In order to further improve the durability and reliability of multi-level-cell (MLC) flash memory, a polar code optimization method based on mutual information (MI) heterogeneity in the MLC flash channel is proposed. By exploiting the differences of log-likelihood ratio (LLR) distribution between MLC flash channels and AWGN (additive white Gaussian noise) channels, and employing MI re-fitting for obeying Gaussian distribution in AWGN channels, the method obtains its equivalent variance of AWGN channels. Thereafter, the polar code optimization design in the high-density storage system is performed according to the obtained new variance. This paper also analyzes the effects of other different polar code construction methods on the error correction of multi-level memory cells, and compares them with the proposed construction method. Simulation results show that the optimization method is better than the traditional construction methods in AWGN channels. It improves bit error rate (BER) by more than 2 orders of magnitudes compared with Monte-Carlo method when program-and-erase (P/E) cycles is 21 000, and it can increase the lifetime of MLC flash memory up to 6 800 P/E cycles at the BER of 2×10-5.
ZHANG Siqi, KONG Lingjun, ZHANG Shunwai, ZHANG Nan
. Optimization Design of Polar Codes Based on MI Heterogeneity in MLC NAND Flash Channel[J]. Journal of Applied Sciences, 2020
, 38(3)
: 431
-440
.
DOI: 10.3969/j.issn.0255-8297.2020.03.009
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