log-likelihood-ratio · shipping · also LLR

Log-likelihood ratio

A log-likelihood ratio is the logarithm of the relative likelihood of two alternatives, used in decoding to express a bit decision and its confidence.

For the NAND convention log(P(bit=0 | observation) / P(bit=1 | observation)), a positive value favors zero; reversing the ratio reverses its sign.

Relations

related

ldpc, soft-decision-decoding

Citations

1. Cai, Ghose, Haratsch, Luo and Mutlu. Error Characterization, Mitigation, and Recovery in Flash Memory Based Solid-State Drives. Author manuscript arXiv:1706.08642, 2017, sections 6.2-6.3. (accessed 2026-10-11)
2. Hesela: LDPC in NAND, the read cost of confidence (accessed 2026-10-11)

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