Design of Protograph-LDPC-Based BICM-ID for Multi-Level-Cell (MLC) NAND Flash Memory

In this letter, the optimization of protograph-low-density parity-check (LDPC)-based bit-interleaved coded modulation with iterative detection and decoding (BICM-ID) with anti-Gray mapping is investigated over multi-level-cell (MLC) NAND flash-memory channels. Since the existing protograph-based extrinsic information transfer (PEXIT) algorithm is not applicable to the BICM-ID MLC flash-memory channels, a voltage-sensing PEXIT (VS-PEXIT) algorithm is proposed to facilitate the threshold analysis of protograph codes. Exploiting the proposed VS-PEXIT algorithm, we find that the optimal AR4JA code over AWGN channels cannot preserve its superiority over BICM-ID MLC flash-memory channels. To tackle this problem, we further propose a design scheme to construct a high-rate protograph code, referred to as optimized accumulate-repeat-accumulate (OARA) code , tailored for such scenarios. Theoretical analyses and simulation results illustrate that the proposed OARA-based BICM-ID appears to be an excellent storage scheme over MLC flash-memory channels.