Non-linear LLR look-up tables
In one implementation, the disclosure provides a system including a detector configured to generate an output of a first log-likelihood ratio for each bit in an input data stream. The system also includes at least one look-up table providing a mapping of the first log-likelihood ratio to a second log-likelihood ratio. The mapping between the first log-likelihood ratio and the second log-likelihood ratio is non-linear. The system also includes a decoder configured to generate an output data stream using the second log-likelihood ratio to generate a value for each bit in the input data stream.
1. A system comprising:
a detector configured to generate an output of a first log-likelihood ratio for each bit in an input data stream read from a storage medium;
a first look-up table providing a mapping of the first log-likelihood ratio to a second log-likelihood ratio, the mapping between the first log-likelihood ratio and the second log-likelihood ratio being non-linear, the first look-up table being selected based on a density parameter of the storage medium; and
a decoder configured to generate an output data stream using the second log-likelihood ratio to generate a value for each bit in the input data stream.
2. The system of claim 1 , wherein the density parameter of the storage medium is tracks per inch.
3. The system of claim 1 , wherein the density parameter of the storage medium is bits per inch.
4. The system of claim 1 , wherein the density parameter of the storage medium is channel bit density.
5. The system of claim 1 , wherein the density parameter of the storage medium is related to a region of the storage medium including the input data stream.
6. The system of claim 1 , wherein the first look-up table being selected based on whether the drive operation is on-the-fly or error recovery.
7. The system of claim 6 , wherein the first look-up table is further selected based on the type of error condition when the drive operation is error recovery.
8. A method comprising:
generating a first log-likelihood ratio for each bit in an input data stream read from a storage medium;
selecting at least one look-up table based on a density parameter of the storage medium;
mapping the first log-likelihood ratio to a second log-likelihood ratio using at least one look-up table, the mapping between the first log-likelihood ratio and the second-log likelihood ratio being non-linear; and
generating an output data stream using the second log-likelihood ratio to generate a value for each bit in the input data stream.
9. The method of claim 8 , wherein the density parameter of the storage medium is tracks per inch.
10. The method of claim 8 , wherein the density parameter of the storage medium is bits per inch.
11. The method of claim 8 , wherein the density parameter of the storage medium is channel bit density.
12. The method of claim 8 , wherein the density parameter of the storage medium is related to a region of the storage medium including the input data stream.
13. The method of claim 8 , wherein the first look-up table being selected based on whether the drive operation is on-the-fly or error recovery.
14. The method of claim 13 , wherein the first look-up table is further selected based on the type of error condition when the drive operation is error recovery.
15. A method comprising:
reading an input data stream from a storage medium;
obtaining information about a density parameter of the storage medium;
generating a first log-likelihood ratio for each bit in the input data stream;
selecting at least one look-up table based on the parameter of the storage medium, the look-up table providing a mapping of the first log-likelihood ratio to a second log-likelihood ratio, the mapping between the first log-likelihood ratio and the second log-likelihood ratio being non-linear; and
generating an output data stream using the second log-likelihood ratio to generate a value for each bit in the input data stream.
16. The method of claim 15 , wherein the density parameter of the storage medium is tracks per inch.
17. The method of claim 15 , wherein the density parameter of the storage medium is bits per inch.
18. The method of claim 15 , wherein the density parameter of the storage medium is channel bit density.
19. The method of claim 15 , wherein the density parameter of the storage medium is related to a region of the storage medium including the input data stream.
20. The method of claim 15 , wherein the first look-up table being selected based on whether the drive operation is on-the-fly or error recovery.