Satellite NTN Architectures

Incorporating LEO D2C Satellites

3GPP Release 17 and later provide specifications for signaling, mobility, authentication, and interoperability to enable integration of NTN D2C with existing mobile core networks. This connectivity is primarily enabled by LEO satellites cooperating with mobile operators to extend the subscriber’s mobile network, effectively functioning as an “antenna or base station in the sky.”

NTN technologies are transitioning from pilot phases to commercialization. By August 2025, there were 170 publicly announced partnerships between mobile and satellite network operators across 80 countries and territories. Additionally, 34 operators in 25 markets have already launched commercial services, underscoring that the integration of Non-Terrestrial Networks with mobile systems is accelerating beyond isolated trials. (Source: GSA September 2025).

Moreover, as part of the 3GPP ecosystem, the spectrum for NTN is well-defined, featuring dedicated frequency bands for both NR NTN and IoT NTN that operate on a global scale. These bands, designated by 3GPP as nXXX , correspond to Mobile Satellite Service (MSS) bands such as S band (n256, n252), L bands (n255, n253, n251, n250), and a combination of both (n254), as well as Ka bands (n512, n511, n510) and Ku bands (n248, n247, n509, n508).

The industry momentum surrounding satellite networks is clear and undeniable, as mobile and satellite network operators are forming numerous partnerships and agreements to develop innovative solutions. Notable collaborations include Apple with Globalstar, T-Mobile with Starlink, Vodafone with AST SpaceMobile, SES with Lynk Global and Omnispace, Space42 with Viasat, Geespace with China Unicom, and partnerships with Sateliot, Ovzon, Eutelsat, Hispasat, SpaceRise, JSAT, and KTSAT. Among these initiatives, many are already committed to deploying 3GPP-based NTN, recognizing the ecosystem’s extensive reach and the associated benefits.
As such, the 3GPP NTN standards are evolving rapidly and redefining the future of satellite connectivity. However, the pace may not be as swift as some media outlets suggest. Currently, messaging and emergency services will serve as the primary use cases, with voice services following closely behind. It will take a few more years before NTN satellite-based wideband and broadband services are deployed at scale.

Two Approaches for Spectrum Utilization

As direct-to-cell standard NTN satellite services gain momentum, two distinct approaches to utilizing spectrum have emerged, each presenting unique opportunities and challenges for device manufacturers and mobile operators.

Approach 1: MSS Spectrum with 3GPP NTN Standards

This approach leverages the 3GPP-defined NTN framework to connect devices using existing satellite deployments that deliver narrowband services over L- and S-band spectrum (1600 MHz, 2100 MHz, and 2400 MHz). It supports use cases ranging from consumer SOS and SMS to industrial IoT and automotive connectivity. The approach is particularly appealing for rapid service deployment due to an established regulatory framework. Additionally, mobile network operators (MNOs) do not need to allocate valuable cellular spectrum for satellite services, and satellite providers can more seamlessly cooperate with multiple MNOs—particularly if they deploy their own core network and leverage standard GSMA roaming mechanisms.

Devices may require minor hardware modifications, such as an additional antenna path and modem support, but many chipset manufacturers, including Qualcomm, Mediatek, Samsung, and Sony Altair, already support this. The downside is that support for smartphones has so far been limited to iPhones and select high-end Android devices in specific regions. However, with Starlink indicating its support for this standards-based approach, broader device compatibility is anticipated.

There is evidence that MSS spectrum is gaining traction within the industry. In January 2025, AST SpaceMobile, initially planning to rely exclusively on mobile operator spectrum (Approach 2), finalized a strategic spectrum access agreement with Ligado, granting AST over 80 years of usage rights to up to 45 MHz (40 MHz primary + 5 MHz in the 1670–1675 MHz range) of premium L-band MSS spectrum in the USA and Canada for satellite broadband on unmodified smartphones. Additionally, in August 2025, AST SpaceMobile secured International Telecommunication Union (ITU) priority rights for S-band MSS spectrum (1980 MHz to 2010 MHz and 2170 MHz to 2200 MHz) and has shown intent to pursue further S-band holdings in Europe, particularly with upcoming spectrum renewals in 2026 expected to be highly competitive.

SpaceX Starlink has also adjusted its strategy following a lengthy regulatory dispute. In September 2025, it agreed to acquire EchoStar’s US MSS spectrum rights in a substantial $17 billion deal. This acquisition grants access to exclusive, interference-free MSS spectrum that could significantly enhance Starlink’s network capacity and global reach.

Approach 2: NTN D2C Services Leveraging Shared Mobile Operator Spectrum

In this approach, satellites utilize the existing cellular spectrum owned by mobile operators. This is advantageous from a device perspective, as it is designed to work seamlessly with all modern mobile devices. Initially, available services will also be narrowband, focusing on SMS and emergency services. This method is better suited for countries with large contiguous landmasses such as the USA, Australia, China, Japan, and New Zealand.

However, scaling satellite services in this manner presents significant challenges. Deployment is still in its early phases, and many more satellites will be necessary to support increased user bases and higher speeds. As spectrum is a limited resource, many MNOs may only be able to share or cede a small portion of their spectrum.

Additionally, potential interference risks may lead regulators to require geographic exclusion zones and impose power restrictions, complicating deployment. Other regulatory hurdles also exist, as each country mandates separate approvals, and so far, no regulator outside the USA, New Zealand, and Japan has approved this approach.

Despite these challenges, there is considerable activity worldwide, with various partnerships forming between mobile operators and satellite providers. It remains to be seen whether this represents merely an “early market land grab” or if spectrum sharing will sustain its relevance over the long term. The most likely outcome is that both approach 1 and approach 2 will coexist, fulfilling different needs in the market.