Soft-Orthogonal Syncmarks for Shingled Track Interference
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Solution Overview
Problem
In data storage devices using multi-dimensional recording, aggressive shingling schemes increase track density, leading to inter-track interference that complicates the detection of syncmarks, which are crucial for identifying the start of user data, potentially resulting in data recovery failures.
Innovation Solution
The generation of soft-orthogonal syncmarks, which are nearly orthogonal to prevent inter-track interference, involves searching for sync patterns with delta-like autocorrelation and small cross-correlation, allowing them to be distinguishable from preamble and user data portions, even with phase offsets, by relaxing cross-correlation constraints between syncmarks for odd- and even-numbered tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If aggressive shingling schemes are used to increase track density, then track density is improved, but inter-track interference increases making syncmark detection difficult
Solution Approach 1:
The patent applies local quality by designing different syncmark patterns for different track sets (odd-numbered tracks use first syncmark pattern, even-numbered tracks use second syncmark pattern). This local differentiation allows each track to have optimized syncmark characteristics that reduce interference from specific neighboring tracks, thereby improving syncmark detectability in high-density shingled recording while maintaining high track density.
2Measurement precision
If orthogonal syncmarks are used to prevent inter-track interference, then syncmark detectability is improved for small phase offsets, but the ability to accommodate larger phase offsets is reduced
Solution Approach 1:
The patent implements dynamics by creating multiple sets of syncmarks with different characteristics (first syncmark set with higher orthogonality for small phase offsets, second syncmark set with relaxed constraints for larger phase offsets). The system dynamically selects which syncmark set to use based on the detected phase offset conditions, thereby adapting to different interference scenarios and maintaining syncmark detectability across a wide range of phase offsets.
3Adaptability or versatility
If cross-correlation constraints are relaxed between syncmarks for odd and even tracks, then larger phase offsets are accommodated, but inter-track interference from neighboring tracks increases
Solution Approach 1:
The patent applies parameter changes by systematically varying key parameters of syncmark patterns including cross-correlation values, autocorrelation characteristics, and pattern structures across different track sets. By adjusting these parameters, the patent achieves an optimal balance where syncmarks can accommodate larger phase offsets while maintaining acceptable levels of inter-track interference through careful parameter optimization.
Data Source
AI summary
The disclosure is directed to a system and method of generating soft-orthogonal syncmarks for at least a first set of tracks and a second set of tracks. Random pairs of sync patterns are searched to identify one or more pairs where the sync patterns of each pair exhibit delta-like autocorrelation and small cross-correlation with each other and with preamble portions of the tracks. Then a pair of sync patterns is selected from the one or more identified pairs, where the selected pair includes sync patterns that are distinguishable from the user data portions of the tracks at least partially based upon a data characteristic of the user data portions of the tracks. The selected pair of sync patterns is then used to generate a first syncmark for the first set of tracks and a second syncmark for the second set of tracks.