Paper Info
Title
Improving the Reliability of MLC NAND Flash Memories Through Adaptive Data Refresh and Error Control Coding
Abstract
NAND Flash memory has become the most widely used non-volatile memory technology. We focus on multi-level cell (MLC) NAND Flash memories because they have high storage density. Unfortunately MLC NAND Flash memory also has reliability problems due to narrower threshold voltage gap between logical states. Errors in these memories can be classified into data retention (DR) errors and program interference (PI) errors. DR errors are dominant if the data storage time is longer than 1 day and these errors can be reduced by refreshing the data. PI errors are dominant if the data storage time is less than 1 day and these errors can be handled by error control coding (ECC). In this paper we propose a combination of data refresh policies and low cost ECC schemes that are cognizant of application characteristics to address the errors in MLC NAND Flash memories. First, we use Gray code based encoding to reduce the error rates in the four subpages (MSB-even, LSB-even, MSB-odd, LSB-odd) of a 2-bit MLC NAND Flash memory. Next, we apply data refresh techniques where the refresh interval is a function of the program/erase (P/E) frequency of the application. We show that an appropriate choice of refresh interval and BCH based ECC scheme can minimize memory energy while satisfying the reliability constraint.
Year
DOI
Venue
2014
10.1007/s11265-014-0880-5
Journal of Signal Processing Systems
Keywords
Field
DocType
MLC NAND Flash,Data retention error,Program interferences error,Data refresh,ECC
Flash file system,Data retention,Computer science,Computer data storage,Parallel computing,NAND gate,Gray code,BCH code,Real-time computing,Interference (wave propagation),Computer hardware,Encoding (memory)
Journal
Volume
Issue
ISSN
76
3
1939-8018
Citations 
PageRank 
References 
2
0.44
16
Authors
4
Name
Order
Citations
PageRank
Chengen Yang1565.47
Hsing-Min Chen2142.48
Trevor N. Mudge320.44
Chaitali Chakrabarti41978184.17