Toward Native NTN Integration in 6G

The 11th open lecture organised by one6G focused on one of the strategically important topics for the 6G era, the integration of non terrestrial networks (NTNs) into a truly converged global infrastructure. Titled Non Terrestrial Networks for 6G Toward Seamless Network Convergence, the session brought together leading researchers and attracted nearly 270 participants worldwide, underlining the growing interest in NTN as a structural element of future communication systems. Chaired by Malte Schellmann from the Huawei Munich Research Center, the lecture explored how terrestrial networks (TNs) and non terrestrial networks (NTNs) can evolve from coexistence to deep architectural integration in 6G.

Alessandro Vanelli-Coralli from the University of Bologna and ETH Zürich opened the technical discussion by positioning NTN not as a sudden innovation, but as the result of decades of satellite communication research. The term NTN entered mainstream mobile standardisation with 5G through studies in 3GPP beginning around 2016, yet the underlying knowledge stems from long standing satellite system development. Lower orbit satellites reduce delay and improve link budgets, but they also increase velocity, Doppler effects, handover frequency and constellation size requirements. These physical realities must be engineered into the radio interface and network architecture rather than treated as afterthoughts.

In 5G and 5G Advanced, NTN integration has been achieved by adapting terrestrial designs. Release 17 introduced support for NTN with mechanisms to handle Doppler, differential delay and timing alignment. Subsequent releases expanded towards regenerative payloads, mesh connectivivity and operation in additional frequency bands, enabling direct to device connectivity using compliant chipsets. However, 6G aims for something more ambitious. Instead of modifying a terrestrial system to accommodate satellites, the objective is native multi layer three dimensional integration from the outset. NTN is not a bolt on feature but a foundational component of the architecture.

A strong message from the lecture was that NTN should be viewed as synergy rather than competition. Industry discussions at events such as Mobile World Congress indicate clear user demand for service continuity beyond terrestrial coverage, particularly for emergency and resilience scenarios. Within ongoing 6G discussions in 3GPP, NTN consistently appears among the top architectural priorities alongside artificial intelligence. This reflects a recognition that future connectivity must be ubiquitous, resilient and integrated across domains.

The integration challenge does not stop at the radio interface. Tomaso de Cola from the DLR addressed the role of NTNs in the edge cloud continuum, arguing that future systems must seamlessly span ground and space computing resources. Rather than viewing satellites as simple bent pipe relays, the next frontier lies in embedding intelligence across terrestrial edge nodes, aerial platforms and space assets. By integrating satellite systems into distributed cloud architectures, NTNs can support low latency services and extend edge capabilities into remote and underserved regions. This vision aligns with a broader shift toward distributed intelligence, where processing is dynamically allocated across domains according to latency, energy and reliability constraints.

Constellation design was another area where assumptions were challenged. The prevailing narrative of mega constellations with tens of thousands of satellites was contrasted with analysis suggesting that global direct to device coverage can be achieved with fewer than 2,000 carefully configured low earth orbit satellites. By selecting suitable orbital parameters and targeting wide area coverage rather than fibre like throughput, it is possible to meet service continuity objectives with significantly fewer space assets. A heterogeneous architecture separating more capable feeder satellites from lighter service nodes can further optimise mass, power consumption and overall system sustainability. This reframes the discussion from scale alone to architectural efficiency.

Sustainability was examined further in the presentation by Symeon Chatzinotas from the University of Luxembourg, who focused on how artificial intelligence, integrated sensing and communications and reconfigurable intelligent surfaces can improve NTN efficiency. The move toward large low earth orbit constellations introduces new pressures in terms of launch frequency, lifecycle management and onboard energy use. Training machine learnning models on the ground and deploying optimised inference models in orbit offers one path toward reducing power consumption. The integration of communication, sensing and positioning functions within shared hardware platforms also promises reductions in payload mass and energy usage, provided that waveform and spectrum sharing challenges are carefully managed.

The lecture concluded with a pragmatic perspective from Miguel Ángel Vázquez Oliver of CTTC, who examined practical 6G NTN deployment from the standpoint of constraints, trade offs and real world feasibility. While the vision of seamless convergence is compelling, it must be grounded in regulatory realities, spectrum coordination, link budget limitations and device complexity considerations. Design options must balance ambition with implementability. Issues such as power amplifier limitations, terminal antenna constraints, mobility management and interoperability across multiple orbital layers all require careful engineering. The transition from research prototypes to scalable deployments will demand close alignment between standardisation, industry investment and realistic business models.

Across all contributions, the overall narrative was consistent. Native NTN integration in 6G requires architectural intelligence, sustainability awareness and cross industry collaboration. It is not about replacig terrestrial networks, nor about pursuing ever larger constellations without discipline. It is about building a unified three dimensional infrastructure in which terrestrial and non terrestrial components operate seamlessly together across radio, cloud and service layers. If 5G marked the first serious step toward satellite integration within mobile standards, 6G is being shaped with the intention of making non terrestrial networks an intrinsic, efficient and resilient part of the global communications fabric.

Selected slides can be downloaded from here and the video of the talk is embedded below:

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