One core, many logical networks.
A network slice is a self-contained logical network on shared infrastructure, identified by an S-NSSAI = SST + SD. The NSSF selects the slice(s) and AMF Set for each UE, and the PCF\u2019s URSP rules steer each app into the right one — so a dedicated satellite slice runs beside terrestrial eMBB and URLLC on the very same core.
One physical core, many isolated slices.
Each S-NSSAI is its own logical network with its own QoS, NFs and isolation — assigned by the NSSF and populated by the URSP. Below, the identifier, the standardised types, and how one core fans into many.
| SST | Standardised slice | Where it fits |
|---|---|---|
| 1 | eMBB — enhanced Mobile Broadband | Direct-to-device broadband gap-fill over NTN (partial) |
| 2 | URLLC — ultra-reliable low-latency | Terrestrial only — the 1 ms budget can't survive satellite RTT |
| 3 | mMTC / MIoT — massive IoT | The strong NTN fit — delay-tolerant, store-and-forward (IoT-NTN) |
| 4 | V2X — vehicle-to-everything | Automotive; NTN as coverage backstop |
| 5 | HMTC — high-perf. machine-type Rel-17 | Industrial automation |
TN ↔ NTN slice continuity — a dedicated S-NSSAI can be provisioned for satellite access, and the URSP rules the PCF pushes to the UE steer each application between the terrestrial and non-terrestrial slice as coverage changes. Bit layout & SST values: TS 23.003 §28.4, TS 23.501 §5.15.2.
URSP steering — terrestrial vs satellite.
The UE Route Selection Policy (pushed by the PCF) maps each application to an S-NSSAI. Flip the coverage and watch the URSP re-steer — and see why URLLC has no satellite path.
How NTN actually uses network slicing.
NTN doesn’t invent a new slicing mechanism — it reuses the exact S-NSSAI framework. What changes is that coverage moves: with LEO cells sweeping the Earth, which slices are available in a given place is time-varying, and Rel-19 adds the tools to serve a slice even when the satellite is out of reach of a gateway.
What you’re watching — as the satellite passes, its beam footprint crosses different Tracking Areas. The NSSF advertises NSSAI availability per TA (Nnssf_NSSAIAvailability), so the Allowed NSSAI the AMF hands the UE changes with coverage. URLLC is never available over NTN; over open ocean with no gateway in view, only Store-and-Forward delay-tolerant slices work.
What Release 19 adds
The Rel-19 satellite work items (frozen Dec 2025) are what make slicing over a moving, sometimes-disconnected constellation actually workable.
Regenerative payload
A full gNB — and, with CUPS, the UPF — runs on the satellite. Per-slice QoS scheduling and user-plane isolation can now be enforced in orbit, with slice-specific local breakout through an onboard UPF.
Store-and-Forward
For delay-tolerant slices (mMTC / IoT-NTN), the satellite buffers traffic onboard and forwards it on the next feeder-link pass — a slice is served with no live path to the ground. Impossible for URLLC. (TR 23.700-29)
Slice availability per area
As LEO cells move, the NSSF advertises which S-NSSAI each Tracking Area supports; the AMF updates the UE’s Allowed NSSAI as the serving cell changes. Nnssf_NSSAIAvailability.
Slice admission control
The NSACF caps the registered UEs and PDU sessions per slice — essential when a single beam’s capacity is scarce and must be shared fairly across slices. (TS 29.536)
TN ↔ NTN continuity
The PCF’s URSP and an equivalent S-NSSAI keep each app on its slice as the UE hands between terrestrial and satellite access — one logical slice across both worlds.
MBS & RedCap over NTN
Rel-19 extends multicast/broadcast (with intended service-area signalling) and RedCap to NR-NTN — enabling efficient broadcast slices and low-cost satellite IoT devices.
The end-to-end flow
The operator defines a dedicated NTN S-NSSAI (e.g. SST = 3 / mMTC with an operator-specific SD) and provisions which Tracking Areas support it.
The UE registers over the satellite. The AMF asks the NSSF which slices are available in the current serving TA — a set that changes as the constellation moves overhead.
The NSSF returns the Allowed NSSAI for that coverage window; the AMF hands it to the UE, along with any mapping to the home-PLMN slices.
The PCF’s URSP steers each application to a permitted S-NSSAI; the NSACF admits it only within that slice’s quota for the beam.
As the serving cell / TA changes with the moving constellation, the AMF updates the Allowed NSSAI. Delay-tolerant slices fall back to Store-and-Forward whenever no feeder link is in view.
Sources & specifications
- TS 23.501 — 5G System architecture · §5.15 slicing
- TS 23.003 — S-NSSAI = SST + SD · §28.4
- TS 23.502 — network-slice selection procedures
- TS 23.503 — URSP & policy framework
- TS 38.300 — NR slicing (RAN)
- TS 29.536 — NSACF · network-slice admission control
- TR 23.700-29 — Rel-19 satellite access Phase 3 (Store-and-Forward)
- TR 38.821 — NTN architecture · slicing over NTN
- Rel-19 — regenerative payload · Store-and-Forward · MBS/RedCap-NTN (frozen Dec 2025)