Adjacent Track Interference Cancellation in Shingled Magnetic Recording
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Solution Overview
Problem
In magnetic recording systems, particularly in Shingled Magnetic Recording, the narrow track pitch and reduced guard bands lead to significant interference from adjacent tracks, causing low data reliability due to the read head picking up signals from adjacent tracks, which existing methods struggle to mitigate effectively.
Innovation Solution
The use of multiple read heads to sample data streams from both the current and adjacent tracks, with controlled sampling and interpolation to align the signals, and a decoder to apply timing signals for synchronous or asynchronous sampling, enabling effective interference cancellation and improved data reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If track pitch is reduced to increase recording density, then more tracks fit on the storage medium, but the read head picks up significant interference from adjacent tracks
Solution Approach 1:
A separate read head is introduced as an intermediary device to read the adjacent track signal. This mediator signal is then processed through a canceller that subtracts the adjacent track contribution from the main track signal, thereby removing the harmful interference while preserving the useful data.
Solution Approach 2:
The system uses feedback by continuously monitoring the adjacent track signal through a separate read head and using this information to dynamically adjust the cancellation process. The canceller receives the main track signal and the adjacent track signal, processes them together, and outputs a corrected main track signal with interference removed.
2Quantity of substance
If track pitch is narrowed below read head width, then recording density increases, but data reliability decreases due to interference
Solution Approach 1:
A separate read head is introduced as an intermediary device to read the adjacent track signal. This mediator signal is then processed through a canceller that subtracts the adjacent track contribution from the main track signal, thereby removing the harmful interference while preserving the useful data.
Solution Approach 2:
The harmful adjacent track interference signal is converted into a beneficial cancellation reference. By using a separate read head to capture the adjacent track signal, the system transforms this harmful interference into useful information that enables precise cancellation of the interference from the main track signal.
3Reliability
If multiple read heads are used to read adjacent tracks, then interference cancellation improves, but device complexity increases
Solution Approach 1:
The reading function is segmented into separate tasks: one read head dedicated to reading the main track and another read head dedicated to reading the adjacent track. This segmentation allows each read head to specialize in a specific function, improving the accuracy of interference cancellation while keeping the overall system manageable through functional division.
Data Source
AI summary
A method for sampling a current track and an adjacent track of a storage medium includes using a first read head to read a first data stream from the current track, using a second read head to read a second data stream from the adjacent track, delaying one of the first and second data streams to account for a position difference between the first and second read heads, and controlling sampling of the first and second data streams to align the first and second data streams. Controlling the sampling may include applying a synchronous sampling signal to control the first and second read heads so that they sample at synchronous locations, or may include sampling the current and adjacent data tracks at asynchronous locations and interpolating the first and second data streams to provide aligned samples. A storage device may operate in accordance with the method.