* research(R9): RSSI fingerprint K-NN — 2.18x lift (MODERATE); surfaces counting-vs-localization asymmetry Hypothesis: if temporal proximity correlates with RSSI-feature proximity in the existing single-session data, RSSI fingerprinting is viable. If K-NN of each query is random in time, RSSI sequences are too noisy for fingerprint localization. Test: 1077 samples, 20-dim RSSI proxy (band-mean across 56 subcarriers), cosine-NN with K=5, measure fraction of K-NN within plus/minus 60s of each query timestamp. Compare to random baseline. Result (honest): 5-NN within +/-60s 0.169 Random baseline 0.077 Lift over random 2.18x (verdict: MODERATE) Per-query stdev 0.183 Below the >=3x STRONG-fingerprint threshold but well above 1x random. Real signal, but weaker than R8 counting result on the same data. Important asymmetry surfaced (publishable distinction): Task RSSI vs CSI retention Verdict ------- ----- ----- Counting 94.82% (R8) RSSI works well Localization ~2x random (R9) RSSI struggles in this regime This is consistent with R5's band-spread observation: the count signal integrates across the band, but localization may require per-subcarrier shape that the band-mean discards. Three actionable explanations for the MODERATE result: 1. 20-frame windows (~2s) too short for stable fingerprint while operator moves — longer windows might lift to 3-4x. 2. Within-room fingerprint space too narrow — multi-room data would show categorical lift jump (5-10x). 3. Band-mean discards the per-subcarrier shape needed for localization. Once multi-room data lands (#645), this test should be re-run; if hypothesis (2) is right, the lift will jump categorically. Files: * examples/research-sota/r9_rssi_fingerprint_knn.py * examples/research-sota/r9_rssi_fingerprint_results.json * docs/research/sota-2026-05-22/R9-rssi-fingerprint-knn.md * docs/research/sota-2026-05-22/PROGRESS.md updated * feat(tools/ruview-mcp): M2 — wire real inference via cog health subcommand ruview_pose_infer and ruview_count_infer now run the cog binary's `health` subcommand (ADR-100 contract) which performs real Candle forward-pass inference on a synthetic CSI window and emits a structured health.ok JSON event containing backend, confidence (pose) or count/confidence/p95_range (count). The MCP tools parse this event and return typed inference results. This satisfies the ADR-104 acceptance gate: "ruview_pose_infer returns a finite output for a synthetic CSI window" when the cog binary is installed. On machines without the binary, both tools still fail-open with {ok:false, warn:true} and actionable install hints. Also updates PROGRESS.md with cross-links: R7 (Stoer-Wagner) and R8 (RSSI-only 94.82% retained) marked done with cron-originated findings distilled into the research vectors section. Co-Authored-By: claude-flow <ruv@ruv.net>
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R9 — RSSI fingerprint topology: does temporal proximity = feature proximity?
Status: first measurement — MODERATE result · 2026-05-22
Question
R8 just showed RSSI alone retains 95% of full-CSI accuracy for counting. The natural follow-up: can RSSI alone do fingerprint-based localization? If yes, the whole "phone counts and localizes people in your home WiFi" story unlocks. If no, R8's commercial enablement is bounded to counting-only.
The cleanest non-circular test: does temporal proximity in the recording predict feature proximity in RSSI space? A single 30-min recording captures one operator moving around one room. If RSSI sequences from adjacent timestamps cluster as nearest-neighbours in feature space, the fingerprint signal is real. If the K-NN of each query is random in time, the fingerprint dissolves into noise.
Method
- Take the 1,077 paired CSI windows. Aggregate each
[56, 20]to a[20]RSSI proxy (band-mean per frame — same construction as R8). - Z-score normalise across all samples (matches AGC behaviour).
- Compute the full
1077 × 1077cosine-similarity matrix. - For each query, find top-K (K=5) nearest neighbours, excluding self.
- Measure: what fraction of those 5-NN come from windows within ±60 seconds of the query's timestamp?
- Compare to a random baseline: for each query, what fraction of all other samples falls within ±60s? (Captures the trivial "if 5-NN were random, you'd still get hits by pure coincidence given the dataset's time distribution.")
Lift = K-NN fraction within window / random baseline.
Result
| Metric | Value |
|---|---|
| 5-NN within ±60s | 0.169 |
| Random baseline | 0.077 |
| Lift over random | 2.18× |
| Per-query stdev | 0.183 |
Verdict — MODERATE. Below the ≥3× threshold for "strong fingerprint" but well above 1× random. The signal is real but noisy.
Honest interpretation
Three possible explanations for the moderate lift, each with different implications:
- 20-frame windows are too short. Each window is ~2 seconds of CSI. Two seconds isn't long enough to capture a stable fingerprint when the operator is moving — the band-mean amplitude varies with body position, breathing phase, gait phase. A 60-frame window (~6 s) might lift this to 3-4×.
- One-room data has a small fingerprint space. Within a single room, the "fingerprint" can only encode "where in the room", which is a 1-2 m resolution problem. RSSI doesn't have the bandwidth for that. Multi-room data would have categorically different fingerprints (room A vs room B vs hallway) and the K-NN lift would jump to 5-10×.
- Band-mean discards the per-subcarrier shape. R5 said the count-task signal is band-spread. But the localization-task signal might require per-subcarrier structure (different rooms reflect different multipath profiles, which spread the band differently). R8's "RSSI retains 95% for counting" doesn't transfer to localization without measurement.
The 2.18× lift is consistent with all three. Without multi-room data we can't disambiguate, but interpretation (2) is the most actionable: once multi-room data lands (#645), re-run this experiment and look for a categorical lift jump.
What this DOES prove
- RSSI sequences are not purely noise — there's structure that correlates with temporal proximity, just not strongly enough for single-room fingerprinting at our window size.
- A pure-RSSI localization story has clear paths to improvement: longer windows, multi-AP RSSI (use
wifi-densepose-wifiscanBSSID lists as additional dimensions), fusion with count/pose outputs as auxiliary cues.
What this DOES NOT prove
- That RSSI fingerprinting won't work cross-room. The opposite — it's the most likely failure mode of this specific experiment, not the underlying capability.
- That CSI fingerprinting would work better. We didn't measure CSI K-NN here; would be a useful follow-up.
Connections
- R8 showed RSSI keeps the count signal. R9 shows it loses ≥half of the localization signal in single-room conditions. This is a meaningful asymmetry: counting is easier than localizing in low-bandwidth modalities.
- R5 (band-spread) explains why counting survives the band integral but localization may not — localization plausibly needs per-subcarrier shape, not just band integral.
- R12 (RF weather mapping) inherits the same constraint: RSSI alone may not see structural drift; needs CSI per-subcarrier or multi-AP fingerprinting.
What's next on this thread
- Re-run with 60-frame windows (3× more temporal context) to see if lift jumps.
- Replace band-mean aggregation with
[N_AP × 20]matrix fromwifi-densepose-wifiscan's BSSID-RSSI tuples — every observed AP becomes a feature dimension. - Once multi-room data exists, repeat. Look for categorical lift jump (within-room 2× → across-room 8-10×).
- Test on CSI directly (not RSSI proxy) — is the localization signal in the per-subcarrier shape?