Many organizations recognize non-terrestrial networks (NTNs) as a key
component to provide cost-effective and high-capacity connectivity in future
6th generation (6G) wireless networks. Despite this premise, there are still
many questions to be answered for proper network design, including those
associated to latency and coverage constraints. In this paper, after reviewing
research activities on NTNs, we present the characteristics and enabling
technologies of NTNs in the 6G landscape and shed light on the challenges in
the field that are still open for future research. As a case study, we evaluate
the performance of an NTN scenario in which satellites use millimeter wave
(mmWave) frequencies to provide access connectivity to on-the-ground mobile
terminals as a function of different networking configurations.Comment: 8 pages, 4 figures, 2 tables, submitted for publication to the IEE
