Navigating testing options: Simulator innovators map out solutions and trends

The number of GNSS signals, the frequency and sophistication of intentional and unintentional threats to those signals, and the need for integration between GNSS and other positioning, navigation and timing (PNT) sources — especially for indoor and autonomous navigation — are continuing to increase, as is the number of new applications for GNSS. In response, manufacturers of GNSS simulators are creating new and improved models able to simulate all these new signals and scenarios.

Additionally, as GNSS chipsets continue to be further commoditized, simulator manufacturers must address the needs of new entrants into the GNSS receiver market that have lower accuracy requirements and require less technical expertise and, therefore, require units that are smaller and cheaper and have simpler interfaces.

No single manufacturer can address the full spectrum of challenges that these trends present. So, while their products overlap in capabilities and SWaP-C (size, weight, power and cost), each one has chosen its market niche and preferred mix of features.
Even on the deceptively simple question of definition (“What is a GNSS simulator?”), the seven manufacturers featured here give different answers, covering the following capabilities:

• Simulating GNSS signals as well as inertial navigation data.
• Enabling users to test hardware, software and new solutions in the lab before deployment.
• Enabling users to test systems under pristine or extreme conditions, including error conditions.
• Enabling users to test systems during rare, transitional and prohibited events.
• Helping to retrofit existing equipment to new and emerging standards.

Innovations being introduced or developed include:

• an anechoic simulator to test continuous radiation pattern antennas (CRPAs).
• simulation of a full M-code modernized signal.
• software-defined simulators.
• increased automation of repetitive tasks.
• the capability to record and replay real-world signals.
• the capability to record and synchronize data on the conditions faced by a test vehicle.

While the universe of GNSS satellites and receivers continues to grow and evolve, the universe of GNSS simulators is keeping pace — or even a step ahead.

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CAST Navigation

In the lab, simulators allow users to “drive” a piece of equipment through 3D space, performing flight testing or checking equipment integration. Simulators also validate operational flight programs (OFPs) for pilots before they are fielded, to ensure that the software is working correctly.

Innovation. CAST’s latest simulator is the CAST 5000 wavefront generator. It allows users to drive GNSS and interference signals that represent a continuous radiation pattern antenna (CRPA), which consists of multiple, smaller antennas all combined into one unit. In real life, each one of those antenna elements is in a different location; therefore, when they receive signals from a jammer or any of the GNSS satellites, each one will see that signal in a slightly different phase from the other elements. “Our simulator allows us to present signals to these antennas that model the same type of phase differentiation that you see in real life,” Clark said.

Coming Next. CAST Navigation is constantly improving its software based on user feedback. “We are in the process of enhancing our user interface to make it much more powerful but also much simpler to use,” Clark said. Hardware is also being improved, with implementation of the latest available GNSS always on the list.

Looking Ahead to 2022. Jamming and spoofing are becoming more prevalent, not just for the military but also for consumers. Consumers are starting to encounter more instances of jamming, denying their phone the ability to track a GPS satellite or transmitting incorrect GPS data so the solution that their device gives them is not correct. “Our focus is on products and capabilities that help our customers simulate those types of environments and mitigate those kinds of reactions,” Clark said.

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Jackson Labs Technologies Inc.

Jackson Labs’ simulators take a position, navigation or timing signal, re-encode it into an RF signal through a GPS simulation procedure, and output a real-time RF signal that encodes the position, navigation and timing (PNT) information, within milliseconds, into an RF signal that can be fed into existing equipment. “We came up with a general-purpose simulator that is basically a no-frills, low-cost, highly accurate, highly stable, highly reliable, extremely small GPS-only simulator,” explained Jackson. “We only provide GPS L1 simulation, to keep the cost of the product down, because GPS L1 C/A code is the only code required to generate an accurate and assured PNT fix, and because we are looking at simulating to embedded systems, where you only need an L1 C/A code simulator.”

Coming Next. Jackson Labs’ simulators don’t require an external computer for data processing or control. That makes it possible for companies like Toyota to plug the unit into a car on the assembly line, and generate RF output that is fed into their GPS-based navigation systems to pass final quality-assurance checks on the production line. Jackson Labs expects to further reduce SWaP-C (size, weight, power and cost) requirements and potentially add other signals. “We are also looking to potentially combine our simulators with other product lines that we have, such as our comprehensive atomic clock product line,” Jackson said.

Looking Ahead to 2022. Jackson predicts that the sector will split into two paths: an industrial sector with units for manufacturing and deployment, and companies that introduce emerging GNSS systems at much lower price points, smaller SWaP, and with more modular deployment. Inertial navigation systems (INS) are critical for autonomous driving and assured capabilities during spoofing and jamming events, Jackson said. “It is not possible today to very easily simulate INS units.There is a market for innovation in terms of integrating what the military calls ‘assured PNT,’ which includes things like dual navigation.”

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Orolia

According to Orolia’s Hamel, a simulator’s purpose is two-fold: first, it must reproduce threats and second, it must prove the solution is working.

Innovation. When Skydel Solutions joined Orolia in March, it brought a professional software-defined simulator that makes possible fast prototyping and development cycles. It integrates advanced interference simulation and can simulate hundreds of threats simultaneously. “When you want to do a repetitive step, automation is the key,” Hamel said. “Our simulator can teach you how to automate, just by clicking on a button and generating source code.” In 2018, Skydel introduced an anechoic simulator to test Controlled reception pattern antennas (CRPAs). Also new is a waveform simulator, so CRPA units can be tested in a conducted (rather than radiated) way.

Coming Next. In the next three years, Orolia is looking at adding Galileo PRS, GPS M-code, or the next-generation signal. “Being software-defined means that we are very flexible and we can allow our partners to develop their own plug-ins,” Hamel said. “They can build custom signals, restricted or modernized signals. Our simulator will take care of the dynamics of the signal and our partners can focus on the characteristics of the signal, or the things that are secret, classified, or if they simply want to protect their IP.”

Looking Ahead to 2022. Resilience to serious spoofing and jamming threats is high on Orolia’s list, as well as ensuring secure or valid positioning, navigation and timing (PNT) in GPS-denied environments. Alternative signals, sensors and increased complexity require a simulator to address all of these. Companies that develop complex proprietary hardware platforms will be challenged to keep up with the increasing complexity. and a software-defined approach will be an advantage.

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Racelogic

Racelogic’s first LabSat was a recorder with player — the signals were recorded outside, and then replayed in the lab. Racelogic’s simulators now also provide simulation of the signals using software to generate the signals as though they are being sent by the satellites.

Innovation. In 2018, Racelogic introduced the LabSat wideband, which uses the company’s SatGen software. It records at 56 MHz and up to 6 bits of resolution and streams the data to an internal SSD hard drive. It can also replay real-world simulations or ones generated with SatGen. For the automotive world, it records and replays signals such as CAN, RS232, RS485, IMU and other data channels, synchronizing them at the same time. VBOX allows users to record and replay video with the perfectly synchronized recording made on the LabSat. “You see exactly the kinds of conditions of the test vehicle or person who has been subjected to the test,” Thomas said.

Coming Next. Racelogic is providing wider bandwidth, greater bit depth, and multiple channels in a small battery-powered device that records even more signals, including lidar, EtherCAT (an automotive Ethernet format) and CAN-FD (a faster version of the CAN format). It will be able to synchronize with multiple video cameras instead of just one in high resolution. “It is basically the same as what we are selling, but on steroids, and at a very similar price point,” Thomas said.

Looking Ahead to 2022. With multi-GNSS going mainstream, both chip manufacturers and simulator manufacturers will be challenged by the cost of test equipment. Chip makers need to be able to test the new signals on their production lines, while simulator makers will need to provide devices at a price point and ease of use for customers with less stringent or slightly less technical requirements. “They need a simpler interface and a smaller, cheaper unit,” Thomas said.

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Rohde & Schwarz

An increasing number of GNSS applications depend on multi-frequency GNSS.

Innovation. In response, Rohde & Schwarz added multi-frequency test capabilities to its entry-level and mid-range test solutions. “We have launched a new GNSS simulator based on the new mid-range vector signal generator R&S SMBV100B,” Irsigler said. A simple and flexible option concept allows users to turn the instrument into a full-featured and powerful GNSS signal source. It addresses a wide range of test applications, from single- and multi-frequency production testing to multi-frequency receiver characterization. The instrument can be equipped with an internal noise generator that allows users to simulate GNSS plus noise or CW interference without using additional external hardware.

Coming Next. GNSS test solutions from R&S are based on general-purpose vector signal generators. With this approach, GNSS and other signals can be generated at the same time in the same instrument allowing coexistence and interference testing without additional external signal sources. As this results in test solutions that are compact and very flexible to use, R&S will continue to use this approach for upcoming product upgrades and enhancements as well as for its next generation of GNSS test solutions. The company’s upcoming activities will mainly focus on the high-end segment, where the R&S SMW200A with up to 4 RF outputs and up to 144 channels addresses multi-antenna and multi-vehicle GNSS test applications.

Looking Ahead to 2022. With the safety demands of autonomous driving or aircraft landing procedures, multi-frequency testing will become standard. Because such applications must be sufficiently robust against spoofing and jamming threats, there will be an increasing need to test navigation systems against such influences. “Simulating GNSS alone is not enough,” Irsigler said. “Test solutions for autonomous driving will require several other techniques and signals to be applied or simulated, such as RTK/PPP or outputs from other vehicle sensors to perform sensor fusion.”

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Spirent Federal Systems

Spirent’s simulators test with “real-world” signals as well as allowing tests under pristine conditions or under extreme conditions that may never occur in the real world, including error conditions.

Innovation. In December 2018, Spirent released the SimMNSA, which provides a full M-code modernized signal solution. Until now, the GPS Directorate limited M-code simulation to either pseudo-M-code, which provides the same spread-spectrum but uses a commercial encryption standard, or a system of playing back a canned set of M-code limited to certain satellites and dates and times. With the policy change, Spirent can now implement M-code based on the modernized Navstar security algorithm (MNSA), and now offers both an M-code solution with the SimMNSA and a full Y-code with the SimSAAS.

Coming Next. Spirent plans to provide customers an increased channel count to help test multi-constellation, multi-frequency receivers against multipath, jamming and spoofing. “We are in a period of intense development in terms of AVs, UAVs, and so forth, which don’t use GNSS exclusively,” Hart said, explaining that Spirent is working on testing of GNSS/sensor-fusion platforms.

Looking Ahead to 2022. “As new interface specifications are released, we are proactive in developing new signals,” Hart said. Spirent also is supporting efforts to achieve assured PNT solutions. It is investigating interference-mitigation techniques such as algorithms, directional antennas, and other anti-jam technologies. Signal authentication is another need. “As the systems are becoming more integrated and networked, we are conscious of cyber-security threats and are looking in that area,” Hart said.

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Syntony GNSS

GNSS receiver manufacturers use simulators to ensure that their products are robust in challenging situations that can’t be clearly assessed using real-world data. “That’s where the GNSS simulator comes into play,” Gernot said, “by offering controlled and repeatable scenarios.”

Innovation. Syntony’s new pseudo-random-noise code (PRN code) server allows the GNSS simulator user to dynamically send the pseudo-random sequence modulating a carrier. It is especially useful for testing encrypted signals such as the GPS military signal or the IRNSS RS signal. “Access to encryption keys is extremely difficult for a simulator manufacturer to obtain,” Gernot said. “However, the simulator does not actually need to have knowledge of those encryption keys; only the resulting pseudo-random sequence to modulate is required.” The Syntony PRN server allows users to dynamically input their own pseudo-random sequences to be modulated on the target carrier into the simulator.

Coming Next. Syntony’s next simulator will simulate spoofing and synchronous multi-antenna signals for CRPA and antenna network testing.

Looking Ahead to 2022. As the threat of spoofing and jamming increases, the receiver industry will have to develop countermeasures and mitigation strategies. One of the best methods remains the use of antenna arrays, Gernot said. “Antenna arrays allow for spatial discrimination that is especially efficient to counter spoofing, jamming or unintentional interferences.To meet the industry’s future demands, Syntony is already working on accurate simulation of antenna arrays while accounting for inherent errors such as inter-antenna phase and amplitude offsets and overcoming obstacles, including phase coherency at the output of the simulator RF channels.”