An improvement of performance to layered index-less indexed flash codes

Index-less indexed flash code (ILIFC) has excellent worst-case performance. The layered ILIFC (L-ILIFC) method proposed by Suzuki and Wadayama enables a change of indices when the layer level of charge increases in a sub-block of memory cells. L-ILIFC allows a larger average number of rewrites than ILIFC. Kuribara and Fujisawa developed the L-ILIFC to improve the average-case performance. We call it change index L-ILIFC (CIL-ILIFC). In this paper, we propose an improved rewriting strategy for L-ILIFC. The proposed method enables a sub-block to hold multiple indices to increase the number of rewrites between block erasures. Simulation results shows that the average number of rewrites of the proposed method is improved compared with the conventional L-ILIFC.