Meanwhile, in the presence of soft-decision memory sensing, the flash-to-controller data transfer latency will accordingly increase.
However, fine-grained soft-decision memory sensing must be used in order to fully leverage the strong error correction capability of LDPC codes, which results in significant data access latency overhead.
To meet a specified P/E cycling endurance limit, the LDPC code decoding with the maximum allowable soft-decision memory sensing precision should be able to tolerate the worst-case raw storage reliability at the end of memory lifetime.
In particular, since NAND flash memory on-chip sensing latency is linearly proportional to the sensing quantization granularity, soft-decision memory sensing will largely increase on-chip memory sensing latency compared with current practice.
For example, in the 2-bit soft-decision memory sensing scheme, there exist N s = 15 SRVs and 4 bits are enough to represent the 16 threshold levels for both LSB and MSB data.
As NAND flash memory uses soft-decision memory sensing with higher and higher sensing quantization granularity, LDPC code decoder can carry out soft-decision decoding (e.g., using the sum product or min sum decoding algorithm) and achieve stronger and stronger error correction capability.
If NAND flash memory uses conventional hard-decision memory sensing (i.e., there are only l − 1 sensing quantization levels for l-level per cell NAND flash memory), LDPC code decoder can only carry out hard-decision decoding (e.g., using the hard-decision bit-flipping decoding algorithm) and achieve relatively poor error correction capability.
Therefore, it is very straightforward to apply a progressive-precision LDPC decoding strategy to reduce the average latency, i.e., we always start with the hard-decision memory sensing (and hence hard-decision LDPC code decoding), and only if LDPC decoding fails, we progressively increase the sensing precision and retry the decoding until LDPC decoding succeeds.
He described it as "the most questionable and curious High Court decision in memory".Experts are divided about how well offshore-processing actually works as a deterrent.
Already, in this decision, Jewish memory is separated from Jewish history; the latter must study the former, but must not rely on it.
