GNSS & Positioning | Dr. Jorge Querol

Joint 5G NR-NTN and GNSS Overlay in MEO: Experimental Assessment of Navigation Data Robustness under DSSS–OFDM Coexistence

Wed, 07 Oct 2026 00:00:00 +0000

Abstract & Overview

Recent advances in Joint Communication and Positioning (JCAP) motivate the integration of navigation signals within communication waveforms. This paper investigates a hybrid Direct-Sequence Spread Spectrum (DSSS)–Orthogonal Frequency-Division Multiplexing (OFDM) waveform in which a low-power legacy Global Positioning System (GPS) L1 Coarse/Acquisition (C/A) signal carrying the Legacy Navigation Message (LNAV) message is intentionally overlaid on a Fifth Generation (5G) New Radio (NR) Non-Terrestrial Network (NTN) downlink. The focus is on the Global Navigation Satellite System (GNSS)-side ability to acquire, track, and demodulate the navigation message in the presence of structured 5G interference. The study considers a Medium Earth Orbit (MEO) scenario representative of the SES O3b mPOWER constellation at an altitude of approximately 8000 km. First, MEO Doppler dynamics are characterized using representative orbital parameters, and Monte Carlo (MC) simulations are performed to evaluate LNAV recovery versus Signal-to-Interference-plus-Noise Ratio (SINR) for different transmitted Signal-to-Interference Ratio (SIR) levels. Performance is assessed using navigation-centric metrics, including Bit Error Rate (BER), valid 6 s subframe decoding, valid decoding of the first three subframes, and complete 30 s LNAV frame recovery. The same 35 s reference composite waveform is then transmitted in a continuous loop through the SES O3b mPOWER transparent MEO relay. For each tested SIR level, 300 s of baseband In-phase and Quadrature (I/Q) samples are recorded and processed offline using a MATLAB-based GNSS receiver with 5G Synchronization Signal Block (SSB)-assisted frequency initialization. Simulation results show that, in the considered MEO scenario, Doppler dynamics are moderate and do not constitute the dominant limitation; performance is mainly governed by thermal noise and 5G interference. Experimental results demonstrate reliable LNAV recovery down to approximately -25 dB transmitted SIR, while end-to-end recovery becomes unreliable at -30 dB and below. Since the effective received SINR is not directly available, the experimental results are interpreted as practical transmitted-SIR thresholds.

Publication Metadata

Authors: Idir Edjekouane, Alejandro Gonzalez Garrido, Jevgenij Krivochiza, Jorge Querol, Symeon Chatzinotas
Venue: Proceedings of the Satellite Division’s International Technical Meeting (Online)/Proceedings of the Satellite Division’s International Technical Meeting (CD-ROM) (2026)
Research Areas: 6G-NTN, Satellite Communications, GNSS & Positioning, SDR & Experimental Testbeds
DOI: 10.33012/2026.20684

When 5G NTN Meets GNSS: Tracking GNSS Signals under Overlaid 5G Waveforms

Sun, 24 May 2026 00:00:00 +0000

Abstract & Overview

Global Navigation Satellite Systems (GNSS) provide the backbone of Positioning, Navigation, and Timing (PNT) but remain vulnerable to interference. Low Earth Orbit (LEO) constellations within Fifth-Generation (5G) Non-Terrestrial Networks (NTN) can enhance resilience by jointly supporting communication and navigation. This paper presents the first quantitative analysis of GNSS tracking and navigation message demodulation under a hybrid waveform where a low-power Direct-Sequence Spread Spectrum (DSSS) component is overlaid on an Orthogonal Frequency-Division Multiplexing (OFDM) 5G downlink. We evaluate a minimally modified GNSS receiver that tracks a legacy Global Positioning System (GPS) L1 Coarse/Acquisition (C/A) overlay aligned with 5G frames while treating the 5G waveform as structured interference. Using Monte Carlo simulations under realistic LEO Doppler dynamics, we analyze the Bit Error Rate (BER) of GPS L1 C/A navigation bits and the subframe decoding probability versus Signalto- Interference-plus-Noise Ratio (SINR) for multiple Signalto- Interference Ratios (SIR) and dynamic classes. Results show reliable demodulation across wide SINR ranges for low and medium dynamics, whereas high dynamics impose strict lock limits. These findings confirm the feasibility of Joint Communication and Positioning (JCAP) using a near-legacy GNSS chipset with minimal receiver modifications.

Publication Metadata

Authors: Idir Edjekouane, Alejandro Gonzalez-Garrido, Jorge Querol, Symeon Chatzinotas
Venue: International Conference on Communications (2026)
Research Areas: 6G-NTN, GNSS & Positioning, AI & Neuromorphic SatCom
DOI: 10.1109/icc59461.2026.11587695

High-Accuracy Ranging in 5G Non-Terrestrial Networks: Receiver Architectures and Interference Analysis

Fri, 01 May 2026 00:00:00 +0000

Abstract & Overview

This research contribution by Idir Edjekouane, Alejandro González-Garrido, Jorge Querol, José A. del Peral-Rosado et al. (2026), published in IEEE Transactions on Vehicular Technology, investigates “High-Accuracy Ranging in 5G Non-Terrestrial Networks: Receiver Architectures and Interference Analysis” within the domains of 6G-NTN, RFI Mitigation & GNSS Security, GNSS & Positioning. The work is part of Dr. Jorge Querol’s research portfolio in advanced satellite communications, non-terrestrial networks (NTN), and radio-frequency signal processing at SnT (University of Luxembourg) and UPC-BarcelonaTech.

Publication Metadata

Authors: Idir Edjekouane, Alejandro González-Garrido, Jorge Querol, José A. del Peral-Rosado, Ivan Lapin
Venue: IEEE Transactions on Vehicular Technology (2026)
Research Areas: 6G-NTN, RFI Mitigation & GNSS Security, GNSS & Positioning
DOI: 10.1109/navitec202669090.2026.11692531

Automatic RFI Detection, Location, and Classification System in GNSS Bands

Thu, 01 Jan 2026 00:00:00 +0000

Abstract & Overview

Global Navigation Satellite Systems (GNSS) are critical infrastructure components in modern Positioning, Navigation, and Timing (PNT) services, playing a vital role in both civilian and defense applications. These systems operate in specific frequency bands that are also utilized by other Earth Observation technologies, such as GNSS-Radio Occultations and GNSS-Reflectometry. Other passive microwave remote sensing techniques such as microwave radiometers, work with very faint signals in nearby frequency bands within the L-Band. However, the increasing prevalence of Radio-Frequency Interferences (RFI) poses a significant threat, potentially compromising the integrity and reliability of PNT services, and corrupting geophysical observations. Effective RFI mitigation relies on accurate detection and classification of interference sources, a task that becomes increasingly challenging due to the complexity and diversity of RFI signals. This work presents an automated classification system for RFI detection and characterization in GNSS bands. The methodology employs advanced digital signal processing techniques and statistical algorithms to improve RFI detection and classification. RFI events are then stored in a long-term database to provide insights into the local spectrum, and to aid in mitigation and law enforcement efforts. This study provides a description of the classification system, including its architecture, implementation, and performance analysis. The results highlight the potential of this system to enhance the resilience of GNSS PNT services against RFI.

Publication Metadata

Authors: Adrián Pérez-Portero, Jorge Querol, Adriano Camps
Venue: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (2026)
Research Areas: RFI Mitigation & GNSS Security, GNSS & Positioning
DOI: 10.1109/jstars.2025.3647776
Open Access Repository: ORBiLu – University of Luxembourg

Statistical Acquisition of DVB-S2X Signal for Positioning in LEONTN

Tue, 10 Jun 2025 00:00:00 +0000

Abstract & Overview

Low Earth Orbit (LEO) mega-constellations are revolutionizing global communication by delivering high-speed internet and supporting a wide range of services. Beyond communication, recent studies have shown that LEO satellites can also provide Positioning, Navigation, and Timing (PNT) services. Leveraging existing LEO Non-terrestrial-network (NTN) for dual-purpose applications has garnered significant attention as a future-oriented approach. This paper investigates the feasibility of re-purposing a well-established satellite communication protocol, Digital Video Broadcasting Second Generation Satellite Extensions (DVB-S2X), for positioning applications within LEONTN. This paper analyses the statistical acquisition performance similar to the Global Navigation Satellite System (GNSS) to evaluate the potential of DVB-S2X for positioning estimation. This analysis can provide a baseline for trade-offs for communication protocol selection when developing a sustainable integrated navigation and communication (Nav-Comm) system within LEONTN.

Publication Metadata

Authors: Harshal More, Idir Edjekouane, Ernestina Cianca, Mauro De Sanctis, Jorge Querol, Ottavio M. Picchi, Francesco Menzione
Venue: International Conference on Localization and GNSS (2025)
Research Areas: 6G-NTN, Satellite Communications, GNSS & Positioning
DOI: 10.1109/icl-gnss65520.2025.11046183
Open Access Repository: ORBiLu – University of Luxembourg

Joint Communication and Navigation From LEO Multi-Beam Satellite

Wed, 01 Jan 2025 00:00:00 +0000

Abstract & Overview

This paper investigates an innovative approach to enable Joint Communication and Positioning (JCAP) in 5G Non-Terrestrial Networks (NTN) using Low Earth Orbit (LEO) multi-beam satellite systems. The integration of communication and navigation services is achieved by aggregating a Direct-Sequence Spread Spectrum (DSSS) as a navigation signal with a 5G Orthogonal Frequency-Division Multiplexing (OFDM) waveform for communication services. Two models are proposed for resource allocation and signal aggregation, referred to as the shared beam model, where communication and navigation signals are aggregated prior to Digital Beamforming (DBF) within the same beam; and the independent beam model, which employs separate beams for communication and navigation, with the navigation beam designed to be significantly wider than the communication beams, resulting in overlap between the two. The performance of these models is assessed using as Key Performance Indicators (KPI) the Cramer-Rao Lower Bound (CRLB) for range estimation used in navigation and the spectral efficiency for the broadband service. The study formulates and addresses a multi-objective optimization problem to derive the Pareto front, highlighting the trade-off between communication and navigation performance. Extensive simulations demonstrate the efficacy of the proposed models in terms of spectral efficiency and accuracy in range estimation, and results have been compared with those obtained from the current 5G positioning system. The models have been evaluated in two distinct scenarios: one without frequency reuse between beams and another incorporating a three-color frequency reuse scheme. The results indicate that the independent beams model outperforms the shared beams model by reducing inter-beam interference in both scenarios. The proposed solution maintains backward compatibility with existing 5G NTN, facilitating uninterrupted positioning and communication services in GNSS-denied environments. Furthermore, the combination of DSSS and OFDM enhances the reliability of the data service by utilizing the DSSS sequence as a digital signature for the waveform. This work establishes a foundation for robust and efficient JCAP implementations, addressing challenges related to multi-beam interference and resource optimization.

Publication Metadata

Authors: Alejandro Gonzalez-Garrido, Jorge Querol, Henk Wymeersch, Symeon Chatzinotas
Venue: IEEE Open Journal of the Communications Society (2025)
Research Areas: Satellite Communications, JCAS & Earth Observation, GNSS & Positioning, Beamforming & MIMO
DOI: 10.1109/ojcoms.2025.3568093
Open Access Repository: ORBiLu – University of Luxembourg

Joint Communication and Positioning Receiver Architecture for DSSS-Overlayed OFDM Waveform

Wed, 01 Jan 2025 00:00:00 +0000

Abstract & Overview

The integration of satellite systems within the 5G new radio (NR) framework, designated as non-terrestrial networks (NTNs), relies on global navigation satellite systems (GNSS) to achieve precise synchronization. However, dependence on GNSS presents significant vulnerabilities in scenarios involving signal degradation, jamming, or spoofing, alongside increased cost and power consumption issues, particularly in extensive internet of things (IoT) deployments. To address these challenges, this paper proposes an innovative joint communication and positioning (JCAP) receiver architecture, which integrates direct sequence spread spectrum (DSSS) signals into the 5G orthogonal frequency division multiplexing (OFDM) waveform, enabling GNSS-free synchronization and positioning capabilities without embedded pilot overhead. The proposed hybrid architecture jointly exploits DSSS for robust channel parameter estimation and OFDM for high-throughput communication, thereby reducing the pilots signals traditionally required for synchronization and channel estimation. Comprehensive evaluations demonstrate that the proposed JCAP receiver achieves reliable detection and accurate estimation of delay and Doppler parameters, maintaining low bit error rates (BER) under realistic signal-to-interference ratios (SIR). The findings underscore the feasibility and effectiveness of the proposed hybrid scheme, paving the way for resilient GNSS-free operations in 5G NTN environments.

Publication Metadata

Authors: Alejandro Gonzalez-Garrido, Idir Edjekouane, Jorge Querol, Henk Wymeersch, Symeon Chatzinotas
Venue: IEEE Open Journal of the Communications Society (2025)
Research Areas: JCAS & Earth Observation, GNSS & Positioning
DOI: 10.1109/ojcoms.2025.3615957

User Equivalent Range Error and Positioning Accuracy Analysis for ToA-Based Techniques Using PRS and SSB in 5G/6G NTN

Wed, 01 Jan 2025 00:00:00 +0000

Abstract & Overview

The integration of Non-Terrestrial Network (NTN) within the Fifth Generation (5G) and Sixth Generation (6G) ecosystem offers new opportunities for global Positioning, Navigation, and Timing (PNT) services, particularly in environments where Global Navigation Satellite System (GNSS) signals are obstructed or degraded. This work investigates the positioning performance of Time of Arrival (ToA)-based techniques using both Positioning Reference Signal (PRS) and Synchronization Signal Block (SSB) signals in 5G NTN scenarios. A comprehensive User Equivalent Range Error (UERE) model is developed, incorporating satellite, receiver, and propagation-related error sources across FR1 and FR2 frequency bands. The influence of satellite geometry is assessed through a Geometrical Dilution of Precision (GDOP) analysis, while a minimum satellite visibility evaluation quantifies the likelihood of observing at least four satellites above various elevation masks for representative LEO constellations at 600 km and 1200 km altitudes. Monte Carlo simulations quantify the impact of UERE on positioning accuracy, revealing that the 95th-percentile horizontal errors range from approximately 8 m to 26 m, depending on signal type, frequency band, and orbital altitude. The results demonstrate that ToA-based positioning using PRS can surpass typical urban GNSS-level accuracy, highlighting its potential in GNSS-challenged environments. In comparison, SSB-based positioning remains a viable alternative, offering reduced complexity at the cost of moderate accuracy trade-offs. The study offers a unified framework for understanding positioning accuracy in 5G/6G NTN, bridging UERE modeling, satellite visibility, and signal design considerations, and supporting the ongoing development of reliable global PNT services.

Publication Metadata

Authors: Idir Edjekouane, Alejandro González-Garrido, Jorge Querol, Symeon Chatzinotas
Venue: IEEE Open Journal of the Communications Society (2025)
Research Areas: 6G-NTN, GNSS & Positioning
DOI: 10.1109/ojcoms.2025.3623669
Open Access Repository: ORBiLu – University of Luxembourg

Interference Analysis and Modeling of Positioning Reference Signals in 5G NTN

Mon, 01 Jan 2024 00:00:00 +0000

Abstract & Overview

The integration of Positioning, Navigation, and Timing (PNT) services within the 5G non-terrestrial networks (NTN) infrastructure is necessary to eliminate the need for a GNSS receiver in the user terminal. Using the positioning reference signal (PRS) in an NTN scenario presents significant challenges, such as interference analysis from the transmission of multiple PRS signals. This study provides a stochastic model for the interference generated by PRS transmissions in a 5G NTN scenario. This model has been derived empirically from a Monte Carlo simulator designed specifically for this purpose, showing that the distribution that best fits the interference is a Generalized Extreme Value (GEV) distribution. The parameters of this distribution are also modeled based on the PRS configuration. Therefore, a designer can use this model to evaluate the probability of encountering certain levels of interference.

Publication Metadata

Authors: Alejandro Gonzalez-Garrido, Jorge Querol, Henk Wymeersch, Symeon Chatzinotas
Venue: IEEE Open Journal of the Communications Society (2024)
Research Areas: 6G-NTN, RFI Mitigation & GNSS Security, GNSS & Positioning
DOI: 10.1109/ojcoms.2024.3503692
Open Access Repository: ORBiLu – University of Luxembourg

Interference analysis of Positioning Reference Signals in 5G NTN

Mon, 01 Jan 2024 00:00:00 +0000

Abstract & Overview

Accurate asset localization holds paramount importance across various industries, ranging from transportation management to search and rescue operations. In scenarios where traditional positioning equations cannot be adequately solved due to limited measurements obtained by the receiver, the utilization of Non-Terrestrial Networks (NTN) based on Low Earth Orbit (LEO) satellites can prove pivotal for precise positioning. The decision to employ NTN in lieu of conventional Global Navigation Satellite Systems (GNSS) is rooted in two key factors. Firstly, GNSS systems are susceptible to jamming and spoofing attacks, thereby compromising their reliability, where LEO satellites link budgets can benefit from a closer distances and the new mega constellations could offer more satellites in view than GNSS. Secondly, 5G service providers seek to reduce dependence on third-party services. Presently, the NTN operation necessitates a GNSS receiver within the User Equipment (UE), placing the service provider at the mercy of GNSS reliability. Consequently, when GNSS signals are unavailable in certain regions, NTN services are also rendered inaccessible.

Publication Metadata

Authors: Alejandro Gonzalez-Garrido, Jorge Querol, Henk Wymeersch, Symeon Chatzinotas
Venue: arXiv preprint arXiv:2401.09157 (2024)
Research Areas: 6G-NTN, RFI Mitigation & GNSS Security, GNSS & Positioning
DOI: 10.48550/arxiv.2401.09157

5G Positioning Reference Signal Configuration for Integrated Terrestrial/Non-Terrestrial Network Scenario

Sun, 01 Jan 2023 00:00:00 +0000

Abstract & Overview

The Fifth Generation (5G) New Radio offers a new Positioning, Navigation, and Timing (PNT) service with larger signal bandwidth and higher frequency carriers than previous generations, delivering more accurate measurements. This allows other vertical industries to benefit from this feature, opening up new possibilities. Furthermore, the 5G network includes Non-Terrestrial Network (NTN) elements such as Unmanned Aerial Vehicle (UAV), High-Altitude Platform Systems (HAPS), and satellites, which are gaining significant attention from the industry to allow for global communication. The future 6G aims to create a single network entity with multiple connectivity layers for all devices in all scenarios. Therefore, when combining both aspects of the 5G networks, the PNT service, and the NTN, there are several benefits such as: an independent and complete communication and navigation system under a single network, higher accuracy on the PNT solution than previous generation, global coverage for join navigation and communication, higher resilience on the positioning estimation, or new services offered. However, this is not free of challenges, as it is expected to achieve an accuracy, at least, similar to Global Navigation Satellite System (GNSS). One of the challenges is the multiplexing of the data and positioning service using a single infrastructure such a satellite. This paper has the purpose of analysing the effect in the accuracy of a delay estimator when a satellite constellation send a Positioning Reference Signal (PRS). Assuming that all satellites share the same frequency carrier and are synchronised between them. This 5G PRS main characteristic is its flexibility in terms of resource usage such as bandwidth, resource element density, symbols periodicity, a muting scheme, etc. This flexibility will be exploited in this paper to get a UE capable to estimate the Downlink Observed Time Difference of Arrival (DL-OTDoA) of the signal. Two challenges are present in this work, both are related to the characteristics of the RF channel between the Next Generation Base Station (gNB) and the User Equipment (UE): the first one is how the UE will cope with the high Doppler shift due to the high speed of the Low Earth Orbit (LEO) gNB increasing the Inter-Carrier Interference (ICI); and the second challenge is the effect of variable delay between OFDM symbols in the same slot and transmitter, increasing the effect of Intersymbol Interference (ISI). The contribution of the authors on this paper is the analysis of different PRS configuration that keeps a low interfere level between the moving gNBs. The result of this research highlight the impact that the length in number of subcarriers and number of OFDM symbol has in the accuracy of the delay estimation. It shows a trade-off in the constellation design, as a higher number of satellites in visibility also increase the ICI and ISI.

Publication Metadata

Authors: Alejandro Gonzalez-Garrido, Jorge Querol, Symeon Chatzinotas
Venue: 2023 IEEE/ION Position, Location and Navigation Symposium (PLANS) (2023)
Research Areas: 6G-NTN, GNSS & Positioning
DOI: 10.1109/plans53410.2023.10140024
Open Access Repository: ORBiLu – University of Luxembourg

Beam centric Doppler pre-compensation for LEO-based 5G-NTN

Sun, 01 Jan 2023 00:00:00 +0000

Abstract & Overview

Integration of Non-Terrestrial Networks (NTN) components with 5G Terrestrial Networks (TN) is getting sig- nificant traction from academia and industry, resulting in the standardization of 5G-NTN in 3GPP. Low Earth Orbit (LEO) based 5G-NTN, especially regenerative payload, are of particular interest as they can provide latency and throughput comparable to terrestrial 5G networks. Initial synchronization is the first step when a User Equipment (UE) attempts to establish a data link with the gNB. However, the excessive Doppler caused by the LEO satellite’s fast movement must be exclusively compensated before the UE can successfully align time and frequency. This work presents an effective method to address this issue. In this method, a regenerative LEO satellite-based 5G gNodeB (gNB) pre-compensates the Doppler with respect to its Beam Center (BC) before any transmission. Further, a UE post-compensates the residual Doppler to achieve successful initial synchronization. With the proposed methodology, we expect the accuracy of initial synchronization to be comparable to 5G-TN without increasing the processing complexity at the UE. Furthermore, for the realistic scenario, our analysis includes the effect of the LEO satellite trajectory error sphere and pointing error.

Publication Metadata

Authors: Ashish Kumar Meshram, Sumit Kumar, Jorge Querol, Symeon Chatzinotas
Venue: IET Digital Library (2023)
Research Areas: 6G-NTN, Satellite Communications, GNSS & Positioning, Beamforming & MIMO
DOI: 10.1049/icp.2024.0815
Open Access Repository: ORBiLu – University of Luxembourg

Doppler effect mitigation in LEO-based 5G non-terrestrial networks

Sun, 01 Jan 2023 00:00:00 +0000

Abstract & Overview

In recent years, integrating Non-Terrestrial Networks (NTN) components with 5G Terrestrial Networks (TN) has led to considerable attention from academia and industry, leading to the standardization of 5G-NTN in 3GPP. Among the various NTN solutions, a notable one is the Low Earth Orbit (LEO)-based 5G-NTN with a regenerative payload. This system stands out because it can provide latency and throughput levels similar to terrestrial 5G networks. However, a significant challenge in this integration arises from the substantial Doppler effect caused by the rapid movement of LEO satellites. This effect must be effectively addressed to establish a successful data link between the User Equipment (UE) and the gNodeB (gNB). This study proposes a simple yet efficient method to tackle this issue. The method involves using a regenerative LEO satellite-based 5G gNB, which pre-compensates the Doppler frequency with respect to its beam center before initiating any data transmission. Subsequently, the UE performs post-compensation to handle residual Doppler frequency and achieve accurate initial synchronization. We evaluated the performance through simulations and demonstrated the effectiveness of the proposed system. The results indicate successful mitigation of Doppler effects, facilitating seamless communication between LEO satellite-based 5G NTN.

Publication Metadata

Authors: Ashish Kumar Meshram, Sumit Kumar, Jorge Querol, Symeon Chatzinotas
Venue: 2023 IEEE Globecom Workshops (GC Wkshps) (2023)
Research Areas: 6G-NTN, Satellite Communications, RFI Mitigation & GNSS Security, GNSS & Positioning
DOI: 10.1109/gcwkshps58843.2023.10464931
Open Access Repository: ORBiLu – University of Luxembourg

Localization as a key enabler of 6G wireless systems: A comprehensive survey and an outlook

Sun, 01 Jan 2023 00:00:00 +0000

Abstract & Overview

When fully implemented, sixth generation (6G) wireless systems will constitute intelligent wireless networks that enable not only ubiquitous communication but also high-accuracy localization services. They will be the driving force behind this transformation by introducing a new set of characteristics and service capabilities in which location will coexist with communication while sharing available resources. To that purpose, this survey investigates the envisioned applications and use cases of localization in future 6G wireless systems, while analyzing the impact of the major technology enablers. Afterwards, system models for millimeter wave, terahertz and visible light positioning that take into account both line-of-sight (LOS) and non-LOS channels are presented, while localization key performance indicators are revisited alongside mathematical definitions. Moreover, a detailed review of the state of the art conventional and learning-based localization techniques is conducted. Furthermore, the localization problem is formulated, the wireless system design is considered and the optimization of both is investigated. Finally, insights that arise from the presented analysis are summarized and used to highlight the most important future directions for localization in 6G wireless systems.

Publication Metadata

Authors: Stylianos E. Trevlakis, Alexandros-Apostolos A. Boulogeorgos, Dimitrios Pliatsios, Jorge Querol, Konstantinos Ntontin, Panagiotis Sarigiannidis, Symeon Chatzinotas, Marco Di Renzo
Venue: IEEE Open Journal of the Communications Society (2023)
Research Areas: 6G-NTN, GNSS & Positioning
DOI: 10.1109/ojcoms.2023.3324952
Open Access Repository: ORBiLu – University of Luxembourg

Hybridization of GNSS and 5G Measurements for Assured Positioning, Navigation and Timing

Sat, 01 Jan 2022 00:00:00 +0000

Abstract & Overview

Positioning, Navigation and Timing (PNT) services based on the Global Navigation Satellite System (GNSS) have a number of known drawbacks that makes them prone to suffer a disruption. These flaws can be exploited to disable this service in critical infrastructures. Therefore, the hybridization of GNSS and 5G measurements enabling Assured PNT (APNT) services is growing up and gaining attention by governmental bodies. 5G signals emitted by terrestrial networks and by Low Earth Orbit (LEO) satellites can complement GNSS, enhancing their reliability, security and accuracy. For example, the larger Signal-to-Noise Ratio (SNR) of a terrestrial system makes them more difficult to suffer a jamming attack as compared to GNSS signals. A joint data and positioning signal enhances the security and reliability of the APNT solution with, for example, the successful decoding of encrypted data, this could be used for system authentication. Moreover, a larger signal bandwidth increases the accuracy of the PNT solution. All of these benefits can be extracted from the 5G terrestrial and non-terrestrial networks that transmit the Positioning Reference Signal (PRS). The rationale for these benefits rely on the flexibility of this pilot signal in terms of bandwidth or symbols used for the APNT service. This paper aims to analyse how this flexibility can be optimized to achieve a specific level of accuracy, minimizing the resources used under certain constrains of bandwidth or latency. The results present the optimal parameters to design a 5G PRS waveform with a target scenario constrains. Then, we compare it with the GNSS service and how to benefit when using them in combination. Finally, the paper concludes with the future research lines proposing a joint communications and positioning system as a closed loop. In such scenario, the user achieved accuracy is sent back to the infrastructure, and using the dynamic PRS flexibility, the system increases or reduces the PRS resources in order to meet the user accuracy requirements.

Publication Metadata

Authors: Alejandro Gonzalez-Garrido, Jorge Querol, Symeon Chatzinotas
Venue: Proceedings of the 35th International Technical Meeting of the Satellite (2022)
Research Areas: 6G-NTN, GNSS & Positioning
DOI: 10.33012/2022.18385
Open Access Repository: ORBiLu – University of Luxembourg

Implementation of a testbed for GNSS-R payload performance evaluation

Wed, 01 Jan 2020 00:00:00 +0000

Abstract & Overview

The functional performance of space-borne instruments must be validated on ground before and after satellite integration. The effects of radio-frequency interference are also becoming more important, even in protected bands for earth observation. In this article, a GNSS and GNSS-R signal simulator is developed as part of a testbed of GNSS receivers and GNSS-R payloads’ performance in high dynamics, and to study the effects of RFI in the GNSS-R observables. This article describes the different concepts and key enabling techniques that have been developed to support this project.

Publication Metadata

Authors: Adrián Pérez-Portero, Joan Francesc Muñoz-Martín, Jorge Querol, Hyuk Park, Adriano Camps
Venue: IEEE Journal of Selected Topics in Applied Earth Observations and Remote (2020)
Research Areas: JCAS & Earth Observation, GNSS & Positioning, SDR & Experimental Testbeds
DOI: 10.1109/jstars.2020.2997717

L-band vegetation optical depth estimation using transmitted GNSS signals: Application to GNSS-reflectometry and positioning

Wed, 01 Jan 2020 00:00:00 +0000

Abstract & Overview

At L-band (1–2 GHz), and particularly in microwave radiometry (1.413 GHz), vegetation has been traditionally modeled with the τ-ω model. This model has also been used to compensate for vegetation effects in Global Navigation Satellite Systems-Reflectometry (GNSS-R) with modest success. This manuscript presents an analysis of the vegetation impact on GPS L1 C/A (coarse acquisition code) signals in terms of attenuation and depolarization. A dual polarized instrument with commercial off-the-shelf (COTS) GPS receivers as back-ends was installed for more than a year under a beech forest collecting carrier-to-noise (C/N0) data. These data were compared to different ground-truth datasets (greenness, blueness, and redness indices, sky cover index, rain data, leaf area index or LAI, and normalized difference vegetation index (NDVI)). The highest correlation observed is between C/N0 and NDVI data, obtaining R2 coefficients larger than 0.85 independently from the elevation angle, suggesting that for beech forest, NDVI is a good descriptor of signal attenuation at L-band, which is known to be related to the vegetation optical depth (VOD). Depolarization effects were also studied, and were found to be significant at elevation angles as large as ~50°. Data were also fit to a simple τ-ω model to estimate a single scattering albedo parameter (ω) to try to compensate for vegetation scattering effects in soil moisture retrieval algorithms using GNSS-R. It is found that, even including dependence on the elevation angle (ω(θe)), at elevation angles smaller than ~67°, the ω(θe) model is not related to the NDVI. This limits the range of elevation angles that can be used for soil moisture retrievals using GNSS-R. Finally, errors of the GPS-derived position were computed over time to assess vegetation impact on the accuracy of the positioning.

Publication Metadata

Authors: Adriano Camps, Alberto Alonso-Arroyo, Hyuk Park, Raul Onrubia, Daniel Pascual, Jorge Querol
Venue: Remote sensing (2020)
Research Areas: JCAS & Earth Observation, GNSS & Positioning, Quantum & Optical Space Links
DOI: 10.3390/rs12152352

Real-time Radio Frequency Interference Detection and Mitigation with the Front-End GNSS Interference eXcisor (FENIX)

Mon, 23 Sep 2019 00:00:00 +0000

Abstract & Overview

This paper presents the real-time hardware architecture and experimental evaluation of the Front-End GNSS Interference eXcisor (FENIX), demonstrating standalone pre-correlation time-frequency excision of continuous-wave, chirp, and pulsed jamming signals across civilian GNSS bands.

Publication Metadata

Authors: Jorge Querol, Adrián Pérez-Portero, Joan Francesc Muñoz-Martín, Adriano Camps
Venue: RFI 2019 - Coexisting with Radio Frequency Interference (2019)
Research Areas: RFI Mitigation & GNSS Security, GNSS & Positioning
DOI: 10.1109/RFI48793.2019.9111819
Open Access Repository: ORBiLu

On the new architecture and capabilities of the front-end GNSS interference excisor (FENIX)

Tue, 01 Jan 2019 00:00:00 +0000

Abstract & Overview

The number of applications based on Global Navigation Satellite Systems (GNSS) has been increasing in the last years. With its proliferation, Radio-Frequency Interference (RFI) has become one of the most concerning topics on GNSS-based devices for navigation, positioning and timing, but also for Earth Observation purposes such as GNSS-Reflectometry and Radio Occultations due to the corruption of the received signal and the corresponding geophysical measurements. The Front-End GNSS Interference eXcisor (FENIX) mitigates the problem of RFI by providing a plug and play solution to excise interferences out of virtually any system. The new version of FENIX is also capable of operating with large signal bandwidths (~50 MHz) and dual-frequency applications. This paper shows the performance of the system for commercial GNSS receivers and GNSS-reflectometry applications. A discussion of the impact of the new architecture on its future capabilities is presented as well.

Publication Metadata

Authors: Adrián Pérez, Adriano Camps, Jorge Querol
Venue: IGARSS 2019-2019 IEEE International Geoscience and Remote Sensing Symposium (2019)
Research Areas: RFI Mitigation & GNSS Security, GNSS & Positioning
DOI: 10.1109/igarss.2019.8900263

The global navigation satellite systems reflectometry (GNSS-R) microwave interferometric reflectometer: Hardware, calibration, and validation experiments

Tue, 01 Jan 2019 00:00:00 +0000

Abstract & Overview

This manuscript describes the Microwave Interferometric Reflectometer (MIR) instrument, a multi-beam dual-band GNSS-Reflectometer with beam-steering capabilities built to assess the performance of a PAssive Reflectrometry and Interferometry System-In Orbit Demonstrator (PARIS-IoD) like instrument and to compare the performance of different GNSS-R techniques and signals. The instrument is capable of tracking up to 4 different GNSS satellites, two at L1/E1 band, and two at L5/E5 band. The calibration procedure of the up- and down-looking arrays is presented, the calibration performance is evaluated, and the results of the validation experiments carried out before the field experiments are shown in this paper.

Publication Metadata

Authors: Raul Onrubia, Daniel Pascual, Jorge Querol, Hyuk Park, Adriano Camps
Venue: Sensors (2019)
Research Areas: Satellite Communications, JCAS & Earth Observation, GNSS & Positioning, SDR & Experimental Testbeds
DOI: 10.3390/s19051019

Radio frequency interference detection and mitigation techniques for navigation and Earth observation

Fri, 09 Nov 2018 00:00:00 +0000

Abstract & Overview

This PhD thesis is devoted to the design, implementation, and experimental validation of innovative Radio-Frequency Interference (RFI) detection, localization, and mitigation countermeasures in the fields of Microwave Radiometry (MWR), Global Navigation Satellite Systems (GNSS), and GNSS-Reflectometry (GNSS-R). It completes the development of the MERITXELL multi-frequency radiometer, introduces the Multiresolution Fourier Transform (MFT) mitigation algorithm, proposes the Generalized Spectral Separation Coefficient (GSSC) metric for GNSS-R under interference, and presents the patented FENIX real-time pre-correlation anti-jamming architecture (US Patent US9596610B1), demonstrating up to 30 dB of jamming resilience across GPS L1 C/A, GPS L2C, and Galileo E1OS signals. Awarded Best PhD Thesis 2018 by the IEEE Geoscience and Remote Sensing Society (GRSS) Spanish Chapter.