Systems and methods for improved short media defect detection
Various embodiments of the present invention provide systems and methods for media defect detection. Data pre-processing is operable to pre-process a symbol based detected output to yield a suspect symbol indicator, and data detection is operable to provide a defect indicator corresponding to a probable defect identified based on the suspect symbol indicator.
1. A data processing system, the data processing system comprising:
a data detector circuit operable to apply a data detection algorithm to a symbol based data set guided by a decoded output to yield a symbol based detected output;
a defect detector circuit including:
a data pre-processing circuit operable to pre-process the symbol based detected output to yield a suspect symbol indicator; and
a data detection circuit operable to provide a defect indicator corresponding to a probable defect identified based on the suspect symbol indicator; and
a data decoder circuit operable to apply a data decode algorithm to a decoder input derived from the detected output modified based on the defect indicator to update the decoded output.
2. The data processing system of claim 1 , wherein the symbol based data set is a series of multi-bit symbols.
3. The data processing system of claim 2 , wherein the multi-bit symbols are selected from a group consisting of: two bit symbols, and three bit symbols.
4. The data processing system of claim 2 , wherein the suspect symbol indicator includes a first product and a second product, wherein the multi-bit symbols are two bit symbols, and wherein the data pre-processing circuit is further operable to:
calculate a first value based upon a first combination of a soft data set corresponding to a symbol of the detected output and a second value based upon a second combination of the soft data set corresponding to the symbol of the detected output;
calculate a third value based upon a first combination of a soft data set corresponding to a symbol of the decoded output and a fourth value based upon a second combination of the soft data set corresponding to the symbol of the decoded output;
multiply the first value by the third value to yield the first product;
multiply the second value by the fourth value to yield the second product; and
assert the suspect symbol indicator indicating a probability that the symbol is incorrect when at least one of the first product and the second product is negative.
5. The data processing system of claim 4 , wherein the soft data set corresponding to the symbol of the detected output includes a first element, a second element, a third element, and a fourth element; and wherein:
calculating the first value includes:
selecting one of the first element and the third element that has the highest value as a first selected value;
selecting one of the second element and the fourth element that has the highest value as a second selected value; and
subtracting the second selected value from the first selected value to yield the first value;
calculating the second value includes:
selecting one of the first element and the second element that has the highest value as a third selected value;
selecting one of the third element and the fourth element that has the highest value as a fourth selected value; and
subtracting the fourth selected value from the third selected value to yield the second value.
6. The data processing system of claim 4 , wherein the soft data set corresponding to the symbol of the decoded output includes a first element, a second element, a third element, and a fourth element; and wherein:
calculating the third value includes:
selecting one of the first element and the third element that has the highest value as a first selected value;
selecting one of the second element and the fourth element that has the highest value as a second selected value; and
subtracting the second selected value from the first selected value to yield the third value;
calculating the fourth value includes:
selecting one of the first element and the second element that has the highest value as a third selected value;
selecting one of the third element and the fourth element that has the highest value as a fourth selected value; and
subtracting the fourth selected value from the third selected value to yield the fourth value.
7. The data processing system of claim 1 , wherein the suspect symbol indicator indicates a probability that a symbol is incorrect when a combination of the decoded output and the detected output is negative.
8. The data processing system of claim 1 , wherein the system is implemented as an integrated circuit.
9. The data processing system of claim 1 , wherein the system is implemented as part of a storage device.
10. The data processing system of claim 1 , wherein the data decoder circuit is a low density parity check decoder circuit.
11. The data processing system of claim 1 , wherein the data detector circuit is selected from a group consisting of: a Viterbi algorithm data detector circuit, and a maximum a posteriori data detector circuit.
12. The data processing system of claim 1 , wherein the data pre-processing circuit is a non-threshold based data pre-processing circuit.
13. The data processing system of claim 1 , wherein the data detection circuit is a binary data detection circuit.
14. A storage device, the storage device comprising:
a storage medium;
a read/write head assembly operable to sense information from the storage medium and to provide a corresponding continuous signal;
an analog to digital converter circuit operable to sample the continuous signal synchronous to a sampling clock to yield a set of digital samples;
an equalizer circuit operable to equalize the set of digital samples and to provide a corresponding symbol based output;
a data detector circuit operable to apply a data detection algorithm to the symbol based output guided by a decoded output to yield a detected output;
a defect detector circuit including:
a non-threshold based data pre-processing circuit operable to pre-process the detected output to yield a suspect symbol indicator; and
a binary data detection circuit operable to provide a defect indicator corresponding to a probable defect identified based on the suspect symbol indicator; and
a data decoder circuit operable to apply a data decode algorithm to a decoder input derived from the detected output modified based on the defect indicator to yield the decoded output.
15. The storage device of claim 14 , wherein the symbol based output includes a series of two bit symbols; wherein the suspect symbol indicator includes a first product and a second product; and wherein the data pre-processing circuit is further operable to:
calculate a first value based upon a first combination of a soft data set corresponding to a symbol the detected output and a second value based upon a second combination of the soft data set corresponding to the symbol of the detected output;
calculate a third value based upon a first combination of a soft data set corresponding to a symbol of the decoded output and a fourth value based upon a second combination of the soft data set corresponding to the symbol of the decoded output;
multiply the first value by the third value to yield the first product;
multiply the second value by the fourth value to yield the second product; and
assert the suspect symbol indicator indicating a probability that the symbol is incorrect when at least one of the first product and the second product is negative.
16. The storage device of claim 14 , wherein the symbol based output is a series of multi-bit symbols.
17. A method for data processing, the method comprising:
applying a data detection algorithm by a data detector circuit to a symbol based data set guided by a decoded output to yield a symbol based detected output;
pre-processing the symbol based detected output to yield a suspect symbol indicator;
providing a defect indicator corresponding to a probable defect identified based on the suspect symbol indicator; and
applying a data decode algorithm to a decoder input derived from the detected output modified based on the defect indicator to update the decoded output.
18. The method of claim 17 , wherein the symbol based data set is a series of multi-bit symbols.
19. The method of claim 18 , wherein the multi-bit symbols are selected from a group consisting of: two bit symbols, and three bit symbols.
20. The method of claim 18 , wherein the suspect symbol indicator includes a first product and a second product, wherein the multi-bit symbols are two bit symbols, and wherein the method further comprises:
calculating a first value based upon a first combination of a soft data set corresponding to a symbol of the detected output and a second value based upon a second combination of the soft data set corresponding to the symbol of the detected output;
calculating a third value based upon a first combination of a soft data set corresponding to a symbol of the decoded output and a fourth value based upon a second combination of the soft data set corresponding to the symbol of the decoded output;
multiplying the first value by the third value to yield the first product;
multiplying the second value by the fourth value to yield the second product; and
asserting the suspect symbol indicator indicating a probability that the symbol is incorrect when at least one of the first product and the second product is negative.
21. The method of claim 20 , wherein the soft data set corresponding to the symbol of the detected output includes a first element, a second element, a third element, and a fourth element; and wherein:
calculating the first value includes:
selecting one of the first element and the third element that has the highest value as a first selected value;
selecting one of the second element and the fourth element that has the highest value as a second selected value; and
subtracting the second selected value from the first selected value to yield the first value; and
calculating the second value includes:
selecting one of the first element and the second element that has the highest value as a third selected value;
selecting one of the third element and the fourth element that has the highest value as a fourth selected value; and
subtracting the fourth selected value from the third selected value to yield the second value.
22. The method of claim 20 , wherein the soft data set corresponding to the symbol of the decoded output includes a first element, a second element, a third element, and a fourth element; and wherein:
calculating the third value includes:
selecting one of the first element and the third element that has the highest value as a first selected value;
selecting one of the second element and the fourth element that has the highest value as a second selected value; and
subtracting the second selected value from the first selected value to yield the third value; and
calculating the fourth value includes:
selecting one of the first element and the second element that has the highest value as a third selected value;
selecting one of the third element and the fourth element that has the highest value as a fourth selected value; and
subtracting the fourth selected value from the third selected value to yield the fourth value.
23. The method of claim 17 , wherein the suspect symbol indicator indicates a probability that a symbol is incorrect when a combination of the decoded output and the detected output is negative.
24. The method of claim 17 , wherein the data decode algorithm is a low density parity check decode algorithm.
25. The method of claim 17 , wherein the data detector circuit is selected from a group consisting of: a Viterbi algorithm data detector circuit, and a maximum a posteriori data detector circuit.