Integrating Non-Terrestrial Networks Into 6G: Architectural and Spectrum Challenges From the ITA-NTN Overview

The studies conducted within the ITA-NTN project and their results provide a vision of future 6G networks by integrating Terrestrial Networks (TNs) and Non-Terrestrial Networks (NTNs), offering insights into emerging standardization directions. Specifically, an architectural evolution is envisaged in which NTN elements will increasingly perform complex routing operations, such as those of 5G radio nodes. Higher-performance transmission techniques are also expected, exploiting new frequency bands, with a proposal to shift high-bit-rate transmission to the W (75-110 GHz) region. Also, Free-Space Optics (FSO) is a particularly promising technology for achieving high-capacity links, though some limitations still need to be overcome. Furthermore, specific modulation techniques appear to be very important in NTN environments, especially for mitigating Doppler-related degradation, as in Non-Orthogonal Multiple Access (NOMA). Finally, management and orchestration require solutions due to a whole series of behaviors that NTNs have, unlike TNs, and in this context, the concept of Intent-Based Networking appears promising.