This solution will be showcased during MWC Barcelona at VIAVI Stand 5A18 in Hall 5, from March 3 to 6, 2025.

Essential networks throughout the world – including 5G/6G telecommunications, AI hyperscale data centers, defense, public safety, transportation, aviation, energy and finance – rely on publicly available GPS and GNSS signals for efficient data synchronization based on timing and location. These vulnerable and single-source signals are occasionally unavailable or at risk of being jammed or spoofed, or satellites themselves can be attacked, with potentially catastrophic consequences. Governments around the world have begun mandating that critical infrastructure providers improve resilience of their networks through more responsible use of PNT services.

SecurePNT and SecureTime from VIAVI offer resilient timing, with multisource assurance combining signals from GNSS-dependent government and GNSS-independent commercial constellations across Medium Earth Orbit (MEO), Geosynchronous Earth Orbit (GEO) and Low Earth Orbit (LEO), respectively. The EdgeGM 7000 integrates advanced and scalable resiliency and PTP speed capabilities in a compact half 19” wide and 1U height rack-mountable unit with scalable software options. For instance, it can be upgraded from 1/10G to 25G PTP with a simple license, and GNSS backup can be activated with an on-demand alternate GNSS GEO-L source license over the air. EdgeGM exceeds Level 4 PNT resiliency as specified in the IEEE P1252 standard. It also incorporates PTP profiles for multiple industries, including telecommunications, enterprise, power and more.

“The world has seen a steady rise in threats to critical infrastructure, including disruption to the Positioning, Navigation and Timing services that are so vital to secure operations,” said Doug Russell, Senior Vice President, AvComm, VIAVI. “With the EdgeGM 7000, VIAVI is enhancing our portfolio to stay ahead of a rapidly evolving threat landscape, providing customers with the industry’s most powerful features in a flexible and scalable architecture.”

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The JRC is now inviting stakeholder input towards shaping the initiative.

Timing has long played third fiddle to positioning and navigation in the PNT triumvirate, in spite of the fact that it underpins every PNT function. Without accurate timing, satellites can’t deliver precise locations, power grids and other critical infrastructure falter, stocks can’t be traded and financial transactions lose sync. Call accurate timing the glue holding all these functions together. At a time when GNSS vulnerability is in the spotlight, resilient timing services via terrestrial networks, fiber, or alternative signals would provide a much-needed safety net.

Piecing together

Underpinning the JRC’s proposed timing backbone are elements in the complementary PNT (C-PNT) ecosystem, comprising a range of terrestrial timing systems, which would:

• Link European infrastructure, interconnecting national metrological institutes (NMIs) and research networks across the EU in a cohesive, resilient network;
• Support critical entities, enhancing timing services for vital infrastructure under the EU’s resilience directive while boosting GNSS redundancy;
• Drive competitiveness, unlocking new commercial applications and cementing Europe’s leadership in timing technologies.

The timing backbone initiative builds on the 2023 European Radio Navigation Plan and reflects years of groundwork by the European Commission (EC), the European Space Agency (ESA), and EU member states. The JRC has also drawn on its own in-depth analyses of Sweden’s distributed timing approach and the UK’s National Physical Laboratory (NPL) clock network, and has studied vulnerabilities recently exposed by Russian GNSS jamming activities in Ukraine.

The EU isn’t alone in its focus on timing resilience. China’s sprawling high-accuracy, ground-based timing system will eventually feature 20,000 km of fiber optics and a nationwide network of eLoran stations. Similar strategies are being pursued in the US and elsewhere.

The JRC market consultation report, issued late last year (2024), emphasizes the JRC’s role in fostering a robust and resilient PNT ecosystem, evidenced by its recent work in support of the development of new, alternative PNT technologies. The need for resilient timing is undeniable. The clock, as they say, is running, and the benefits are likely to be enormous.

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Working with partners Luminous Cyber Corporation and Eritek Inc., the team recently completed Preliminary Design Review (PDR).

The Air Force Research Laboratory (AFRL) and SpaceWERX, the innovation arm of the U.S. Space Force and a unique division within AFWERX, have partnered to streamline the Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) process by accelerating the small business experience through faster proposal-to-award timelines, changing the pool of potential applicants by expanding opportunities to small business and eliminating bureaucratic overhead by continually implementing process improvement changes in contract execution.

The DAF started the Open Topic SBIR/STTR program in 2018 to expand the range of innovations that it funds. Under this program, Xairos is creating groundbreaking capabilities that strengthen the national defense of the United States of America.

“Xairos is thrilled to have this opportunity to address a critical need for secure PNT and communications in a GPS-denied environment for the Alt-PNT Challenge,” said David Mitlyng, Xairos CEO. “This program gives us an opportunity to integrate Quantum Time Transfer (QTT) with Luminous Cyber’s novel clock ensemble and Eritek’s compact optical communications terminal to demonstrate a field deployable terminal that is a major step towards the commercialization of a resilient and accurate global timing network.”

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A Chip-Scale Atomic Clock (CSAC) provides the necessary precise and stable timing where traditional atomic clocks are too large or power-hungry and where other satellite-based references may be compromised.

Microchip has developed the Evacuated Miniature Crystal Oscillator (EMXO) technology and integrated it into a CSAC, enabling the model SA65-LN to offer a reduced profile height of less than ½ inch, while maintaining a power consumption of < 295 mW. The new design is optimal for aerospace and defense mission-critical applications such as mobile radar, dismounted radios, dismounted IED jamming systems, autonomous sensor networks and unmanned vehicles due to its compact size, low power consumption and high precision. Operating within a wider temperature range of −40°C to +80°C, the new LN-CSAC is designed to maintain its frequency and phase stability in extreme conditions for enhanced reliability.

“A significant advancement in frequency technology, our next generation LN-CSAC provides exceptional stability and precision in a remarkably compact form,” said Randy Brudzinski, corporate vice president of Microchip’s frequency and time systems business unit. “This device enables our customers to achieve superior signal clarity and atomic-level accuracy, while also benefiting from reduced design complexity and lower power consumption.”

The LN-CSAC combines a crystal oscillator and an atomic clock in a single compact device. The EMXO offers low-phase noise at 10 Hz < −120 dBc/Hz and Allan Deviation (ADEV) stability < 1E-11 at a 1-second averaging time. The atomic clock provides initial accuracy of ±0.5 ppb, low frequency drift performance of < 0.9 ppb/mo, and maximum temperature-induced errors of < ±0.3ppb. Together, the LN-CSAC can save board space, design time and overall power consumption compared to designs that feature two oscillators.

The crystal signal purity and low-phase noise of LN-CSAC are designed to ensure high-quality signal integrity, which is essential for frequency mixing. The atomic-level accuracy allows for longer intervals between calibrations, which can help extend mission durations and potentially reduce maintenance requirements.

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It is designed to meet the demands of industries requiring ultra-stable short-term timing. The module achieves performance levels comparable to the passive hydrogen maser, which is no longer available in the Western market.

The ESTU module improves short-term frequency stability, measured through Allan Deviation, providing the synchronization accuracy and reliability essential for sectors including metrology, space exploration and defense. It enables more stable data collection, satellite communication and measurement operations.

“With our precision timing module, we’re setting new benchmarks in short-term frequency stability, addressing the critical demands of sectors ranging from scientific research labs to aerospace companies,” said Gil Biran, GM of Oscilloquartz, Adtran. “This advanced ESTU module enhances our industry-first high-performance optical cesium atomic clocks, delivering substantial benefits, including reduced Allan Deviation. These improvements are essential for ensuring the stability and accuracy of timing network infrastructure. Our solutions are the first in the market to combine the short-term stability of a passive hydrogen maser with the long-term stability of a high-performance cesium clock. This innovation underscores our commitment to providing advanced technology tailored to mission-critical applications.”

This latest addition to Adtran’s comprehensive portfolio of Oscilloquartz synchronization technologies is designed to optimize short-term frequency stability. By improving frequency precision, the new ESTU module ensures greater timing accuracy for high-stakes operations. It supports both 5MHz and 10MHz output frequencies, making it a versatile solution for various high-precision operations, including systems using passive hydrogen masers. The enhanced short-term stability delivered by the new ESTU module is crucial for industries that rely on ultra-precise synchronization, such as satellite communication systems, metrology labs and deep-space exploration.

“With over 75 years of expertise in timing and synchronization, Oscilloquartz has established a lasting legacy of innovation and trust. This latest upgrade of our high-end optical cesium clocks continues that tradition, delivering significant improvements in short-term frequency stability while maintaining the superb long-term stability for industries that rely on ultra-precise timing,” commented Patrick Berthoud, time and frequency chief scientist at Oscilloquartz, Adtran. “Leveraging our world-renowned Swiss expertise, this new ESTU module enhances our high-performance optical cesium atomic clocks, providing the short-term stability that mission-critical applications demand. It reflects our team’s ongoing commitment to pushing the boundaries of synchronization technology and ensuring unmatched accuracy for our customers.”

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NUNZIO GAMBALE, DAVID SMALL, JOEL BARNES, IAN SAINSBERY, CLAYTON GUMBRELL, MUSTAFA KANLI, MIKE SKEEN AND THE LOCATA TEAM, LOCATA

Global Navigation Satellite Systems (GNSS) form the foundation of modern Positioning, Navigation and Timing (PNT) systems, continuously delivering accurate time and position data worldwide. This service is indispensable across numerous economic sectors, including transport, telecommunications, energy, finance, agriculture, security and defense.

Although highly advanced and technologically sophisticated, GNSS is extremely vulnerable to deliberate jamming, accidental interference, space weather events, and system malfunctions. The press reporting failure of GNSS systems, especially for aviation, automation and military systems (both positioning and timing), have multiplied exponentially in recent years. Moreover, GNSS cannot reliably provide service in areas with limited sky visibility, such as indoor environments, urban canyons or dense forests. Given its predominant role as the primary source of PNT for almost every nation, it has become crucial to explore alternative platforms or complementary systems that can serve as backups to GNSS services or improve and extend PNT capabilities for emerging and future applications.

Because of this, nations around the world are starting to plan and construct new terrestrial time distribution networks, including extremely high-accuracy, sovereign-controlled National Timing Backbones that reduce their nation’s single-point-of-failure dependency on time obtained via GNSS systems.

These “metrology grade” non-GNSS or non-satellite-based systems demand exacting sub-nanosecond time distribution performance. In the past, that meant national timing institutes had only two real options: (a) expensive atomic clocks on each site that could be aligned regularly to Coordinated Universal Time (UTC), or (b) advanced optical fiber networks employing cutting-edge scientific research techniques such as White Rabbit, NPLTime and ELSTAB. 

While fiber networks can (and are) being deployed for metrology grade time distribution, they are expensive to establish and run and need high-level expertise for calibration. However, their greatest shortcoming is they are inherently point-to-point systems—they totally lack the radio-based “available anywhere across an area” flexibility that has made GNSS so powerful and ubiquitous. It’s analogous to the difference between a desk land-line phone and a mobile phone.

Locata addresses that issue, providing sub-nanosecond over-the-air (OTA) time transfer distribution.

Improving Timing Stability 

Locata Corporation is a privately-owned company with headquarters in Canberra, Australia, plus engineering offices in the U.S. and the EU. Locata has developed radio-based position, navigation and time transfer technology that delivers precise positioning and timing in environments where GNSS is marginal or unavailable for modern applications [1,2,3]. Locata has decades of experience delivering centimeter-level positioning in challenging environments, particularly for industrial-scale, fully autonomous machine control systems.

The Locata system can be likened to a terrestrial GNSS network, where ground-based LocataLite™ transceivers serve as the equivalent of GNSS satellites, and Locata rover receivers function similarly to typical GNSS receivers.

Locata’s technology can be used stand-alone, or readily mixed and matched with fiber networks to enable deployment of National Timing Backbones that deliver picosecond performance levels across regional, local or campus-scale areas. And the Locata signals can be used for high-accuracy non-GNSS-based positioning as well, if desired. Locata’s new TimeLoc™ technology promises to establish a level of timing precision, flexibility, wide-area coverage and ease-of-use that was previously only available from GNSS. TimeLoc’s family of patented technologies leverage broadcast RF ranging signals to synchronize the network [4]. The rovers use the exact same RF broadcast signals to calculate high-accuracy position solutions within the network coverage area.

LocataLites currently operate in the 2.4 GHz ISM band, typically using two 20 MHz-wide channels with a transmit power of 100 mW (20 dBm). Figure 1 illustrates a typical frequency plan configuration currently used for positioning. The broadcast CDMA signal structure is similar to GPS but incorporates a TDMA overlay as well. Rover measurements include pseudorange, integrated carrier phase, and angle of arrival when Locata-developed VRay™ antennas are used [5,6]

These measurements enable rovers to compute centimeter-level real-time autonomous precise positioning solutions without requiring differential corrections or base stations like GNSS. This survey-grade positioning capability is made possible by the precise time and frequency synchronization of LocataLites within the Locata Network (LocataNet™) via the TimeLoc technique. Typically, a network of LocataLites is deployed around a specified work area to provide ranging signals to rovers operating within the area. The LocataLites are time and frequency synchronized using TimeLoc.

A Closer Look at The Technology

TimeLoc

For LocataNets, which are used solely for positioning, TimeLoc operates as a one-way ranging process in which LocataLites synchronize with one or more reference LocataLites to maintain time and frequency stability. LocataNet time is governed by a “Master” LocataLite, with “Secondary-Master” LocataLites providing redundancy. While the Master and Secondary-Masters may optionally synchronize to an external time reference, such as GNSS or an atomic clock, this is not required for TimeLoc or the LocataNet to synchronize internally or to provide a position solution.

TimeLoc maintains synchronization in a LocataNet through a continuous real-time control loop, eliminating the need for atomic clocks (which are an essential requirement for synchronization of the GNSS satellites). Instead of atomic clocks, LocataLites use very inexpensive temperature-compensated crystal oscillators (TCXOs), or oven-controlled crystal oscillators (OCXOs). In a positioning LocataNet, the coordinates of the LocataLite antennas must be determined to centimeter-level accuracy to enable centimeter-level positioning at the rover. This is typically achieved using traditional survey techniques or a self-survey technique developed by Locata. Time synchronization offsets among LocataLites in a deployed network are typically within several nanoseconds, with stability at the tens-of-picoseconds level. These small time biases are accounted for in the navigation solution to achieve centimeter-level positioning accuracy.

For LocataNets used for timing networks, TimeLoc incorporates two-way ranging, which improves time synchronization accuracy to the sub-nanosecond or picosecond level while maintaining the high time and frequency stability of standard TimeLoc. The two-way ranging process allows biases (including multipath) to be eliminated and variations in signal path delay caused by tropospheric changes to be corrected. Unlike LocataNets used solely for positioning, timing LocataNets do not require surveying the coordinates of the LocataLites, as the two-way ranging compensates for positional uncertainties.

Locata TBase

A LocataLite designed and enhanced specifically for time-transfer applications is called a Locata TBase™. It delivers sub-nanosecond to picosecond-level performance without requiring fiber infrastructure. The TBase can support both point-to-point and point-to-multipoint network topologies, enabling rapid, flexible deployment and redeployment mobility. It integrates seamlessly with other clock and time-transfer technologies through standard 1 PPS, 10 MHz and Time-of-Day (ToD) interfaces.

Site-to-site links between TBase devices are ideally line-of-sight (LOS). Consequently, locations such as existing antenna masts, towers or elevated sites (e.g. buildings, hills) are commonly chosen to maximize LOS ranges. Currently, link distances of up to 125 km have been achieved using standard LocataLites transmitting 100 mW (+20 dBm) signals in the 2.4 GHz ISM band, using high-gain antennas. When LOS is not available, it is still possible to achieve accurate time transfer over non-LOS paths (e.g. to indoor locations), given sufficient stable signal power is available.

Master LocataLites can synchronize to an external time source, such as a reference atomic clock, or another timing backbone system such as White Rabbit. This external synchronization uses 1 PPS, 10 MHz and ToD inputs. TBases can currently transfer time to one or more additional TBases via up to four separate antennas that can be arrayed to cover large or disparate areas. Multiple access (time transfer to more than one Locata TBase at a time) is supported via TDMA. 

LocataLite networks typically begin with a connection to an external time source. However, a floating time base within the LocataNet is also possible, where synchronization is maintained between LocataLites without linking to a specific time standard. Notably, Locata TimeLoc technology does not require an external time standard like an atomic clock to sustain picosecond-levels of synchronization between transceivers.

The current early-stage Locata TBase device, shown in Figure 2, is a 2U rackmount enclosure that supplies the following features:

• Five RF ports: For up to five antennas to carry Locata RF signals.

• Two RF ports: Optional LTE modem support.

• Two RJ45 Ethernet ports

• Two Serial ports: For ToD input and output.

• Four BNC ports: Includes 1-PPS input, 10 MHz input, N-PPS output (typically 1 PPS) and 10 MHz output.

The Locata TBase operates in Master, Client/Reference or Client mode:

1. Master Mode: The TBase determines the time base for the entire LocataNet. It may optionally synchronize to an external time reference (such as GNSS, UTC, etc) via 1 PPS and 10 MHz inputs. The Master then acts as a time reference for one or more other TBases, via TimeLoc OTA, fiber or coaxial links supplied in the enclosure.

2. Client/Reference Mode: The TBase time synchronizes to the Master TBase or to another reference TBase that already has synchronization with the LocataNet. The TBase then acts as a time reference to one or more additional TBases, enabling an extremely flexible and configurable network topology that handles real-world deployment challenges very well.

3. Client Mode: The TBase synchronizes to the Master TBase or to another Reference TBase that already has synchronization with the LocataNet.

All Locata TBase devices output N-PPS and 10 MHz signals to enable time transfer to external devices.

In 2022, the use of Locata TBase devices for time transfer was successfully demonstrated at the European Commission’s Joint Research Centre (JRC) located near Milan, in the Lake Maggiore region of Northern Italy.

Put to the Test

After decades of R&D, continually refining the TimeLoc radio-based synchronization techniques the team invented from scratch, Locata has begun demonstrating sub-nanosecond radio-based time distribution to metrology labs and the timing industry. The performance Locata originally demonstrated over a 105 km network in the European Directorate General for Defence Industry and Space (DEFIS) tests in 2022 was exceptional, yet it also highlighted one area that required further development. After two years of additional R&D, Locata recently ran a demonstration of its improved system for the National Measurement Institute (NMI) in Sydney, Australia. The performance recorded during these NMI tests heralds the arrival of new and useful radio-based time transfer distribution options for the timing markets—fiber levels of performance, without requiring the fiber.

Europe’s DEFIS Alternative PNT Testing 

Locata was one of seven companies selected to participate in the European Commission DEFIS Alternative PNT (A-PNT) test campaign (DEFIS/2020/OP/0007). The tests, facilitated by the JRC of the European Commission, aimed to assess the performance of all available non-GNSS-based positioning and timing technologies in challenging or GNSS-denied environments. Thirty two companies applied for the seven available contracts. Locata was granted two of the seven contracts, to measure its positioning and timing capabilities. Notably, Locata was one of only three participants that demonstrated both positioning and timing services. A summary of the test campaign results for all participants is provided in [7], with Locata’s specific technical report detailed in [8].

Table 1 summarizes the timing performance results extracted from [7], including both internal and external (in brackets) time transfer performance statistics at the 99.7th percentile. External time transfer includes synchronization between the first LocataLite TBase (Master) and the reference time source.

Locata’s technology achieved OTA picosecond-level internal (400 ps) and nanosecond-level (6.1 ns) external time transfer performance, across both long-range (>105 km) and campus-wide (2.2 km) environments. It was the only system tested by the EU capable of delivering timing in every timing and synchronization test conducted.

Additionally, Locata demonstrated exceptional versatility by achieving picosecond-level timing through OTA, fiber and coaxial cable. Its performance quality surpassed all other OTA systems by orders of magnitude, delivering precision thousands of times better than other tested candidates.

The long-range time transfer included eight TimeLoc links (“hops”) over a total distance of approximately 105 km, with the longest single hop covering 44 km.

NMI Australia Testing 

Since the EU’s DEFIS tests in 2022, Locata has continued enhancing its time transfer capabilities. Specifically, Locata engineers believed TimeLoc was capable of delivering much better external synchronization perfomance than was achieved at DEFIS. An R&D effort was therefore initiated, with particular focus on delivering dependable sub-nanosecond external synchronization.

In October 2024, Locata conducted time distribution technology tests at the Time and Frequency Standards Laboratory of the NMI. The NMI, Australia’s peak measurement body for biological, chemical and physical measurements, operates as a division of the Australian Government’s Department of Industry, Science and Resources. The Time and Frequency Standards Laboratory is responsible for maintaining Australia’s official time using atomic clocks, which also contribute to UTC. 

NMI approached Locata to perform technology demonstrations, aiming to gain firsthand experience of TimeLoc capabilities, and independently assess Locata’s performance in local and regional RF-based time distribution.

This time distribution demonstration was designed to illustrate how Locata technology could connect to a national timing backbone infrastructure node and then form an OTA timing backbone. This backbone could then distribute time to local clients, as shown in Figure 3.

Typically, time distribution at major nodes, such as metrology labs, relies on a fiber backbone, as proposed by the European Commission in [9]. Figure 4 is a slide extracted from a recent EC JRC presentation to an IEEE Conference, titled “Time Transfer within the proposed EU C-PNT Ecosystem.” It clearly highlights the scale of the planning now taking place for National Timing Backbone networks. Locata believes that, whenever deploying optical fiber infrastructure is impractical, or where timing for wide-area coverage could benefit from radio-based OTA signal broadcasting to complement fiber networks, Locata TimeLoc systems can provide a viable solution.

Locata addresses these needs through an OTA long-range regional/local timing backbone design, using Locata TBase devices optimally installed on existing antenna masts, towers or high buildings. With a Locata OTA wide-area timing backbone in place, time can be distributed to multiple timing clients within the coverage area in a practical and cost-effective manner. These Locata TBase clients would typically be located within several kilometers of the wider-area Locata timing backbone nodes, but designs can vary greatly depending upon available transmit power levels and the frequency plan that can be used for the network.

NMI Test Equipment and Deployment

This Locata time distribution design was demonstrated at NMI using an installation of four Locata TBases, as illustrated in Figure 5. The Locata OTA timing backbone was formed by NMI-1, LIN-1, and NMI-2, while the client functionality was demonstrated using NMI-3.

To assess the timing accuracy of the Locata OTA backbone, NMI-1 and NMI-2 were co-located at the NMI lab, while LIN-1 was installed offsite, approximately 2 km away at an Airbnb apartment in Lindfield (Figure 6). The NMI tests were constrained by only having a 10-day window when the TBase devices were available for the tests, and hence scouting “permanent sites” was not warranted in this instance. Simply hiring an Airbnb apartment to serve as a transceiver site was therefore a practical and expedient decision.

The OTA backbone began with the synchronization of NMI-1 to the NMI UTC reference clock (Microchip 5071A, referred to henceforth as NMI-Clock) that provided 1 PPS and 10 MHz input signals. Additionally, a Microchip SyncServer S650 provided UTC ToD to NMI-1 via an NMEA ZDA message over RS232. The Locata TBase NMI-1 used these input signals for external synchronization to the NMI-Clock.

The transmit/receive antenna for NMI-1 was mounted on the rooftop above the NMI lab (Figure 7) and aligned to point toward the first node of the OTA timing backbone in Lindfield. The first “hop” of the backbone, from the NMI lab to LIN-1, with the antenna initially installed on an outdoor balcony, encountered challenges because trees obstructed the line-of-sight. Consequently, the TBase antenna at LIN-1 was moved indoors, near a window facing the NMI lab, as shown in Figure 8.

From an RF perspective, the line-of-sight between the NMI Lab roof and LIN-1 was suboptimal, with signals attenuated by approximately 8 dB due to transmission through laminated glass, as well as the proximity of trees within the RF signal’s Fresnel zone as clearly shown in Figures 9 and 10.

The second “hop” of the timing backbone was from LIN-1 back to NMI-2 at the NMI lab. Like NMI-1, the transmit/receive antenna for NMI-2 was mounted on the lab roof (Figure 7) and cabled to Locata TBase equipment inside the NMI Lab. The round-trip configuration, with NMI-1 and NMI-2 co-located (Figure 11), allowed synchronization performance accuracy to be evaluated. However, in a practical time distribution network, these TBase nodes can be situated more than 100 km apart.

The timing client, NMI-3, was also located at the NMI lab, with its transmit/receive antenna mounted on the roof (Figure 7). NMI-3 synchronized to the OTA backbone node at LIN-1, approximately 2 km away. Because it was acting as a timing client that could in principle have been placed anywhere within the transmitter coverage area (Figure 6),NMI-3 was configured with a lower-gain patch antenna.

Performance Assessment of Locata OTA Time Distribution 

To evaluate the performance of the Locata OTA time distribution network, Time Interval Counters (TICs) from Keysight (53230A) were employed to measure the differences between time sources. The LocataLite TBase provided outputs including Time-of-Day (ToD) via NMEA ZDA messages, configurable N-PPS (set to 1 PPS), and a 10MHz signal, as shown in Figure 12.

The external time transfer accuracy of the path NMI-Clock  NMI-1  LIN-1  NMI-2 was assessed by connecting the TIC to the 1PPS outputs of NMI-Clock and NMI-2. In contrast, the internal time transfer accuracy for the segment NMI-1  LIN-1  NMI-2 was measured by connecting the TIC to the 1 PPS outputs of NMI-1 and NMI-2.

For the client node NMI-3, the external time transfer accuracy was evaluated by connecting the TIC to the 1 PPS outputs of NMI-Clock and NMI-3.

The test ran continuously for seven days, with the TIC data logged throughout the entire period.

Locata OTA Time Transfer: Distribution Results

Figure 13 presents the time series and statistical summary results of Locata’s external (NMI-Clock to NMI-2) and internal (NMI-1 to NMI-2) time transfer performance for the seven-day OTA backbone test.

For the seven day test span:

• The internal time transfer demonstrated a mean offset of 179 ps and a standard deviation of 28 ps. The time series of TIC differences for the internal transfer showed a stable mean offset with no significant step changes.

• The external time transfer achieved a mean offset of 295 ps and a standard deviation of 119 ps. However, the time series for the external transfer revealed variations in the mean offset, occurring briefly during the seven-day period. These variations were attributed to a bug in the external synchronization process (NMI-Clock to NMI-1), which used 1 PPS, 10 MHz signals and ToD data.

Post-test analysis identified the bug in the external synchronization algorithm, which related to how the 1 PPS and 10 MHz reference inputs were being used. This bug has since been resolved. To illustrate the expected indicative performance, the first three days of measurements were reanalyzed, as shown in Figure 14.

For the first three days, reprocessed with bug removed:

• Internal time transfer: Mean offset of 173 ps, standard deviation of 27 ps, and a peak-to-peak variation of 220 ps. These values were consistent with the seven-day analysis.

• External time transfer: Mean offset of 211 ps, standard deviation of 53 ps, and a peak-to-peak variation of 488 ps, reflecting significant improvement over the seven-day results. Continued R&D efforts are underway to further reduce external synchronization noise.

The external and internal time transfer performance for the timing client NMI-3 was comparable to that of NMI-2 and has therefore been omitted for brevity.

Tropospheric Effects

Tropospheric effects significantly contribute to time transfer errors, as they depend on changing local weather conditions. These effects equate to errors of approximately 300 to 600 ppm (1 ns to 2 ns per km). If tropospheric effects were not accounted for during these tests, they could introduce time errors in the range of 4 to 8 ns.

Locata’s TimeLoc technology with two-way ranging continuously measures signal differences between LocataLites to maintain precise alignment. Changes in tropospheric conditions are reflected in these measurements and are compensated for via real-time link adjustments encoded and broadcast within the Locata ranging signal. This technique does not require meteorological data, GNSS, or total station surveys for backbone node coordinate determination.

Figure 15 illustrates the seven-day internal time series of TIC differences, the TimeLoc link adjustments (zeroed at the start), and meteorological parameters (temperature, pressure, relative humidity, and wind speed) recorded by a nearby meteorological station. The time series shows variations in relative humidity and temperature correlate closely with changes in TimeLoc link adjustments that varied up to 500 ps over the seven days.

Allan Deviation 

Allan deviation (ADEV) is a statistical measure used to evaluate the stability and noise characteristics of a time signal and a key tool in time and frequency metrology. The fractional ADEV was calculated for the seven-day test for both external and internal Locata time transfer and is shown in Figure 16.

The respective ADEV values for Locata Internal and External Time Transfer were 3.4e-16 and 1.2e-15 at 100,000 second averaging time. ADEV values were also calculated for the first three days for a comparison of statistics in the absence of the external synchronization bug. These values were calculated at a common averaging time of 20,000 seconds that was computable over both data sets. The external time transfer for the first three days was 2.4e-15 whereas the seven-day result was higher at 6.3e-15 at 20,000 seconds.

These external time transfer statistics show significant improvement over Locata’s best DEFIS results of 1.1e-14 at 20,000 seconds (as shown in Table 6-8 of [8]), because of the recent R&D improvements in external synchronization. For Locata’s internal time transfer, the ADEV value of 2.4e-15 at 20,000 seconds is consistent with those reported during DEFIS (Table 6-4 of [8]).

Summary

The Locata TimeLoc system represents a transformative advancement in OTA time distribution and synchronization technology. By using proprietary innovations such as TimeLoc, LocataLites and TBase devices, the Locata system delivers sub-nanosecond to picosecond-level time transfer performance OTA, without dependency on GNSS or fiber infrastructure.

The 2022 EU DEFIS A-PNT Test Campaign and the recent 2024 NMI trials demonstrated Locata’s exceptional precision and adaptability across diverse environments, including long-range and urban scenarios with challenging RF conditions.

Locata’s continuous advancements in TimeLoc with two-way radio-based ranging and enhanced time synchronization algorithms have significantly improved timing stability. The system’s ability to mitigate tropospheric effects and address external synchronization challenges brings new and robust performance to the science of time transfer. Metrics from the NMI trials, including Allan deviation statistics, validate Locata’s reliability as both an alternative and complementary solution to fiber-based and other timing technologies.

Locata offers a scalable, cost-effective, and resilient solution for wide-area, radio-based precise time distribution. Locata believes this innovation has the potential to revolutionize the large number of critical infrastructure sectors demanding high-accuracy timing, including telecommunications, finance and defense. It is a superb complement to fiber-based systems, enhancing the industry’s ability to more easily and flexibly distribute sub-nanosecond metrology-grade timing over large urban or geographical areas.

Acknowledgements

We wish to thank the researchers and staff at the National Measurement Institute (NMI) in Sydney, Australia, for reaching out to learn more about our synchronization technology and its application to metrology-grade time transfer. Initial discussions quickly led to test plans, entry to their campus in Lindfield, access to NMI’s UTC atomic clock lab and finally applying their expertise and rigor to analyze and validate the vast quantity of data logged during the tests. Without the enthusiasm and assistance provided by NMI’s Dr. Michael Wouters (Project Leader-Standards for Time and Frequency) and Dr. Robert Williams (Research Scientist, Standards for Time and Frequency), these world-first metrology trials would not have been possible. We also gratefully acknowledge Dr. Wouter’s efforts to review and edit this article before publication. 

References 

(1) Sofranec, D, “Robots Emerge from Stealth–Positioning, navigation and timing (PNT) orbs guide 50-ton robots carrying containers at the Ports of Auckland,” GPSWorld, January 2021. 

(2) Staff, G.W, “Leica and Locata offer solution to the mining puzzle,” GPS World, March 2017. 

(3) Aylor, D., Pick, A., Austin, P., Parry, M., “Safety testing in indoor and challenged environments,” GPSWorld, August 2018. 

(4) Barnes, Joel, Rizos, Chris, Wang, Jinling, Small, David, Gavin Voigt, Gambale Nunzio, “High Precision Indoor and Outdoor Positioning using LocataNet,” Journal of Global Positioning Systems, vol. 2 (2), no. December, pp. 73-82, 2003. 

(5) Rizos, Chris, Kealy, Allison, Li, Binghao, Choudhury, Mazher, Choy, Suelynn, Feng, Yanming, “Locata’s VRay™ Antenna Technology–Multipath Mitigation for Indoor Positioning,” in Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014. 

(6) LaMance, Jimmy, Small, David, “Locata Correlator-Based Beam Forming Antenna Technology for Precise Indoor Positioning and Attitude,” in roceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011. 

(7) Bonenberg, L, Motella, B, Guasch, J.F, “Assessing alternative positioning, navigation and timing technologies for potential deployment in the EU,” Publications Office of the European Union, https://publications.jrc.ec.europa.eu/repository/handle/JRC132737, 2003.

(8) Locata, “Technical Report and Test Plan Locata Corporation Pty Ltd D210 1.5,” Publications Office of the European Union, June 2022.

(9) EC JRC, “Market Consultation on Terrestrial Time Backbone,” Publications Office of the European Union, October 2024.

Authors

Nunzio Gambale is co-founder and CEO of Locata. He is a serial entrepreneur who’s founded three companies. He has been responsible for business development, partnerships and fund raising since he and David Small started to work together to revolutionize PNT.

David Small is co-founder and president of innovation of Locata. He’s invented almost all Locata, TimeLoc and VRay technologies now being successfully sold around the world. He has been granted more than 150 patents for technology he’s invented from scratch. He is technical lead and the driving force of the Locata R&D team.

Joel Barnes is Locata’s director of navigation. He has been at the cutting edge of navigation algorithm design for more than 20 years. He’s designed, tested and implemented all Locata navigation solutions since the very beginning. He has a Ph.D. in GNSS from the University of Newcastle upon Tyne, UK.

Ian Sainsbery is Locata’s director of engineering. He is the architect of core Locata software and is responsible across the board for the millions of lines of code now underpinning Locata’s revolutionary perfomance. He has a Bachelor of Engineering and a Bachelor of Information Technology from the Australian National University, Canberra, Australia.

Clayton Gumbrell is Locata’s manager of hardware development. He spent 20+ years at the forefront of RF and digital design. He is responsible for overseeing design and development of new Locata hardware. He has a Bachelor of Electronic Engineering (Honours), University of Canterbury, New Zealand.

Mustafa Kanli is senior engineer, Locata R&D. He’s been deeply involved in R&D for the design, simulation, testing and constant refinement of Locata’s core timing for many years. He has a Bachelor of Engineering (Computer) and Master of Engineering (Biomedical) from UNSW Sydney, Australia.

Mike Skeen is manager of production at Locata. He has more than 25 years of experience in electronics manufacturing. He is responsible for the design, testing and manufacture of both Locata’s R&D prototype devices, and the products that ship to customers around the world. He has a Bachelor of Engineering (Honours) in Industrial Engineering from from UNSW Sydney, Australia.

The Locata Team: While the above are named authors, the reality is many years of effort have been contributed by the entire Locata team to achieve the milestones reported in these NMI metrology timing tests. Literally every person in the company, in Australia, the U.S. and the EU has contributed in some material way to our collective success. None of this is possible without the efforts of our entire team.

The post Locata: Time Flies…Breakthrough Timing, Over the Air  appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

Synch Industries is working to build a national time distribution network free from GNSS-dependency. They will offer Time as a Service (TaaS) to a wide range of industries, such as telecom, media companies, fintech, data centers and power utilities. The implementation of GNSS-independent time distribution will strengthen national resilience and eliminate reliance on foreign influence in this vital national service. The network will go live in Q1, 2025 and the plan is to expand it further during the year.

“We are thrilled to achieve this technologically advanced network through the collaboration with Net Insight and GDS Technologies and we are excited to see that the project is in its final stages of going commercial,” says Neeren Ramharakh, Founder and CEO of Synch Industries. “In an increasingly interconnected world, the demand for precise, accurate, and secure time has never been more critical. Our commitment to providing a trustworthy source of time lays the foundation for businesses to thrive, enhance their operational efficiency, and forge ahead in the digital age.”

“We are very proud to welcome a new customer in time synchronization, which serves as a strong testament to the relevance and the growing demand for our solution. This milestone opens a new market and creates opportunities in this region,” says Per Lindgren, Group CTO and Head of Synchronization at Net Insight. “We look forward to teaming up with GDS Technologies and Synch Industries to create a network for distribution of national time in South Africa.”

The post Net Insight Wins Order for GNSS-Independent National Time Distribution Network in South Africa appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

This initiative developed in partnership with Timing Solutions, a NovaUCD and ESA BIC Ireland client company, marks a step forward in ensuring secure and reliable Global Navigation Satellite System (GNSS) data, vital for government organizations, public institutions and business sectors including communications, energy, and transportation, public services, financial services and cloud data centers as a source of accurate time.

The VGDS service provides verified GNSS data in the form of Radio Technical Commission for Maritime Services (RTCM) packets via the internet, allowing users to verify their own GNSS data streams.

David Fleming, NSAI Technical Manager for Time and Frequency said, “We are so excited to be launching in Ireland, Europe’s first ever Verified GNSS/GPS Data Stream service. As Ireland’s digital economy continues to grow and more services and public safety aspects are dependent on GNSS/GPS data, the importance of verifiable GNSS/GPS data in Ireland is paramount which made the establishment of this service a key priority for the NSAI NML.”

As Ireland’s national authority for measurement standards, NSAI NML is responsible for creating, maintaining and developing the national measurement standards for physical quantities (e.g. kilogram, second, meter, etc.) and making these standards available to Irish users.

The VGDS service is being delivered by NSAI NML and led by specialist partner Timing Solutions.

Dr Zdenek Chaloupka, Founder, Timing Solutions said, “The Timing Solutions team is delighted to be taking the lead in establishing Ireland as one of the leading countries around the world with respect to the provision of safe GNSS/GPS data and signals thereby improving the resiliency of the Critical Infrastructure sectors.”

By offering a verified stream of GNSS data, the VGDS service mitigates risks like jamming and spoofing, ensuring that users in Ireland and beyond can trust the accuracy and reliability of their location and timing data. This service is particularly critical for Critical Infrastructure sectors, which depend on GNSS for accurate timekeeping, communications, and operational efficiency.

Dr Chaloupka will be presenting this new initiative at the International Time and Sync Forum (ITSF 2024), the world’s largest timing and sync event, gathering in Seville in November 2024.

The post Ireland National Metrology Laboratory Launches Verified GNSS Data Stream Service appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

In April, 2 of the remaining G1 satellites were launched via SpaceX’s Falcon 9 launcher.

See in-depth reporting by Inside GNSS European Editor, Peter Gutierrez regarding the technology challenges which led to ESA utilizing SpaceX in April. The launch of Ariane 6 sets the stage for the scheduled 2026 deployment of the G2 satellites, utilizing ESA’s launcher.

This inaugural flight, designated VA262, is a demonstration flight with the goal of testing the capabilities of Ariane 6 in escaping Earth’s gravity and operating in space. It had several passengers on board. The next Ariane 6 is planned for launch this year on its first commercial flight under Arianespace as operator and launch service provider. “The success of this first flight marks the start of Ariane 6’s operational career, giving Europe an autonomous access to space,” added Stéphane Israël, CEO of Arianespace.

“A completely new rocket is not launched often, and success is far from guaranteed. I am privileged to have witnessed this historic moment when Europe’s new generation of the Ariane family lifted off – successfully – effectively reinstating European access to space,” said ESA’s Director General Josef Aschbacher.

The post Ariane 6 Launches: Impacts for Galileo G2 appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

The Iridium STL service, capable of operating globally, is designed to ensure the fidelity of timing systems with a signal 1,000 times more powerful than GPS. This makes it particularly suited for indoor use without the need for rooftop antennas, offering a secure and cost-effective solution for sectors such as transportation, energy grids, data centers, telecommunications networks, and financial services.

Market Demand and Expansion

The expansion follows a significant rise in GPS jamming and spoofing activities in Europe and parts of Asia, posing serious threats to critical infrastructure. The newly available STL service will be marketed by Iridium’s partners in these regions, helping to safeguard essential systems and improve operational security and efficiency.

“We’re cognizant of the threats facing GNSS-reliant critical infrastructure around the world and our responsibility to deploy the antidote as quickly as possible,” said Matt Desch, CEO of Iridium. He emphasized the importance of expanding market availability for the STL service, particularly following Iridium’s acquisition of Satelles.

The STL solutions are designed to be small, cost-effective, and easy to install, with technology partners increasing their focus on the new markets. These solutions can be integrated into existing GNSS-reliant systems or used as stand-alone units.

Global Reach and Future Plans

With the expanded authorization, Iridium STL can now be purchased by companies in North America, parts of Europe, and the Asia Pacific region. The company plans to continue scaling and training sales and support staff to further extend the service’s global reach.

Iridium’s commitment to enhancing PNT solutions demonstrates its proactive approach to addressing emerging threats and supporting critical infrastructure worldwide. Further expansions are anticipated as demand continues to grow.

The post Iridium Expands Satellite Time and Location Service to Europe and Asia Pacific appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.