Reliability Enhancement for Multi-level Cell NAND Flash Memory Using Error Asymmetry

This paper presents the jointly use of constraint code (CC) and error correction codes (ECC) for the reliability enhancement in Multi-level cell NAND flash memories. In the proposed system, the constraint code helps transform the user data distribution, adapting to the asymmetry in error behavior of MLC NAND flash memories and the ECC corrects more errors thanks to the prior information from the data distribution. The compatibility of CC and ECC is analyzed, and the information loss is shown to be negligible, especially for the use in MLC NAND flash memories. Simulation under practical MLC NAND flash error model has shown that the proposed scheme can improve remarkably output error rate and reduce read latency in these memories.