OTFS Achievable Ranging Performance in LEO Urban Areas

During the past decades, seamless navigation has become crucial for numerous Position-Navigation-Timing (PNT)-based applications, with Global Navigation Satellite Systems (GNSS) serving as the primary provider for PNT solutions. However, GNSS faces limitations and severe threats which are limiting to the increasing needs in positioning applications. The use of Low-Earth-Orbit (LEO) satellites for positioning is projected to be a strong alternative to standard GNSS due to its potential improvements in key metrics for positioning. In this regard, the present paper unveils the use of the Orthogonal Time Frequency Space (OTFS) modulation for a standalone LEO-PNT system, and it discusses how OTFS can be tailored to any LEO-PNT scenario to obtain excellent multipath mitigation capabilities. Specifically, these are achieved by using the Doppler characterisation of LEO multipath signals, which combines well with the high Doppler resolution of OTFS. A statistical analysis on the relative delay and Doppler of the reflected signals is conducted during several passes of two real LEO satellites over a receiver in an urban environment, from which OTFS is configured given a requirement on ranging accuracy. Subsequently, the hypothetical use of OTFS for these two real LEO satellites is analysed through simulations on its ranging accuracy, demonstrating its improvements over the standard Binary Phase Shift Keying (BPSK) modulation used in GNSS.