ADR-273: Unified RF Spatial World Model — one shared representation, not another isolated RF classifier

Field	Value
Status	Accepted — P1 implemented (new v2 workspace crate `ruview-unified`; 66 unit + 3 acceptance-pipeline tests, 0 failed; criterion benches)
Date	2026-07-26
Deciders	ruv
Codebase target	`v2/crates/ruview-unified/` (new leaf crate; single internal dep on `wifi-densepose-core` for `CsiFrame`)
Sub-ADRs	ADR-274 (universal RF encoder + adapter registry), ADR-275 (RF-aware Gaussian spatial memory), ADR-276 (physics-guided synthetic RF worlds), ADR-277 (edge sensing control plane), ADR-278 (radar inverse rendering research program)
Relates to	ADR-152 (WiFi-Pose SOTA intake: geometry conditioning), ADR-153 (802.11bf protocol model), ADR-260/262 (RuField MFS + bridge), ADR-135/136 (calibration + canonical frame provenance), ADR-024 (AETHER), ADR-027 (MERIDIAN domain generalization)
Scope	Decide the target architecture for RuView + RuVector sensing through 2026-H2: one persistent, queryable spatial world model that vision, WiFi CSI, cellular CFR/SRS, radar, geometry, semantics, uncertainty, and time all update — and the priority order for building it.

0. PROOF discipline

Every number in this ADR family is one of:

MEASURED-SYNTHETIC — produced by this repo's tests/benches on data from the ADR-276 physics generator. Reproducible: cd v2 && cargo test -p ruview-unified / cargo bench -p ruview-unified. No claim of real-world accuracy is made or implied.
MEASURED-CODE — a structural property of the implementation (parameter counts, gradient-check error, determinism), verified by a named test.
EXTERNAL-UNVERIFIED — a number reported by an external paper/preprint (WiFo-2, WiLHPE, RISE, DiffRadar, HybridSim, OAI SRS demo, …) that this repo has not reproduced. These motivated design choices; they are never presented as our results.

1. Context

Through mid-2026 the field moved decisively away from task-specific RF classifiers:

RF foundation models (WiFo-2 scaling across 11.6 B CSI points/12 tasks; WiLLM's dataset adapters + shared self-supervised transformer; age-aware CSI fusion) — the architectural signal: standardize heterogeneous CSI, pretrain with masked reconstruction, attach small task adapters (all EXTERNAL-UNVERIFIED).
Gaussian fields as spatial memory (EmbodiedSplat online semantic 3-D Gaussian mapping; TGSFormer bounded temporal Gaussian memory; July's physics-informed channel-gain mapping with incremental Gaussian insertion) — the missing bridge between RuView sensing and a queryable digital twin.
Synthetic RF worlds (WaveVerse phase-coherent ray tracing; HybridSim's 92 % vs 54 % synthetic-to-real gap when physics parameters, not textures, are randomized) — the fastest path out of data scarcity.
Standards became actionable: IEEE 802.11bf-2025 published (2025-09), 802.11bk (320 MHz positioning), ETSI ISAC architecture (2026-02) + security report (19 privacy/security issue classes), 3GPP Rel-20 sensing studies, OAI SRS xApp localization demo.
Generalization lessons: PerceptAlign (condition on TX/RX geometry), RePos (factor root-relative pose from absolute localization), JITOMA (task-gated scene memory).

RuView already has the ingredients (calibration ADR-151, canonical frames ADR-136, ruvsense multistatic stack, RuField bridge ADR-262) but they update separate state. The decision is to converge on one shared representation with persistent scene memory.

2. Decision

Build the unified model as five pillars in strict priority order (scored 35 % business value / 25 % readiness / 20 % defensibility / 20 % strategic learning):

#	Pillar	Score	Sub-ADR	P1 status
1	Universal RF foundation encoder + hardware adapter registry	4.7	ADR-274	implemented
2	RF-aware Gaussian spatial memory	4.5	ADR-275	implemented
3	Age/geometry/uncertainty-aware inference (folded into the encoder contract)	4.4	ADR-274 §3	implemented
4	Physics-guided synthetic RF world generator	4.1	ADR-276	implemented
5	Edge sensing control plane (802.11bf / ETSI ISAC aligned)	3.9*	ADR-277	implemented (policy engine; O-RAN xApp is roadmap)
6	Radar inverse rendering + differentiable RF SLAM	3.6	ADR-278	research program (not implemented)

* the 3.9-scored item is the O-RAN SRS xApp; its policy plane and its SRS adapter seam ship in P1 because they are cheap and gate everything else.

The representation contract every pillar shares:

z = Encoder(RF tokens) ⊙ σ(AgeEncoder(age)) + GeometryEncoder(sensor_pose)

served from one canonical tensor (RfTensor, ADR-274 §2) and persisted into one scene memory (GaussianMap + task-gated SceneGraph, ADR-275).

3. Architecture (implemented, `v2/crates/ruview-unified/src/`)

vendor captures ──▶ adapters.rs (WiFi CSI / FMCW cube / UWB CIR / 5G SRS)
                        │  normalize: layout → gain → phase   (ADR-274 §2.3)
                        ▼
                 tensor.rs  RfTensor (links × 56 bins × 8 snapshots, complex)
                        │
                 tokenizer.rs  amplitude/delay/Doppler/phase/age/geometry/
                        │      clock/uncertainty tokens (CFO-aligned,
                        │      median-scale-normalized)
                        ▼
                 encoder.rs + pretrain.rs   masked-reconstruction pretraining,
                        │      exact hand-derived backprop (gradient-checked)
                        ▼
        ┌── heads.rs  ≤1 % task adapters (presence/activity/localization/anomaly)
        │
        ├── gaussian/  RF-aware Gaussian memory: fusion, decay, channel-gain
        │              queries, inverse updates, task-gated scene graph
        │
        └── policy.rs  purposes/zones/retention/identity gating; BoundedEvent
                       is the only exportable type (raw RF unrepresentable)

synth/ (ADR-276) generates the labeled physics worlds that train and gate all of it; eval.rs implements the anti-leakage protocol below.

4. The non-negotiable evaluation protocol (anti-leakage)

The biggest failure mode in this field is domain leakage disguised as accuracy: random frame splits let a model recognize the room, session, person, device, or trajectory. Bigger models make it worse. Therefore:

No result counts unless the test set holds out complete rooms, days, people, chipsets, firmware versions, and antenna layouts. eval::StrictSplit constructs such splits and verify() independently proves disjointness (eval.rs; test verify_catches_a_manufactured_leak).
Track relative degradation known→unknown (relative_degradation, gate < 20 %), calibration (expected_calibration_error), and abstention quality (selective_metrics — an uncertain result must become no decision, not a confident guess).
Every synthetic number is labeled SYNTHETIC in test output and in these ADRs.

5. Acceptance gates — P1 (synthetic analogue) results

The ADR's acceptance test (frozen shared encoder, adapters < 1 % of backbone, unseen rooms/chipsets/layouts) is implemented end-to-end in tests/e2e_acceptance.rs. MEASURED-SYNTHETIC results on the ADR-276 generator (8 rooms × 20 windows × 3 links, seed 273273):

Gate (ADR target)	P1 synthetic result	Verdict
Presence F1 ≥ 0.90, unseen rooms	1.0000 (rooms 6–7 held out of pretraining and head training)	pass
Presence F1 ≥ 0.90, unseen chipset	1.0000 (`chip-2` held out; per-room random gain/phase/CFO/noise)	pass
Cross-environment degradation < 20 %	0.0000	pass
Adapter budget < 1 % of backbone	presence 129 / activity 268 / localization 387 / anomaly 2 params vs 40,856-param backbone (< 408)	pass (MEASURED-CODE)
Edge latency p95 < 50 ms	2.0 ms debug profile (tokenize+encode); 105 µs encode / 67 µs tokenize release (criterion)	pass
Held-out ECE	0.0122; abstention risk monotone in threshold	pass
Raw RF never crosses the trust boundary	structural: only `policy::BoundedEvent` exports (no tensor-carrying variant exists)	pass
Every output carries uncertainty, provenance, model version, purpose	enforced at `BoundedEvent::new` (construction fails otherwise)	pass

Honest reading: a synthetic world where presence ⇔ a moving scatterer is separable by construction; F1 = 1.0 here validates the pipeline and the anti-leakage machinery, not real-world performance. The real-data gate (5 unseen rooms, 2 unseen chipsets, 2 unseen layouts, measured CSI) is P2 and remains open.

6. Consequences

RuView gains a single, tested substrate that all future sensing work (vision fusion, SRS xApp, radar) updates instead of forking.
The synthetic-first discipline means every accuracy claim is grade-labeled; publishing an unlabeled number is now a process violation.
The Gaussian memory becomes the integration point for RuVector (vector retrieval → graph constraints → geometric verification; the LLM plans the query, the renderer verifies the answer).
Cost: a new crate to maintain (~4.6 k lines incl. tests); mitigations: zero heavy deps, deterministic tests, files < 500 lines each.

7. Roadmap after P1

Phase	Content	Gate
P2	Replay real `.csi.jsonl` (rvCSI / ADR-262 corpus) through the WiFi adapter; calibrate the anomaly head on real empty-room captures	strict-split F1/ECE on measured data, reported with degradation vs synthetic
P3	Wire `GaussianMap` into `wifi-densepose-sensing-server` behind the ADR-277 boundary; RuVector embedding of Gaussian clusters	live map consistency + bounded-event-only egress audit
P4	OAI SRS xApp feeding `CellularSrsAdapter` (the adapter + registry seam already exists)	0.5 m p90 localization under non-random splits
P5	ADR-278 radar inverse rendering reproduction (RISE first)

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