Disk Drive ITI Correlation and Cancellation for Dense Track Reading
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Solution Overview
Problem
In hard disk drives, closely packed tracks experience significant inter-track interference (ITI), leading to reduced Signal-to-Noise Ratio (SNR) and increased Sector-Failure-Rate (SFR), making data recovery challenging due to noise from adjacent tracks.
Innovation Solution
Implementing an ITI removal procedure that correlates and cancels interference by cross-correlating the received signal with known data from adjacent tracks, using correlation coefficients to generate ITI samples and cancel them from the read data, which can be performed either offline or on-the-fly without degrading data detection/decoding throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If tracks are placed closer to each other to increase TPI, then hard drive capacity increases, but inter-track interference increases reducing SNR
Solution Approach 1:
The patent correlates the ITI signal with adjacent track data to extract interference characteristics, then uses this extracted information to cancel the harmful ITI effect. By converting the harmful interference into usable correlation data, the system eliminates the adverse effect while maintaining high track density for increased capacity
Solution Approach 2:
The patent introduces an intermediary ITI removal procedure that acts as a mediator between the read channel and data decoder. This intermediary process correlates and cancels ITI samples from the received signal, allowing closely spaced tracks to be read accurately without the interference propagating to the decoder
2Reliability
If ITI removal procedure is implemented to reduce noise, then data recovery reliability improves, but processing complexity increases
Solution Approach 1:
The patent performs ITI correlation and cancellation as a preliminary action before data detection and decoding. By removing ITI interference in advance, the subsequent data recovery processes operate on cleaner signals, improving reliability while the modular preliminary structure manages complexity through staged processing
Solution Approach 2:
The ITI removal procedure uses the known adjacent track data itself to generate the correlation coefficients needed for cancellation. The system serves itself by using its own stored reference data to eliminate interference, reducing the need for external complex interference cancellation systems
3Productivity
If ITI correlation is performed in parallel with data detection iterations, then throughput is maintained, but computational load increases
Solution Approach 1:
The patent performs ITI correlation during the data detection iterations as a preliminary preparation step. By computing correlation coefficients in parallel with the existing detection loop, the system prepares ITI cancellation data without adding sequential processing steps, maintaining throughput while distributing computational load across available processing cycles
Data Source
AI summary
Inter-track-interference correlation and cancellation for disk drive application includes receiving an input sequence of samples; and simultaneously processing the input sequence in at least a detector over one or more iterations while processing the input sequence to produce inter-track-interference information during at least a portion of one of the one or more iterations.