Concept 4I.3 Measurement Validation

Concept 4I.3 is an isolated evidence ledger for measured path-loss campaigns. It establishes the data contract, quantity semantics, reference-model adapters, deterministic comparison/holdout diagnostics, and a conservative readiness gate. It does not introduce a new propagation equation, path-loss exponent, ML model, arbitrary regression, or production RF model.

Boundary and invariance

The workflow is exposed at POST /api/sub-thz-validation. It consumes imported campaign JSON and calls only the versioned reference adapters. It does not call or mutate the canonical 2.6 GHz, 28 GHz, research_sub_thz, Concept 4I.2A atmospheric, Concept 4I.2B P.1411, building-entry, diffraction, interference/radio-quality, or optimization result paths. The pre-change audit and invariance targets are recorded in concept-4i3-pre-change-baseline.json; the post-change comparison is recorded in concept-4i3-post-change-comparison.json.

The legacy /api/measurements/evaluate RSRP workflow remains unchanged. Its 4G/5G radio-quality semantics are not silently reused as sub-THz path-loss evidence.

Campaign and measurement contract

Every campaign has a schema version, stable campaign ID/version, source and provenance, frequency range, equipment/antenna/calibration metadata, environment and weather metadata, sites, and measurement records. Every record has a stable measurement ID and may carry location_pair_id and beam_id so repeated beams and correlated observations are visible rather than counted as independent evidence.

The machine-readable contract is concept-4i3-validation-schema.json. Coordinates, numeric values, IDs, timestamps, duplicate campaign/site/measurement IDs, and enumerations are strictly validated. JSON NaN/Infinity are rejected by the decoder and all finite numeric fields are range checked.

The canonical comparison domain is path loss in dB. The residual sign is:

residual = measured_path_loss_db - predicted_path_loss_db

Received power is normalized only when conducted transmit power, transmit/receive gains, cable losses, calibration status, and a compatible isotropic-equivalent or synthesized-omnidirectional basis are explicit:

PL = Pt_conducted + Gt + Gr - Ltx - Lrx - Pr_received

Path gain is converted as PL = -path_gain_db only with explicit quantity, antenna/cable embedding, calibration, and compatible basis metadata. Directional or best-beam observations remain ambiguous unless a synthesized-omnidirectional or isotropic-equivalent basis is supplied. Rx power, path loss, and path gain are never mixed without an explicit normalization decision.

Below-detection and not-detected records are counted as censored and excluded from ordinary residual metrics. No censoring threshold is converted into a fabricated path-loss value.

Reference adapters

The shared adapter contract evaluates applicability before residuals and returns applicable, inapplicable, ambiguous, unsupported, or censored status:

• p525_fspl: exact wavelength-form P.525 free-space path loss at the normalized 3D distance.
• sub_thz_atmospheric_reference_v1: the existing opt-in P.525/P.676/P.838/P.840 ledger, only when explicit weather and rain/fog-known flags exist. Atmospheric totals are side-by-side evidence, not additions to an empirical model.
• p1411_below_rooftop_los_v1, p1411_urban_highrise_nlos_v1, and p1411_urban_lowrise_nlos_v1: existing Table 4 row implementations with strict frequency, distance, morphology, rooftop, and LOS applicability. The empirical sigma is compared with observed residual spread; no random fading is sampled.
• research_sub_thz: comparison-only 140 GHz planning profile requiring an explicit wall-event count. Its 80 dB per-wall heuristic is never inferred or calibrated.
• p526-single-edge-v1: diagnostic-only adapter requiring an explicit obstacle/diffraction loss profile. It is not a canonical propagation path.

Metrics and diagnostics

For every applicable common sample set, the response reports count, mean bias, median bias, MAE, RMSE, standard deviation, p10, and p90. It also reports strata by LOS/NLOS, morphology, distance bin, frequency, campaign, and site; residual diagnostics versus log-distance and frequency; common-sample pair comparisons; censored counts; and directional-basis warnings. No R² score or universal model winner is used as a primary decision.

Calibration is constant-bias-only. A fitted bias is the mean calibration-set residual and is applied only to a held-out diagnostic comparison. Calibration and validation sets are explicit or deterministically separated by site, campaign, location group, or spatial component. Status is stable, unstable, or insufficient_validation_data; promoted is always false.

Spatial holdout uses deterministic meter cells and connected neighboring-cell components so nearby observations cannot leak between calibration and validation folds. Leave-one-site-out and leave-one-campaign-out are also available. The response contains the cell size, minimum-separation policy, fold IDs, counts, and no-leak evidence. The validation fingerprint excludes timestamps, runtime, UI state, and file paths.

External evidence policy

concept-4i3-external-evidence.json registers a small set of previously audited 100–200 GHz sources as metadata-only references. No numeric sample is redistributed, plot-digitized, or invented. A source becomes a numeric campaign only after access/license, quantity semantics, antenna basis, calibration, geometry, labels, and duplicate-beam policy are established.

Synthetic controls

concept-4i3-synthetic-validation.json covers exact P.525, a controlled +5 dB bias, exact P.1411 median evaluation, deterministic residual statistics, spatial-region offset, censored observations, and directional ambiguity. These fixtures test implementation behavior; they are not field validation.

Ankara 140 GHz campaign gap

The current repository contains no redistributable Ankara 140 GHz measurement campaign. A future campaign must capture, per link:

• georeferenced Tx/Rx coordinates and antenna heights, plus the coordinate reference system;
• exact carrier frequency, bandwidth, waveform/sounding configuration, timestamp, and synchronization state;
• conducted Tx power, Tx/Rx cable losses, receiver calibration state, noise/detection floor, receiver dynamic range, and hardware identifiers;
• antenna gain/pattern metadata, beam pointing/beamwidth, polarization, beam ID, and whether the value is directional, best-beam, isotropic-equivalent, or synthesized omni;
• received power/path loss/path gain quantity with an explicit definition and embedded-gain/cable-loss flags;
• LOS/NLOS, morphology, rooftop relation, street width/corner, building/roof intersections, wall events, terrain/vegetation, and the source/provenance of each label;
• temperature, pressure, humidity/water vapour, rain and fog observations with explicit known/unknown flags.

Until that gap is closed, the readiness taxonomy remains reference_only, synthetic_controlled_only, or diagnostic_only; Concept 4I.3 has no production_candidate state.