What LEO satellite connectivity actually is

Most people understand satellite communication in one of two ways: the dish on a house receiving TV, or the GPS chip in a phone. Both involve satellites — but neither involves what the industry now means when it talks about LEO satellite connectivity.

Low Earth Orbit satellites operate at altitudes between roughly 500 and 2,000 kilometres above Earth’s surface. At that height, a satellite completes an orbit in approximately 90 minutes. It is moving fast relative to the ground — which means a single satellite doesn’t stay overhead for long. To provide continuous coverage, LEO systems deploy constellations of hundreds or thousands of satellites, ensuring that at least one is always within line of sight of any point on Earth.

The key advantage of LEO over traditional geostationary satellites is latency. A signal travelling to a GEO satellite at 35,786km and back takes around 600 milliseconds. A signal to a LEO satellite at 550km and back takes 20–40 milliseconds — close enough to terrestrial broadband that it supports video calls, interactive applications and real-time data exchange without the lag that made GEO broadband frustrating for anything other than basic web browsing.

LEO, MEO, GEO and HAPS compared

The term Non-Terrestrial Network (NTN) — the 3GPP designation — covers all four platform types. Each has different characteristics that make it suited to different use cases.

Direct-to-device: the shift that changes everything

Until 2022, accessing satellite broadband required specialist terminal equipment — a dish, a modem, proprietary hardware costing thousands of pounds and requiring trained installation. Satellite connectivity was for oil rigs, research stations and remote enterprise sites. Not for classrooms. Not for ordinary smartphones.

Direct-to-device (D2D) satellite changes that. It describes the ability of a LEO satellite to communicate directly with an unmodified consumer smartphone — no ground dish, no specialist terminal, no bespoke hardware. The satellite acts as a cell tower in the sky, and a standard 4G or 5G handset connects to it just as it would connect to a terrestrial base station.

D2D is not a single service tier. It ranges from basic SMS and SOS messaging (already available via Apple Emergency SOS via Satellite and Android satellite messaging) through to full broadband data — the latter now being deployed commercially by AST SpaceMobile and Lynk Global.

The spectrum model for D2D also has two main variants: licensed spectrum, where the satellite operator uses a mobile network operator’s existing spectrum allocation under a roaming agreement, and supplemental downlink, where additional spectrum augments terrestrial coverage in areas where terrestrial signals are absent. Each has different regulatory, commercial and technical implications — covered in detail in the articles below.

The 3GPP NTN standard explained

The technical foundation that makes all of this interoperable — rather than a collection of proprietary systems — is the 3GPP NTN (Non-Terrestrial Network) standard, introduced formally in Release 17.

The practical significance of the Release 17 standardisation is that Qualcomm, MediaTek and other chipset manufacturers can now build NTN support into standard mobile chipsets. A phone with NTN capability doesn’t require separate satellite hardware — the same antenna and modem that handles 5G terrestrial can handle LEO satellite connectivity, within the parameters of the standard.

Key players in LEO direct-to-device

The LEO D2D market is moving fast. These are the principal operators and what distinguishes each:

AST SpaceMobile

Operating large-aperture BlueBird satellites in LEO, AST SpaceMobile is pursuing full broadband direct-to-device — targeting speeds comparable to terrestrial 4G. Their partnership model works with existing mobile network operators (AT&T, Vodafone, Rakuten) who provide the licensed spectrum, with AST providing the satellite infrastructure. Commercial service launched in 2025.

Lynk Global

Lynk operates on a carrier-agnostic model, using a supplemental downlink approach that works with any existing SIM without requiring MNO partnerships for every market. Focused initially on messaging and basic data, with particular emphasis on developing market deployments and emergency communications.

SpaceX Starlink Direct to Cell

Starlink’s direct-to-cell service uses the existing Starlink LEO constellation to provide SMS, voice and data services to standard LTE devices. T-Mobile is the primary US partner; international partnerships are expanding. The advantage is constellation density — Starlink has more satellites in LEO than any other operator, giving better coverage continuity.

Apple and Android satellite messaging

Both iOS (via Globalstar) and Android (via various partners) now include emergency satellite SOS and basic messaging as standard features on new devices. This is the first tier of D2D — limited bandwidth, but demonstrating that satellite connectivity is now a standard consumer expectation, not a specialist feature.

LEO satellite connectivity and global education access

273 million children worldwide have no access to school. The reason is almost never a lack of political will or curriculum — it is geography. The children who most need education live in precisely the communities that terrestrial infrastructure — fibre, towers, roads — will never reach economically.

LEO direct-to-device satellite changes that calculation. A child with a mid-range smartphone in a village with no mobile coverage can, for the first time, receive structured educational content via satellite — synchronised during daily LEO passes, processed offline by AI-powered adaptive learning systems, and assessed and credentialled via periodic uplink.

This is the model the ReachED Foundation is developing: LEO D2D connectivity as the delivery infrastructure, AI-powered personalised learning as the pedagogical layer, and repurposed smartphones as the access device — targeting secondary-education-standard learning for unreached children, without building new physical infrastructure.

The policy frameworks to support this already exist. Giga (UNICEF/ITU) has mapped school connectivity globally and provides the data infrastructure for deployment targeting. Partner2Connect provides the ITU pledge mechanism for committing connectivity capacity. The Global Partnership for Education 2030 Summit is the milestone for demonstrating pilot-scale deployment.

What has been missing is a technically credible, deployable architecture. The convergence of LEO constellation density, the 3GPP NTN standard, and edge AI capability has now provided that architecture.

All articles in this series

Each article below goes deeper on a specific aspect of LEO satellite connectivity and direct-to-device technology. They are written from a practitioner perspective — drawing on 30 years of RF and satellite systems engineering, direct engagement with Ofcom and GSMA policy frameworks, and the technical research underpinning the ReachED Foundation.