LEO-based network-centric localization in 6G: challenges and future perspectives

The future releases of 3rd Generation Partnership Project (3GPP) specifications, that is, beyond release 18, will consider the possibility to localize the User Equipment (UE) at network-side, eventually using satellite constellations of the integrated Terrestrial-Non-Terrestrial networks (T-NTN). Satellite network-centric localization schemes can be categorized into single- and multi-satellite localization using spatio-temporal measurements or instantaneous spatial diversity, respectively Direct channel measurements such as Doppler, Received Signal Strength (RSS), Round Trip Time (RTT) and Angle-of-Arrival (AoA) or differential measurements such as Time-Difference-of-Arrival (TDoA) and Frequency-Difference-of-Arrival (FDoA) have been considered in the literature to aid the localization operation. This paper focuses on the applicability of an RTT approach, which has some advantages with respect to the other approaches in case of satellite network-centric localization in the integrated T-NTN. The paper shows some preliminary results of the proposed RTT approach. Finally, challenges and research trends of this novel research field have been highlighted.