Convolutional Neural Network (CNN)-Based Detection for Multi-Level-Cell NAND Flash Memory

Abstract

With the increase of program/erase (PE) cycles and retention time, it is difficult to predict the threshold-voltage distributions for detection in NAND flash memory. To accurately acquire the log-likelihood ratios (LLRs) without the knowledge of threshold-voltage distributions, a convolutional neural network (CNN)-based detection algorithm is proposed for the multi-level-cell (MLC) flash memory. The CNN-based detection algorithm employs the trained CNN to accurately calculate the LLRs for each threshold-voltage region. Furthermore, we develop a CNN-aided read-voltage design scheme to optimize the read voltages by maximizing the mutual information between the coded bits and their corresponding LLRs. Exploiting the proposed scheme, we first design three hard-decision read voltages, and then formulate more soft-decision read voltages to further improve the detection performance. Simulation results demonstrate that the CNN-based detection algorithm can achieve performance approaching that of the optimal detection algorithm.