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W6 - ntn-slice

ntn-slice is the ns3-ntn-toolkit module that brings 3GPP-compliant network slicing to non-terrestrial networks, running eMBB, URLLC and mMTC slices over LEO and GEO satellites with per-slice PRB orchestration, TS 22.261 demand profiles, and a GEO mode-skip policy that keeps URLLC traffic off the orbital latency floor.

Why it matters. 5G slicing is straightforward when every cell is a few kilometers away, but in NTN a URLLC slice's 5 ms p99 budget is hard-bounded by orbital geometry: a GEO leg adds roughly 120 ms of one-way slant propagation, blowing the budget by more than an order of magnitude regardless of any radio-side allocator. ntn-slice gives 6G NTN researchers a slicing layer that understands the orbital floor, so they can study isolation, PRB allocation and latency-aware routing across mixed LEO and GEO constellations.

What it simulates

  • Three co-existing slices on one satellite. eMBB, URLLC and mMTC (plus a V2X SST) with S-NSSAI identifiers, seeded from DefaultEmbb(), DefaultUrllc() and DefaultMmtc() profiles in ntn-slice-types.h.
  • TS 22.261 demand profiles. Per-slice latency budget, min/max throughput, reliability target, priority and allowGeo flag drawn from TS 22.261 Table 7.1-1.
  • Per-slice PRB orchestration. SliceOrchestratorXapp reserves min-throughput first (the classical isolation guarantee), then distributes the remainder by priority-weighted unmet demand, or by externally supplied RL shares via StepWithShares().
  • Flow-to-slice selection. NtnSliceSelector performs first-match-wins association by DSCP, destination port range or app label.
  • GEO mode-skip routing. ShouldSkipGeo() keeps URLLC traffic on LEO satellites whose round-trip time is compatible with the slice target, recognizing that GEO altitudes (>= 30,000 km) carry a ~240 ms ground-satellite-ground penalty.
  • Isolation monitoring. SliceIsolationMonitor tracks rolling-window p99 latency and loss rate and emits a BreachEvent whenever a slice violates its SLA.
  • Real measured radio stack. Examples run real mmwave NR PHY/MAC/RLC/PDCP/RRC/EPC over SGP4 orbital passes with TR 38.811 UE placement and geometric slant-range latency.
Three 5G network slices co-existing on a LEO and GEO non-terrestrial network
eMBB, URLLC and mMTC slices sharing one satellite with GEO mode-skip routing for URLLC

Standards & references

  • 3GPP TS 22.261 - IMT-2020 KPI baseline (Table 7.1-1) for default eMBB/URLLC/mMTC latency, throughput and reliability profiles.
  • 3GPP TS 23.501 - 5G system architecture and S-NSSAI (SST + SD) slicing concepts.
  • 3GPP TR 38.811 - NTN study item, used for UE placement in the slicing examples.
  • 3GPP TR 38.913 - NR channel models and IMT-2020 requirements.

Use cases

  • URLLC over LEO. Verifying that mission-critical control traffic stays on low-latency LEO links while bulk traffic uses GEO.
  • Slice isolation guarantees. Stress-testing whether a saturated eMBB slice can starve URLLC or mMTC on a shared satellite.
  • RL-driven orchestration. Feeding learned PRB shares from the ns3-ai SliceEnv into StepWithShares() and measuring satisfaction.
  • Mixed LEO/GEO planning. Studying how slice admission and routing change as a constellation blends LEO and GEO assets.
  • SLA breach detection. Characterizing p99 latency and loss thresholds that trigger isolation breach events.

Run it

./ns3 run "ntn-three-slice-leo-geo --simTime=30 --numUes=3 --urllcViaGeo --totalPrb=273 --outputDir=ntn-three-slice-output"