Storage Controller State Shaping for NV Memory Reliability
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Solution Overview
Problem
As the number of bits stored in a memory cell increases, it becomes increasingly difficult to identify and write data robustly due to the exponential increase in the number of states, leading to reliability issues in nonvolatile memory devices.
Innovation Solution
A storage device with a controller that performs error correction encoding and state shaping to reduce the number of states expressed by the data, allowing for reliable writing and reading of data in memory cells, even with an increased number of bits per cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of bits stored in one memory cell increases, then the storage capacity increases, but the number of states expressed by the memory cell increases exponentially making it difficult to identify and write data robustly
Solution Approach 1:
The patent changes the parameter of state representation by introducing shaped data with a reduced alphabet size. Instead of directly storing and reading 2^m states for m bits, the system transforms data into a shaped representation with fewer states (e.g., ternary states), writes this shaped data to memory, and then transforms it back during reading. This parameter transformation resolves the contradiction by making the effective state space manageable even when the theoretical state space is large.
Solution Approach 2:
The patent introduces shaped data as an intermediary representation between the original binary data and the physical memory states. The shaped data acts as a mediator that simplifies the interface between the high-capacity storage requirement and the practical limitations of robust state identification. By writing shaped data with fewer states to memory cells and then transforming it back during reading, the system achieves both high storage capacity and reliable data access.
2Adaptability or versatility
If the number of states expressed by a memory cell increases, then more bits can be stored, but it becomes increasingly difficult to identify states independently and write data robustly
Solution Approach 1:
The patent applies parameter changes by transforming the state representation from a high-dimensional space (2^m states for m bits) to a lower-dimensional shaped space with fewer states. This transformation makes state identification and measurement practical while preserving the ability to store multiple bits per memory cell. The shaped data representation reduces the complexity of state detection without sacrificing storage capacity.
3Productivity
If data is written with more states per memory cell, then storage density increases, but error correction and data reliability become more challenging
Solution Approach 1:
The patent changes the parameter of data representation by using shaped data with a reduced alphabet size. This transformation improves reliability by reducing the number of distinguishable states that need to be reliably differentiated in the presence of noise and errors. The shaped representation makes error correction more effective while maintaining high storage density through efficient use of memory cell capacity.
Data Source
AI summary
A storage device includes a nonvolatile memory device that includes a plurality of pages, each of which includes a plurality of memory cells, and a controller that receives first write data expressed by 2m states (m being an integer greater than 1) from an external host device. The controller in a first operating mode shapes the first write data to second write data, which are expressed by “k” states (k being an integer greater than 2) smaller in number than the 2m states, performs first error correction encoding on the second write data to generate third write data expressed by the “k” states, and transmits the third write data to the nonvolatile memory device for writing at a selected page from the plurality of pages.