Bilayer LDPC Codes Combined with Perturbed Decoding for MLC NAND Flash Memory.

Area of Science:

• * Digital storage technologies
• * Error correction coding
• * Semiconductor memory devices

Background:

• * Multi-level cell (MLC) NAND flash memory faces challenges with data integrity and limited lifespan.
• * Traditional coding schemes struggle to fully exploit the asymmetric channel characteristics of MLC NAND flash.
• * Enhancing error correction is crucial for improving the reliability and endurance of flash memory.

Purpose of the Study:

• * To propose a novel coding scheme for MLC NAND flash memory.
• * To leverage the asymmetric properties of the MLC flash channel for improved error correction.
• * To extend the operational lifetime of MLC NAND flash memory.

Main Methods:

• * Development of a bilayer low-density parity-check (LDPC) code structure.
• * Exploitation of MLC NAND flash channel asymmetry by storing parity bits in the lower page.
• * Integration of a genetic algorithm (GA)-based perturbation process into the decoding algorithm to correct uncorrectable read sequences.

Main Results:

• * The proposed bilayer LDPC coding scheme effectively utilizes channel asymmetry.
• * The GA-based perturbation decoding demonstrates efficiency, particularly in low program-and-erase (P/E) cycle regions.
• * Simulation results indicate a potential lifespan extension of MLC NAND flash memory up to 10,000 P/E cycles.
• * The scheme achieves a superior balance between performance and complexity compared to single LDPC schemes.

Conclusions:

• * The bilayer LDPC coding scheme offers a practical solution for enhancing MLC NAND flash memory reliability.
• * The integration of GA-based perturbation decoding significantly improves error correction capabilities.
• * The proposed scheme is well-suited for practical applications in MLC NAND flash memory, balancing performance and complexity.