Program Error Mitigation in MLC NAND Flash Memory with Soft Decision Decoders  

作　　者：Zequn Fang Zheng Ma Xiaohu Tang Yue Xiao Youhua Tang 

机构地区：[1]School of Information Science and Technology,Southwest Jiaotong University,Chengdu 610031,China [2]National Engineering Laboratory for integrated traffic data application technology,Southwest Jiaotong University,Chengdu 610031,China

出　　处：《China Communications》2021年第4期76-87,共12页中国通信（英文版）

基　　金：This work was supported by Key Project of Sichuan Province(no.2017SZYZF0002);Marie Curie Fellowship(no.796426).

摘　　要：Benefiting from strong decoding capabilities,soft-decision decoding has been used to replace hard-decision decoding in various communication systems,and NAND flash memory systems are no exception.However,soft-decision decoding relies heavily on accurate soft information.Owing to the incremental step pulse programming(ISPP),program errors(PEs)in multi-level cell(MLC)NAND flash memory have different characteristics compared to other types of errors,which is very difficult to obtain such accurate soft information.Therefore,the characteristics of the log-likelihood ratio(LLR)of PEs are investigated first in this paper.Accordingly,a PE-aware statistical method is proposed to determine the usage of PE mitigation schemes.In order to reduce the PE estimating workload of the controller,an adaptive blind clipping(ABC)scheme is proposed subsequently to approximate the PEs contaminated LLR with different decoding trials.Finally,simulation results demonstrate that(1)the proposed PE-aware statistical method is effective in practice,and(2)ABC scheme is able to provide satisfactory bit error rate(BER)and frame error rate(FER)performance in a penalty of negligible increasing of decoding latency.

关 键 词：program errors soft-decision decoder NAND flash memory clipping approximation 

分 类 号：TP333[自动化与计算机技术—计算机系统结构]