Channel Models for Multi-Level Cell Flash Memories Based on Empirical Error Analysis

We propose binary discrete parametric channel models for multi-level cell (MLC) flash memories that provide accurate ECC performance estimation by modeling the empirically observed error characteristics under program/erase (P/E) cycling stress. Through a detailed empirical error characterization of 1X-nm and 2Y-nm MLC flash memory chips from two different vendors, we observe and characterize the overdispersion phenomenon in the number of bit errors per ECC frame. A well studied channel model such as the binary asymmetric channel (BAC) model is unable to provide accurate ECC performance estimation. Hence we propose a channel model based on the beta-binomial probability distribution (2-BBM channel model) which is a good fit for the overdispersed empirical error characteristics and show through statistical tests and simulation results for BCH, LDPC and polar codes, that the 2-BBM channel model provides accurate ECC performance estimation in MLC flash memories.