Physics / mechanism
Direct-to-cell (D2C) LEO connectivity uses low-earth-orbit satellites (altitude 400–600 km) to communicate directly with unmodified LTE/5G handsets — no specialist terminal required. The key constraint is link budget: a phone antenna has ~0 dBi gain, so satellites need large phased arrays (AST SpaceMobile’s BlueBird blocks carry ~64 m² aperture) and aggressive beamforming to close the link. Lynk operates narrowband (SMS/data bursts, ~1–2 kbps); AST targets broadband (up to ~14 Mbps per beam in early trials). Both use standard 3GPP NTN (non-terrestrial network) extensions (Rel-17/18). Current SOS-mode deployments — Apple/Globalstar, T-Mobile/SpaceX — are separately architected but inform the same regulatory and spectrum pathway.
Competitive landscape
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.