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

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;
• obtaining a value, h, representing data stored for at least one aggressor cell in said flash memory;
• selecting one or more probability density functions based on a pattern of values stored in at least a portion of said flash memory, wherein said probability density functions comprises pattern-dependent disturbance of one or more aggressor cells on said at least one target cell in said flash memory;
• evaluating at least one selected probability density function based on said measured read value, r;
• and
• computing one or more log likelihood ratios based on a result of said evaluating step.

A system for reading a target cell in a flash memory device capable of storing at least two data levels, s, per cell, comprising:

• a memory;
• and
• at least one processor, coupled to the memory, operative to:
• obtain a measured read value, r, for at least one target cell in said flash memory;
• evaluate 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
• compute one or more log likelihood ratios based on a result of said evaluation;
• wherein said computation comprises 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.

A system for reading a target cell in a flash memory device capable of storing at least two data levels, s, per cell, comprising:

• a memory;
• and
• at least one processor, coupled to the memory, operative to:
• obtain a measured read value, r, for at least one target cell in said flash memory;
• obtain a value, h, representing data stored for at least one aggressor cell in said flash memory;
• select one or more probability density functions based on a pattern of values stored in at least a portion of said flash memory, wherein said probability density functions comprises pattern-dependent disturbance of one or more aggressor cells on said at least one target cell in said flash memory;
• evaluate at least one selected probability density function based on said measured read value, r;
• and
• compute one or more log likelihood ratios based on a result of said evaluation.