, comprising:

waiting for at least one decoding iteration;

after said at least one decoding iteration, calculating a bit-based input log-likelihood ratio for each bit based on a confidence value for a cell containing said each bit; and

providing the calculated bit-based input log-likelihood ratio for each bit to a decoder of an electronic non-volatile computer storage apparatus for a subsequent decoding iteration.

8. The method of claim 7 , wherein the bit-based input log-likelihood ratio for each bit is calculated as

C

^

=



∑

i

=

0

d

v

-

1

⁢

u

i



,

wherein u i denotes check node to variable node messages and d v denotes a variable degree.

9. The method of claim 8 , wherein the decoder passes +Ĉ for 1 and passes −Ĉ for 0.

10. The method of claim 8 , wherein the decoder implements iterative message passing, wherein message update on variable nodes of the decoder is calculated as

v

j

=

u

ch

+

∑

i

=

0

,

i

≠

j

d

v

-

1

⁢

u

i

and message update on check nodes of the decoder is calculated as

tan

⁢

⁢

h

⁢

u

i

2

=

∑

j

=

0

,

j

≠

i

d

c

-

1

tan h v j , wherein v j denotes variable node to check node messages, u ch denotes channel information, u i denotes check node to variable node messages, d v denotes a variable degree, and d c denotes a check degree.

11. The method of claim 8 , further comprising:

identifying at least one least reliable bit based on the calculated bit-based input log-likelihood ratio for each bit; and

setting the bit-based input log-likelihood ratio for at least one least reliable bit to 0 prior to providing the bit-based input log-likelihood ratio to the decoder.

12. The method of claim 8 , wherein the decoder is a belief-propagation decoder or a min-sum decoder.

13. An electronic non-volatile computer storage apparatus, comprising:

an encoder configured to encode data written to the electronic non-volatile computer storage apparatus;

a storage module configured to store encoded data from the encoder;

a log-likelihood ratio handler configured to provide an input log-likelihood ratio to a decoder, wherein the input log-likelihood ratio is at least one of:

a uniform input log-likelihood ratio for all bits calculated based on a ratio of an estimated raw bit error rate (BER) to (1−BER) for a particular data unit, and

a bit-based input log-likelihood ratio for each bit calculated based on a confidence value for a cell containing said each bit; and

the decoder configured to decode the encoded data at least partially based on the input log-likelihood ratio from the log-likelihood ratio handler.

14. The electronic non-volatile computer storage apparatus of claim 13 , wherein the log-likelihood ratio handler is configured to provide the uniform input log-likelihood ratio for all bits calculated based on the estimated raw bit error rate for said particular data unit, and wherein the raw bit error rate is estimated by comparing converged data with channel observations for that particular data unit.

15. The electronic non-volatile computer storage apparatus of claim 14 , wherein the input log-likelihood ratio is calculated as

log

⁢

BER

1

-

BER

.

16. The electronic non-volatile computer storage apparatus of claim 15 , wherein the decoder passes

log

⁢

BER

1

-

BER

for 0 and passes

-

log

⁢

BER

1

-

BER

for 1.

17. The electronic non-volatile computer storage apparatus of claim 16 , wherein the decoder is a belief-propagation decoder.

18. The electronic non-volatile computer storage apparatus of claim 13 , wherein the log-likelihood ratio handler is configured to provide the bit-based input log-likelihood ratio for each bit calculated based on the confidence value for the cell containing said each bit, and wherein the bit-based input log-likelihood ratio for each bit is calculated as

C

^

=



∑

i

=

0

d

v

-

1

⁢

u

i



,

wherein u i denotes check node to variable node messages and d v denotes a variable degree.

19. The electronic non-volatile computer storage apparatus of claim 18 , wherein the decoder passes +Ĉ for 1 and passes −Ĉ for 0.

20. The electronic non-volatile computer storage apparatus of claim 18 , wherein the log-likelihood ratio handler is configured to set the bit-based input log-likelihood ratio for at least one least reliable bit to 0.