Ubiquitous 6G Service Through Non-Terrestrial Networks

Non-Terrestrial Networks (NTN) are expected to be part of 6G from the start of its use, with the main objective to provide ubiquitous global coverage, including indoor coverage. As NTN are being first introduced in a late phase of 5G, it is natural to use an evolution of 5G to 6G rather than a disruptive approach. In this article we describe the current state of NTN in 5G based on 3GPP Release-17 and 18, which serves as the reference for 6G. We outline the six building blocks which should be addressed in 6G NTN: coverage enhancements, GNSS independent operation, new architectures featuring regenerative satellites, integration of multiple network layers, spec-trum reuse including terrestrial bands, and support of a wide range of smartphone and loT devices.