Shaping Codes for Structured Data

In this work, we study data shaping codes for flash memory. We first review a recently proposed direct shaping code for SLC (one bit per cell) flash memory that reduces wear by minimizing the average fraction of programmed cells. Then we describe an adaptation of this algorithm that provides data shaping for MLC (two bits per cell) flash memory. It makes use of a page- dependent cost model and is designed to be compatible with the standard procedure of row-by- row, page-based, wordline programming. We also give simulation results demonstrating the performance of these data shaping codes when applied to English language text. Finally, we use a random walk model to analyze the potential error propagation properties of direct shaping codes when used in a noisy memory.