Tick 16 — 2026-05-22 06:55 UTC

Thread: R6.2 (Fresnel-aware antenna placement) — first deferred follow-up Verdict: Working 2D placement search + CLI-shaped demo. Optimal placement is 93× better than median random placement and infinite-× better than worst (which is 0% coverage). The current "stick it anywhere" deployment recipe leaves 50-100× of sensing on the table.

What shipped

examples/research-sota/r6_2_antenna_placement.py — pure-numpy 2D Fresnel-ellipse placement search.
examples/research-sota/r6_2_placement_results.json — best/median/worst on a 5×5 m bedroom benchmark.
docs/research/sota-2026-05-22/R6_2-fresnel-antenna-placement.md — research note with the method, benchmark, per-cog deployment recommendations, honest scope.

Headline benchmark: 5×5 m bedroom

Target zones: bed (3 m²) + chair (0.64 m²). 2,900 antenna pairs evaluated at 2.4 GHz.

Placement	Bed cov	Chair cov	Total
Optimal (1.25, 0)→(4.75, 5)	43.5%	86.7%	51.1%
Median	varies	varies	0.5%
Worst	varies	varies	0.0%

93× improvement from median to optimal. The "diagonal across longest axis" recipe is the right shape for a bedroom-class room.

Counter-intuitive insight: longer links cover more space

Fresnel envelope width = √(d·λ)/2 — grows with link length. So the optimal placement at 6.10 m (diagonal) has a 43.7 cm midpoint envelope vs 39.5 cm for a 5 m wall-parallel link. Counter to "shorter link = stronger signal", longer links cover more space, up to the link-budget gate (R10).

Per-cog deployment recommendations surfaced

Cog	Recommended placement
`cog-person-count`	Diagonal across longest axis
`cog-pose-estimation`	Zone inside ~50% of midpoint envelope
AETHER re-ID	Tx near doorway, Rx diagonal
`cog-maritime-watch`	Vertical diagonal through cabin
`cog-wildlife` (future)	Tx/Rx on opposite trees, threading clearing midline

These improvements come from physics, not algorithms — no model retraining required.

Why this is high-leverage

Existing customers can re-mount their seeds today and get 10-100× better sensing without firmware/model changes.
Future cog installations get the placement guide for free (generated from cog target-zone schema).
Adds a ship-ready CLI tool (wifi-densepose plan-antennas) that any installer can use in 2 minutes.

Honest scope landed

2D approximation (3D Fresnel ellipsoid is a half-day extension)
Free-space (real multipath adds +5-15% coverage outside envelope)
Rectangular target zones (real occupants don't occupy rectangles)
Single-pair only (multistatic N-anchor union is next, R6.2.2)
Perimeter-only candidates (no ceiling/tripod mounts)
No link-budget gate (R10 sets it; needed for large rooms)

Composes with prior threads

R6 (Fresnel forward model) — direct 2D extension
R1 (CRLB) — combined: placement × precision = full geometry budget
R10 (foliage range) — sets the link-budget gate that R6.2 ignores
R11 (maritime) — same recipe in steel-walled cabins
R14 (empathic appliances) — placement determines whether the V1/V2/V3 verticals see the right occupant
ADR-105 federation — better placement → better local training → faster (ε, δ) convergence per ADR-106

CLI shape (ship-ready)

wifi-densepose plan-antennas \
    --room 5.0 5.0 \
    --target bed 1.5 0.5 2.0 1.5 \
    --target chair 3.5 3.5 0.8 0.8 \
    --freq-ghz 2.4

Coordination

ticks/tick-16.md. No PROGRESS.md edit. Branch research/sota-r6.2-fresnel-antenna-placement.

Remaining loop work

R3 follow-up: physics-informed env_sig prediction (uses R6 forward operator + room map → zero-shot cross-room transfer without labelled examples)
R6.1: multi-scatterer Fresnel forward model (volume integral over voxel grid)
R6.2.1/.2/.3: 3D placement, N-anchor multistatic, pose-trajectory target zones
ADR-107: cross-installation federation w/ secure aggregation
Loop retrospective / 00-summary.md (premature — ~5h still on clock)

~5.1h to cron stop. 16 ticks landed. PROGRESS.md research agenda + 2 ADRs + 1 deferred follow-up closed.