Error correction code for Flash memory
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摘要: Flash闪存是一种非易失性的存储器件,随着工艺尺寸的不断减小,存储容量需求的不断增加,存储可靠性与寿命成为Flash生产与应用过程中最严重的两个挑战.基于多级 (MLC,Multilevel Cell) "与非(NAND)型" Flash的层级结构特征与读写操作特性,构造了一种基于正交映射的纠错编码方法,给出其编解码原理与结构,并分析其纠错能力.在此基础上,分析了该编码方法在Flash存储系统中的两种典型应用场景,即分布式多用户共享存储以及历史数据的无差错恢复.此外,Flash存储单元的可靠性受擦除次数的限制,其寿命相当有限,该编码方法可以有效地利用坏块来提高Flash的整体生命周期.分析结果表明:不改变整体结构,只需对编码模块进行简单调整,即可实现多种实际应用需求.Abstract: Flash memory is a non-volatile storage device, as the technology continuously scales down and storage density requirement increases up, the storage reliability and lifetime of flash memory become two of the most serious challenges. According to the multi-level cell (MLC) NAND Flash structural features and operating characteristics, an error correction coding approach based on orthogonal mapping was proposed, and the error correcting ability was analyzed. On this basis, two typical application scenarios in flash memory system were presented, i.e., distributed multi-user access storage and error-free recovery of historical data. Moreover, the lifetime of flash is strictly limited by the block-erasures operation; this coding scheme could utilize the bad block to enhance the flash lifetime. The analysis shows that this coding scheme could achieve multiple practical applications with simple adjustment to the encoder module.
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Key words:
- Flash memory /
- error correction code /
- orthogonal mapping /
- multi-user access /
- data recovery
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