Q: Why do we need to take integrity seriously in the vehicle environment?
Chris Rizos, Professor, Geodesy and Navigation, University of New South Wales
A: Since the 1980s, surveyors and geodesists have used GPS for high-accuracy positioning. We take for granted centimeter- and even millimeter-level accuracy positioning capability that is faster, more reliable, at a lower cost and with fewer constraints than ever before. However, the demand for “trustworthy positioning” dismisses such achievements, and the mantra is more “availability” and greater “integrity” to support highly automated driving. Our positioning and navigation community must rise to this challenge.
Rod Bryant, Senior Director, Technology, Positioning, u-blox
A: In autonomous vehicles, a GNSS/inertial module will be just one of several sensors used for location. The risk of contributing to accidents and serious injury will be decomposed and allocated between subsystems by the OEM or system designer. Taking aviation as a model, the allocation to GNSS may be in the form of an alarm limit of a few meters with integrity risk less than 10-6/hour. However, multipath and obstructed sky make automotive risk far more difficult than aviation. Carrier-phase techniques will come into play and new approaches to protection limit estimation will be needed.
Sam Pullen, Senior Research Engineer, Stanford University; Consultant, Sam Pullen Consulting
A: Advanced sensor fusion techniques now make it possible to achieve very accurate PVT results by combining multiple dissimilar sensors. Once we rely on these capabilities for autonomous driving, the primary threat to safety will come from confluences of rare events that were not observed or foreseen during system development. Design for integrity focuses attention on the identification and mitigation of potentially hazardous anomalies before they happen, not afterward.
A strategic alliance announced on Dec. 15 between Orolia and Satelles includes product development and go-to-market activities of positioning, navigation and timing (PNT) solutions provided by the Iridium satellite constellation, independent of GPS/GNSS signals. The companies intend to provide PNT solutions to military, defense, government and commercial customers worldwide.
Orolia, the parent of GNSS-active companies Spectracom and Spectratime, among others, has formed a strategic alliance, including an equity investment, with Satelles Inc. to develop, market and sell PNT solutions based on Satelles’ satellite time and location (STL) signal technology.
STL is a unique space-based PNT technology that provides location and timing data independent from traditional GPS and other GNSS satellite signals. By using STL, Orolia’s Spectracom and McMurdo solutions will, according to the company, be less susceptible to vulnerabilities such as spoofing, interference and jamming that are associated with GPS/GNSS.
Based on the low-Earth orbit (LEO) Iridium satellite constellation, STL signals are up to 1,000 times stronger than GPS/GNSS; this signal strength, due in part to the constellation’s closer proximity to users, helps to prevent jamming and enables signal reach into buildings and other difficult locations. STL’s additional cryptographic security also ensures performance, productivity and security.
For further background on Iridium, see GPS World’s June 2016 Defense PNT column, “Iridium and GPS revisited: A new PNT solution on the horizon?” Projected applications and use cases include energy/utility grids, enterprise data networks including financial systems, maritime/aviation navigation, fleet/asset tracking management, search and rescue, and data center management.
Many highly sensitive military, defense, government and commercial applications and operations require accurate and reliable PNT data. Today, these applications rely on signals from GPS/GNSS satellites. There are instances, however, where GPS/GNSS signal strength and security are not sufficient and prone to signal disruption. For these cases, the companies jointly state, STL can be used as a secure signal of opportunity to complement GPS/GNSS, making the applications more accurate and secure, and less prone to interference and attack.
“There is a growing need for precise and robust positioning, navigation and timing information especially in business-critical, high-risk and life-saving operations,” said Jean-Yves Courtois, Orolia CEO. “By augmenting Orolia’s GPS/GNSS-based solutions with Satelles’ STL technology, we will have the industry’s first essentially fail-safe, resilient PNT solution. This breakthrough offering will be ideal for mission-critical applications in which the smallest discrepancy in PNT data accuracy, availability and stability can produce a network outage, a system crash or a loss of life.”
Signal strength, availability
The technical advantages provided by adding ranging satellites in low-Earth orbit (LEO) to the GNSS satellites in medium-Earth orbit (MEO) were explored in a 2012 Institute of Navigation paper by Per Enge, Bert Ferrell, David Whelan, Greg Gutt and David Lawrence. GPS World plans to publish an updated version of that paper, with key new material on current STL performance statistics, in an upcoming issue.
Briefly, the paper concluded that “Due to their proximity, signals received from LEO are approximately 30 dB stronger than the signals from MEO. Indeed, we show data collected inside an industrial-strength metal storage container. The power of a LEO signal received inside the container is approximately equal to the power of a GPS signal received under the open sky. On the other hand, LEO proximity also dictates that only a few Iridium satellites are in view of the ground-based user. We show typical examples where six to 11 GPS satellites are joined by one or two LEO satellites.”
The authors then examine the effect of the swift mean motion of LEO satellites, analyzing the ability to whiten multipath based on the rapid motion of the line-of-sight vectors from the user to the LEO satellites. In sharp contrast to MEO, the LEO satellites attenuate errors due to multipath solely based on satellite motion, and do not require user motion. They also analyze Doppler-based positioningvusing the rapid mean motion of the LEO satellites. The Doppler shift projects onto the line-of-sight vectors from the user to the LEO satellites. Over 100 or 200 seconds, this projection is a sharp function of the user location, and this connection enables Doppler-based positioning similar to the Transit satellite system. The authors’ analysis shows that position accuracies of 5 meters can be based on noncoherent code tracking of the LEO plus GPS signals.
This paper also discusses the broadcast of UTC time to sites with known locations, describing experimental results with absolute time accuracies of one microsecond. The broadcast of high-accuracy frequency from LEO would enable a high-accuracy hot clock to replace the relatively low-quality oscillator in GNSS receivers, allowing longer coherent and non-coherent averaging times and improving the sensitivity of GNSS receivers by several decibels. Many other navigation applications would benefit from one LEO satellite in view, the authors assert.
Market view from operator’s CEO
“We are a manufacturer and integrator of timing equipment,” Orolia CEO Jean-Yves Courtois told GPS World. Orolia is the parent company of GPS/GNSS product and service providers Spectracom, McMurdo and Spectratime. “This new STL service is not fully commercialized yet, but it’s operational and it can be tested. Receivers are available and can be integrated into our equipment.
“The timing signal is very accurate and close enough to GPS for most timing applications, although the positioning accuracy is lower than what GPS users are accustomed to. It is an augmentation for timing primarily, and secondarily for positioning,” Courtois continued.
“In terms of timing accuracy, it provides on the order of tenths of microseconds in accuracy, and this covers a lot of timing applications. This is an ideal timing backup or augmentation of GPS. In positioning it’s closer to 50 meters or more, much better for fixed objects than for mobile objects. The faster the vehicle, the lower the positioning accuracy. It’s not directly usable for GPS applications that require a few meters’ accuracy, but it can be associated with inertial navigation for much better results.
“The STL signal penetrates buildings well, it has unique features, and it performs at a high level. The signal is encrypted, so you have to subscribe to a service to receive a key, allowing access to the signal. Applications are developing based on equipment that will be STL-enabled. For the user it will be transparent. The user will have a different antenna.
“We are also active in tracking and emergency location devices, where this is also of interest. It has some authentication capability, to guarantee that the person who accesses the signal is in the location that he pretends to be.
“For customers to be able to use this service, there is some integration work to be done, some dedicated STL receivers to integrate into our current hardware set up, and software modifications. We are ready to work with government and defense organizations and other new clients. Our basic interest is to add some robustness to our equipment for our current customers, and then of course to develop new customers worldwide.”
Grab It’n’Go Drive-By Shopping
Four years ago, retail giant Amazon, a leader in the elimination of human interaction, started to explore what shopping would look like if you could walk into a store, grab what you want, and leave. In early December, the company rolled out its new vision: Amazon Go.
Currently in private beta testing in Seattle and scheduled to open to the public in early 2017, the system employs a fusion of sensor technologies including RFID to detect when a shopper takes an item from the shelf, sync the data to the shopper’s handheld device, sense when the shopper leaves the store area, then charge all collected items to the shopper’s Amazon account. No muss, no fuss.
The company is keeping a tight lid on exactly how its system works, but earlier patent filings give some description of the confluence of sensor data.
“In some implementations, data from other input devices may be used to assist in determining the identity of items picked and/or placed in inventory locations. For example, if it is determined that an item is placed into an inventory location, in addition to image analysis, a weight of the item may be determined based on data received from a scale, pressure sensor, load cell, etc., located at the inventory location. … By combining multiple inputs, a higher confidence score can be generated increasing the probability that the identified item matches the item actually picked from the inventory location and/or placed at the inventory location.”
The U.S. Defense Advanced Research Projects Agency (DARPA) has awarded HRL Laboratories LLC $4.3 million to develop vibration- and shock-tolerant inertial sensor technology that enables future system accuracy needs without using GPS.
Positioning, navigation and timing are key to ensuring the location accuracy critical to the success of modern military missions. Today’s military systems typically rely on GPS to ensure position accuracy. While GPS provides sub-meter accuracy in optimal conditions, the signal is often lost or degraded due to natural interference or malicious jamming.
“The ATLAS project will deliver a comprehensive approach to breaking performance and cost, size, weight and power barriers in inertial sensor technology that prevent robust, GPS-independent, military positioning, navigation and guidance,” said Logan Sorenson, principal investigator and research staff member in HRL’s Sensors and Materials Laboratory.
ATLAS will combine intimate locking of a micro-electro-mechanical systems (MEMS) Coriolis Vibratory Gyroscope (CVG) sensor with an atomically stable frequency reference in order to exploit the intrinsic accuracy of the atomic hyperfine transition frequency.
“The engineering challenge lies in developing a system architecture to transfer the stability from the atomic reference to the CVG sensor without introducing unintended noise,” Sorenson said. “We are very excited to explore this novel approach to addressing long-standing precision navigation need faced by the U.S. military.”
HRL Laboratories is located in Malibu, California. It is a corporate research-and-development laboratory owned by The Boeing Company and General Motors specializing in research into sensors and materials, information and systems sciences, applied electromagnetics, and microelectronics. HRL provides custom research and development and performs additional R&D contract services for its LLC member companies, the U.S. government, and other commercial companies.
It has been a good year for all global navigation satellite systems (GNSS), as the chief executives of each system testify here. Alternative positioning, navigation and timing (PNT) also thrives. In this roundup of the latest highlights from the past year and forecasts for the future, 2017 augurs very well indeed! Let’s look at the newest alternative-PNT offerings first, followed by forecasts from the chief executive officers (CEOs) of each of the conventional GNSS.
Alternative PNT grows and expands
Two new entrants to the positioning, navigation and timing (PNT) marketplace offer key capabilities to fill in the gaps left by GNSS. A new satellite timing and location (STL) service from low-Earth orbit satellites, provided by Satelles and Orolia, gives a strong signal capable of penetrating buildings.
Satellite Time and Location (STL) Service. Pursuant to a recent announcement of new PNT solutions independent of GPS/GNSS signals, provided via the Iridium constellation, GPS World talked with Jean-Yves Courtois, CEO of Orolia. Orolia has partnered with Satelles to bring new PNT products and services to the global market, with a focus on military, and defense, government and commercial customers worldwide.
Jean-Yves Courtois, CEO of Orolia.
“We are a manufacturer and integrator of timing equipment,” Courtois said. Orolia is the parent company of GPS/GNSS product and service providers Spectracom, McMurdo and Spectratime. “This new STL service is not fully commercialized yet, but it’s operational and it can be tested. Receivers are available and can be integrated into our equipment.
“The timing signal is very accurate and close enough to GPS for most timing applications, although the positioning accuracy is lower than what GPS users are used to. It is an augmentation for timing primarily, and secondarily for positioning.
“In terms of timing accuracy, it provides on the order of tenths of microseconds in accuracy, and this covers a lot of timing applications, very familiar to us and to our customers. This is an ideal timing backup or augmentation of GPS. As number 2 worldwide in high-precision timing, we know this market and its applications very well.”
Correlator beamforming. The Locata Corporation announced a patented correlator beamforming technology to stem multipath mitigation. The new technique’s performance under rigorous testing by the U.S. Air Force Institute of Technology will be detailed in the January 2017 issue. Look for it! Here are a series of snippets as a preview of that lengthy technical article appearing in Richard Langley’s Innovation column.
“Unlike conventional or traditional beamsteering technology, the new correlator beamforming approach combines RF signals received by any number of individual antenna elements into a single switched-RF signal. This time-multiplexed signal is then downconverted and digitized by a single RF front-end. The correlator beamforming design will should offer cost savings because the resulting data stream is processed using a single correlator channel per beam. This markedly reduces the complexity when compared to the traditional beamsteering methodology.
“The correlator beamforming technique performs antenna array signal processing to form beams as part of a receiver’s correlation process. The complete explanation of this technology can quickly get complex, even for the seasoned RF engineer. To describe this process more simply, we will assume noiseless signals and no multipath (except as noted), as well as equal noise figures for all front-end processing chains. To further simplify our explanation, modulation on the carrier and switching losses will be ignored.”
“To evaluate the performance of correlator beamforming as fairly as possible compared to traditional beamsteering and single-element processing, AFIT set up its data collection such that all three approaches could be implemented in a software receiver. Additionally, a seven-element Naval Air Systems Command GPS Antenna System 1 (GAS-1) antenna was used for this experiment. The antenna was mounted on a 51-inch (130-centimeter) diameter rolled-edge ground plane provided to the ANT Center by the MITRE Corporation.”
“The testing focused on demonstrating an easily modified GNSS receiver to potentially deliver a low-cost solution for mitigating multipath — specifically targeting short delay and carrier multipath. The results presented here show that the multipath rejection performance nearly equals that of a traditional beamsteering GNSS receiver. Applications that can significantly benefit from this technology include stationary GNSS monitoring installations such as those used in satellite-based and ground-based augmentation systems and GNSS receivers for autonomous vehicles and UAVs in high multipath areas such as urban canyons.”
GPS III ready, steady
Col. Steve Whitney, Director, U.S. Air Force GPS Directorate
“The [GPS III] program is working to solve several technical challenges as we progress to completion,” Col. Steve Whitney, director of the U.S. Air Force GPS Directorate, wrote in GPS World’s December issue. “SV-01 testing uncovered electro-magnetic interference between a payload component and a hosted payload. Testing also uncovered electron impact issues on the L-band antenna elements. In partnership with Lockheed Martin, the program developed corrective action and design mitigations for both of these issues and is implementing these steps within our production flow for all the SVs.”
“In the coming year, SV-02, the second GPS III satellite, will also be progressing towards completing production. Currently, all of the SV-02 sub-assemblies have been received by Lockheed Martin and are being integrated into the spacecraft. The next major step in the production flow for SV-02 will be to mate it with its propulsion core.
“Recently, we completed negotiations with Lockheed Martin to extend the production line with purchases of SV-09 and SV-10. These satellites will be technically equivalent to SV-01 through SV-08. This $395 million purchase of two satellites marks a significant affordability milestone for the procurement of GPS III satellites.
“Looking ahead, we are analyzing how to acquire satellites beyond SV-10. We are executing a phased strategy which starts first with determining the viability of a GPS III production design existing beyond the current contractor. We awarded an initial phase of contracts to the Boeing Company, Lockheed Martin Space Systems Company, and Northrop Grumman Aerospace Systems in May 2016 to provide a feasibility assessment of the readiness of their satellites designs. In this phase, the contractors will provide a GPS III production design, manufacturing plans and a navigation payload brassboard test report, along with manufacturing/production processes and facilities maturity.”
Galileo coming on strong
Director of the Galileo Programme Paul Verhoef of the European Commission wrote in that same issue of the magazine, “The production of the satellites continues to maintain a steady rhythm, with a production line stretching from suppliers across Europe to OHB and SSTL and then to ESA’s ESTEC Test Centre in the Netherlands for acceptance testing, based on a wide range of simulated space tests.”
Paul Verhoef, director of the Galileo Programme and Navigation-related Activities, European Space Agency.
“The acceptance of the next satellites to launch is scheduled for this year’s end,” continued Verhoef. “Along with the two more Ariane 5 launches to come — one in the second half of 2017 and another in 2018 — the current plan is to commission further launch services as well as additional satellites in order to have Galileo fully operational by 2020. For these launches, Galileo may be the first customer of the new Ariane-6 launch vehicle.
“2017 will see the upgrade of various elements of the Galileo Ground Segment to reinforce its robustness, including updated releases to the Galileo Control Segment overseeing the satellites and the Galileo Mission Segment, overseeing the navigation signals. A new release of elements of the Galileo Security Facility, for security monitoring of the system, as well as the secure Public Regulated Service, will be deployed at the two Galileo Security Monitoring Centres.
“The Galileo Ground Segment will gain a sixth tracking telemetry and control facility, for monitoring the satellite platforms in Papeete, Tahiti, and additional processing chains for increased redundancy will be deployed across the Uplink Stations in Kourou, Reunion and Noumea used to update the navigation message information. Similar redundant chains will be finalized for all 15 current Galileo Sensor Stations, which perform continuous collection of Galileo signals to identify the tiniest clock error or satellite drift.”
EGNOS. “Along with the progress of Galileo, contracts are planned to cater for the further development of the ESA-designed European Geostationary Navigation Overlay Service, Europe’s first navigation system. EGNOS was certified for safety-of-life aviation use in 2011, and is managed by the European Commission through a contract with operator the European Satellite Services Provider, based in France. ESA will support the technical evolution of EGNOS version 3, intended as multi-constellation in nature, again through the Horizon 2020 framework.”
GLONASS looks forward to a new signal: CDMA!
Sergey Karutin, GLONASS Chief Designer, wrote “On the threshold of the first GLONASS-K2 launch, new GLONASS reference documents were published in October 2016, describing the family of code-division multiple-access (CDMA) radionavigation signals. The draft GLONASS Open Service Performance Standard has been developed. The GLONASS User Information Support System continues to evolve.”
From left: Sergey Karutin, GLONASS designer general; Nicolay Testoedov, director general, SC Information Satellite Systems; and Andrey Tulin, director general, SC Russian Space Systems.
“The system transmitting CDMA navigation signals is referred to in four interrelated interface control documents containing general information on signals and the detailed description of signal structures and digital message data. The new signals make it possible to include 63 satellites in the constellation, not only in circular medium-Earth orbit but also on geostationary and high-Earth orbits.
“The transition to the flexible string-type structure of the message data produces 2-second periodicity of integrity information delivery to users. The increased number of digits occupied by the ephemeris and clock parameters contributes to a better orbit and clock broadcast accuracy. The ephemeris broadcast precision improves from 0.4 to 0.001 meters. Time-stamp length in CDMA signal has increased to 30 bits, compared to 12 bits of frequency-division multiple-access signals.”
BeiDou approaches full regional services
Li Wang
“In 2017, three to four launches of BeiDou satellites will occur,” wrote Li Wang, Director of the International Cooperation Center in China’s Satellite Navigation Office. “BDS will provide basic services to the countries along the Belt and Road region by 2018, and possess global service capability by 2020.”
“BDS will keep improving its nationwide reference station network and steadily enhance its service performance. The dense reference stations for the nationwide frame network will be constructed by 2018, providing meter and decimeter level real-time location services for users in China, even centimeter level service in some areas.
“BDS will carry out the design, validation and construction of SBAS in accordance with international civil aviation standards. The first GEO satellite of BDSBAS will be launched in around 2018. The satellite-based augmentation services covering China and surrounding regions will be provided from 2020, to provide CAT-I services to civil aviation users.
“China will promote construction of a national comprehensive positioning, navigation and timing (PNT) system based on BDS, and strive to establish such a national PNT system with a united benchmark, no-gap coverage, security and effectiveness by 2030, as well as to upgrade capabilities to provide time and space information.”
A strategic alliance announced on Dec. 15 between Orolia and Satelles includes product development and go-to-market activities of positioning, navigation and timing (PNT) solutions provided by the Iridium satellite constellation, independent of GPS/GNSS signals. The companies intend to provide PNT solutions to military, defense, government and commercial customers worldwide.
Orolia, the parent of GNSS-active companies Spectracom and Spectratime, among others, announced that it has formed a strategic alliance, including an equity investment with Satelles Inc. to develop, market and sell PNT solutions based on Satelles’ satellite time and location (STL) signal technology. STL is a unique space-based PNT technology that provides location and timing data independent from traditional GPS and other GNSS satellite signals. By using STL, Orolia’s Spectracom and McMurdo solutions will, according to the company, be less susceptible to vulnerabilities such as spoofing, interference and jamming that are associated with GPS/GNSS.
Iridium satellite, courtesy Iridium.
Based on the low-Earth orbit (LEO) Iridium satellite constellation, STL signals are up to 1,000 times stronger than GPS/GNSS; this signal strength, due in part to the constellation’s closer proximity to users, helps to prevent jamming and enables signal reach into buildings and other difficult locations. STL’s additional cryptographic security also ensures performance, productivity and security.
Projected key applications and use cases include energy/utility grids, enterprise data networks including financial systems, maritime/aviation navigation, fleet/asset tracking management, search and rescue and data center management. Further details on planned projects and products of the Orolia-Satelles partnership will be posted to this site in a follow-up story in coming days.
Many highly sensitive military, defense, government and commercial applications and operations require accurate and reliable PNT data. Today, these applications rely on signals from GPS/GNSS satellites. There are instances, however, where GPS/GNSS signal strength and security are not sufficient and prone to signal disruption. For these cases, the companies jointly state, STL can be used as a secure signal of opportunity to complement GPS/GNSS, making the applications more accurate and secure and less prone to interference and attack.
“In today’s increasingly dynamic and mobile world, there is a growing need for precise and robust positioning, navigation and timing information especially in business-critical, high risk and life-saving operations,” said Jean-Yves Courtois, Orolia CEO. “By augmenting Orolia’s market-leading GPS/GNSS-based solutions with Satelles’ STL technology, we will have the industry’s first essentially fail-safe, resilient PNT solution. This breakthrough offering will be ideal for mission critical applications in which the smallest of discrepancies in PNT data accuracy, availability and stability can result in a network outage, a system crash or a loss of life.”
“Satelles’ pioneering role in STL technology is a perfect fit with Orolia’s proven Resilient PNT strategy,” said Michael O’Connor, Satelles CEO. “We look forward to working together to introduce new products and solutions that will provide our customers with the utmost confidence that their positioning, navigation and timing data is accurate, secure and accessible.”
Q: What significant new developments in positioning, navigation or timing can we anticipate in 2017?
Dan Conway, Executive VP, Guidance & Stabilization, KVH Industries
A: With increasing focus on robust and resilient positioning, navigation and timing (PNT), the industry must respond with improved access to accurate and trusted position and timing, particularly for the warfighter. For military vehicles, this translates to a requirement for improved navigation systems that will provide commanders and onboard vehicle electronic systems with resilient PNT in contested environments. Secure and more robust navigation systems must now, more than ever, assure position and timing regardless of access to satellites.
Jeff Martin, VP of Business Development & Sales, Spirent Federal
A: Global navigation satellite systems have continually evolved, and 2017 should be no exception. With the scheduled launch of GPS III satellites, the world will see two new signals: M-code from a directional antenna and L1C (new civil signal). The European Galileo system may become operational. Russia is not expected to launch the new GLONASS K-2 satellites in 2017, but it’s not far off. Developers, integrators and users will have lots of options in 2017!
A: With approximately 65 percent of mass-market receiver chipsets already capable of multi-constellation tracking — and with this figure set to rise significantly in the near future — the demand for cost-effective but highly capable consumer goods with GNSS capabilities is clearly growing at an exponential rate. The forthcoming civilian signals offer huge opportunity to many sectors, but also present a challenge in the test and validation of new products, which will require highly capable and flexible simulation equipment.
A: Next year will bring huge strides in autonomous navigation. Multi-band high-precision GNSS will be a key enabler for robotics applications. Customers are demanding navigation solutions that are accurate, fast, robust and affordable. Multi-band enables convergence times measured in seconds, not minutes. Rapid time to first fix and reacquiring fix quickly after passing under obstructions will be essential for autonomous driving applications. Low-cost L1/L2 RTK GNSS will help bring these autonomous robotic applications to life.
The U.S. Department of Transportation is seeking feedback on the potential use by the federal government of one or more positioning, navigation and timing (PNT) technologies to back up GPS signals and ensure resiliency of PNT for critical infrastructure (CI).
A Federal Register notice was published Nov. 30, with a deadline for comments of Jan. 30, 2017.
The Transportation Department also said it is interested in “leveraging PNT service technology initiatives under consideration or currently undertaken by industry.”
“The federal government is presently documenting civil requirements for PNT capabilities to serve as the basis for potential future acquisition activity. The initial objective is to support sustainment of domestic CI timing continuity with the capability to extend service(s) in the future to provide positioning/navigation continuity as well.”
The “Presidential Policy Directive on Critical Infrastructure Security and Resilience” (PPD-21; Feb. 12, 2013) designates 16 CI sectors: Chemical; Commercial Facilities; Communications; Critical Manufacturing; Dams; Defense Industrial Base; Emergency Services; Energy; Financial Services; Food and Agriculture; Government Facilities; Healthcare and Public Health; Information Technology; Nuclear Reactors, Materials, and Waste; Transportation Systems; and Water and Wastewater Systems. To support the initial objective, CI sectors need access to timing information for both nationwide applications and, in some cases, for more stringent regional and local applications.
Tests of the robustness of commercial GNSS devices against threats show that different receivers behave differently in the presence of the same threat vectors. A risk-assessment framework for PNT systems can gauge real-world threat vectors, then the most appropriate and cost-effective mitigation can be selected.
Vulnerabilities of GNSS positioning, navigation and timing are a consequence of the signals’ very low received power. These vulnerabilities include RF interference, atmospheric effects, jamming and spoofing. All cases should be tested for all GNSS equipment, not solely those whose applications or cargoes might draw criminal or terrorist attention, because jamming or spoofing directed at another target can still affect any receiver in the vicinity.
GNSS Jamming. Potential severe disruptions can be encountered by critical infrastructure in many scenarios, highlighting the need to understand the behavior of multiple systems that rely on positioning, and/or timing aspects of GNSS systems, when subject to real-world GNSS threat vectors.
GNSS Spoofing. This can no longer be regarded as difficult to conduct or requiring a high degree of expertise and GNSS knowledge. In 2015, two engineers with no expertise in GNSS found it easy to construct a low-cost signal emulator using commercial off-the-shelf software–defined radio and RF transmission equipment, successfully spoofing a car’s built-in GPS receiver, two well-known brands of smartphone and a drone so that it would fly in a restricted area.
In December 2015 the Department of Homeland Security revealed that drug traffickers have been attempting to spoof (as well as jam) border drones. This demonstrates that GNSS spoofing is now accessible enough that it should begin to be considered seriously as a valid attack vector in any GNSS vulnerability risk assessment.
More recently, the release of the Pokémon Go game triggered a rapid development of spoofing techniques. This has led to spoofing at the application layer: jailbreaking the smartphone and installing an application designed to feed faked location information to other applications. It has also led to the use of spoofers at the RF level (record and playback or “meaconing”) and even the use of a programmed SDR to generate replica GPS signals — and all of this was accomplished in a matter of weeks.
GNSS Segment Errors. Whilst not common, GNSS segment errors can create severe problems for users. Events affecting GLONASS during April 2014 are well known: corrupted ephemeris information was uploaded to the satellite vehicles and caused problems to many worldwide GLONASS users for almost 12 hours. Recently GPS was affected. On January 26, 2016, a glitch in the GPS ground software led to the wrong UTC correction value being broadcast. This bug started to cause problems when satellite SVN23 was withdrawn from service. A number of GPS satellites, while declaring themselves “healthy,” broadcast a wrong UTC correction parameter.
Atmospheric Effects. Single frequency PNT systems generally compensate for the normal behavior of the ionosphere through the implementation of a model such as the Klobuchar Ionospheric Model.
Space weather disturbs the ionosphere to an extent where the model no longer works and large pseudorange errors, which can affect position and timing, are generated. This typically happens when a severe solar storm causes the Total Electron Count (TEC) to increase to significantly higher than normal levels.
Dual-frequency GNSS receivers can provide much higher levels of mitigation against solar weather effects. However, this is not always the case; during scintillation events dual frequency diversity is more likely to only partially mitigate the effects of scintillation.
Solar weather events occur on an 11-year cycle; the sun has just peaked at solar maximum, so we will find solar activity decreasing to a minimum during the next 5 years of the cycle. However that does not mean that the effects of solar weather on PNT systems should be ignored for the next few years where safety or critical infrastructure systems are involved.
TEST FRAMEWORK
Characterization of receiver performance, to specific segments within the real world, can save either development time and cost or prevent poor performance in real deployments. Figure 1 shows the concept of a robust PNT test framework that uses real-world threat vectors to test GNSS-dependent systems and devices.
OPENING GRAPHIC
FIGURE 1. Robust PNT test framework architecture.
Figure 2. Detected interference waveforms at public event in Europe.
We have deployed detectors — some on a permanent basis, some temporary — and have collected extensive information on real-world RFI that affects GNSS receivers, systems and applications.
For example, all of the detected interference waveforms in Figure 2 have potential to cause unexpected behavior of any receiver that was picking up the repeated signal. A spectrogram is included with the first detected waveform for reference as it is quite an unusual looking waveform, which is most likely to have originated from a badly tuned, cheap jammer. The events in the figure, captured at the same European sports event, are thought to have been caused by a GPS repeater or a deliberate jammer. A repeater could be being used to rebroadcast GPS signals inside an enclosure to allow testing of a GPS system located indoors where it does not have a view of the sky.
The greatest problem with GPS repeaters is that the signal can “spill” outside of the test location and interfere with another receiver. This could cause the receiver to report the static position of the repeater, rather than its true position. The problem is how to reliably and repeatedly assess the resilience of GPS equipment to these kinds of interference waveforms. The key to this is the design of test cases, or scenarios, that are able to extract benchmark information from equipment. To complement the benchmarking test scenarios, it is also advisable to set up application specific scenarios to assess the likely impact of interference in specific environmental settings and use cases.
TEST METHODOLOGY
A benchmarking scenario was set up in the laboratory using a simulator to generate L1 GPS signals against some generic interference waveforms with the objective of developing a candidate benchmark scenario that could form part of a standard methodology for the assessment of receiver performance when subject to interference.
Considering the requirements for a benchmark test, it was decided to implement a scenario where a GPS receiver tracking GPS L1 signals is moved slowly toward a fixed interference source as shown in Figure 3.
The simulation is first run for 60 seconds with the “vehicle” static, and the receiver is cold started at the same time to let the receiver initialise properly. The static position is 1000m south of where the jammer will be. At t = 60s the “vehicle” starts driving due north at 5 m/s. At the same time a jamming source is turned on, located at 0.00 N 0.00 E. The “vehicle” drives straight through the jamming source, and then continues 1000m north of 0.00N 0.00E, for a total distance covered of 2000m. This method is used for all tests except the interference type comparison where there is no initialization period, the vehicle starts moving north as the receiver is turned on.
The advantages of this simple and very repeatable scenario are that it shows how close a receiver could approach a fixed jammer without any ill effects, and measures the receiver’s recovery time after it has passed the interference source. We have anonymized the receivers used in the study, but they are representative user receivers that are in wide use today across a variety of applications. Isotropic antenna patterns were used for receivers and jammers in the test. The test system automatically models the power level changes as the vehicle moves relative to the jammer, based on a free-space path loss model.
RESULTS
Figure 4 shows a comparison of GPS receiver accuracy performance when subject to L1 CHIRP interference. This is representative of many PPD (personal protection device)-type jammers.
Figure 5 shows the relative performance of Receiver A when subject to different jammer types — in this case AM, coherent CW and swept CW.
Finally in Figure 6 the accuracy performance of Receiver A is tested to examine the change that a 10dB increase in signal power could make to the behavior of the receiver against jamming — a swept CW signal was used in this instance.
Figure 4. Comparison of receiver accuracy when subject to CHIRP interference.
Figure 5. Receiver A accuracy performance against different interference types.
Figure 6. Comparison of Receiver A accuracy performance with 10db change in jammer power level.
Discussion. In the first set of results (the comparison of receivers against L1 CHIRP interference), it is interesting to note that all receivers tested lost lock at a very similar distance away from this particular interference source but all exhibited different recovery performance.
The second test focused on the performance of Receiver A against various types of jammers — the aim of this experiment was to determine how much the receiver response against interference could be expected to vary with jammer type. It can be seen that for Receiver A there were marked differences in response to jammer type. Finally, the third test concentrated on determining how much a 10dB alteration in jammer power might change receiver responses. Receiver A was used again and a swept CW signal was used as the interferer. It can be seen that the increase of 10dB in the signal power does have the noticeable effect one would expect to see on the receiver response in this scenario with this receiver.
Having developed a benchmark test bed for the evaluation of GNSS interference on receiver behavior, there is a great deal of opportunity to conduct further experimental work to assess the behavior of GNSS receivers subject to interference. Examples of areas for further work include:
Evaluation of other performance metrics important for assessing resilience to interference
Automation of test scenarios used for benchmarking
Evaluation of the effectiveness of different mitigation approaches, including improved antenna performance, RAIM, multi-frequency, multi-constellation
Performance of systems that include GNSS plus augmentation systems such as intertial, SBAS, GBAS
CONCLUSIONS
A simple candidate benchmark test for assessing receiver accuracy when subjected to RF interference has been presented by the authors.
Different receivers perform quite differently when subjected to the same GNSS + RFI test conditions. Understanding how a receiver performs, and how this performance affects the PNT system or application performance, is an important element in system design and should be considered as part of a GNSS robustness risk assessment.
Other GNSS threats are also important to consider: solar weather, scintillation, spoofing and segment errors.
One of the biggest advantages of the automated test bench set-up used here is that it allows a system or device response to be tested against a wide range of of real world GNSS threats in a matter of hours, whereas previously it could have taken many weeks or months (or not even been possible) to test against such a wide range of threats.
Whilst there is (rightly) a lot of material in which the potential impacts of GNSS threat vectors are debated, it should also be remembered that there are many mitigation actions that can be taken today which enable protection against current and some predictable future scenarios.
Carrying out risk assessments including testing against the latest real-world threat baseline is the first vital step towards improving the security of GNSS dependent systems and devices.
ACKNOWLEDGMENTS
The authors would like to thank all of the staff at Spirent Communications, Nottingham Scientific Ltd and Qascom who have contributed to this paper. In particular, thanks are due to Kimon Voutsis and Joshua Stubbs from Spirent’s Professional Services team for their expert contributions to the interference benchmark tests.
MANUFACTURERS
The benchmarking scenario described here was set up in the laboratory using a Spirent GSS6700 GNSS simulator.
The plenary talk by John O’Keefe at ION GNSS+ stimulated a lot of neuron firing inside this old noggin. For a synopsis of “The Positioning System of the Brain,” see this column by Managing Editor Tracy Cozzens. I had the difficult task of following this brilliant scientist to the podium and introducing ION’s track chairs for previews of the conference’s technical content. Here’s how I attempted to stitch together the two parts of the evening program.
Dr. O’Keefe’s talk called two things powerfully to my mind. The first is us, here, now. In the Oregon Convention Center, where we have gathered four times before. How do we remember its hallways, spaces, electronic stairways? What will direct us to technical sessions over the next three days? Our neural system enables us to orient within an environment, to navigate from one place to another and to remember spatial information. I’ve always struggled to understand aspects and workings of memory. Now to find that place is a key driver, that’s powerful.
The second thing it called to mind is a book I read forty years ago, that has lingered with me since. In Cheyenne Autumn, Mari Sandoz evokes the Native American precursive sense of place. Both past and future exist simultaneously in the present. When the nomadic tribe on their annual migration cycle rode to their summer hunting grounds or through their autumn passages, the events in their past that took place in those areas became very much alive in their awareness. And the figures from their history spoke to them and rode with them through the sandhills, ravines and river crossings of Nebraska and Wyoming.
In their tragic 1878 outbreak for freedom, the Cheyenne eluded the technological might of the U.S. Army sent to intercept them. They did so through their multisensory connection, through memory, to place and direction. Though ultimately defeated, they left us a legacy, an awareness, a state of mind to nurture: understanding memory — with place. And understanding place — with memory.
Spirent Communications plc’s Positioning Technology Unit, a company that provides solutions for improving positioning, navigation and timing (PNT) system performance, was yesterday presented with the Royal Institute of Navigation (RIN) Duke of Edinburgh Navigation Award for Technical Achievement.
The award was presented at the Institute’s Annual Meeting, held at the Royal Geographical Society in London Jul.y 21, by the Institute’s Patron, His Royal Highness The Duke of Edinburgh. It was received by Eric Hutchinson, Spirent’s chief executive officer.
Eric Hutchinson, Spirent CEO, (left) receives the RIN Duke of Edinburgh Navigation Award for Technical Achievement from the Institute’s Patron, His Royal Highness The Duke of Edinburgh (right). Looking on is the President of the RIN, Captain James Taylor.
Spirent was selected for this year’s award to recognize its leading role in the evolution of global navigation satellite systems (GNSS) since 1985, and joins the European Space Agency, the UK National Air Traffic Services (NATS), the Russian GLONASS system, and others who have previously received the award.
“We are extremely honoured to have been recognized by the Institute in this way,” said Martin Foulger, general manager of Spirent’s Positioning Technology Unit. “Spirent has been at the forefront of GPS and other GNSS development for 30 years, so to join the other winners of this award is a great acknowledgement of the technical innovation and commercial success driven by the Spirent team in Paignton.”
His Royal Highness The Duke of Edinburgh (right) congratulates Eric Hutchinson, Spirent’s Chief Executive Officer (left), after receiving the Royal Institute of Navigation (RIN) Duke of Edinburgh Navigation Award for Technical Achievement.
Peter Chapman-Andrews, Director of the Royal Institute of Navigation, commented: “Spirent is a well-known and well-respected leader in PNT testing. This wholly-deserved award is the Institute’s way of recognizing Spirent’s significant contribution over many years towards helping the world evaluate and improve performance of navigation and timing receivers, systems and applications.”
Spirent delivers navigation and positioning test equipment and services to governmental agencies, major manufacturers, integrators, test facilities and space agencies worldwide. Spirent’s portfolio has recently been updated with new technology that includes innovations not seen elsewhere, including the most flexible simulation systems covering the full range of GNSS signals and the world’s smallest hi-fidelity, portable PNT record and playback system. Spirent has recently opened three services labs, in UK, USA and China, to further support positioning and timing development and innovation.
Secondary receiver uses eLoran to back up GPS time
Spectracom has been selected to provide Interference, Detection and Mitigation (IDM) capability to its SecureSync precision time and frequency reference system to support Rohde & Schwarz Benelux B.V. and the Netherlands Ministry of Defence for secure long-range military communications systems.
The upgrade, which is based on a secondary receiver that extracts precision timing signals from the eLoran system when GPS signals are not available, will increase the reliability of the overall communication system by further enhancing the resiliency of the precision timing core.
As part of its expanding set of resilient PNT solutions, Spectracom systems synchronize to a variety of precision references whenever and wherever available.
In this deployment, signals from the eLoran system are constantly monitored and act as the primary reference when GNSS signals are not available due to interference or jamming. This new capability supports the goal of a sustainable and reliable network for ongoing global operations.
The modularity of the SecureSync precision time and frequency platform allows customers and integrators to easily and incrementally increase system capabilities, such as multiple reference signals, as they become available.
Sponsored by: Loctronix Corporation Broadcast Date: Thursday, August 1, 2013 Moderator: Alan Cameron, Editor & Publisher, GPS World Speakers: Dr. Michael B. Mathews – CEO / Founder, Loctronix Corporation, Peter F. MacDoran – Chief Scientist, Loctronix Corporation, John Taylor – President, Mercury Data Systems, Tsega Emmanuel – Product Manager,TeleCommunications Systems Summary: Learn how combining signals of opportunity GNSS, and inertial sensors provides high-performance positioning and navigation information in a variety of GNSS-challenged applications. Topics present an overview of latest solutions using software defined radio techniques to deliver continuous, critical PNT data in a flexible implementation ideal for applications including soldier navigation, spacecraft PNT, commercial indoor/outdoor asset tracking, GNSS signal assurance and interference detection. Download the White Paper by Loctronix
