Prime-sized multilevel flash memory with non-binary LDPC
Author(s)Al Ai Baky, Mohammed (Mohammed M.)
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
James Fitzpatrick and Yury Polyanskiy.
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Flash memory companies are increasing the number of bits per cell to obtain higher information capacity per cell, starting from 1 bit/cell and going to 4 bits/cell recently. This scaling is enabled by the advancements in flash semiconductor technology, specifically the Bit Cost Scalable (BiCS) technology. However, capacity per cell scaling comes with performance, reliability, and endurance challenges. The industry has only used integer number of bits per cell, which makes the tradeoff between the capacity and the other system features less flexible than using fractional bits. This project explores programming 13 levels of charge ( 3.7 bits) into a QLC flash cell that normally carries 16 levels of charge (4 bits). We evaluate the 13-ary scheme against the 16-ary one and we show that the 13-ary has the same reliability at a lower SNR as the 16-ary, or the 13-ary has higher reliability than the 16-ary at the same SNR. We design binary and non-binary Quasi-Cyclic LDPC codes and implement Belief Propagation decoders for them.
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 65-67).
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology
Electrical Engineering and Computer Science.