Orthogonal Time Frequency Space Modulation (OTFS) for Positioning Using LEO Satellites

Abstract

This paper analyses the achievable delay and Doppler estimation accuracies and the Multipath Error En- velopes (MEE) of Low Earth Orbit (LEO) Position-Navigation- Timing (PNT) systems, using the novel Orthogonal Time Fre- quency Space (OTFS) modulation. In this paper we investigate the advantages the OTFS modulation, which has originally been designed for communication purposes, may bring to the positioning field in LEO-PNT systems, in particular in the presence of doubly-selective wireless fading channels exhibiting both delay and Doppler spreads. We show how a LEO air-to- ground channel fits this description due to its fast dynamics, and we present the improvements of using OTFS with respect to the standard spread-spectrum single-carrier Binary Phase Shift Keying (BPSK) modulation in terms of delay-Doppler estimation accuracy, in addition to a comparison of their performance in LEO multipath scenarios through their respective MEEs.

Keywords

• leo-pnt
• otfs
• delay-doppler processing