ISAC Sensing Data Pipeline (Design Note)

July 16, 2026 · View on GitHub

Non-normative 6G research. 3GPP ISAC work is study-stage only (SA1 TR 22.837; SA2 Rel-19 study, TR 23.700-series) — no frozen Stage-3 specification or normative SBI exists for any interface described here. This is a research shape, not a conformance target. Tracking issue: #16.

Flow

producer (gNB/UE sensing engine)
    │  POST /nnwdaf-sensingdata/v1/results   (JSON SensingResult)
    ▼
nwdafd collection endpoint  ──►  bounded in-memory ring buffer (100 results)
    │                             in NwdafContext
    ├── publishes SbiEventCategory::Isac ("SENSING_RESULT") on the NF-owned
    │   pub-sub broker (nextgcore-sbi pubsub, 6g-extensions)
    ├── increments the ISAC_SENSING_RESULTS counter
    │   (AiMetricCategory::IsacSensing, nextgcore-metrics ai_native)
    ▼
consumer: GET /nnwdaf-analyticsinfo/v1/analytics?event-id=ISAC_SENSING
    → 200 {"isacSensingSummary": {ingestedTotal, buffered, latest}}
    → 204 when nothing has been ingested

Everything is behind the sensing cargo feature of nextgcore-nwdafd (off by default; it also enables nextgcore-sbi/6g-extensions for the pub-sub bus). The default build and default nwdafd behaviour are unchanged.

Design choices

  • One canonical type set. nextgcore-proto::isac (serde-capable) is the wire type; the duplicate non-serde SensingResult/SensingConfig that lived in nextgcore-proto::types was removed, and the isac types are re-exported at the proto crate root.
  • Reuse nwdafd, not a new NF. NWDAF is the natural analytics sink; a future NEF (no nextgcore-nefd exists today) would re-expose the summary northbound to AFs — out of scope here.
  • ISAC_SENSING is not a TS 29.520 NwdafEvent. The analytics GET intercepts the token before AnalyticsId parsing so the real TS 29.520 surface stays untouched.
  • Bounded store, NF-context lock rules. RwLock<VecDeque> capped at 100 (matching AnalyticsEngine::MAX_SAMPLES house style); callers take the outer context read lock first, then exactly one interior lock at a time.
  • Event bus liveness. There was no EventBroker instance anywhere in the tree; nwdafd now owns one, making SbiEventCategory::Isac the first live event category. Delivery is in-process bookkeeping (matched subscribers returned/counted) — no outbound notification HTTP yet.

Verification

cargo test -p nextgcore-nwdafd --features sensing sensing   # 3 tests: round-trip, event, fail-closed
cargo build -p nextgcore-nwdafd                             # default build unchanged