Systems, methods and devices for decoding codewords having multiple parity segments

• US 8,924,815 B2
• Filed: 11/16/2012
• Issued: 12/30/2014
• Est. Priority Date: 11/18/2011
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Enterprise IP LLC (Western Digital Corporation)
• Inventors: Frayer, Jack Edward, Olbrich, Aaron K.
• Primary Examiner(s): LAMARRE, GUY J
• Application Number:
  US13/679,969
• Publication Number:
  US 20130132804A1
• Time in Patent Office: 774 Days
• Field of Search: 714/752, 714/755, 714/763, 714/780, 714/786, 714/784, 714/782, 714801-801
• US Class Current: 714/755
• CPC Class Codes: G06F 11/1012 using codes or arrangements adapted for a specific type of error G06F11/1048 takes precedence
• CPC Class Codes: H03M 13/13 Linear codes

Abstract

An error control decoding system decodes a codeword that includes a data word and two or more parity segments. The system includes a first decoder to decode the codeword by utilizing one or more first parity segments and the data word included in the codeword, and a second decoder to decode the codeword by utilizing one or more second parity segments and the data word included in the codeword, wherein the one or more first parity segments are different from the one or more second parity segments. An error estimation module estimates the number of errors in the codeword, and a controller selects which of the first decoder and second decoder to start decoding the codeword, wherein the selection is based on the estimate of the number of errors in the codeword provided by the error estimation module.

Claims

1. An error control decoding system operable to decode a codeword including a data word and two or more parity segments, the system comprising:

a first decoder configured to decode the codeword by utilizing one or more first parity segments and the data word included in the codeword;

a second decoder configured to decode the codeword by utilizing one or more second parity segments and the data word included in the codeword, wherein the one or more first parity segments are different from the one or more second parity segments;

an error estimation module configured to estimate a number of errors in the codeword, wherein;

the error estimation module comprises an encoder, corresponding to the second decoder, configured to produce one or more third parity segments from the data word included in the codeword; and

the error estimation module estimates the number of errors in the codeword by evaluating the one or more second parity segments and the one or more third parity segments; and

a controller configured to select which of the first decoder and second decoder to start decoding the codeword, wherein the selection is based on the estimated number of errors in the codeword provided by the error estimation module.

2. The decoding system of claim 1, wherein the controller is configured to select:

the first decoder to start decoding the codeword when the estimated number of errors satisfies a threshold; and

the second decoder to start decoding the codeword when the estimated number of errors does not satisfy a threshold.

3. The decoding system of claim 2, wherein the threshold corresponds to a number of errors that will cause the first decoder to fail when selected first.

4. The decoding system of claim 2, wherein the threshold corresponds to a number of errors that will cause the first decoder to fail a particular percentage of the time when selected first.

5. The decoding system of claim 2, wherein the threshold corresponds to a number of errors that can be successfully corrected by the first decoder.

6. The decoding system of claim 1, wherein the controller is configured to select:

the first decoder to start decoding the codeword using soft decision decoding when the estimated number of errors satisfies a first threshold; and

the first decoder to start decoding the codeword using hard decision decoding when the estimated number of errors satisfies a second threshold different from the first threshold.

7. The decoding system of claim 1, wherein the controller is configured to select:

the second decoder to start decoding the codeword using soft decision decoding when the estimated number of errors satisfies a first threshold; and

the second decoder to start decoding the codeword using hard decision decoding when the estimated number of errors satisfies a second threshold different from the first threshold.

8. The decoding system of claim 1, further comprising:

a third decoder configured to decode the codeword in combination with a plurality of other codewords; and

wherein the controller is configured to select the third decoder for decoding when the estimated number of errors satisfies a threshold.

9. The decoding system of claim 8, wherein the controller is configured to select one of the first, second and third decoders when the estimated number of errors satisfies a respective one of first, second and third thresholds.

10. The decoding system of claim 1, wherein the first decoder comprises a Bose Chaudhuri Hocquenghem (BCH) code decoder.

11. The decoding system of claim 1, wherein the second decoder comprises a low density parity check (LDPC) code decoder.

12. The decoding system of claim 1, wherein the decoding system comprises a portion of a memory controller.

13. The decoding system of claim 1, further comprising, a storage medium interface configured to retrieve the codeword from a storage medium.

14. The decoding system of claim 1, wherein the controller is further configured to provide a result produced by the selected one of the first and second decoders to the other of the first and second decoders.

15. A method of decoding codewords, comprising:

at an error control decoding system that includes a first decoder, a second decoder, and an error estimation module with an encoder that corresponds to the second decoder;

decoding a codeword including a data word and two or more parity segments, wherein the two or more parity segments include one or more first parity segments and one or more second parity segments different from the one or more first parity segments, the decoding including;

producing, with the encoder, one or more third parity segments from the data word included in the codeword;

generating, with the error estimation module, an estimate of a number of errors in the codeword by evaluating the one or more second parity segments and the one or more third parity segments;

selecting one of the first decoder and the second decoder to start decoding the codeword, wherein the selection is based on the estimated number of errors in the codeword;

in accordance with a determination that the first decoder is selected, starting decoding the codeword, with the first decoder, by utilizing the one or more first parity segments and the data word included in the codeword; and

in accordance with a determination that the second decoder is selected, starting decoding the codeword, with the second decoder, by utilizing the one or more second parity segments and the data word included in the codeword.

16. The method of claim 15, wherein selecting one of the first decoder and the second decoder to start decoding the codeword includes:

selecting the first decoder to start decoding the codeword when the estimated number of errors satisfies a threshold; and

selecting the second decoder to start decoding the codeword when the estimated number of errors does not satisfy a threshold.

17. The method of claim 16, wherein the threshold corresponds to a number of errors that will cause the first decoder to fail when selected first.

18. The method of claim 16, wherein the threshold corresponds to a number of errors that will cause the first decoder to fail a particular percentage of the time when selected first.

19. The method of claim 16, wherein the threshold corresponds to a number of errors that can be successfully corrected by the first decoder.

20. The method of claim 15, wherein selecting one of the first decoder and the second decoder to start decoding the codeword includes:

selecting the first decoder to start decoding the codeword using soft decision decoding when the estimated number of errors satisfies a first threshold; and

selecting the first decoder to start decoding the codeword using hard decision decoding when the estimated number of errors satisfies a second threshold different from the first threshold.

21. The method of claim 15, wherein selecting one of the first decoder and the second decoder to start decoding the codeword includes:

selecting the second decoder to start decoding the codeword using soft decision decoding when the estimated number of errors satisfies a first threshold; and

selecting the second decoder to start decoding the codeword using hard decision decoding when the estimated number of errors satisfies a second threshold different from the first threshold.

22. The method of claim 15, further comprising, providing a decoding result produced by the selected decoder to the other decoder for use in continued decoding of the codeword.