Foundation: orbit sets everything
A satellite's altitude decides its physics, and the physics decides the service. Geostationary (GEO, ~35,786 km) satellites hover over one spot but impose a long round trip; low-Earth-orbit (LEO, ~300–1,200 km) satellites are close — low delay, strong signal — but scream across the sky in minutes, so you need a moving constellation and constant handovers. There is no free lunch; 6G NTN designs around this trade-off rather than escaping it.
What 6G adds beyond 5G NTN
This does not start from zero. 3GPP introduced NTN support in 5G (from Release 17), including direct-to-device satellite access. The mechanisms for huge propagation delay and Doppler — timing advance, frequency pre-compensation — already exist and are the foundation 6G refines.
3gpp.org 2026-06-15ITU-R IMT-2030 lists Ubiquitous Connectivity as one of the six usage scenarios, and 3GPP's 6G scenario study (TR 38.914) includes non-terrestrial deployments. Coverage everywhere is a requirement-level ambition for 6G, not a niche add-on.
3gpp.org — TR 38.914 2026-03-01The 6G goal is deeper than "satellites can connect too": a single architecture where terrestrial and non-terrestrial access are managed together, with seamless mobility between them. How the 6G core models this convergence is part of the architecture study, and is not yet specified.
wirelessbrew.com 2026-03 secondary| Orbit tier | Altitude range | Best-case one-way delay | Orbital period | Doppler | 5G support | 6G role |
|---|---|---|---|---|---|---|
| LEO | 300–1,200 km | ~1–4 ms | ~90–110 min | High (fast pass) | foundation Rel-17 | candidate primary 6G path |
| MEO | 8,000–20,000 km | ~27–67 ms | ~2–12 h | Moderate | foundation partial | candidate positioning / filler |
| GEO | 35,786 km (fixed) | ~119 ms | 24 h (stationary) | Near-zero | foundation Rel-17 | candidate broadcast / wide-area |
| HAPS | ~20 km (stratosphere) | ~0.07 ms | N/A (station-keeping) | Low | foundation Rel-17 study | candidate regional coverage |
| Challenge | Terrestrial 5G | LEO NTN | GEO NTN | Mitigation (5G foundation) |
|---|---|---|---|---|
| Propagation delay | < 1 ms | 1–4 ms (one-way) | ~119 ms (one-way) | Extended timing advance; pre-compensation by UE |
| Doppler shift | Small (UE speed) | up to ±24 kHz @2 GHz | near zero | Frequency pre-compensation at UE or satellite |
| Path loss | ~100–130 dB | ~170–185 dB @2 GHz | ~190 dB @2 GHz | High-gain satellite antennas; spot beams |
| Handover rate | Minutes–hours | Every ~5–10 min (LEO pass) | Rare (fixed) | Predictive HO; ephemeris-assisted timing |
Where this connects
NTN realises a requirement (ubiquitous connectivity), depends on the core architecture to make convergence seamless, and shares the high-delay/high-Doppler challenges that shape the physical layer.