A few weeks ago, Sridhar Kuppanna, CTO of ST Engineering iDirect talked here about our 5G NTN Strategy and Shravan Gaddam, also from our CTO Office, discussed our proof-of-concept for non-3GPP access to the 5G Core and inter-provider roaming. Now we are featuring Geert Adams, VP R&D Programs, talking about an important milestone in 5G NR NTN development.
We have demonstrated a major step forward for reliable, global connectivity using native 5G architecture and 5G New Radio (NR) waveform. In an over-the-air set up we tested successful 5G NR connectivity between the 5G user equipment (UE) and a 5G base station (gNodeB) via a Non-Geostationary Satellite (NGSO), without relying on satellite position and UE position data. We successfully tested the 5G NR waveform using our innovative hybrid tracking system demonstrating that it doesn’t have to rely on Global Navigation Satellite System (GNSS) inputs for satellite and UE synchronization and timing. This breakthrough proves that stable, high-precision satellite communications are possible even in challenging conditions, where reliable GNSS input is not available.
Q: How far in development is the 5G NR standard and what is the importance of GNSS?
Geert: 5G NR is the global standard for 5G wireless technology. Non-Terrestrial Networks (NTN) extend 5G to satellites enabling high-speed connectivity in areas where terrestrial networks can’t reach—like airplanes, ships, and remote regions. 5G NR is the first waveform introduced in 3GPP Release 15 as the foundation for 5G networks. In 3GPP Release 17 5G NR capabilities expanded to include NTN and advanced use cases. 5G NR over satellite faces unique challenges. Satellites operate over vast distances and at high speeds, causing significant signal delays and frequency shifts that are far more extreme than in ground-based networks. 5G NR heavily relies on GNSS. GNSS is used for pre-compensation by the terminal of timing and satellite frequency shifts, but its dependency can present significant operational challenges.
What are the challenges 5G NTN faces when using 5G NR with GNSS?
Geert: Reliance of GNSS to align position of the satellite with the 5G UE introduces several vulnerabilities. The accuracy of GNSS data can be compromised during satellite maneuvers, and signals may be entirely unavailable in certain environments or at a minimum increase logon time and add more power requirements. Furthermore, GNSS signals are susceptible to external threats such as jamming and spoofing, which can disrupt network integrity. By removing the need for GNSS signaling for network synchronization, we can create more reliable, secure, and efficient networks that ensure uninterrupted connectivity in environments where GNSS signals are weak, unavailable, or compromised. This is especially critical for applications like aviation, maritime, and emergency response, where reliable communication is essential.
Is the 3GPP consortium looking at these drawbacks?
Geert: Yes, there is an ongoing study item in the 3GPP Radio Access Network (RAN) working group to study GNSS-resilient NR-NTN operation and ST Engineering iDirect is actively involved in this study. The iDirect Team explored solutions for GNSS-independent synchronization of 5G NR-NTN and has presented its findings at the last 3 Ka-Band Conferences where technical experts come together to present research findings among peers. We are also proposing the solutions in the ongoing study of 3GPP, with the goal to have GNSS-independent synchronization methods included in 3GPP Release 20 and beyond, which will define the future of 5G-Advanced and 6G.
Has GNSS independence been demonstrated?
Geert: In September 2025, ST Engineering iDirect showcased a solution for GNSS-independent logon and tracking over NGSO satellites. This solution emerged from addressing multiple operational challenges and limitations when it comes to relying on GNSS for time and frequency synchronization. The demonstration showed a native 5G NTN network consisting of 5G NTN (gNodeB) base station connected to two user equipment (UE) units operating in different conditions using a transparent NGSO satellite. One UE was static while the other emulated a highly mobile UE, introducing rapid Doppler and delay variations to replicate real-world challenges in satellite mobility and terminal dynamics. The key to this solution is a dual-loop mechanism that dynamically adjusts for delays and Doppler shifts caused by satellite motion. This ensures stable synchronization and connectivity, even in extreme conditions. Our demonstration proved successfully that the dependency on GNSS can be replaced with an innovative tracking architecture to achieve high precision satellite communications with 5G NTN.
What makes this achievement groundbreaking?
Geert: This was the industry’s first successful over-the-air demonstration of a GNSS-independent 5G NR connection via a satellite. This achievement is significant for several reasons. First, it demonstrates how 5G NTN systems can be made more resilient, proving they can operate without relying on GNSS and thereby overcoming vulnerabilities such as interference or outages. Second, it enhances accessibility by enabling reliable 5G NTN connectivity in remote areas or environments where GNSS signals are unavailable. Finally, this technology is future-ready, with the potential to influence the development of 5G-Advanced and subsequent standards releases, paving the way for more standards-based autonomous and scalable networks. For iDirect this was also one of the first over-the-air 5G NR tests using a NGSO satellite.
This achievement is part of ST Engineering iDirect’s broader strategy to integrate satellite and terrestrial networks seamlessly. This work also aligns with the vision for 6G, which prioritizes network resilience and security. By proving the feasibility of this approach, we’re helping to shape the next generation of global connectivity.