{
  "slug": "npml-detection",
  "term": "Noise-predictive maximum-likelihood detection",
  "aliases": [
    "NPML"
  ],
  "definition": "Noise-predictive maximum-likelihood (NPML) detection incorporates noise prediction or whitening into sequence-detector branch metrics for a partial-response recording channel.",
  "note": "Eleftheriou and Hirt (1996) describe incorporating noise prediction into a Viterbi detector and report simulation gains over PRML and EPRML for the studied configurations. This is a detector refinement, not a new storage medium or an error-correcting code. The 2001 Cideciyan et al. study distinguishes bit, byte and sector error performance when combining detection with parity post-processing and Reed-Solomon decoding. Its abstract reports that an improvement in bit and byte metrics did not yield the same sector-level separation for two compared schemes. Neither abstract supplies a universal improvement for arbitrary drives, firmware or workloads.",
  "status": "unknown",
  "advantages": [
    {
      "text": "Models noise structure within sequence detection rather than treating noise prediction as a separate storage technology.",
      "citationIds": [
        "ibm1996"
      ]
    }
  ],
  "limitations": [
    {
      "text": "Published simulated gains depend on the channel, detector and coding configuration; current product support is not established by these historical papers.",
      "citationIds": [
        "ibm1996",
        "ibm2001"
      ]
    }
  ],
  "related": [
    "prml-encoding",
    "reed-solomon-code",
    "bit-error-rate"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-11",
  "citations": [
    {
      "id": "ibm1996",
      "title": "E. Eleftheriou and W. Hirt, Improving performance of PRML/EPRML through noise prediction (1996), IBM Research abstract",
      "url": "https://research.ibm.com/publications/improving-performance-of-prmleprml-through-noise-prediction",
      "accessed": "2026-10-11"
    },
    {
      "id": "ibm2001",
      "title": "Cideciyan et al., Noise predictive maximum likelihood detection combined with parity-based post-processing (2001), IBM Research abstract",
      "url": "https://research.ibm.com/publications/noise-predictive-maximum-likelihood-detection-combined-with-parity-based-post-processing",
      "accessed": "2026-10-11"
    }
  ]
}