When Xona began its journey into commercial satellite navigation in 2019, four global systems were already operational in Medium Earth Orbit, and three regional systems deployed in Geosynchronous Orbit. Legacy constellations and nation-states had made extraordinary investments to establish the infrastructure for global navigation and positioning.
But with these achievements, the industry became deeply reliant on infrastructure it could not easily change. While innovation has introduced new ways to navigate with novel signals, adoption remains the central obstacle. With over 6 billion GNSS-enabled devices in use worldwide, any service provider that asks manufacturers to add new, non-compatible hardware will see integration challenges, restricting advanced capability to the most expensive solution and reinforcing the status quo for all other devices. Broadcasting in the frequencies that are already in use by GNSS is rightly met with intense scrutiny before any broadcast can begin. GPS is simply too critical – even a short outage will cause widespread disruption, with estimated economic impacts exceeding $1B per day across North America.
Overcoming these barriers is slow and expensive, demanding regulatory, technical, and financial resources that many new entrants do not have.
Rapid innovation, then, becomes essential. Not just to introduce new capability, but to secure compatibility, market access, and meaningful adoption at all user levels. After launching our pathfinder satellite Huginn in 2022, we had to ask ourselves: what does rapid innovation look like in an industry that depends on entrenched infrastructure?
A Three-Body Problem on Earth
The answer was not a single breakthrough, but an acknowledgement of complexity. GNSS is not a single product, but an ecosystem made up of three distinct, tightly coupled communities: satellites, receivers, and test equipment. Each needs the other to work.
In orbital mechanics, the “three-body problem” refers to the challenge of predicting motion when three objects are interacting at once. Each one affects the others, so there’s no simple, one-time solution—only continuous adjustment. GNSS adoption follows the same pattern. In order to properly integrate into such an entrenched market, and to secure seamless adoption as an outcome, a company has to address the satellite, simulators and test equipment, and receiver communities on their individual levels.
The First Body: Satellites, Signals, and Spectrum
Any new entrant to satellite networking begins with spectrum. International and U.S. spectrum allocations define what is possible, providing three primary options: the well-established L-band; the lesser-used S-band, employed regionally by India’s NAVIC and China’s BeiDou; and C-band, which in 2019 remained largely unused. Because Wi-Fi and Bluetooth are prevalent in S-band, interference risks were already well understood. For Huginn, launched in 2022, we chose to build for both L-band and C-band.
C-band was more open in what we could do as a nascent domain, but L-band ultimately set the constraints that mattered most. To succeed, we had to coexist with legacy GNSS systems, protect aviation services operating in L5, and still deliver meaningful improvements in performance.
Traditionally, GNSS systems have protected aviation by maintaining uniformly low transmit power. But rising interference and growing demand for indoor and resilient navigation called for a different approach. Our team identified a key insight: aviation receivers have much higher gain at low elevation angles, with most of their effective received power coming from satellites near the horizon. Based on this, we designed a system in which satellites remain silent as they rise above the horizon, then gradually increase transmit power as they climb higher in the sky.
This design has enabled Pulsar to deliver up to 100x higher signal power without impacting aviation services.
Adoption, however, depends on more than power. Receiver manufacturers needed a signal that was GNSS-like, while customers demanded new capabilities: security, authentication, and data services. The solution came from a neighboring industry.
What’s old is new with CDMA
Digital signal processing and Code Division Multiple Access (CDMA) first saw widespread use in GPS in the 1970s. The GPS L1 C/A signal uses Binary Phase Shift Keying (BPSK), which encodes one bit per symbol by shifting the carrier phase by 180 degrees. As telecommunications networks scaled in the late 1980s, they adopted Quadrature Phase Shift Keying (QPSK), which uses four phase states to encode two bits per symbol—doubling data throughput in the same bandwidth.
As phones proliferated and terrestrial cellular networks became inundated with traffic, even QPSK became insufficient. From pressure to push bandwidth efficiency even further, Enhanced Feher’s Quadrature Phase Shift Keying (EFQPSK) was born. Developed between the late 1980s and early 2000s, this digital waveform has the same characteristics as QPSK, keeping 2 symbols per bit, but smooths phase transitions to reduce fluctuations. This reduces the sidelobes of the signal in the frequency domain, meaning it isn’t as wide for the same information and doesn’t step on (or interfere with) neighboring signals nearly as much. From a GNSS receiver perspective, EFQPSK can be treated like the familiar BPSK signal, but from an interference perspective, it is much more efficient in its use of bandwidth, concentrating its power in the central lobe.
From a GNSS receiver perspective, EFQPSK can be treated much like the familiar BPSK signal. From an interference perspective, it is significantly more spectrum efficient.
In a full circle moment – from navigation influencing telecom, then telecom influencing navigation, we adopted EFQPSK on for Pulsar’s signal architecture. Our demonstration mission transmitted EFQPSK in C-band, letting us test our technology quickly in a more greenfield frequency band.
In all our early trials, feedback from the community was consistent and decisive: use L-band. C-band, by contrast, required new RF components and long design cycles, significantly slowing adoption.
Xona ultimately aims to serve all users of GNSS. Our business model is not to build new GNSS receivers, but to work with those who already build them and upgrade their capabilities with a new class of signal. Receiver partners can now integrate our L-band signal in weeks or even days with software updates to their existing hardware. Our path was clear – meaningful, frictionless adoption required innovation within L-band.
The Second Body: Receivers & Receiver Partners
Xona’s business model has never been to build commercial receivers. But, in our earliest mission, we soon learned the value that came from understanding how they were built, and how we would build them.
To test the precision of our satellites, we need receivers that can evolve as quickly as our signals. To validate simulator implementations, we need reference receivers. To verify third-party receivers, we need baseline signal reception for comparison. For Pulsar-0, that meant building receivers alongside satellites as tools to lead the ecosystem with best practices and accelerate development.
Today, Pulsar supports a thriving ecosystem of receivers and simulators that can track Pulsar-0 on orbit and simulate our complete constellation today. Unlike legacy GNSS which evolves at generational timescales and through the introduction of new signals, we expect to introduce new features much faster. As such, our satellites are software-defined with a flexible message structure.
This means that new data products could be delivered tomorrow on our frequency bands, enabling the latest devices with new capability and without breaking previous implementations. Constant evolution and introduction of new features means leading in receiver implementation to support rapid prototyping, simulator validation, and verification of Pulsar-capable receivers with the latest capabilities.
GPS L1 and L5 (gray) and Pulsar X1 and X5 (teal) signals exist in the frequency domain. The adjacent nature of Pulsar means that the same hardware path allows Xona signals to enter existing receivers while the separation and different modulation (shape) means Pulsar does not interfere with GPS.
On the heels of launching Pulsar-0, we now broadcast signals adjacent to GPS L1 and L5, known as X1 and X5.
This milestone came after extensive coordination at both U.S. and international regulatory levels, making Xona the first commercial operator licensed by the FCC to operate in the GNSS L-band.
The ease of integration in the receiver industry is being witnessed firsthand, with several commercial receivers tracking Pulsar-0’s signals within days of launch. It also speaks to the ecosystem and verification processes built to facilitate receiver development, specifically with the GNSS simulator community.
The Third Body: GNSS Simulators
GNSS simulators are where satellite navigation systems come to life before our constellation is complete. These lab-based systems generate real RF signals that model orbits, Doppler shift, modulation, security, and data frames in full detail. They allow receivers to acquire, track, decode, authenticate, and produce time and position in a controlled environment.
With simulators, device manufacturers and customers are able to visualize the value of Pulsar in real-world scenarios, like navigating in dense cities. Pulsar’s faster orbital motion helps receivers distinguish reflections. Simulators, like this instance from Spirent, show where satellite signals are blocked (orange) or reflected in the form of multipath (blue), where only some maintain direct line of sight (green).
For a startup without a complete constellation in orbit, simulators are essential. To enable receiver partners to integrate Pulsar before launch, simulator support had to come first. That early access delivers two critical advantages: it allows partners to hit the ground running once signals are live, and it derisks the technology stack by validating integration ahead of time – making signal integration easier for our partners in the industry.
But simulators also introduce a familiar three-body problem. Without live satellites, simulator partners implement signals based on interface control documents. Receiver partners do the same. When signals finally arrive from orbit, all three—the satellite, simulator, and receiver—must agree. If they don’t, which one is right?
As with the orbital three-body problem, there is no static solution. For Xona, that meant becoming fluent in all three domains: satellites, simulators, and receivers.
The Solution to the Industry’s Three Body Problem
Universal compatibility does not emerge from a single design choice or technical breakthrough. It is built through continuous coordination across an ever changing and shifting ecosystem—and through active collaboration with the user community.
GNSS has long been treated as static infrastructure, shaped primarily by government requirements and generational timelines. By working directly with commercial users, integrators, and partners, Xona is helping reshape that model—introducing a system that evolves with customer needs while remaining compatible with the devices and infrastructure the world already relies on.
Collaboration is what makes compatibility possible.
