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arxiv: 2509.16183 · v3 · submitted 2025-09-19 · 📡 eess.SP

Xona Pulsar Compatibility with GNSS

Tyler G. R. Reid , Matteo Gala , Mathieu Favreau , Argyris Kriezis , Michael O'Meara , Andre Pant , Paul Tarantino , Christina Youn This is my paper

Pith reviewed 2026-05-18 15:02 UTC · model grok-4.3

classification 📡 eess.SP
keywords LEO navigationGNSS compatibilityinterference testingPulsar constellationL-band signalsPNT ecosystemreceiver testingsignal coexistence
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The pith

Xona's Pulsar LEO signals cause no adverse interference to GPS and Galileo receivers.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper tests whether Xona's Pulsar, a planned 260-satellite LEO navigation system, can operate in the same L-band frequencies as existing GPS and Galileo without degrading their performance. It measures carrier-to-noise ratio changes in commercial receivers during both lab simulations and limited live-sky passes, using the compact QPSK signal design to keep interference low even at higher power. Results show no meaningful degradation, which matters because at least ten new LEO navigation providers are emerging and their success hinges on peaceful coexistence with the current global infrastructure. A sympathetic reader cares because confirmed compatibility would allow firmware updates to existing receivers to unlock centimeter accuracy, added resilience, and authentication from the new layer without replacing hardware.

Core claim

Through theoretical analysis and hardware-in-the-loop testing, the study establishes that Pulsar's X1 and X5 signals produce no adverse interference effects on GPS and Galileo, confirming that the constellation can coexist with and integrate into the existing GNSS ecosystem.

What carries the argument

Spectrally compact QPSK modulation of the X1 and X5 signals combined with C/N0 degradation measurements across commercial receivers in simulated and live-sky conditions.

If this is right

  • Existing GNSS receivers can add Pulsar support via firmware update alone.
  • Coexistence enables a layered PNT system with higher accuracy and better resilience.
  • Other emerging LEO constellations can adopt similar signal designs for compatibility.
  • Pulsar authentication features can be added without disrupting legacy GNSS users.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Full constellation deployment would support hybrid receivers that combine LEO and MEO signals for improved urban and indoor performance.
  • The testing approach offers a template for spectrum regulators evaluating future navigation systems.
  • Widespread compatibility could accelerate commercial and governmental adoption of LEO-based augmentation services.

Load-bearing premise

The tested commercial receivers and the lab-plus-limited-live-sky conditions represent the full variety of real-world hardware, environments, and processing implementations that will encounter Pulsar.

What would settle it

Significant C/N0 loss or tracking failure observed across a wider range of receiver models or in diverse real-world environments when Pulsar signals are active.

read the original abstract

At least ten emerging providers are developing satellite navigation systems for low Earth orbit (LEO). Compatibility with existing GNSS in L-band is critical to their successful deployment and for the larger ecosystem. Xona is deploying Pulsar, a near 260-satellite LEO constellation offering dual L-band navigation services near L1 and L5. Designed for interoperability, Pulsar provides centimeter-level accuracy, resilience, and authentication, while maintaining a format that existing GNSS receivers can support through a firmware update. This study examines Pulsar's compatibility with GPS and Galileo by evaluating C/N0 degradation caused by the introduction of its X1 and X5 signals. Using spectrally compact QPSK modulation, Pulsar minimizes interference despite higher signal power. Theoretical analysis is supported by hardware testing across a range of commercial GNSS receivers in both lab-based simulation and in-orbit live-sky conditions. The study confirms Pulsar causes no adverse interference effects to existing GNSS, supporting coexistence and integration within the global PNT ecosystem.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper examines compatibility between Xona's Pulsar LEO constellation (dual L-band X1/X5 signals using spectrally compact QPSK) and existing GPS/Galileo GNSS. It combines theoretical interference analysis with hardware-in-the-loop C/N0 degradation measurements on commercial receivers in both lab simulations and limited live-sky passes, concluding that Pulsar introduces no adverse interference and supports coexistence and firmware-based integration.

Significance. If the empirical results hold under broader conditions, the work provides concrete support for integrating emerging LEO PNT systems into the existing GNSS ecosystem without disrupting current receivers. The dual theoretical-plus-hardware approach and explicit focus on spectral compactness are strengths that directly address a practical deployment barrier for the growing number of LEO navigation providers.

major comments (2)
  1. [Hardware testing description and results section] The central coexistence claim (abstract and §5) rests on C/N0 measurements from a finite set of commercial receivers. The manuscript does not enumerate the exact receiver models, correlator architectures, or interference-mitigation algorithms tested, nor does it report the number of independent trials or statistical power for the live-sky passes. This leaves open whether the null result generalizes to untested receiver classes (e.g., aviation-grade or high-multipath urban implementations) whose response to the X1/X5 signals may differ.
  2. [Live-sky testing subsection] Live-sky test conditions are described as 'limited.' Without explicit reporting of the number of satellite passes, simultaneous multi-Pulsar visibility cases, or quantitative comparison of C/N0 variance against the lab baseline (e.g., in a table or figure), it is difficult to confirm that the tested scenarios bound the worst-case interference environments cited in the introduction.
minor comments (2)
  1. [Theoretical analysis] Notation for the X1 and X5 signal spectra could be clarified with an explicit equation or reference to the power spectral density formula used in the theoretical analysis.
  2. [Results figures] Figure captions for the C/N0 plots should include the exact number of receivers and averaging window to allow direct comparison with the text.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and detailed comments, which have helped us improve the clarity and completeness of the manuscript. We address each major comment below and indicate the revisions made.

read point-by-point responses

  1. Referee: [Hardware testing description and results section] The central coexistence claim (abstract and §5) rests on C/N0 measurements from a finite set of commercial receivers. The manuscript does not enumerate the exact receiver models, correlator architectures, or interference-mitigation algorithms tested, nor does it report the number of independent trials or statistical power for the live-sky passes. This leaves open whether the null result generalizes to untested receiver classes (e.g., aviation-grade or high-multipath urban implementations) whose response to the X1/X5 signals may differ.

    Authors: We agree that greater specificity on the tested hardware would strengthen the presentation. In the revised manuscript we have expanded the hardware testing section to enumerate the exact commercial receiver models used, along with available public information on their correlator architectures and interference-mitigation features. We have also added the number of independent trials performed in the laboratory campaign and a brief discussion of the statistical power of those measurements. Regarding generalization, the theoretical interference analysis in the paper is based on the spectral occupancy of the compact QPSK signals and is therefore largely independent of specific receiver architecture; we have added an explicit statement acknowledging that the empirical results apply directly to the tested consumer and professional receivers and that dedicated studies would be required to confirm behavior in aviation-grade or high-multipath urban equipment. revision: yes

  2. Referee: [Live-sky testing subsection] Live-sky test conditions are described as 'limited.' Without explicit reporting of the number of satellite passes, simultaneous multi-Pulsar visibility cases, or quantitative comparison of C/N0 variance against the lab baseline (e.g., in a table or figure), it is difficult to confirm that the tested scenarios bound the worst-case interference environments cited in the introduction.

    Authors: We accept that the live-sky description required more quantitative detail. The revised subsection now reports the number of satellite passes observed, the instances of simultaneous multi-Pulsar visibility, and includes a new table that directly compares C/N0 variance measured in the live-sky passes with the corresponding laboratory baseline. While the live-sky campaign remains limited by the current number of operational Pulsar satellites, the scenarios exercised include the highest-power and closest-approach geometries feasible at the time of testing; we have clarified in the text how these conditions relate to the worst-case interference environments outlined in the introduction. revision: yes

Circularity Check

0 steps flagged

Empirical compatibility study with no derivation chain

full rationale

The paper's central claim rests on direct C/N0 measurements from commercial GNSS receivers under lab simulation and live-sky conditions. No load-bearing theoretical derivation, fitted parameters, or self-citation chain is present that reduces the result to its own inputs by construction. The analysis is self-contained against external hardware benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The study relies on standard GNSS signal models and receiver processing assumptions rather than new theoretical constructs.

axioms (1)
  • domain assumption Standard models of C/N0 degradation due to in-band interference apply to the tested receiver architectures.
    Invoked when interpreting measured C/N0 changes as representative of interference effects.

pith-pipeline@v0.9.0 · 5714 in / 1124 out tokens · 35117 ms · 2026-05-18T15:02:05.334582+00:00 · methodology

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Reference graph

Works this paper leans on

25 extracted references · 25 canonical work pages

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    INTRODUCTION More than fifty navigation satellites have been launched in recent years into LEO, with thousands more announced by more than ten emerging providers. These systems range in spectrum usage from traditional RNSS L -bands to C, S, UHF, VHF, and others. Compatibility with existing medium (MEO) and geosynchronous (GSO) orbit GNSS, specifically in ...

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    The characteristics of the signal are summarized in Table 2 for the Full Operational Capability (FOC) – the full 258 satellite deployment

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    external

    THEORETICAL COMPATIBILITY ANALYSIS This section evaluates the interference caused by Pulsar on GPS and Galileo analytically. The metric under consideration is the carrier to noise density ratio, C/N0 and the degradation analysis that evaluates the RNSS inter-system interference. There is no official limit for the maximum C/N0 degradation an RNSS system ma...

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    LAB HARDWARE TESTING ITU recommendation s rely exclusively on theoretical C/N0 degradation calculations to evaluate the compatibility of new systems with existing ones. Xona has gone beyond these baseline assessments to ensure that its Pulsar system does not introduce harmful interference to existing systems operating in adjacent frequency bands by includ...

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    This value represents a conservative assumption, as it is lower than the noise floor calculated in the theoretical compatibility assessment

    A fixed noise floor of –200.3 dB(W/Hz) was applied across all test cases to simplify the evaluation process. This value represents a conservative assumption, as it is lower than the noise floor calculated in the theoretical compatibility assessment. The selected input parameters are representative of the Pulsar Full Operational Capability (FOC) system as ...

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    This IOV satellite features both Pulsar X1 and X5 signals at production power levels

    LIVE SATELLITE TESTING In June 2025, Xona successfully launched its first production-class satellite, Pulsar-0, shown in Figure 10. This IOV satellite features both Pulsar X1 and X5 signals at production power levels . Since entering operation in July of 2025, Pulsar-0 has been demonstrating the compatibility of Pulsar signals with existing GNSS under liv...

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