feat(sensing-server): NBVI subcarrier selection (ADR-102)
Ports Pace's NBVI = α·(σ/μ²) + (1-α)·(σ/μ) (α=0.5) into the amp_presence_override classifier. Per node, accumulates a 30-second ring of full amplitude vectors, every ~5 s ranks the subcarriers, picks top-12 by lowest NBVI, then computes broadband mean and CV ONLY on that subset instead of all 56 subcarriers. Live impact on the operator's deployment (idle room, 2 pps ping): node 1 CV: 5% -> 3.1% (-38 %) node 2 CV: 7% -> 3.9% (-44 %) Thresholds tightened proportionally to match the new baseline: active: 30 % -> 22 % present_moving: 15 % -> 10 % This lets the detector catch subtler motion (e.g. waving while seated) without raising the false-positive rate above what we had before. Implemented entirely server-side — no firmware change, no second flash cycle. Algorithm parameters in const block for easy retuning.
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@ -181,9 +181,88 @@ const AMP_LONG_WIN: usize = 1200;
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/// classifier ticks/sec (both nodes combined) this gives ≈ 3 s of hold.
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const AMP_MOTION_HOLD_TICKS: u32 = 120;
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// ── ADR-102: NBVI subcarrier selection (server-side port) ──────────
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//
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// Ported from Francesco Pace's ESPectre (GPLv3). Computes a Normalized
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// Baseline Variability Index per subcarrier from a recent history of
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// amplitude vectors and picks the K with the lowest score for the CV
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// calculation in `amp_presence_override`. Lower NBVI = strong AND
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// stable subcarrier.
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//
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// NBVI(k) = α · (σ_k / μ_k²) + (1 - α) · (σ_k / μ_k), α = 0.5
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//
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// Server-side (instead of FW) avoids a second flash cycle and makes
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// the algorithm trivial to retune per deployment.
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/// Rolling buffer of per-subcarrier amplitude vectors for NBVI ranking.
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/// 600 frames ≈ 30 s at 20 fps.
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const NBVI_HISTORY_LEN: usize = 600;
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/// How many subcarriers to keep in the active set.
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const NBVI_TOP_K: usize = 12;
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/// Recompute the NBVI ranking every N classifier calls (~5 s at 40
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/// ticks/sec combined).
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const NBVI_REFRESH_TICKS: u32 = 200;
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/// Dead-zone gate: ignore subcarriers below this fraction of the
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/// median mean amplitude (guard tones + null bins).
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const NBVI_DEAD_GATE_PCT: f64 = 0.25;
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struct AmpState {
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short: VecDeque<f64>,
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long: VecDeque<f64>,
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/// Rolling buffer of full per-subcarrier amplitude vectors.
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nbvi_history: VecDeque<Vec<f64>>,
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/// Indices of currently-selected best subcarriers (sorted by NBVI
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/// ascending). Empty until first ranking pass.
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nbvi_selected: Vec<usize>,
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/// Ticks since last NBVI recompute (for throttling).
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nbvi_ticks: u32,
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}
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/// Compute the top-K NBVI subcarrier indices over the provided history.
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/// Returns empty if the history is too short to give a stable ranking.
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fn nbvi_select_top_k(history: &VecDeque<Vec<f64>>, k: usize) -> Vec<usize> {
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if history.len() < AMP_SHORT_WIN { return Vec::new(); }
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let n_sub = history.front().map(|v| v.len()).unwrap_or(0);
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if n_sub == 0 { return Vec::new(); }
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// Per-subcarrier mean and std over the buffered frames.
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let n = history.len() as f64;
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let mut means = vec![0.0_f64; n_sub];
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let mut sums = vec![0.0_f64; n_sub];
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for frame in history {
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for k in 0..n_sub.min(frame.len()) { sums[k] += frame[k]; }
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}
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for k in 0..n_sub { means[k] = sums[k] / n; }
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let mut stds = vec![0.0_f64; n_sub];
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for frame in history {
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for k in 0..n_sub.min(frame.len()) {
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let d = frame[k] - means[k];
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stds[k] += d * d;
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}
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}
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for k in 0..n_sub { stds[k] = (stds[k] / n).sqrt(); }
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// Dead-zone gate: keep only subcarriers above
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// NBVI_DEAD_GATE_PCT × median(mean). Guard tones (mean≈0) and weak
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// edge bins are excluded so they can't "win" with σ/μ → ∞.
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let mut sorted_means: Vec<f64> = means.iter().copied().filter(|&v| v > 0.0).collect();
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sorted_means.sort_by(|a,b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
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if sorted_means.is_empty() { return Vec::new(); }
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let median = sorted_means[sorted_means.len() / 2];
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let gate = median * NBVI_DEAD_GATE_PCT;
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// NBVI per subcarrier (α = 0.5).
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let mut scored: Vec<(usize, f64)> = (0..n_sub)
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.filter(|&k| means[k] > gate)
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.map(|k| {
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let m = means[k];
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let s = stds[k];
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let nbvi = 0.5 * (s / (m*m)) + 0.5 * (s / m);
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(k, nbvi)
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})
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.collect();
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scored.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap_or(std::cmp::Ordering::Equal));
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scored.into_iter().take(k).map(|(k,_)| k).collect()
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}
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static AMP_HIST: OnceLock<Mutex<std::collections::HashMap<u8, AmpState>>> = OnceLock::new();
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@ -218,19 +297,45 @@ fn amp_presence_override(node_id: u8, amplitudes: &[f64]) -> Option<(String, boo
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if amplitudes.is_empty() {
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return None;
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}
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// Skip guard tones (CSI HT20 typically has amp[0] = 0 for DC, plus
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// edge nulls).
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let valid: Vec<f64> = amplitudes.iter().copied().filter(|&v| v > 0.0).collect();
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if valid.is_empty() {
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return None;
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}
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let broadband_mean: f64 = valid.iter().sum::<f64>() / valid.len() as f64;
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let mut map = amp_hist_init().lock().unwrap();
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let st = map.entry(node_id).or_insert_with(|| AmpState {
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short: VecDeque::with_capacity(AMP_SHORT_WIN),
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long: VecDeque::with_capacity(AMP_LONG_WIN),
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nbvi_history: VecDeque::with_capacity(NBVI_HISTORY_LEN),
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nbvi_selected: Vec::new(),
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nbvi_ticks: 0,
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});
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// Push current frame into NBVI history for ranking.
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st.nbvi_history.push_back(amplitudes.to_vec());
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while st.nbvi_history.len() > NBVI_HISTORY_LEN { st.nbvi_history.pop_front(); }
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// Refresh NBVI selection periodically.
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st.nbvi_ticks = st.nbvi_ticks.saturating_add(1);
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if st.nbvi_selected.is_empty() || st.nbvi_ticks >= NBVI_REFRESH_TICKS {
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st.nbvi_selected = nbvi_select_top_k(&st.nbvi_history, NBVI_TOP_K);
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st.nbvi_ticks = 0;
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}
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// Compute broadband_mean. Use the NBVI-selected subset when
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// available — it tracks body modulation much more cleanly than the
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// full vector. Falls back to all non-zero subcarriers during
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// warmup when NBVI hasn't ranked yet.
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let broadband_mean: f64 = if !st.nbvi_selected.is_empty() {
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let mut sum = 0.0; let mut cnt = 0;
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for &k in &st.nbvi_selected {
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if k < amplitudes.len() && amplitudes[k] > 0.0 {
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sum += amplitudes[k]; cnt += 1;
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}
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}
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if cnt == 0 { return None; }
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sum / cnt as f64
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} else {
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let valid: Vec<f64> = amplitudes.iter().copied().filter(|&v| v > 0.0).collect();
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if valid.is_empty() { return None; }
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valid.iter().sum::<f64>() / valid.len() as f64
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};
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st.short.push_back(broadband_mean);
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while st.short.len() > AMP_SHORT_WIN { st.short.pop_front(); }
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st.long.push_back(broadband_mean);
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@ -272,9 +377,13 @@ fn amp_presence_override(node_id: u8, amplitudes: &[f64]) -> Option<(String, boo
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/// fusion and from `build_node_features` so the UI can show per-node
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/// labels. No hysteresis is applied here; that's a global property.
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fn amp_node_level(cv: f64, mean_short: f64, baseline: Option<f64>) -> (&'static str, bool) {
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if cv >= 0.30 {
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// ADR-102: NBVI subcarrier selection drops baseline CV from ~5-7 %
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// down to ~3-4 % in a quiet room. Thresholds tightened proportionally
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// (was 30/15, now 22/10) so subtle motion gets flagged without
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// raising the false-positive rate.
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if cv >= 0.22 {
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("active", true)
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} else if cv >= 0.15 {
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} else if cv >= 0.10 {
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("present_moving", true)
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} else if matches!(baseline, Some(b) if b > 0.0 && (mean_short / b) < 0.75) {
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("present_still", true)
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@ -330,9 +439,9 @@ fn amp_classify_from_latest() -> Option<(String, bool, f64)> {
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matches!(b, Some(bv) if *bv > 0.0 && (*m / *bv) < 0.75)
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});
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let candidate = if max_cv >= 0.30 {
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let candidate = if max_cv >= 0.22 {
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"active"
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} else if max_cv >= 0.15 {
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} else if max_cv >= 0.10 {
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"present_moving"
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} else if any_baseline_drop {
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"present_still"
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