COMBINED SOFT DETECTION/SOFT DECODING IN TAPE DRIVE STORAGE CHANNELS

• US 20130279040A1
• Filed: 04/24/2012
• Published: 10/24/2013
• Est. Priority Date: 04/24/2012
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Cideciyan, Roy D., Hutchins, Robert A., Mittelholzer, Thomas, Oelcer, Sedat
• Granted Patent: US 8,854,759 B2
• Time in Patent Office: Days
• US Class Current: 360/53
• CPC Class Codes: G11B 20/10379 based on soft decisions, e.g. confidence values, probability estimates, likelihoods values or path metrics of a statistical decoding algorithm
• CPC Class Codes: G11B 20/1833 by adding special lists or symbols to the coded information G11B20/1806, G11B20/1866 take precedence
• CPC Class Codes: G11B 2020/185 using an low density parity check [LDPC] code
• CPC Class Codes: G11B 5/00813 magnetic tapes
• CPC Class Codes: H03M 13/1111 Soft-decision decoding, e.g. by means of message passing or belief propagation algorithms
• CPC Class Codes: H03M 13/13 Linear codes
• CPC Class Codes: H03M 13/2957 Turbo codes and decoding
• CPC Class Codes: H03M 13/3905 Maximum a posteriori probability [MAP] decoding or approximations thereof based on trellis or lattice decoding, e.g. forward-backward algorithm, log-MAP decoding, max-log-MAP decoding
• CPC Class Codes: H03M 13/3972 using sliding window techniques or parallel windows
• CPC Class Codes: H03M 13/6325 Error control coding in combination with demodulation
• CPC Class Codes: H03M 5/145 Conversion to or from block codes or representations thereof

Abstract

In one embodiment, a tape drive system includes a soft detector for executing a first forward loop of a detection algorithm on a first block of signal samples during a first time interval; and logic for executing forward and reverse loops during several time intervals; and logic adapted for outputting a first decoded block of signal samples based on the executing the decoding algorithm on the first block during a sixth time interval, wherein a sum of second, third, fourth, fifth, and sixth time intervals are about equal in duration to the first time interval.

Claims

1. A tape drive system, comprising:

a soft detector, comprising;

logic, implemented in a first hardware engine, adapted for executing a first forward loop of a detection algorithm on a first block of signal samples during a first time interval;

logic, implemented in a second hardware engine, adapted for executing a first reverse loop of the detection algorithm on the first block during a second time interval and for executing a second reverse loop of the detection algorithm on the first block during a fifth time interval;

logic, implemented in a fourth hardware engine, adapted for executing a second forward loop of the detection algorithm on the first block during a fourth time interval using second soft information,

wherein the soft detector passes first soft information to a soft decoder based on the executing of the first forward and reverse loops, and

wherein the soft detector passes third soft information to the soft decoder based on the executing of the second forward and reverse loops;

the soft decoder, comprising;

logic, implemented in a third hardware engine, adapted for executing a decoding algorithm on the first block during a third time interval using the first soft information and for executing the decoding algorithm on the first block during a sixth time interval using the third soft information, wherein the soft decoder produces the second soft information based on the executing of the decoding algorithm during the third time interval; and

logic adapted for outputting a first decoded block of signal samples based on the executing the decoding algorithm on the first block during the sixth time interval,

wherein a sum of the second, third, fourth, fifth, and sixth time intervals are about equal in duration to the first time interval.

2. The tape drive system as recited in claim 1,

wherein the second time interval is about ¼

of the first time interval and occurs immediately subsequent to the first time interval,

wherein the third time interval is about ⅛

of the first time interval and occurs immediately subsequent to the second time interval,

wherein the fourth time interval is about ¼

of the first time interval and occurs immediately subsequent to the third time interval,

wherein the fifth time interval is about ¼

of the first time interval and occurs immediately subsequent to the fourth time interval, and

wherein the sixth time interval is about ⅛

of the first time interval and occurs immediately subsequent to the fifth time interval.

3. The tape drive system as recited in claim 1, wherein the first hardware engine executes the first forward loop of the detection algorithm on a second block of signal samples contemporaneous with the second, third, fourth, fifth, and sixth time intervals.

4. The tape drive system as recited in claim 3, further comprising:

a magnetic head;

a drive mechanism adapted for passing a magnetic medium over the magnetic head;

a controller electrically coupled to the magnetic head, the controller being adapted for controlling operation of the magnetic head;

logic adapted for receiving the signal samples via the magnetic head; and

buffer storage memory adapted for storing;

the first block of signal samples;

the second block of signal samples;

branch metric calculations for the detection algorithm associated with the first block of signal samples; and

branch metric calculations for the detection algorithm associated with the second block of signal samples.

5. A tape drive system, comprising:

a soft detector, comprising;

logic, implemented in a first hardware engine, adapted for executing a first forward loop of a detection algorithm on a first block of signal samples during a first time interval;

logic, implemented in a second hardware engine, adapted for executing a first reverse loop of the detection algorithm on the first block of signal samples during the first time interval to produce first soft information;

logic, implemented in a third hardware engine, adapted for executing a second forward loop of the detection algorithm on the first block during a third time interval; and

logic, implemented in a fourth hardware engine, adapted for executing a second reverse loop of the detection algorithm on the first block during the third time interval to produce third soft information;

a soft decoder, comprising logic, implemented in a fifth hardware engine, adapted for executing a decoding algorithm on the first block during a second time interval using the first soft information to produce the second soft information and for executing the decoding algorithm on the first block during a fourth time interval using the third soft information; and

logic adapted for outputting a first decoded block of signal samples based on the executing the decoding algorithm on the first block during the fourth time interval using the third soft information,

wherein a sum of the second, third, and fourth time intervals are about equal in duration to the first time interval.

6. The tape drive system as recited in claim 5,

wherein the second time interval is about ⅓

of the first time interval and occurs immediately subsequent to the first time interval,

wherein the third time interval is about ⅓

of the first time interval and occurs immediately subsequent to the second time interval, and

wherein the fourth time interval is about ⅓

of the first time interval and occurs immediately subsequent to the third time interval.

7. The tape drive system as recited in claim 5, wherein the first hardware engine executes the first forward loop and the second hardware engine executes the first reverse loop of the detection algorithm on a second block of signal samples contemporaneous with the second, third, and fourth time intervals.

8. The tape drive system as recited in claim 7, further comprising:

a magnetic head;

a drive mechanism adapted for passing a magnetic medium over the magnetic head;

a controller electrically coupled to the magnetic head, the controller being adapted for controlling operation of the magnetic head;

logic adapted for receiving the signal samples via the magnetic head; and

buffer storage memory adapted for storing;

the first block of signal samples;

the second block of signal samples;

branch metric calculations for the detection algorithm associated with the first block of signal samples; and

branch metric calculations for the detection algorithm associated with the second block of signal samples.

9. The tape drive system as recited in claim 5, wherein the detection algorithm is a sliding window dual-max algorithm (SW-DMAX) and the decoding algorithm is a low-density parity check (LDPC) decoding algorithm.

10. A tape drive system, comprising:

a soft detector, comprising;

logic, implemented in a first hardware engine, adapted for executing a first forward loop of a detection algorithm on a first block of signal samples during a first time interval;

logic, implemented in a second hardware engine, adapted for executing a first reverse loop of the detection algorithm on the first block during a second time interval;

logic, implemented in a fourth hardware engine, adapted for executing a second forward loop of the detection algorithm on the first block during a fourth time interval using second soft information; and

logic, implemented in a fifth hardware engine, adapted for executing a second reverse loop of the detection algorithm on the first block during a fifth time interval using the second soft information,

wherein the soft detector passes first soft information to a soft decoder based on the executing of the first forward and reverse loops of the detection algorithm on the first block, and

wherein the soft detector passes third soft information to the soft decoder based on the executing of the second forward and reverse loops of the detection algorithm on the first block;

the soft decoder, comprising;

logic, implemented in a third hardware engine, adapted for executing a decoding algorithm on the first block during a third time interval using the first soft information and for executing the decoding algorithm on the first block during a sixth time interval using the third soft information, wherein the soft decoder produces the second soft information based on the executing of the decoding algorithm on the first block during the third time interval; and

logic adapted for outputting a first decoded block of signal samples based on the executing the decoding algorithm on the first block during the sixth time interval,

wherein a sum of the second, third, fourth, fifth, and sixth time intervals are about equal in duration to twice the first time interval.

11. The tape drive system as recited in claim 10,

wherein the second time interval is about ½

of the first time interval and occurs immediately subsequent to the first time interval,

wherein the third time interval is about ¼

of the first time interval and occurs immediately subsequent to the second time interval,

wherein the fourth time interval is about ½

of the first time interval and occurs immediately subsequent to the third time interval,

wherein the fifth time interval is about ½

of the first time interval and occurs immediately subsequent to the fourth time interval, and

wherein the sixth time interval is about ¼

of the first time interval and occurs immediately subsequent to the fifth time interval.

12. The tape drive system as recited in claim 10, wherein the first hardware engine begins executing the first forward loop of the detection algorithm on a second block of signal samples immediately subsequent to the executing the first forward loop of the detection algorithm on the first block, and wherein the first hardware engine begins executing the first forward loop of the detection algorithm on a third block of signal samples immediately subsequent to the executing the first forward loop of the detection algorithm on the second block.

13. The tape drive system as recited in claim 12, further comprising:

a magnetic head;

a drive mechanism adapted for passing a magnetic medium over the magnetic head;

a controller electrically coupled to the magnetic head, the controller being adapted for controlling operation of the magnetic head;

logic adapted for receiving the signal samples via the magnetic head; and

buffer storage memory adapted for storing;

the first block of signal samples;

the second block of signal samples;

the third block of signal samples;

branch metric calculations for the detection algorithm associated with the first block of signal samples;

branch metric calculations for the detection algorithm associated with the second block of signal samples; and

branch metric calculations for the detection algorithm associated with the third block of signal samples.

14. A tape drive system, comprising:

a soft detector, comprising;

logic, implemented in a first hardware engine, adapted for executing a first forward loop of a detection algorithm on a first block of signal samples during a first time interval;

logic, implemented in a second hardware engine, adapted for executing a first reverse loop of the detection algorithm on the first block during the first time interval;

logic, implemented in a fourth hardware engine, adapted for executing a second forward loop of the detection algorithm on the first block during a third time interval using second soft information; and

logic, implemented in a fifth hardware engine, adapted for executing a second reverse loop of the detection algorithm on the first block during the third time interval using the second soft information,

wherein the soft detector passes first soft information to a soft decoder based on the executing of the first forward and reverse loops of the detection algorithm on the first block, and

wherein the soft detector passes third soft information to the soft decoder based on the executing of the second forward and reverse loops of the detection algorithm on the first block;

the soft decoder, comprising;

logic, implemented in a third hardware engine, adapted for executing a decoding algorithm on the first block during a second time interval using the first soft information and for executing the decoding algorithm on the first block during a fourth time interval using the third soft information, wherein the soft decoder produces the second soft information based on the executing of the decoding algorithm on the first block during the second time interval; and

logic adapted for outputting a first decoded block of signal samples based on the executing the decoding algorithm on the first block during the fourth time interval,

wherein a sum of the second, third, and fourth time intervals are about equal in duration to twice the first time interval.

15. The tape drive system as recited in claim 14,

wherein the second time interval is about ½

of the first time interval and occurs immediately subsequent to the first time interval,

wherein the third time interval is about equal to the first time interval and occurs immediately subsequent to the second time interval, and

wherein the fourth time interval is about ½

of the first time interval and occurs immediately subsequent to the third time interval.

16. The tape drive system as recited in claim 14, wherein the first hardware engine begins executing the first forward loop and the second hardware engine begins executing the first reverse loop of the detection algorithm on a second block of signal samples immediately subsequent to the executing of the first forward and reverse loops of the detection algorithm on the first block, and wherein the first hardware engine begins executing the first forward loop and the second hardware engine begins executing the first reverse loop of the detection algorithm on a third block of signal samples immediately subsequent to the executing of the first forward and reverse loops of the detection algorithm on the second block.

17. The tape drive system as recited in claim 16, further comprising:

a magnetic head;

a drive mechanism adapted for passing a magnetic medium over the magnetic head;

a controller electrically coupled to the magnetic head, the controller being adapted for controlling operation of the magnetic head;

logic adapted for receiving the signal samples via the magnetic head; and

buffer storage memory adapted for storing;

the first block of signal samples;

the second block of signal samples;

the third block of signal samples;

branch metric calculations for the detection algorithm associated with the first block of signal samples;

branch metric calculations for the detection algorithm associated with the second block of signal samples; and

branch metric calculations for the detection algorithm associated with the third block of signal samples.

18. The tape drive system as recited in claim 14, wherein the detection algorithm is a sliding window dual-max algorithm (SW-DMAX) and the decoding algorithm comprises a low-density parity check (LDPC) decoding algorithm.

19-25. -25. (canceled)