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Lightweight Pilot Estimation on LEO Satellite Signals for Enhanced SOP Navigation

Francesco Zanirato, Alessio Curzio, Francesco Ardizzon, Elisa Sbalchiero, Luca Canzian, Stefano Tomasin, Nicola Laurenti, Jaron Samson

TL;DR

The paper tackles PNT using signals of opportunity from LEO satellites by focusing on Starlink's Ku-band downlink and the challenge of unknown modulation and synchronization. It introduces a lightweight receiver chain and a beacon-estimation algorithm that extracts a recurring beacon through Kalman-filtered phase tracking, FFT-based correlation, and beacon refinement, enabling reliable Doppler observables. Using a 600 s Doppler dataset, the authors perform a Doppler-based least-squares navigation that achieves a post-fit positioning error of approximately 268 m, demonstrating practical SOP-based PNT with modest hardware. The results show that full beacon estimation is feasible without high-gain antennas or wide bandwidth, suggesting this approach can extend SOP-based PNT to broader deployments and other LEO constellations.

Abstract

The computation of positioning, navigation and timing (PNT) via signal of opportunity (SOP), where signals originally transmitted for communication, such as 5G, Wi-Fi, or DVB-S, are exploited due to their ubiquity and spectral characteristics, is an emerging research field. However, relying on these signals presents challenges, including limited knowledge of the signal modulation and the need to identify recurring sequences for correlation. We offer a guide to implement a receiver capable of capturing broadband downlink Ku-band signals from low Earth orbit (LEO) satellites (e.g., Starlink and OneWeb) and estimating the recurring symbols for SOP measurements. The methodology integrates recent approaches in the literature, highlighting the most effective aspects while guiding the replication of experiments even under limitations on the front-end gain and bandwidth. Using the proposed model, we can identify recurring symbols transmitted by Starlink satellites, which are then used to collect Doppler shift measurements over a 600 s interval. A position, velocity, and time (PVT) solution is also computed via least squares (LS), which achieves a positioning error of approximately 268 m after a post-fit refinement.

Lightweight Pilot Estimation on LEO Satellite Signals for Enhanced SOP Navigation

TL;DR

The paper tackles PNT using signals of opportunity from LEO satellites by focusing on Starlink's Ku-band downlink and the challenge of unknown modulation and synchronization. It introduces a lightweight receiver chain and a beacon-estimation algorithm that extracts a recurring beacon through Kalman-filtered phase tracking, FFT-based correlation, and beacon refinement, enabling reliable Doppler observables. Using a 600 s Doppler dataset, the authors perform a Doppler-based least-squares navigation that achieves a post-fit positioning error of approximately 268 m, demonstrating practical SOP-based PNT with modest hardware. The results show that full beacon estimation is feasible without high-gain antennas or wide bandwidth, suggesting this approach can extend SOP-based PNT to broader deployments and other LEO constellations.

Abstract

The computation of positioning, navigation and timing (PNT) via signal of opportunity (SOP), where signals originally transmitted for communication, such as 5G, Wi-Fi, or DVB-S, are exploited due to their ubiquity and spectral characteristics, is an emerging research field. However, relying on these signals presents challenges, including limited knowledge of the signal modulation and the need to identify recurring sequences for correlation. We offer a guide to implement a receiver capable of capturing broadband downlink Ku-band signals from low Earth orbit (LEO) satellites (e.g., Starlink and OneWeb) and estimating the recurring symbols for SOP measurements. The methodology integrates recent approaches in the literature, highlighting the most effective aspects while guiding the replication of experiments even under limitations on the front-end gain and bandwidth. Using the proposed model, we can identify recurring symbols transmitted by Starlink satellites, which are then used to collect Doppler shift measurements over a 600 s interval. A position, velocity, and time (PVT) solution is also computed via least squares (LS), which achieves a positioning error of approximately 268 m after a post-fit refinement.
Paper Structure (15 sections, 17 equations, 11 figures, 3 tables, 1 algorithm)

This paper contains 15 sections, 17 equations, 11 figures, 3 tables, 1 algorithm.

Table of Contents

  1. Introduction
  2. Signal Capture Setup
  3. Receiver Chain Overview
  4. Recording Configuration
  5. Relation to the State-of-the-art Setups
  6. Signal Model
  7. Beacon Estimation Procedure Model
  8. Kalman Filter for Phase Tracking
  9. Beacon Update
  10. Ambiguities resolution
  11. Starlink Beacon Estimation Results
  12. Acquisition and Navigation Framework
  13. Doppler Least Square Navigation Engine
  14. Positioning Results
  15. Conclusions

Figures (11)

  • Figure 1: Receiver Chain.
  • Figure 2: LNB used to capture the Starlink signal placed on the rooftop of the building at the Qascom's premise.
  • Figure 3: Working flow of the beacon estimator.
  • Figure 4: Forward beacon estimate update.
  • Figure 5: Estimated Doppler and Doppler rate by the kf as a function of the iteration.
  • ...and 6 more figures