Error-Correcting Schemes With Dynamic Thresholds in Nonvolatile Memories
Predetermined fixed thresholds are commonly used in nonvolatile memories for reading binary sequences, but they usually result in significant asymmetric errors after a long duration, due to voltage or resistance drift. This motivates one to construct error-correcting schemes with dynamic reading thresholds, so that the asymmetric component of errors is minimized. In this paper, the authors discuss how to select dynamic reading thresholds without knowing cell level distributions, and present several error-correcting schemes. Analysis based on Gaussian noise models reveals that bit error probabilities can be significantly reduced by using dynamic thresholds instead of fixed thresholds, hence leading to a higher information rate.