Code Phase Estimation with Live 5G NR-NTN Ka-band Signal from LEO Satellite Using STARE

Future 5G and 6G non-terrestrial networks (NTNs) will incorporate a low earth orbit (LEO) satellite component, offering an opportunity to complement communication services with positioning. One of the available solutions for positioning with the New Radio NTN (NR-NTN) is the downlink time-of-arrival (TOA) technique in which the user equipment (UE) computes its position with code phase measurements estimated from downlink signals. In this work, the update of a publicly available real-time software receiver called STARE enabling estimation of code phase and Doppler frequency from 5G NR-NTN signals is presented and evaluated. The update includes a new snapshot processing mode, importable custom pilot patterns, and an extended carrier frequency offset (CFO) search algorithm covering large Doppler shifts experienced in NTN. STARE is evaluated with a 100 MHz wide 5G NR-NTN downlink signal transmitted live in Ka-band from Telesat LEO 3 demonstration satellite operating as a bent pipe. To allow the code phase estimation, the current definition of the positioning reference signal (PRS) is taken to facilitate the generation of three 5G NR-NTN waveforms with various numerologies and signal bandwidths. The waveforms are evaluated in terms of achievable code phase errors using Cramér-Rao lower bound (CRLB) and the most suitable waveform with 100 MHz signal bandwidth is used for transmission. To transmit and capture the signal, a setup based on a software-defined radio (SDR) running STARE is deployed at the European Space Agency (ESA) European Space Research and Technology Centre (ESTEC). To the best of the authors’ knowledge, this is the first documented live transmission and reception of a 100 MHz wide 5G NR-NTN signal with PRS in the Ka-band.