The satellite-connected smartphone: towards D2D-IMT

22 April 2026
In Star Trek, explorers could communicate with their mothership under any circumstances. But today, on Earth, mobile communication still depends on terrestrial network coverage. Outside covered areas—remote regions, rugged terrain, or sparsely populated locations—satellite phones are still required, although they involve bulkier devices and lower data rates.

This technological boundary is now fading. The 3GPP, which develops specifications for mobile networks, now includes non-terrestrial networks (NTN): a mobile phone can also communicate directly with a satellite.

 

Two technical models

Two approaches are emerging:

  • In the D2D-MSS model, the terminal integrates specific technology required to use frequency bands that are not used by terrestrial networks but are allocated to the mobile satellite service.
  • In the D2D-IMT model, it is the satellite that adopts the protocols and frequency bands of terrestrial mobile telephony. When terrestrial coverage is absent or insufficient, a standard smartphone can then connect to a satellite, which it perceives as just another base station.

Since IMT frequencies are assigned to mobile operators, the deployment of D2D-IMT is only possible if a mobile operator voluntarily prevents its terrestrial base stations from using certain frequencies in areas where the satellite is expected to handle connectivity. This requires an agreement between mobile and satellite operators.

 

 

Uses beyond the general public

The value of D2D goes beyond consumer connectivity. Railway operators (GSM-R/RMR) and public protection and disaster relief services (PPDR) could use it as a complementary or backup solution.

 

A regulatory framework to be built

 

The introduction of a base station in orbit changes the conditions for spectrum coexistence. Ongoing work, particularly under Agenda Item 1.13 of WRC-27 and within CEPT and the European Union, aims to define a framework that ensures the protection of existing networks.

The European Commission has mandated CEPT to propose an initial regulatory framework for harmonized mobile bands by July 2027, ahead of WRC-27, followed by an update in November 2028.

Among the issues to be addressed are out-of-block emissions within the beam, which could affect an adjacent operator in the same country, as well as co-channel emissions outside the beam that could impact an operator in a neighboring country.

The definition of epfd limits to protect terminals is a preferred solution, already adopted by CEPT in the case of D2D-SRD.

In harmonized TDD bands (3.4–3.8 GHz and millimeter-wave bands at 26 and 42 GHz), the protection of base stations must also be ensured. In the context of WRC-27, France proposes defining epfd limits based on a reference antenna pattern for base stations, in order to protect networks in neighboring countries.

Applications operating in adjacent bands, notably radar systems and radio astronomy above 2,690 MHz, must also be protected.

Finally, the implementation of D2D-IMT will require the satellite operator to obtain support from a European administration to have its system recognized among satellites approved by CEPT and the EU, under a mechanism already in place for D2D-SRD, and for national licenses of mobile operators to be adapted accordingly.

 

The convergence between terrestrial and space-based networks is paving the way for truly ubiquitous connectivity: communicating anywhere from a standard smartphone is no longer science fiction.