Flexible WOM codes for NAND flash memory based on raptor-like codes

Write-once memory (WOM) codes aim to extend the lifetime and improve the writing efficiency of storage devices such as NAND flash memory by reducing the number of erase operations. In this paper, a new rewriting scheme for NAND flash memory is proposed, which supports two writes (or only one rewrite) and allows the second write incrementally done multiple times by using raptor-like codes as rate-compatible (RC) low-density generator matrix (LDGM) codes. The proposed scheme improves writing efficiency of the NAND flash memory when combined with a proper page selection method. It is verified via numerical analysis that the proposed WOM codes outperform the conventional WOM codes in terms of writing efficiency.