Methods and apparatus for soft demapping and intercell interference mitigation in flash memories

摘要

Methods and apparatus are provided for soft demapping and intercell interference mitigation in flash memories. In one variation, a target cell in a flash memory device capable of storing at least two data levels, s, per cell is read by obtaining a measured read value, r, for at least one target cell in the flash memory; obtaining a value, h, representing data stored for at least one aggressor cell in the flash memory; selecting one or more probability density functions based on a pattern of values stored in at least a portion of the flash memory, wherein the probability density functions comprises pattern-dependent disturbance of one or more aggressor cells on the at least one target cell in the flash memory; evaluating at least one selected probability density function based on the measured read value, r; and computing one or more log likelihood ratios based on a result of the evaluating step.

主权项

1. A method for reading a target cell in a flash memory device capable of storing at least two data levels, s, per cell, said method comprising:
obtaining a measured read value, r, for at least one target cell in said flash memory; evaluating at least one probability density function based on said measured read value, r, wherein said probability density function indicates a probability of measuring a read value, r, for a given data level, s; and computing one or more log likelihood ratios based on a result of said evaluating step; wherein said computing step further comprises the step of: aggregating for each of two possible binary values said probability of measuring a read value, r, for a given data level, s, for multiple data levels associated with said two possible binary values.