Flash Memory Coding Across Unequal-Reliability Pages
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Solution Overview
Problem
Flash memory devices face challenges in maintaining reliability across different pages due to unequal error rates, leading to inefficiencies in data storage and access times, as some pages are more prone to errors than others.
Innovation Solution
Implementing a multi-phase decoding concatenated code construction that allows for efficient access by protecting small data amounts individually using sub-codes stored as short sub-words, with the option to read and decode these sub-codes separately to improve read performance, and using techniques like adjusting reading thresholds and error correction to retrieve data even in case of errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple bits are stored in each flash memory cell to increase storage density, then storage capacity is improved, but error rate increases due to unequal reliability across pages
Solution Approach 1:
The patent segments the codeword into multiple parts and distributes them across different physical pages. Specifically, a codeword is divided such that some portions are stored in more reliable pages while others are stored in less reliable pages, balancing the overall error correction capability across the storage medium.
Solution Approach 2:
The patent applies different error correction strategies to different physical pages based on their local reliability characteristics. Pages with higher error rates receive additional redundancy or are paired with more reliable pages in a concatenated code structure, while more reliable pages use standard error correction.
2Reliability
If codeword length is increased to provide additional redundancy for low reliability pages, then error correction capability is improved, but programming latency increases
Solution Approach 1:
The patent segments the codeword and distributes it across multiple pages, allowing the error correction capability to be achieved without requiring a single excessively long codeword that would increase programming time.
Solution Approach 2:
The patent applies partial redundancy to pages based on their specific reliability needs rather than uniformly applying excessive redundancy to all pages, optimizing the balance between error correction capability and programming efficiency.
3Reliability
If data is split across multiple physical pages to maintain reliability, then error correction is improved, but read latency increases due to additional access operations
Solution Approach 1:
The patent segments the codeword across multiple pages but designs the segmentation and error correction code structure to enable efficient parallel or sequential recovery, minimizing the impact on read latency while maintaining data integrity.
4Reliability
If reading thresholds are dynamically adjusted to recover data from pages with errors, then data recovery capability is improved, but system complexity increases
Solution Approach 1:
The patent implements dynamic threshold adjustment during the read operation based on the reliability characteristics of different physical pages. The reading thresholds are adapted in real-time to optimize data recovery from pages with varying error rates, improving overall data recovery capability.
Data Source
AI summary
A method of writing data includes receiving a data page to be stored in a data storage device and initiating an encode operation to encode the data page. The encode operation generates first encoded data and a first portion of the first encoded data is stored to the first physical page of the data storage device. The method includes initiating storage of a second portion of the first encoded data to a second physical page of the data storage device. The method also includes initiating a decode operation to recover the data page. The decode operation uses a representation of the first portion of the first encoded data that is read from the first physical page without using any data from the second physical page.