What is NTN?
Non-Terrestrial Network (NTN) is the term used by 3GPP — the international body that defines mobile communications standards — to describe the integration of satellites and aerial platforms into the 5G (and future 6G) system architecture. NTN extends mobile coverage to areas where terrestrial base stations cannot economically reach: oceans, deserts, polar regions, and airspace.
3GPP release timeline
NTN standardisation has progressed through multiple 3GPP releases. Release 15 (2018) defined NTN channel models and deployment scenarios. Release 17 (2022) introduced the first complete NTN specifications for FR1 (sub-6 GHz) and defined how standard 5G NR protocols are adapted for the long propagation delay of satellite links. Release 18 adds NTN-IoT and enhanced NTN enhancements. Release 19 (latest) defines regenerative payload architectures where a full gNB (5G base station) runs on the satellite itself.
Transparent vs. regenerative payloads
In a transparent (bent-pipe) NTN architecture, the satellite simply relays signals between the ground and a 5G core network on the ground — simpler but limited by satellite-to-ground latency. A regenerative NTN satellite runs 5G protocol stack layers onboard, enabling local processing and reducing the round-trip delay seen by user devices. This is critical for making NTN work with standard 5G handset protocol timing.
Direct-to-Cell
The most visible NTN application is Direct-to-Cell (D2D): standard unmodified smartphones connecting directly to LEO satellites as if they were a very distant terrestrial base station. Starlink's T-Mobile partnership launched text-only D2D service in 2024 and is expanding to voice and data. AST SpaceMobile is deploying a constellation targeting 4G/5G-quality broadband direct to phones. Qualcomm and MediaTek have integrated NTN chipsets into flagship smartphone platforms.