The Coastal States of the Baltic Sea and the North Sea have published an open letter to the international maritime community insisting on the protection of GNSS-based navigtion. The countries point the finger squarely at the Russian Federation for causing disruption in both critical navigation and timing services for sea vessels.
“Modern maritime transport is fundamentally built on the reliability of satellite-based navigation,” reads the letter. “For over three decades, global shipping has advanced by developing vessel operations to increasingly depend on the position, timing and navigation data provided by satellite systems. This shift has brought great efficiency but has also created a new dependency.
The letter highlights the importance of GNSS as a critical safety requirement, not only ship navigation but also precise time synchronization vital for systems such as the Global Maritime Distress and Safety System (GMDSS).
Risks to the Automatic Identification System
Another GNSS service, the Automatic Identification System (AIS), plays a key role in traffic coordination, situational awareness and emergency response. “Spoofing or falsifying AIS data undermines maritime safety and security, increases the risk of accidents, and severely hampers rescue operations,” the letter states.
“We are now facing new emerging safety situations due to growing GNSS interference in European waters, particularly in the Baltic Sea region. These disturbances, originating from the Russian Federation, degrade the safety of international shipping. All vessels are at risk.”
The countries ask for cooperation developing alternative terrestrial radionavigation systems as a GNSS backup. They also want vessels crews properly trained to operate safely during navigation system outages.
“Maintaining trust in maritime navigation requires more than technology – it demands responsibility, transparency, and decisive action,” the letter states. “We must ensure that our seas remain safe, including when systems fail or face disturbances.”
Tokyo-based satellite company ArkEdge Space Inc. has signed letters of intent with three international organizations to develop a PNT satellite network in low-Earth orbit (LEO).
The agreements with TrustPoint Inc., the Royal Institute of Navigation in the United Kingdom and FrontierSI aim to strengthen satellite-based PNT capabilities for civil, commercial and security applications.
The collaboration represents an early phase in ArkEdge Space’s effort to build international partnerships for PNT infrastructure. The company, which designs and operates small satellite constellations, said the project will focus on improving resilience of positioning and timing systems that support critical infrastructure.
The partners plan to examine policy frameworks and national PNT strategies as the project moves into a demonstration phase. ArkEdge Space said it will expand its network of international partners to support the development of space-based positioning systems.
“By working together, this collaboration represents an important step as we accelerate the development of resilient, trusted PNT capabilities that support critical infrastructure and informed decision-making worldwide,” ArkEdge Space CEO Takayoshi Fukuyo said.
TrustPoint has transmitted its first Low-Earth Orbit Navigation System (LEONS) time-transfer and tracking signals from a ground node to spacecraft in orbit. The milestone advances the development of commercial navigation infrastructure independent of GPS.
GNSS satellites require knowledge of their own time and orbital position to provide accurate data to Earth-based users. Most LEO spacecraft currently rely on GPS or medium-Earth orbit (MEO) signals for that information. Interference and jamming are increasingly affecting these LEO connections, degrading or blocking signals.
LEONS provides GPS-independent time transfer and orbit tracking. Initially developed for TrustPoint’s planned constellation, the system can be adapted for other LEO operators requiring timing and navigation for their spacecraft. The ground-to-space infrastructure is designed to support a GPS-independent PNT layer in orbit.
“With the pace of modern threats accelerating, the difference between concepts and capabilities matters,” said Nicole Hilliard, director of government programs at TrustPoint. “This milestone demonstrates that commercial partners can field resilient, GPS-independent PNT capabilities that strengthen national security architectures and justify continued investment in companies that deliver.”
The demonstration supports TrustPoint’s participation in the SpaceWERX AltPNT Challenge, which awarded the company two contracts to develop alternative PNT capabilities. The program seeks to deploy new options for precise, dual-use PNT systems.
Throughout the past several decades, GNSS has become one of the most significant technologies in modern engineering, supporting transportation, communications, finance, emergency response, and critical infrastructure [1]. Its precision, global reach, and reliability have enabled entire industries to scale in ways that would otherwise have been impossible. Yet as GNSS is used more deeply in autonomy-driven and safety-critical domains, the limitations of relying on a single-layer PNT architecture are becoming increasingly apparent.
Urban canyons degrade satellite geometry and tracking performance; intentional and unintentional interference is now commonplace [2]; spoofing has shifted from a theoretical concern to an operational reality; and indoor environments, which are essential for robotics, logistics, and emergency services, remain largely outside GNSS’s physical reach. These challenges are not shortcomings of GNSS itself. They reflect what the system was originally designed to provide: a globally available positioning and timing reference, not the entire resilience burden for every PNT-dependent application.
In parallel, communications technologies have undergone rapid transformation. The evolution from LTE to 5G, and soon to 6G, has introduced wider bandwidths, massive MIMO antenna arrays, improved network synchronization, and dense deployment across urban and indoor environments [3]. At the same time, LEO broadband constellations have matured into powerful satellite infrastructures capable of delivering strong signals, rapid Doppler dynamics, and frequent visibility. Although these systems were built primarily for data connectivity, their physical characteristics naturally lend themselves to positioning and timing.
Taken together, these developments point toward a new direction for resilient PNT: a multi-layer architecture in which GNSS serves as the global reference layer and is complemented by high-power, high-dynamics LEO satellites, terrestrial 5G/6G networks and Wi-Fi systems, and a suite of onboard sensors that provide short-term stability and dead-reckoning capability. Figure 1 illustrates this emerging architecture and highlights how each layer contributes specific observables, coverage strengths, and levels of robustness. The remainder of this article examines the physical foundations of communications-based PNT, the role of LEO as an augmentation space segment, the engineering challenges inherent in multi-source navigation, and the system-level architecture that is now taking shape to deliver resilient and ubiquitous PNT.
Figure 1. Multi-layer architecture for resilient PNT. (All figures provided by the author)
2. 1 Growing Dependence on PNT and GNSS Vulnerability
Nearly every sector of modern life depends on GNSS-based positioning and timing. As reliance grows, exposure to GNSS limitations grows with it. Dense urban environments create severe multipath and signal blockage; jamming and spoofing incidents are now regularly reported near conflict zones and busy ports [4]; and autonomy concepts in aviation and ground mobility increasingly assume reliable PNT even when GNSS performance is degraded or unavailable.
GNSS will remain the global reference layer, but it was never intended to carry the full burden of these mission-critical demands on its own. A complementary set of technologies is needed, systems that continue to function in GNSS-challenged environments and provide redundancy when satellite signals are unavailable, corrupted, or intermittent.
Error! Reference source not found. illustrates this challenge in a representative urban-canyon environment. Tall buildings restrict line-of-sight to GNSS satellites and generate strong multipath reflections, resulting in weak and unreliable signals (Figure 2a). By contrast, terrestrial networks such as 5G/6G and Wi-Fi maintain strong signal levels and robust geometry because their transmitters are embedded within the built environment, often only tens or hundreds of meters away (Figure 2b). This complementary coverage is a fundamental motivation for integrating communications signals into future PNT architectures.
Figure 2. Comparison of GNSS and terrestrial network coverage in urban canyons.
2.2 Communication Networks Have Quietly Become PNT-Capable
Modern communication networks have evolved far beyond their original purpose of data transport [5]. Several physical-layer characteristics now make 5G, Wi-Fi 7, and future 6G systems surprisingly well suited to PNT:
Wideband signals. Wi-Fi 7 supports 320-MHz channels and 5G FR2 offers up to 400 MHz, with multi-GHz bandwidths anticipated for 6G [6]. Wider bandwidth directly improves time-of-arrival (ToA) precision. The ToA uncertainty can be approximated by:
Massive MIMO. Multi-element antenna arrays estimate angle-of-arrival (AoA) and angle-of-departure (AoD), effectively turning base stations into spatial sensors capable of separating line-of-sight from multipath.
Dense deployment. Unlike GNSS satellites, orbiting at roughly 20,000 km, terrestrial networks are woven directly into the environment. Small cells and access points provide excellent geometry in exactly the locations where GNSS performance is weakest, including city centers, campuses, factories, and warehouses.
High signal power. Terrestrial signals arrive at the receiver tens of decibels stronger than GNSS, improving indoor penetration, acquisition speed, and robustness to interference.
These features were introduced to enhance connectivity, yet they collectively create an RF landscape that is inherently PNT-capable.
2.3 The Rise of LEO Constellations as a Complementary Space Layer
A third major driver behind communications-enabled PNT is the rapid proliferation of LEO satellite constellations. Broadband systems such as Starlink and OneWeb, together with several emerging PNT-dedicated LEO constellations, offer distinct advantages [7]:
Stronger received power. LEO satellites operate at altitudes of roughly 500–1,200 km, far closer than GNSS satellites at 20,000 km or higher, resulting in significantly stronger received signals.
Rapid Doppler dynamics. The relative motion of LEO satellites produces large, fast-varying Doppler shifts, which improve observability of user velocity and, over short intervals, position.
Large constellation sizes. Hundreds or thousands of satellites create rich geometry and frequent visibility, enhancing availability and resilience.
Although many LEO systems were designed primarily for communications, their signals can already be exploited opportunistically for positioning and timing. Purpose-built LEO-PNT systems extend these capabilities by offering wideband navigation signals, multi-frequency operation, and security features intended specifically for resilient PNT [7].
These characteristics make LEO a natural augmentation layer, strengthening GNSS performance and providing additional robustness in degraded, obstructed, or contested environments.
3. Technical Foundations of Communications-Based PNT
Modern communication and LEO satellite systems provide a diverse set of physical-layer measurements that can be fused with GNSS to create a resilient, multi-layer PNT solution. These observables go well beyond traditional GNSS code and carrier measurements and include Doppler, ranging, time-of-arrival, round-trip time, angle-of-arrival, angle-of-departure, and received signal strength. Figure 3 summarizes this heterogeneous measurement landscape and shows how each layer contributes distinct observables to the fusion engine.
Figure 3. PNT measurement diversity across GNSS, LEO-PNT, and terrestrial networks.
3.1 High-Resolution Ranging from Wideband Waveforms
Ranging accuracy is fundamentally linked to signal bandwidth. GNSS signals typically occupy 1–20 MHz, whereas modern communication waveforms may span hundreds of megahertz. Wider bandwidth enables finer temporal resolution, allowing receivers to separate closely spaced multipath components and improve time-of-arrival (ToA) precision [6].
In practice, Wi-Fi 7 and 5G FR2 waveforms can support sub-meter ranging in favorable conditions and substantially enhance relative positioning indoors and in dense urban environments. Techniques such as two-way ranging, cooperative localization, and inertial smoothing can extend performance even further. As shown in Error! Reference source not found., these wideband ToA and RTT observables form an essential input to the PNT measurement fusion layer.
3.2 Spatial Sensing with Massive MIMO
Massive MIMO arrays are one of the most powerful enablers of communications-based PNT. By comparing the phase and amplitude across many antenna elements, base stations estimate angles of arrival (AoA) and departure (AoD), turning terrestrial infrastructure into distributed RF sensor arrays [8].
Angle-based measurements offer several important benefits:
Improved localization geometry in 3D urban canyons
Ability to distinguish line-of-sight (LOS) from multipath
High update rates suitable for UAVs and advanced air mobility (AAM) platforms
A simplified Cramér–Rao lower bound (CRLB) illustrates how antenna geometry and signal power influence the accuracy of AoA estimation:
3.3 Infrastructure Density and Geometric Strength
From a PNT perspective, measurement geometry can be as important as measurement precision. Dense deployments of base stations, small cells, and access points give 5G, 6G, and Wi-Fi networks inherently strong geometric diversity, especially in environments where GNSS geometry collapses.
In indoor settings or street canyons, a receiver may have ten or more RF sources within a few hundred meters. This density improves dilution of precision (DOP), increases redundancy, and enables fallback positioning even when GNSS availability drops to zero. Within the multi-layer architecture described in Figure 1, terrestrial networks therefore provide crucial observability in GNSS-restricted environments.
3.4 High Signal Power and Robust Tracking
Terrestrial and LEO communication signals enjoy a link-budget advantage of roughly 50–100 dB over GNSS. This additional power yields several practical benefits:
Better performance with small or non-ideal antennas
Increased resilience to interference and jamming
Faster acquisition and re-acquisition after outages
More reliable tracking under fast dynamics or partial obstruction
In many scenarios, 5G, Wi-Fi, and LEO signals remain trackable long after GNSS signals fall below usable thresholds, providing essential continuity for navigation filters and multi-sensor fusion engines.
3.5 Timing and Synchronization in Communication Networks
Modern wireless networks rely on tight synchronization for scheduling, beamforming, and coordinated MIMO. They obtain timing from GNSS, fiber distribution, and packet-based protocols such as IEEE 1588 Precision Time Protocol (PTP) [9]. As these timing infrastructures mature, communication networks increasingly become timing providers rather than solely timing consumers.
Although terrestrial networks do not yet match the long-term stability of GNSS-disciplined oscillators, they provide valuable short-term holdover and regional timing continuity. These capabilities play an important role in multi-layer PNT systems, particularly during GNSS outages.
4. Engineering Challenges and Limitations
Although communications-based PNT provides powerful complementary capabilities, significant engineering challenges remain. These challenges do not diminish the value of multi-layer PNT; rather, they highlight the technical rigor required to deploy these systems reliably on a scale.
4.1 Multipath and Non-Line-of-Sight Propagation
For terrestrial PNT, multipath and non-LOS propagation remain the dominant contributors to ranging and angle errors. Buildings, vehicles, reflective indoor structures, and metallic industrial environments introduce secondary paths that bias ToA, RTT, AoA, and Doppler measurements. A simplified model of multipath-induced ToA bias is:
Massive MIMO beamforming, high-resolution channel estimation, and machine-learning LOS classifiers can mitigate these errors, but performance is highly environment-dependent and cannot be guaranteed in all cases. Figure 3, introduced earlier, highlights how diversity in measurement types helps reduce susceptibility to any single error mechanism.
4.2 Synchronization Constraints and Timing Drift
Communication networks require precise time alignment for scheduling, beamforming, and coordinated MIMO. However, network clocks do not yet match the long-term stability of GNSS-disciplined oscillators. Backhaul delay variability, oscillator drift, and partial GNSS visibility at base stations introduce timing uncertainty that must be explicitly modeled in a PNT fusion engine.
Figure 4 illustrates timing error growth during a GNSS outage, comparing:
GNSS-only timing, which diverges quickly without satellite visibility
Network timing holdover, which slows but does not halt drift
Multi-layer timing fusion, which maintains the lowest error accumulation
These behaviors demonstrate why communication-based timing is best used as a complementary layer rather than a standalone reference.
Figure 4. Timing error comparison during a GNSS timing outage.
4.3 Waveform and Structural Limitations
Modern communication waveforms such as OFDM were optimized for throughput and spectral efficiency, not navigation. Several characteristics constrain raw positioning performance:
Finite pilot density limits effective ranging bandwidth
High peak-to-average power ratio (PAPR) stresses nonlinear receivers
4.4 Coverage Variability and Regulatory Constraints
Terrestrial network density varies sharply by geography. Urban cores, industrial sites, and indoor campuses enjoy strong 5G/6G and Wi-Fi coverage, whereas rural, maritime, and mountainous regions may see limited improvements without LEO-PNT augmentation. Spectrum policy, privacy rules, and operator-controlled access to timing and positioning features further constrain how widely these capabilities can be exposed. Figure 5 summarizes the relative contribution of each PNT layer—GNSS, LEO-PNT, terrestrial networks, and onboard sensors—across open-sky, urban, and indoor environments.
Figure 5. Relative contribution of PNT layers across operational environments.
4.5 Security and integrity
As communication signals begin supporting navigation functions, they must meet higher standards for robustness, integrity, and security. PNT observables are vulnerable to spoofing, replay, meaconing and cyber-attacks on timing sources [10]. GNSS experience demonstrates the value of:
Cross-layer consistency checks
Cryptographic authentication
Fault detection and exclusion (FDE)
Monitoring for anomalies in Doppler, timing, or angle domains
Redundancy across multiple constellations and layers.
These functions are visualized in Figure 6, which illustrates how a multi-layer PNT system performs integrity monitoring across heterogeneous measurements.
5. A Multi-Layer Architecture for Future PNT
The earlier sections described why GNSS alone cannot meet emerging PNT requirements and how communications and LEO signals provide new sources of observability. Building on those foundations, Figure 1 introduces a multi-layer architecture in which GNSS, LEO-PNT, terrestrial networks, and onboard sensors cooperate to deliver resilient positioning and timing. This section outlines the role of each layer and how they integrate into a unified system.
5.1 GNSS as the Foundational Global Layer
GNSS will continue to provide the global reference frame, absolute positioning, and precise timing that anchor the entire architecture. Its worldwide availability, mature error modeling, and extensive user base make it the natural reference for other layers to align with whenever GNSS is available and reliable. In this sense, GNSS remains the “truth model” for time and coordinates, even as additional layers enhance resilience.
5.2 LEO-PNT as the High-Power, High-Dynamics Space Layer
LEO satellites provide diversity in orbit, signal power, geometry, and dynamics. Their lower altitude results in significantly stronger signals and rapid Doppler variations that improve motion observability. These characteristics reinforce GNSS performance in interference, urban canyon, and high-dynamics environments. As shown in Figure 3, LEO adds Doppler-based range-rate observables that are particularly valuable for maintaining continuity when GNSS quality fluctuates.
5.3 Terrestrial Networks as the Urban and Indoor Layer
5G, Wi-Fi 7, and future 6G networks form the densest PNT-capable infrastructure ever deployed. Their wideband signals, massive MIMO arrays, and strong received power position them as the dominant layer for indoor and urban navigation. Where GNSS geometry collapses, terrestrial networks provide ToA, AoA, AoD, RTT, and coverage exactly where users most often need it. Figure 5 highlights how their contribution becomes primary indoors and highly complementary in urban canyons.
5.4 Onboard Sensors and Local References
IMUs, odometry, barometers, cameras, radar, and lidar provide short-term stability and immediate awareness of the immediate environment, independent of external RF conditions. These sensors bridge outages and reduce reliance on any single external signal source. Their role within architecture mirrors their role in autonomy today: providing the continuity needed when GNSS, LEO, or terrestrial signals fluctuate. Together with RF observables, they form a robust solution space consistent with the measurement diversity shown in Figure 3.
5.5 Fusion, Standards, and System Engineering
Realizing a multi-layer PNT system is fundamentally a system-engineering effort. Success depends on:
Common timing and reference frameworks across GNSS, LEO, and terrestrial layers
Standardized quality indicators and integrity metrics
Interfaces that expose PNT-relevant observables from communication networks while respecting privacy and operational constraints
Cross-layer consistency checks that ensure no single measurement dominates unchecked
Standards bodies, including 3GPP, IEEE and aviation authorities, are beginning to address these needs, but operationalizing multi-layer PNT at scale will require continued collaboration across industries. Figure 6 illustrates how integrity information from each layer contributes to fault detection, cross-checking, and integrity-bound estimation within the fusion engine.
Figure 6. Integrity monitoring in multi-layer PNT architecture.
6. Conclusion
The era of single-layer PNT is coming to an end. As reliance on precise positioning and timing accelerates across aviation, ground autonomy, critical infrastructure, and networked systems, GNSS alone cannot shoulder the growing resilience burden. Fortunately, a rich set of complementary technologies already surrounds us. Dense terrestrial networks, emerging LEO constellations, and increasingly capable onboard sensors provide observables that naturally augment GNSS and extend PNT into environments where satellite signals struggle.
The opportunity now is to treat communications and PNT not as separate domains but as elements of a unified system. A multi-layer architecture — such as the one outlined in this article — offers stronger availability, improved measurement diversity, and inherent resilience against interference, outages, and environmental constraints. The key challenge ahead lies not in inventing new signals, but in system engineering: establishing shared timing frameworks, standardizing measurement interfaces, ensuring integrity across heterogeneous sources, and building trust in signals not originally designed for navigation.
Most of the technical ingredients are already in place. The next decade will determine how effectively industry, government, research institutions, and standards bodies can integrate them into certifiable, interoperable, and widely deployable solutions. If successful, multi-layer PNT will become a foundational capability — providing trustworthy positioning and timing wherever future autonomous systems, vehicles, and critical infrastructure require it.
Today’s commercial innovation requires infrastructure that moves at the same pace.
Essence
The rise of commercial satnav
Everyday life is saturated with location-dependent devices. They are multiplying faster than ever and their requirements have surpassed what GPS can support. Innovation in low-Earth orbit (LEO) satellites have seen exponential growth in the last ten years, unlocking new possibilities in further connecting our world.
In 2016, the total number of satellites operational in space from commercial and government operators was approximately 1,500. This number had been stable for decades, with linear growth since the launch of Sputnik in 1957. Today, there are now more than 8,000 satellites operational in space — with nearly all growth happening in LEO.
There are multiple reasons why. The cost of space access has decreased with reusable rockets and greater competition. The demand for connectivity has driven deployment of multiple constellations to deliver Internet from space. Latency is extremely important in communications and resolution in Earth observation.
While innovation in LEO satellites has primarily focused on connectivity and Earth observation, there is a generational opportunity to innovate in the position, navigation and timing (PNT) infrastructure that silently powers modern life.
There are now more than ten entities working toward deployment of dedicated PNT functions in LEO, amounting to more than 2,500 satellites if every constellation was complete today. As shown in Figure 1, five of these entities have already collectively launched more than 50 satellites. This market signal is not surprising, as demand for greater precision, power and protection are becoming fulfilled with diversification in LEO.
Figure 1. Launches of LEO PNT satellites.
Essentials
Medium-Earth orbit (MEO) has been the traditional choice of satellite navigation for global systems, with GPS, Galileo, BeiDou and GLONASS all being deployed in this regime. This altitude in the outer Van Allen belts is the harshest radiation environment Earth orbit satellites are subjected to and is a major driver in the cost and complexity of the satellites. From a commercial standpoint, deployment in LEO is more attractive as the more benign radiation environment allows for the use of more commercial off-the-shelf (COTS) parts in satellite designs, facilitating volume production. With a healthy ecosystem and supply chain now developed around LEO for both satellites and launch vehicles, the opportunity for commercial PNT to set a new standard in performance and protection is open.
The time for innovation in PNT could not be more urgent. Innovators are pushing the frontiers of technology across every industry and market. Physical intelligence is proliferating in the form of self-driving cars, humanoid robotics, automated farming, unmanned aerial systems and more. As these systems begin to coexist in the real world, the tools they rely on have never been more at risk. Commercial aviation is regularly jammed in Europe and the Middle East due to ongoing conflicts. And ships at sea are struggling to adapt to an environment where spoofing is commonplace.
The commercial world has different and increasingly more stringent requirements than government-focused systems like GPS. GPS was designed primarily around military requirements and is longstanding infrastructure that is difficult to change with the myriad number of deployed devices that depend on it. This responsibility makes GPS too big to fail, but also incredibly difficult to change.
GNSS infrastructure has unlocked so much in commercial activity. There are now more devices using GNSS than the Internet, and GPS is by far the majority user of the technology (based on nearly 7 billion active GNSS devices on Earth and around 6 billion users of the Internet.) However, commercial users have limited input to the evolution of GNSS constellations, which has led to a widening gap between technology and wants, which provides for the current commercial opportunity.
Simply put, today’s commercial innovation requires commercial infrastructure that moves at the same pace to support.
Elements
Architecting LEO PNT
For a LEO satellite navigation system, many designs could be considered, as reflected in Table 1 from Reid et al. (2025) outlining current public information about systems already announced. These constellations range from government-supported systems, which could act as extensions of already deployed global or regional systems, to commercial systems that target potentially unique, independent markets.
Table 1. Comparison of dedicated LEO PNT systems, deployments, and plans. Note that satellites already deployed were verified on celestrack.org .
These constellations all have one thing in common: they aim for between 200 and 300 LEO satellites. The reason is simple: as LEO satellites have a footprint of approximately 1/10th that of medium Earth orbit (MEO) satellites, and between 20 and 30 MEOs are required for global PNT, approximately 10x more LEOs are needed to obtain similar coverage. A consequence is that in LEO, the radio energy is spread over 1/10th the area compared to MEO, which has implications for power needs at the satellite — 10x less in LEO for the same MEO power in the same band.
There is another crucial parameter to consider in LEO PNT design: spectrum. Table 1 shows that many approaches are being considered. Xona’s approach with its Pulsar constellation was centered around three major areas of commercial appeal: seamless operation with existing devices; increased native accuracy; and added resilience to jamming and spoofing. An important philosophy adopted early in the company’s culture was to not make development a science project — that is, do not reinvent the wheel, but rather upgrade the engine. GPS was a revolutionary technology, which is why it is so heavily adopted and brings so much value to the world. Therefore, stand on the shoulders of this giant to look out to the future.
Ease of integration was the first consideration, as it has been the most important aspect in accelerating adoption of any new system. And spectrum is key to Integration. By launching a new system that uses the existing L-band signals, the GNSS ecosystem producing approximately one billion new units per year can seamlessly upgrade their capability without new hardware. Xona’s first technology pathfinder satellite in 2022 validated this hypothesis. While the pathfinder mission supported two satellite frequencies already in the regional navigation satellite system (RNSS) bands — one near L-band E6 and the other in the yet unused C-band near 5 GHz — it became apparent that receiver companies were willing to develop hardware for the L-band signal, and did so quickly with their existing hardware. There was resistance and longer timelines to global adoption for C-band signals.
In response, Xona shifted the production signals to a dual L-band system, which already has nearly a dozen commercial receiver partners tracking the recently launched production satellite — some within weeks of the launch. The challenge is to choose a waveform that is near existing GNSS bands, familiar in form and function and digital signal processing techniques to what is already fielded today, and to not cause harmful interference to the existing GNSS services in orbit. The resulting design is shown in Figure 2, on the right. The key innovation was the selection of a bandwidth efficient form of quadrature phase shift keying (QPSK), which focuses the energy in the central lobe and rolls off quickly compared to a traditional binary phase shift keying (BPSK) signal, shown in Figure 2 on the left for comparison. The result is a 100x stronger signal that does not cause harmful interference to existing GNSS signals, while offering resilience through more signal power. This selection process was iterative, taking feedback from the receiver community. More information on the design and testing for compatibility can be found in Reid et al. (2025).
Figure 2. (Left) GPS BPSK-based signal waveform, and (right) Pulsar QPSK-based signal waveform.
In addition to compatibility and ease of integration, accuracy and resilience are critical design drivers. For example, farmers rely on their equipment positional accuracy to efficiently distribute seeds, fertilizer and water, reducing waste and improving crop yields. Positional accuracy also enables accurate, repeatable field operations year after year, saving time, fuel and money while protecting the soil. Because GNSS typically offers meter-level positioning, today many farmers buy positional accuracy through GNSS correction services to obtain centimeter-level positioning. The Xona architecture leverages these techniques in precise point positioning (PPP), delivering precise ephemerides direct from the space segment, and combining them with the fast motion from LEO satellites (compared to MEOs) to reduce position solution convergence times from ~10 minutes to nearly instantaneous (see, for example, Mah and O’Keefe, 2025). This geometry also boosts coverage, as correction services today typically rely on geostationary satellites and do not service high latitudes, where they would benefit missions such as mining operations for critical minerals and polar navigation.
Connectivity relies on resilient timing. Passing more data through a network means efficiently meshing data packets in synchronized manner. Telecommunications and data centers need such connectivity to function. Authentication is expected in our communications systems, which is largely unavailable in civil GNSS signals. In an age where GNSS spoofing is done to cheat at games like Pokémon Go and now more frequently for nefarious purposes, authentication becomes essential for a modern system (Anderson, 2025, and Xona, 2025a). For resilience to spoofing, Xona included not just data authentication, but also range authentication, so that users can ultimately authenticate their position.
Defense applications require resilience to jamming. World conflicts, particularly currently in Ukraine and the Middle East, have showcased GNSS vulnerabilities in the presence of widespread GNSS jammers. However, this problem is no longer only a defense issue. In 2025, nearly 123,000 commercial flights in Europe were disrupted between January and April alone by GNSS jamming (GPS World, 2025). For resilience to jamming, one method is more power. LEO being 20x closer to Earth than MEO affords nearly a 10x boost in power for the same power transmitted at the satellite. Xona’s target was 100x more power to the end user to significantly reduce the effective range of a jammer by more than six times as shown by recent field trials. Such a transmission power translates to a >97% reduction in affected area and means threats shift to larger and less practical platforms for adversaries, i.e., from requiring handheld devices to backpacks or even truck-sized jammers.
More signal power also has implications for indoor positioning. Internet of things (IoT) devices such as asset trackers are commonly affected by signal obstruction and attenuation during transit, particularly in indoor environments, urban canyons, under foliage, or when obstructed by vehicles and cargo. Warehouses, shipping containers, and other constraints limit where position can be determined. Even coarse indoor positions can support operational intelligence for asset management.
Launching LEO PNT
Pulsar is designed to launch in stages as shown in Figure 3, which unlocks capability in tranches that expands the number of features and ultimately the user base. While Pulsar will achieve persistent coverage across major markets at the deployment of 16 operational satellites, earliest customers in time transfer will see value from Pulsar much sooner as an independent source of timing synchronization for devices with holdover clocks. At 16 satellites, Pulsar will achieve persistent 1-satellite-in-view service, unlocking precise time transfer and coarse positioning for stationary users, including indoors. Pulsar also provides a link to stream GNSS corrections, building on a partnership with Trimble. Full resilient positioning will come online with GPS-level satellite visibility. First in the midlatitudes, with 192 satellites, and then globally with the deployment of an additional 66 satellites into polar orbit, bringing the total to 258 operational satellites.
Xona launched its in-orbit-validation stage in June 2025 with Pulsar-0, the first production-class satellite representative of the scaled capability in terms of signal modulation, power and features. Pulsar-0 allowed for performance validation of the complete system, not just of the payload in space but also the tangible benefit to users on the ground. For scale, Figure 4 shows the 150 kg class satellite pre-launch, including its integration on the Falcon 9 launch vehicle. Launch cost has been become more accessible, unlocking the ability to launch larger spacecraft by commercial entities, which can have larger positive impact on the ground (Xona, 2025b).
Figure 4. Xona’s first production satellite Pulsar-0.
LEO PNT on-orbit
In almost 6 months since launch, Pulsar-0 has been tracked in more than 6 countries, 12 third-party receiver protypes, and has achieved several performance milestones that signal the groundbreaking capability Pulsar will deliver to users everywhere when the full constellation is operational. Early performance tests are built to showcase the value and features most important to commercial users in realistic settings.
Accuracy. Figure 5 illustrates a signal-in-space user-range-error (SISRE) of 43 mm — about the diameter of a golf ball. This performance represents a more than tenfold increase in accuracy compared to that reported by GPS (Refro et al., 2024). The implication is an ability to natively perform PPP at the centimeter level, without an additional data link or correction layer.
Figure 5. Estimate of SISRE for Pulsar-0 ranging signal compared with nominal GPS.
Security. Xona is the first organization to show pseudorange authentication from orbit, accomplished using the Pulsar-0 satellite within weeks of the launch (Anderson, 2025). Pulsar is built from the ground up to be secure by design, combining cryptographic authentication of both navigation data and satellite ranging signals with rapidly authenticated signal verification — aiming for a time-to-authentication of approximately four seconds. This layered security significantly raises the technical and financial bar for would-be spoofers. A spoofer spoofing a single satellite continuously should succeed in fooling one second of a Pulsar receiver’s ranging once every 130 years (Xona, 2025a).
Jamming. Pulsar-0 signal testing has been conducted under live-sky jamming conditions at several jamming events, including Jammertest 2025 in Norway. These campaigns confirmed that using the Pulsar X5 signal can reduce the effective radius of a jammer by 6.3 times as compared to GPS L5 — in other words, less than 3% of the affected area compared to GPS. The same targeted power, bandwidth and type of jammer waveform was used against GPS and Pulsar, including center frequency. For context, Figure 6 shows the implications for a 1 Watt jammer scenario in San Francisco and the reduction brought by a 6.3x reduction in radius.
Figure 6. ffective jamming areas for Pulsar X5 and GPS L5 from a 1 W jammer in San Francisco based on Jammerfest 2025 test results.
Indoor. Data were collected for several navigation passes per day at multiple locations, including indoors. These include passes at Xona headquarters in Burlingame, California, and its office in Montreal, Canada. The most challenging indoor environment was Montreal, on the third floor of an industrial and primarily concrete building with two floors above. Figure 7 shows the Pulsar-0 power profile during a typical pass, peaking at the highest point in the sky. This structure is an artifact of the antenna gain pattern used in this mission. Designed for a higher altitude for deployment of later satellites, the pattern will be more isotropic with future satellites launched near 1100 km altitude compared to Pulsar-0, which is closer to 500 km. Near apex, the signal penetrates indoors, and this short segment proves to be sufficient for indoor positioning for stationary users. Leveraging techniques based on Doppler and including pseudorange, early results indicate sub-10 meters both outdoors and indoors.
Figure 7. Comparison of Pulsar and GPS signal strengths on roof and indoors at the Xona Montreal office.
EVOLUTIONARY
The coming years will be about gaining operational experience and in scaling the constellation with a near-term focus on the first batch of 16 satellites. Pulsar-0 has already confirmed its value proposition: attaining major milestones in performance including accuracy, security and jamming, but perhaps most importantly in the integration of user equipment. The next year is about working with customers in specific industries and use cases as Xona moves towards deployment of early operational service.
The future of LEO PNT is bright. Theory has evolved to prediction, which is now evolving to reality. The early results appear to lead to an exciting PNT future with LEO PNT expanding the GNSS revolution in terms of security, interference mitigation and system availability both outdoors and indoors for a myriad of current and new applications and users.
Further Reading
Anderson J (2025). World’s First Authenticated Satellite Pseudorange from Orbit, Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 738-748.
Eissfeller B, Pany T, Dötterböck D and Förstner R (2024). A Comparative Study of LEO-PNT Systems and Concepts, Proceedings of the ION 2024 Pacific PNT Meeting, Honolulu, Hawaii, April 2024, pp. 758-782.
Li W, Yang Q, Du X, Li M, Zhao Q, Yang L, Qin Y, Chang C, Wang Y, Qin G (2024). LEO augmented precise point positioning using real observations from two CENTISPACE™ experimental satellites. GPS Solutions, 28(1): 44.
Mah C, O’Keefe K (2025). Hardware Simulation of Low-Earth-Orbit GNSS for Carrier Phase Ambiguity Resolution, Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 2431-2443.
Prol FS, Ferre RM, Saleem Z, Välisuo P, Pinell C, Lohan ES, Elsanhoury M, Elmusrati M, Islam S, Çelikbilek K, Selvan K, Yliaho J, Rutledge K, Ojala A, Ferranti L, Praks J, Bhuiyan MZH, Kaasalainen S and Kuusniemi H (2022). Position, Navigation, and Timing (PNT) Through Low Earth Orbit (LEO) Satellites: A Survey on Current Status, Challenges, and Opportunities, IEEE Access, (10): 83971-84002
Reid TGR, Chan B, Goel A, Gunning K, Manning B, Martin J, Neish A, Perkins A and Tarantino (2020). Satellite Navigation for the Age of Autonomy, 2020 IEEE/ION Position, Location and Navigation Symposium (PLANS), Portland, Oregon, April 2020, pp. 342-352.
Reid TGR, Gala M, Favreau M, Kriezis A, O’Meara M, Pant A, Tarantino P and Youn C (2025). Xona Pulsar Compatibility with GNSS. Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 929-943.
Reid TG, Neish AM, Walter T and Enge PK (2018). Broadband LEO constellations for navigation. NAVIGATION: Journal of the Institute of Navigation, 65(2): 205-20.
CPI Electron Device Business – TMD Technologies Division has successfully completed sea trials of its cquantum-hybrid inertial navigation system (INS) aboard the THV Galatea, operated by Trinity House, the General Lighthouse Authority for England, Wales, the Channel Islands and Gibraltar.
This milestone shows that quantum-enabled sensing hardware can operate stably in maritime conditions, with the potential to provide resilient positioning without continuous reliance on GNSS.
Research indicates that a 24-hour GNSS outage could cost the UK economy £1.4 billion through cascading effects on logistics, transportation and critical infrastructure, underscoring the need for GNSS-independent solutions. By proving that quantum sensors can operate in operational conditions aboard a working vessel, CPI TMD is advancing technologies that reduce reliance on satellite navigation and improve resilience across maritime, defense and commercial sectors.
The Harlequin System: Quantum-Enhanced INS
The Harlequin system is a quantum-classical hybrid INS designed to extend GNSS holdover — the ability to maintain accurate position when satellite signals are unavailable or unreliable. Developed under an Innovate UK funded project, with partners from industry and academia, including the University of Strathclyde, and Joseph Cotter’s group at Imperial College London, Harlequin integrates classic INS components (a precise clock, a ring laser gyroscope, and a MEMS accelerometer) with CPI TMD’s gMOT-based quantum accelerometer.
Onboard team for the sea trial. (Photo: CPI TMD)
The gMOT cold atom source, developed by CPI TMD, the University of Strathclyde and Kelvin Nanotechnology, is a grating-based magneto-optical trap that provides a source of ultra-cold atoms that forms the basis of a portable, rugged quantum sensor.
Conventional INS technology accumulates errors over time, causing position estimates to drift. By integrating its cold-atom accelerometer technology with classical INS technology, Harlequin leverages quantum-enhanced sensing to perform periodic drift corrections, extending the period over which a vessel can maintain accurate position in the absence of satellite-derived timing and positioning.
Real-world trials: Operating around a working vessel
The Harlequin trial demonstrates that quantum sensors can operate reliably outside the lab, functioning in the harsh conditions of real-world maritime operations—a crucial validation step toward field-deployable systems.
The sea trial took place aboard the THV Galatea, which is not a scientific test vessel but an operational ship with a demanding day job: keeping shipping routes safe by ensuring buoys and lights are correctly placed and maintained, surveying the seabed for hazards, marking wrecks, and supporting marine-infrastructure projects such as cables and pipelines.
The Harlequin system had to be loaded, tested and unloaded around the Galatea’s regular operational schedule, adding complexity to the trial and underscoring the system’s ability to integrate into real-world maritime workflows.
Next Steps: System Upgrades and Second Trial
Data gathered during the trial will inform a program of system upgrades aimed at improving performance and enhancing suitability for long-term shipboard operation. A second field trial is planned for the end of 2026 to validate improvements and bring it closer to operational readiness.
Low-Earth orbit (LEO) systems have emerged as a promising complement to GNSS, offering higher received power, better satellite geometry and broader spectrum options. Researchers aim to evaluate whether LEO-PNT can complement or enhance GNSS performance through large-scale simulations and design comparisons.
Researchers from Tampere University and Universitat Autònoma de Barcelona published (DOI: 10.1186/s43020-025-00186-5) a comparative analysis in the December 2025 issue of Satellite Navigation. The study investigates how different LEO constellation configurations perform in positioning accuracy and interference robustness when operating alone or jointly with GNSS.
Using semi-analytical modeling and 192,000 Monte Carlo simulations, the team evaluated 400 users across European regions in five outdoor scenarios. Key variables included carrier bands (1.5/5/10 GHz), effective isotropic radiated power (EIRP) levels and constellation geometry design.
The team simulated multiple standalone and hybrid constellation architectures, analysing carrier-to-noise ratio (C/N0), geometric dilution of precision (GDOP), position dilution of precision (PDOP) and lower bound 3D accuracy.
Results indicate that an EIRP of 50 dBm is sufficient for high-quality outdoor positioning when operating in L- and C-bands. While 10 GHz platforms require higher power to compensate for path loss, hybrid LEO + GNSS modes show markedly improved stability and reliability.
Multi-shell constellations such as Çelikbilek-1 and Marchionne-2 delivered a favorable balance between satellite count and global geometry, outperforming single-shell layouts. In harsh urban canyon conditions, GNSS accuracy degraded up to seven-fold, whereas LEO-PNT maintained stable ranging performance with limited loss.
Interference resistance also improved. Stronger LEO signal power means jammers require far greater intensity to cause equal degradation. Hybrid designs provided the most significant gains. Combinations such as Çelikbilek-1 + GPS/Galileo, or CentiSpace + BeiDou, yielded better PDOP distributions, faster fix availability and broader user coverage.
The authors conclude that LEO systems are not aimed at replacing GNSS, but rather to enhance availability and resilience under signal-challenged environments.
“Our results show that moderate-power LEO constellations can substantially strengthen outdoor positioning without requiring expensive satellite hardware,” the authors noted. “Geometry plays a major role — carefully designed multi-shell constellations achieve strong accuracy even with fewer satellites. As LEO-PNT develops, hybrid integration with GNSS offers the most cost-effective path toward secure, robust PNT solutions. This work provides guidance for future system designers evaluating frequency, transmission power and constellation configuration trade-offs.”
The findings suggest a realistic rollout pathway for resilient satellite navigation. LEO-enhanced PNT could benefit autonomous vehicles, UAV routing, emergency response, precision farming and critical infrastructure monitoring — especially where GNSS falters in interference-dense or high-rise environments.
Lower-power LEO transmission also reduces deployment cost, opening access for commercial operators.
Future work may assess indoor positioning potential, bandwidth expansion, and real-orbit testing to refine simulation assumptions. As global demand for secure PNT grows, the integration of LEO and GNSS could become a cornerstone for next-generation navigation technology.
The United Kingdom has issued a summary of input it requested on positioning, navigation and timing (PNT) technologies. The UK deems PNT resilience critical for the UK’s economy.
After a call for evidence, the UK Department for Science, Innovation & Technology received 128 responses from business, industry, academics and the public. These views on opportunities and challenges for the UK’s PNT industry are gathered in a document available online.
Key themes identified
A viable market exists for GNSS-independent PNT, with respondents citing applications in defense and critical infrastructure.
Awareness of GNSS vulnerabilities in end users and critical infrastructure sectors is low.
Potential opportunities in GNSS-independent PNT and other technologies include eLoran, LEO-PNT, 5G, quantum PNT, inertial systems, and applications for GNSS-denied environments.
Short-term challenges include funding constraints and a lack of legislation and standards.
Long-term challenges include scalability, lack of sovereign manufacturing capability, and insufficient planning .
The industry is experiencing a skills shortage, especially in engineering, with a limited talent pipeline and lack of dedicated training opportunities.
In all, 128 responses were received from businesses (sellers and users of PNT), academics, industry bodies and the public. Respondents could select multiple sectors when describing their background; the defense sector was selected most frequently (39 responses), followed by space (35 responses), aviation and drones (28 responses), maritime (28 responses) and communications (27 responses).
Responses will be used, along with wider research, to inform future government policy interventions to support the UK PNT sector.
The U.S. Army is starting market research for possible sources of an optical tracking solution for its test ranges to use in GNSS-denied environments.
The Army Contracting Command – Orlando issued a Sources Sought Notice Dec. 11 on behalf of the Test Resource Management Center Test and Evaluation/Science and Technology (T&E/S&T) Program.
The Army wants to identify potential sources in the market having the interest, skills and ability to complete a thorough technology study and trade space analysis related to the viability of Time-Space-Position Optical Tracking (T-SPOT) for use on test ranges. The technology would be used as a time-space-position information (TSPI) truth sensor in GNSS-denied environments.
Required capabilities
The primary objective of a T-SPOT prototype effort would be to develop the system architecture, concept of operations, and comprehensive trade space analysis based on the results of modeling and simulation of the future-state system. The intent of the effort would not be to deliver the fieldable system itself but rather to answer whether/how such a system would achieve its performance goals.
A future T-SPOT system should
achieve 3D TSPI accuracy comparable to the accuracy of real-time kinematic positioning (RTK) GNSS navigation systems.
be generated in a near-continuous manner, notionally at an update rate comparable to GNSS navigation systems.
achieve full performance during daylight and in good visibility conditions, with the goal of operating at day and at night and in all-weather conditions.
support temporary and modular integration with airborne systems being tested, operating at altitudes typical for the operation of U.S. Air Force cargo and single-engine training aircraft, with the goal of supporting aircraft closer to or on the ground.
minimize its size, weight and power (SWaP) budget for integration with crewed aircraft, with the goal of supporting integration with small uncrewed aerial systems.
In addition to the sensor hardware hosted on the SUT, a future T-SPOT system should rely on terrestrial features solely comprised of passive landmarks (no active emissions; no required power). The system may employ synthetic landmarks (e.g., purposely installed fiducials) and/or pre-existing landmarks (of either natural or human origin). While the system must operate independently of GNSS, GNSS may be used pre- and post-test (i.e., for landmark surveying).
More details are on the announcement page. The deadline for responses is Jan. 30.
The 5G PNT network in Santa Clara County will mark the first real-world demonstration of a 5G-powered backup to GPS
NextNav Inc., a leader in next-generation terrestrial positioning, navigation, and timing (PNT) and 3D geolocation solutions, will commence operations of a 5G PNT network in Santa Clara County, California, as early as Dec. 11.
Network operations of positioning, navigation and timing applications represent the next milestone toward commercial readiness and the mission to deliver a resilient complement to GPS.
The 5G PNT network will consist of multiple fixed base station locations using a standards-compliant 5G signal with a positioning reference signal (PRS) enabled, a standalone 5G core, and NextNav’s 3D PNT architecture. The network’s authorized technical parameters will align with those in NextNav’s proposal to optimize the lower 900 MHz band to enable a terrestrial, widescale backup to GPS that is broadly available to critical infrastructure, public safety and American consumers.
“We’re incredibly pleased to continue demonstrating our technology in a real-world operational environment,” said Mariam Sorond, CEO of NextNav. “Activating this network is a critical step in our commercialization process, proving that robust 5G broadband service and high-integrity PNT can be delivered together, at scale, using standard 5G equipment.”
The 5G PNT network will validate NextNav’s 5G PRS-based PNT end-to-end architecture under real-world conditions.
“This is the first public demonstration of a full-scale and operational 5G-based PNT in live deployment, delivering both resilient PNT and broadband service simultaneously,” said Arun Raghupathy, NextNav Co-Founder and CTO. “Through this commercialization deployment, we’re validating our 5G-based network can deliver accurate 3D location, improved timing synchronization, and enhanced resilience. This real-world deployment is critical to establishing U.S. leadership in next-generation PNT technologies.”
The 5G PNT network will support the broader adoption of 5G-based terrestrial PNT with 5G broadband capabilities for operators, enterprises and ecosystem partners. This deployment will also prove that NextNav’s software solution is ready to scale and deliver commercial PNT while serving the critical national security and public safety needs of the United States.
On Nov. 11, the chair of the Z-Wave Alliance, Avi Rosenthal, published an opinion piece in GPS World, urging a delay in addressing one of America’s most pressing national security and economic vulnerabilities. I am talking about the need for a terrestrial complement to GPS. By ignoring both the urgency of the threat and the strength of the engineering analysis supporting near-term solutions like 5G-powered 3D PNT, Mr. Rosenthal argues the U.S. can afford to wait. At NextNav, we strongly disagree.
Around the world, GPS disruptions are no longer hypothetical. As this publication has documented, incidents of GPS jamming and spoofing have become routine in places like the Middle East and the Baltic states. And the increasing severity of these disruptions is spilling over into civilian life, putting us all at risk. We’ve seen the consequences here at home, too. Major airports have experienced manmade GPS disruptions of unknown origin, and farmers have seen how even temporary GPS loss can upend precision agriculture.
Whether caused by jamming, spoofing or natural disasters, the vulnerabilities are real and growing.
These threats are why the Federal Communications Commission (FCC) made it a priority to advance additional technologies and solutions as part of a whole-of-government approach to strengthen PNT resiliency. At NextNav, we are doing the hard work necessary to help enable a system-of-systems capable of delivering greater PNT resilience into America’s critical infrastructure, while Mr. Rosenthal and his allies continue to rely on flawed studies and broad mischaracterizations of our proposal. They preach delay rather than moving to the logical next step of the FCC process, specifically designed to allow the commission to fully evaluate competing technical claims.
We have filed multiple comprehensive engineering studies demonstrating that 5G operations in the lower 900 MHz band will not cause unacceptable interference to unlicensed devices. Those studies specifically examined five different unlicensed technologies, including the Z-Wave technology. To ensure this discussion is fact-based, we’d like to set the record straight.
The SIA-sponsored paper that Mr. Rosenthal cited for his unrealistic claims of interference does not hold up under scrutiny and contains a number of fundamental technical errors. As we’ve outlined in detail, NextNav’s detailed technical analysis has identified significant flaws in the Pericle paper, pointing out fundamental errors in the paper’s assumptions and methodology.
For instance, Pericle’s predicted 5G emission levels exceed levels found in theoretical free-space conditions — an impossibility that undermines the entire paper. The Pericle paper also seems to ignore how 5G positioning signals work, failing to mention comb patterns and muting that are core to the technology, and thereby further inflating perceived 5G emission levels. Attempts to reproduce Pericle’s simulations with Pericle’s stated methods and parameters yield dramatically different results, which serve as clear evidence of computational errors or faulty execution of the depicted scenario.
Perhaps most remarkably, no credible analysis could replicate Pericle’s conclusion that 5G interference would occur more than 50 percent of the time when the ostensibly interfering transmitter operates only 50 percent of the time.
The most glaring issue with the paper that Rosenthal cites is that it never directly analyzes the very devices that the security industry states are predominant in home and business security systems today. Specifically, it fails to analyze Z-Wave, the technology that, according to the Z-Wave Alliance, is utilized by more than 90% of professionally monitored security systems in North America. In fact, Z-Wave operates primarily on frequencies that are outside of the frequencies which NextNav’s proposes to use for 5G.
It is a fact that unlicensed lower 900 MHz devices today successfully coexist with a wide range of unlicensed users that operate without coordination or interference protection. Pericle never accounts for the resilience mechanisms Part 15 devices use every day, including frequency hopping, bursty transmissions, adaptive modulation, redundant paths (meshing), self-healing and other features.
Lastly, Mr. Rosenthal’s characterization of the Department of Transportation’s action also fails to mention that the DOT has already evaluated NextNav’s technology, ranking NextNav first in every category of its 2021 evaluation. In 2024, DOT awarded NextNav the largest grant, $1.8M, for Rapid Phase I field testing of PNT technologies. NextNav supports DOT’s ongoing work to advance complements to GPS, but its testing should not stand in the way of swiftly advancing solutions that are ripe for action now.
Waiting for DOT to conclude its testing of multiple additional PNT technologies before the commission acts within its authority to take the next step towards enabling one or more potential solutions not only runs contrary to a Presidential Executive Order for agencies to remove barriers to private sector investment, but also risks the same analysis paralysis that slowed deployment of resilient PNT in the previous administration.
At NextNav, we are serious about solving an urgent national security problem, and we will continue to do the hard work necessary to support the FCC’s engineering-driven decision making. The FCC is the expert authority on commercial spectrum issues, and we believe it has all of the information it needs to take the next step in this process by issuing a Notice of Proposed Rulemaking (NPRM). Issuing an NPRM would also give the FCC the opportunity to ask any remaining technical or economic questions that it may deem necessary to complete its evaluation.
It’s time to roll up our sleeves and do the hard work necessary to enable a system-of-systems approach to building great PNT resilience. The longer we delay, the more vulnerable we become.
Renee Gregory is the vice president of regulatory affairs at NextNav.
SpacePNT SA, a global provider of high-accuracy, radiation-tolerant spaceborne GNSS receiver equipment for missions ranging from Earth to cislunar orbit, has completed extensive qualification testing of its second-generation product, including vibration, shock, thermal vacuum and electromagnetic compatibility tests.
The multi-frequency, multi-GNSS receiver resulted from two European Space Agency (ESA) ARTES Competitive & Growth (C&G) development projects supported by ESA and the Swiss Space Office.
The first project enabled SpacePNT to develop an industrialized second-generation product for large-scale production targeting low-Earth orbit, LEO position-navigation-timing and geostationary orbit telecommunications constellations. The receiver includes a proprietary Precise Orbit Determination algorithm that provides sub-decimeter real-time positioning and timing aboard spacecraft. The company validated the POD algorithm in a hardware-in-the-loop environment and retrofitted it into two first-generation flight models delivered to a customer for satellite integration.
Under the second project, SpacePNT developed a Radiation Hardiness Assurance approach for long-duration missions in harsh radiation environments. ESA’s GENESIS satellite mission, which will operate in a challenging medium Earth orbit environment, will be the first to use this RHA approach. SpacePNT will supply the mission’s GNSS receiver equipment.
Though the second-generation receiver uses largely the same hardware, software and firmware technology as the company’s flight-proven first-generation product, SpacePNT performed a complete qualification campaign to validate design changes.
After passing all qualification and performance tests, SpacePNT will begin manufacturing first flight models of its second-generation products for several customers. The receivers will fly on demanding Earth observation, in-orbit servicing and space exploration missions at altitudes from LEO through medium Earth orbit, geosynchronous transfer orbit, geostationary orbit and lunar distances.
The views expressed herein do not reflect the official opinion of the European Space Agency.
