Performance Analysis of Time of Arrival Estimation on OTFS for LEO PNT

Broadband low Earth orbit (LEO) constellations have the potential to become a source of reliable navigation. In recent years, OTFS has been considered a candidate modulation for broadband LEO constellations due to its superior performance in highly dynamic scenarios. This work analyses the time of arrival (TOA) estimation performance of three orthogonal time frequency space (OTFS) variants with different pseudorandom noise (PRN) code arrangements in delay-Doppler grid, including the timedomain oversampled waveform, power spectral density (PSD), autocorrelation function (ACF), and the Cramer-Rao lower bound (CRLB) for TOA estimation. Despite the obvious differences in the time-domain waveforms of the three OTFS variants, their PSDs and ACFs are almost the same. The simulation results show that the three OTFS variants have the same TOA estimation performance using a delay-locked loop (DLL). The TOA estimation accuracy of OTFS is higher than that of binary phaseshift keying (BPSK) with the same bandwidth, and the carrier-power-to-noise-density ratio (C/N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>) required to achieve the same accuracy is 8 dB lower than that of BPSK, which is an advantage for TOA positioning applications.