Decoding Flash Memory with Progressive Reads and Independent vs. Joint Encoding of Bits in a Cell
Nathan Wong, Ethan M. Liang, Haobo Wang, Sudarsan V. S. Ranganathan, Richard D. Wesel · 2019
This paper develops a paradigm for optimizing progressive reads for flash memory cells that maximize the conditional mutual information (MI) given previous reads and shows that some progressive reads provide substantially more MI than others. We study two flash storage techniques: 1) the common practice of independently encoding each bit of a cell into a separate codeword and 2) jointly encoding all the bits in the cell into the same codeword. We quantify the MI gap between joint and independent encoding and show that this gap becomes negligible when progressive reads are available. The paper provides LDPC simulations that confirm the MI analysis.