Subex Blog

How a terrestrial-to-satellite handover turns one session into two settlement events

IN BRIEF

When a subscriber’s session hands over from a terrestrial network to a non-terrestrial network (NTN), it produces two usage records with two commercial owners. The terrestrial leg stays with domestic rating; the satellite leg is settled wholesale with the satellite operator on a roaming model, not interconnect, often through an aggregator. Operators need mediation, correlation and partner models ready before launch.

Why is NTN settlement becoming an urgent problem?

Satellite-to-device is no longer a 2030 story. Commercial services connecting ordinary phones to satellites went live with subscribers in 2025, and according to GSMA Intelligence, as reported by S&P Global Market Intelligence, 118 mobile operators had satellite service partnerships by December 2025, with 33 of those services already live. Most of the industry conversation has focused on coverage, spectrum and device support. The harder problem sits downstream: once a subscriber’s session moves between a terrestrial network and a satellite network, the commercial record of that session changes shape.

How does one call become two settlement events?

When a device hands over from terrestrial to non-terrestrial coverage mid-session, the network does not produce one clean usage record. It produces a partial record at the boundary, in the same way a session crossing a tariff period does. The result is two legs with two different commercial owners:

• The terrestrial leg stays with domestic rating and retail billing, exactly as before.
• The NTN leg is settled wholesale with the satellite network operator, correlated back to the terrestrial leg by IMSI and session reference.

This correlation is the operational heart of the problem. If the two legs cannot be stitched back together reliably, the operator cannot prove what it is being billed for.

Is the NTN leg roaming or interconnect?

The instinct in many billing teams is to treat a new network partner as an interconnect relationship. For NTN that is the wrong model. The satellite operator functions as a visited network: the subscriber’s own operator retains the customer and settles with the satellite party for usage carried on its behalf. That is a roaming construct. Interconnect remains relevant only in the separate case where the call terminates on a third party’s network.

The market is already treating it this way. Deutsche Telekom has described Iridium as its next non-terrestrial roaming partner for IoT, and in September 2026 the two confirmed a global roaming agreement for Iridium NTN Direct.

The NTN leg maps to roaming-style wholesale settlement with the satellite operator, not to interconnect.

Who are the parties in an NTN settlement chain?

It is rarely a two-party relationship. An aggregator layer usually sits in the middle: capacity is sourced from one or more satellite operators, packaged by a virtual satellite operator or aggregator, and consumed by mobile operators. That produces a multi-tier chain, from satellite operator to aggregator to mobile operator to subscriber, where each hop has a different commercial character. The upstream hop behaves like a capacity or spectrum wholesale arrangement. The downstream hop behaves like conventional roaming.

What should operators do before launching NTN services?

• Check the mediation layer. Confirm it can carry satellite-specific metadata, not only terrestrial fields.
• Check handover correlation. Confirm that partial records generated at the handover boundary can be correlated and re-rated by origin.
• Model the partner early. Add the satellite partner to the partner hierarchy before the first commercial launch, not after the first invoice

NTN monetisation will not be decided by coverage maps. It will be decided by whether the settlement layer can account for a session that changed networks halfway through.