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Extends R6.2 from 2D ellipse to 3D ellipsoid + 3D target zones (bed at z=0.3-0.6, chair at z=0.5-1.2, standing at z=1.0-1.7 in a 5x5x2.5 m room). Counter-intuitive headline: | Strategy | Coverage | |-------------------------------------------|---------:| | Desk-height (0.8 m walls) | 22.2% | | Wall-mount (1.5 m walls) | 17.4% | | Ceiling-only (2.5 m grid) | 0.0% | <-- FAILS | Mixed walls + ceiling | 25.7% | <-- BEST Ceiling-only fails because both antennas at 2.5 m create a Fresnel ellipsoid sitting AT ceiling height (2.1-2.9 m vertically). Target zones at 0.3-1.7 m are below the envelope by 0.4-2.0 m. The 39 cm transverse radius is symmetric around LOS, so a flat horizontal link at any height misses targets at any OTHER height. This is the 3D version of R6.1's on-LOS-degeneracy finding. A horizontal link at any single height has its envelope concentrated at that height. Why mixed wins: best placement is Tx (5.0, 4.0, 0.8) + Rx (0.0, 4.0, 1.5). The diagonal-in-z link tilts the ellipsoid through multiple elevations. Covers chair AND standing AND bed simultaneously. Vertical link diversity is the 3D insight 2D analysis missed. Installation-guide updates: - Single pair: one low (0.8 m) + one high (1.5 m), opposite walls - 4-anchor: 2x low corners + 2x high opposite corners - 5-anchor knee: mix 0.8 / 1.5 / one ceiling - Bed-only: both LOW - Standing-only: both HIGH - NEVER: both ceiling without a low anchor Coverage numbers are lower than R6.2's 2D 51% because 3D volumetric coverage is inherently lower than 2D area coverage -- honest 3D physics. Composes: - R6.2 (2D) -- incomplete; height matters as much as horizontal - R6.2.2 (N-anchor) -- N=5 knee should distribute across heights - R6.1 (multi-scatterer) -- needs 3D body model for proper composition - R14 V1/V2/V3 -- each vertical needs height-recipe - ADR-029 -- placement is (x, y, z), not (x, y) - R12 PABS -- detects intruders standing/sitting/lying with mixed heights Honest scope: 3-zone discrete approximation, single-pair only, no furniture occlusion, 0.1 m resolution, greedy search. Coordination: ticks/tick-21.md, no PROGRESS.md edit.
6.2 KiB
6.2 KiB
R6.2.1 — 3D antenna placement: ceiling-only mounting is the WORST option
Status: 3D Fresnel ellipsoid + height-strategy benchmark · 2026-05-22
Counter-intuitive headline
| Strategy | Coverage of 3 zones |
|---|---|
| Desk-height (0.8 m, walls) | 22.2% |
| Wall-mount (1.5 m, walls) | 17.4% |
| Ceiling-only (2.5 m, full ceiling grid) | 0.0% |
| Mixed (any height, walls + ceiling) | 25.7% ← best |
Ceiling-only mounting completely fails — the Fresnel envelope sits at ceiling height (2.1-2.9 m) and never reaches floor-level targets (bed 0.3-0.6 m, chair 0.5-1.2 m, standing 1.0-1.7 m).
The physics
In 3D the first Fresnel zone is a prolate ellipsoid with foci at Tx and Rx. The transverse radius at the midpoint is sqrt(d·λ)/2. For a 5 m link at 2.4 GHz: 39 cm transverse. This is a symmetric envelope around the LOS line.
A ceiling-mounted link (Tx at 2.5 m, Rx at 2.5 m, horizontal LOS) has its Fresnel envelope vertically centred at 2.5 m, extending from 2.1 m to 2.9 m. Targets at 0.3-1.7 m are below the envelope by 0.4-2.0 m. Completely missed.
This is the 3D extension of the on-LOS-degeneracy finding from R6.1 — except now the issue is on-CEILING degeneracy. A flat horizontal link at any height blocks sensing in the perpendicular dimension.
Why mixed wins
The optimal mixed placement picks Tx at (5.0, 4.0, 0.8) — desk height — and Rx at (0.0, 4.0, 1.5) — wall-mount height. The link is diagonal in z as well as x. The Fresnel ellipsoid is tilted to thread multiple elevations: covers chair (z=0.5-1.2) AND standing zone (z=1.0-1.7) AND a portion of bed (z=0.3-0.6).
Vertical link diversity is the key 3D insight that 2D analysis missed.
Recommendations
| Use case | 3D placement recipe |
|---|---|
| Single Tx-Rx pair | One low (desk height ~0.8m), one high (wall ~1.5m), opposite walls |
| 4-anchor multistatic (R6.2.2) | 2× low corners + 2× high opposite corners |
| 5-anchor (R6.2.2 knee) | Mix of 0.8 m / 1.5 m / one ceiling at 2.5 m for top-down coverage |
| Bed-only (sleep monitoring) | Both antennas low (0.5-0.8 m) and opposite sides of bed |
| Standing-only (gym, kitchen) | Both antennas high (1.5 m) |
| NEVER | Both antennas ceiling-mounted with no low-anchor |
What this says about the installation guide
Current RuView installer instructions are 2D: "place seeds on opposite walls". The 3D scrutiny says:
- Heights matter as much as horizontal positions. Mixed-height placement gives +15.8% coverage over desk-height-only.
- Ceiling-mount fails alone. If using ceiling as part of a multi-anchor configuration, MUST also have at least one low-height anchor to bring the envelope down to floor-level targets.
- Bedside sensing wants low anchors. A bed at 0.3-0.6 m can only be covered by low-height links. High-mounted antennas miss the bed entirely.
These should be added to the installer-guide as height recipes, alongside R6.2's horizontal-placement recipes.
Composes with prior threads
- R6.2 (2D placement) — 2D analysis hides height issues entirely; R6.2 alone gives wrong installer guidance.
- R6.2.2 (N-anchor multistatic) — N=5 anchors should be distributed across heights, not all at one elevation.
- R6.1 (multi-scatterer) — the multi-scatterer body model is 2D top-down; a 3D body model (head at z=1.7, chest at z=1.3, legs at z=0.5) would tighten the per-body-part contribution estimates per height.
- R14 (empathic appliances) — V1 lighting (bedroom: detect sleeper) needs low anchors. V3 (cognitive load at desk) needs mid-height. The placement strategy depends on the empathic-appliance use case.
- ADR-029 (multistatic) — anchor-count + placement-height are both required configuration parameters.
Honest scope
- Coverage numbers (22%, 17%, 26%) are lower than R6.2's 2D 51% because targets are 3D volumes now, not 2D areas. Volumetric coverage is inherently lower; a 3D point must be inside the ellipsoid in all three axes.
- 3 zones at distinct heights. Real rooms have continuous human occupancy distributions (people stand, sit, lie); the 3-zone setup is a discrete approximation.
- Single-pair only. Multi-anchor 3D (R6.2.2.1) would saturate much earlier than the 2D version because each anchor's ellipsoid is sparser in 3D.
- No furniture occlusion in 3D either.
- 0.1 m resolution. Finer resolution would refine the numbers slightly.
- Greedy single-pair search. Global optimum may be slightly higher; brute-force is feasible at this candidate count.
What this DOES enable
- Updates the installation-guide recipe from "place on opposite walls" to "place at mixed heights on opposite walls".
- Quantifies why ceiling-only WiFi sensing doesn't work — common mistake in DIY deployments.
- Provides height-strategy recommendations per use case (sleep / sitting / standing).
- A 3D placement search that can be added to
wifi-densepose plan-antennasas a--3dflag.
What this DOES NOT enable
- Continuous occupancy distribution modelling (would need pose-trajectory data, R6.2.3).
- Multi-pair 3D optimisation (R6.2.2.1 — composition with R6.2.2 in 3D).
- Furniture / wall occlusion modelling (would need a 3D ray-tracing extension).
- Per-empathic-appliance optimised placement (would need V1/V2/V3 task-specific zones).
Next ticks (R6.2 family)
- R6.2.2.1: 3D multi-anchor union coverage — does the 5-anchor knee hold in 3D?
- R6.2.3: chest-centric target zones (R6.1 says chest is 27.6% of signal — placement should target chest specifically).
- R6.2 productisation: add
--3dflag to the CLI tool.
Connection back
- R6 Fresnel forward model — direct 3D extension.
- R6.1 multi-scatterer — needs a 3D body model to compose properly with R6.2.1.
- R6.2 — 2D was incomplete; height matters as much as horizontal position.
- R6.2.2 — N-anchor knee likely shifts in 3D; needs follow-up benchmark.
- R14 V1/V2/V3 — each vertical needs its own height-recipe.
- ADR-029 — anchor placement specification needs (x, y, z) per anchor, not (x, y).
- R12 PABS — PABS sensitivity to structural changes inherits R6.2.1's coverage; mixed-height placements detect intruders standing AND sitting AND lying.