Hard-Decision LDPC Decoding Across Memory Die Using Scaling Factors
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Solution Overview
Problem
Existing error correction solutions for non-volatile memory, such as LDPC-based systems, require additional data like confidence information that hard decision reads cannot provide, but soft decision reads are slow and incompatible with certain memory technologies like memristors or STT MRAM.
Innovation Solution
Applying scaling factors to hard decision reads based on the raw bit error rate (RBER) of each die in a non-volatile memory, allowing recovery of reliability information similar to soft decision reads, even when only hard decision reads are performed, by distributing codewords across multiple die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft decision reads are performed to provide additional data for LDPC decoding, then decoding accuracy is improved, but read speed deteriorates and compatibility with certain memory technologies is lost
Solution Approach 1:
The patent creates a virtual copy of soft decision information by applying scaling factors to hard decision read data. Instead of performing actual soft decision reads, the system generates equivalent reliability information through mathematical transformation of hard decision outputs, achieving soft decision functionality without the performance penalty
Solution Approach 2:
The patent transforms hard decision read outputs by applying scaling factors that modify the parameter representation of the data. By changing the scaling parameter based on die-specific RBER characteristics, the system recovers reliability information that would normally require soft decision reads, thus resolving the speed-accuracy tradeoff
2Productivity
If hard decision reads are used for fast processing, then read speed is improved, but reliability information required for LDPC decoding is lost
Solution Approach 1:
The patent introduces scaling factors as an intermediary element between hard decision reads and LDPC decoding. These scaling factors act as mediators that carry reliability information from the physical read process to the logical decoding process, enabling fast hard decision reads to provide the same information that would otherwise require slow soft decision reads
Solution Approach 2:
The patent performs preliminary calculation of scaling factors based on die-specific RBER characteristics before the actual decoding process. This preliminary action prepares the reliability information in advance, allowing the main decoding operation to proceed quickly using pre-computed scaling factors rather than requiring slow soft decision reads during decoding
Data Source
AI summary
Embodiments include methods, apparatuses, and instructions for encoding a codeword of data as codeword portions stored across multiple die in a non-volatile memory. Embodiments further include a decoder which may be configured to decode the portions of the codeword using hard decision reads. The decoder may then be configured to estimate the quality of each die, and apply a scaling factor to the decoded codeword portions such that confidence or reliability information can be determined for the codeword.