GPS World

Tag: spoofing

  • Innovation: Better GNSS navigation and spoofing detection with chip-scale atomic clocks

    Innovation: Better GNSS navigation and spoofing detection with chip-scale atomic clocks

    Getting there more safely

    INNOVATION INSIGHTS with Richard Langley
    INNOVATION INSIGHTS with Richard Langley

    It’s all physics. How things work, that is. You’ve heard me say that before in this column, but I suppose I’m a little biased (or realistic) as my first degree is in physics — applied physics, to be more precise. Mind you, some chemists might disagree that it’s all down to physics. But as Sheldon Cooper in the popular American TV sitcom The Big Bang Theory stated in a radio interview with real science journalist Ira Flatow following his apparent discovery of the first stable super-heavy element, “Yes, yes, I’d be a physicist with a Nobel in chemistry. Everyone laugh at the circus freak. You know, I don’t need to sit here and take this, Flatow. It is because of bullies like you, every day more and more Americans are making the switch to television.”

    But in all seriousness, it really was physicists who first explained the physical phenomena associated with a range of technologies that had to be understood before global navigation satellite systems could become a reality. From orbital mechanics, to relativity theory, to semiconductors, to transatmospheric propagation of radio signals, to atomic clocks, the fundamental understanding of how these worked was provided by physicists.

    This was particularly true for atomic clocks. An atomic clock, like any clock, consists of two basic components: a resonator or oscillator and a counter. The oscillator generates a stable frequency, whose cycles are counted, converted to units of seconds, minutes, hours and perhaps days, and continuously displayed. This is the case whether we are describing a wristwatch with a quartz crystal oscillator or an atomic clock whose oscillator is made up of atoms undergoing quantum energy transitions. A crystal oscillator is stimulated to vibrate at its design frequency and thereby generate a fluctuating electrical current with that frequency. The atomic oscillator works thanks to the principles of quantum physics. Atoms have energies, but the energies are quantized, meaning that only specific energy levels are possible. An atom may exist at a particular energy level and spontaneously transition to a lower energy level and in so doing emit electromagnetic radiation (such as radio waves or light) of a specific frequency equal to the change in energy divided by a fundamental physical constant called Planck’s constant, named after Max Planck, who introduced it in 1900. The atom can be stimulated to return to the higher energy level by exposing it to radiation of that same exact frequency. A practical atomic oscillator can be constructed by confining a collection of atoms in an enclosure and bathing them in electromagnetic radiation from a tunable generator. By automatically tuning the frequency of the generator to maximize the number of stimulated atoms through a feedback loop, a very pure and constant frequency will result.

    The first clocks based on an energy transition of the cesium atom were developed in the mid-1950s. Later on, clocks based on energy transitions of the rubidium and hydrogen atoms were developed. By the 1960s, commercial rack-mountable cesium and rubidium clocks became available. But a need existed for miniaturized atomic clocks that could be easily embedded in equipment requiring a very stable frequency source. Funded in part by the Defense Advanced Research Projects Agency, the first chip-scale atomic clock was demonstrated by physicists in 2004, and by 2011, a chip-scale atomic clock based on a cesium atom transition became commercially available.

    In this month’s column, we look at how chip-scale atomic clocks can help us navigate more safely by allowing a GNSS receiver to position itself more accurately even with only three satellites in view, and to protect itself by being able to detect a sophisticated spoofing attempt. Physics — isn’t it wonderful!

    GNSS positioning and navigation are based on one-way range measurements. Synchronization of the receiver and satellite timescales is carried out with respect to a third time scale of higher stability, such as GNSS system time, by introducing so-called clock errors. To account for the time and frequency offsets of the satellites, the user can obtain appropriate corrections from the broadcast navigation message in real time. In post-processing, more accurate corrections are provided by various products of the International GNSS Service (IGS).

    Due to the generally poor accuracy and limited long-term frequency stability of a quartz oscillator built into a GNSS receiver, the receiver clock error has to be estimated epoch-by-epoch. This is the typical case for single-point positioning (SPP) based on code (pseudorange) observations only. This comes with certain drawbacks:

    • The up-coordinate is determined two to three times less precisely than the horizontal coordinates,
    • Higher dilution of precision values are obtained than in the hypothetical case of trilateration,
    • High correlations of up to 99 percent between the receiver’s up-coordinate and clock error persist, and
    • At least four satellites are necessary for positioning.

    Especially in the case of kinematic positioning, this situation can be significantly improved by using a more stable (atomic) clock for the receiver and introducing the information about its frequency stability into the estimation process. This approach is called receiver clock modeling (RCM), and basically requires that the integrated clock noise is smaller than the receiver noise during the modeling interval. Besides SPP, this method can also be applied in a common-clock setup in relative positioning using single-differenced observations (which, by their nature, contain more information) instead of typically used double-differenced observations, or precise point positioning.

    The recent development of chip-scale atomic clocks (CSACs) offers the required frequency stability and accuracy, and opens up the possibility of using atomic clocks in real kinematic GNSS applications without any severe restrictions regarding power supply or environmental influences on the clocks. When connecting one of these clocks to a GNSS receiver, replacing or steering the internal oscillator accordingly, and modeling its behavior in a physically meaningful way instead of epoch-wise estimation, the navigation performance can be improved distinctly.

    The receiver clock parameter absorbs signal delays common to all simultaneous line-of-sight signals whether these delays represent the physical clock or any other common delay. Thus, it is especially vulnerable to delays caused by jammers or spoofers. If the clock behavior is predictable, information about jamming or spoofing can be retrieved, and thus the integrity of the positioning solution can be improved.

    Chip-Scale Atomic Clocks

    For our test purposes, we used two different commercially available CSACs, dubbed CSAC A and CSAC B. To gain knowledge about their frequency stabilities, we compared them against an active hydrogen maser at the Physikalisch-Technische Bundesanstalt (PTB), Germany’s official metrology institute. We analyzed the raw fractional phase measurements and computed individual Allan variances for our devices. The resulting frequency stabilities are shown in FIGURE 1.

    Clock Model

    Basically, a clock is an oscillator generating a sinusoidal signal with a given nominal frequency coupled with a frequency counter. The deviation of the signal’s nominal frequency with respect to a reference time scale can be described by a frequency offset and drift plus random frequency fluctuations. In the time domain, the resulting clock error δt, that is, the difference between nominal time t and the time read simultaneously on the clock, can be approximated by the following equation:

    (1)
    atomic-clock-equation-1

     

    with systematic time offset b0, frequency offset b1, frequency drift b2, and random noise x(t,t0). Thus, the main (deterministic) part of a clock model can be described by a quadratic polynomial.

    The more interesting characteristics of a clock are contained in the underlying noise processes. The time-dependent Allan deviation (ADEV) enables the determination of a modeling or predicting interval τp over which receiver clock modeling is physically meaningful; that is, the integrated clock noise x(t,t0) is smaller than GNSS receiver noise:

    (2)
    atomic-clock-equation-2

     

    The noise σrx of a typical commercial GNSS receiver can be assessed to approximately one percent of the chip or wavelength of the signal in use, such as 3 meters, 0.3 meter, or 2 millimeters for C/A-code, P-code, or L1 carrier-phase observations, respectively.

    To apply the knowledge gained about the devices’ frequency stabilities, appropriate models for GNSS data analysis should be established. One prerequisite is that the clock noise has to be well below the GNSS receiver noise; that is, the integrated random frequency fluctuations of CSACs cannot be resolved by the GNSS observations in use. We assume typical values for code and ionosphere-free carrier-phase observations from modern geodetic GNSS receivers of 1 meter and 5 millimeters, respectively. Since these observations are phase-based measures, we can model the dominating underlying noise process as white-noise phase modulation (WPM) over time. The corresponding graphs are depicted in FIGURE 1 as dashed lines. The intersection points between these lines and the ADEV curves define maximal time intervals Δt for physically meaningful receiver clock modeling in our case study. Depending on the CSAC in use, RCM is applicable over time intervals of at least ten minutes and up to one hour in C/A-code-based applications, such as SPP.

    GNSS Applications

    We have tested and validated our receiver clock modeling approaches for GNSS navigation.

    Kinematic Experiment

    We carried out a real kinematic experiment on a cart track in farm fields with an approximately 500 × 800 square meter area with only a few natural obstructions in the form of a tree-lined lane (see FIGURE 2). The basic measurement configuration consisted of four GNSS receivers running the same firmware version connected to a GNSS antenna via an active signal splitter. Three of these receivers were fed by the 10-MHz signals of our CSACs. For comparison purposes, the fourth receiver was driven by its internal quartz oscillator.

    Each test drive with our motor vehicle lasted approximately 8 to 10 minutes. We recorded GPS and GLONASS data with a sampling interval of one second. (Only GPS-based results are described herein.) That was also the case for our temporary local reference station, which consisted of a GNSS antenna mounted on a tripod and connected to another GNSS receiver. Hence, we were able to generate reference solutions for the vehicle trajectories in relative positioning mode with baselines of up to only some hundred meters, yielding 3D coordinate accuracies below 20 centimeters.

    The RCM algorithms presented here were implemented in the Institut für Erdmessung GNSS Matlab Toolbox. To compute a typical real-time SPP navigation solution based on GPS C/A-code observations only, broadcast ephemerides were used. Tropospheric and ionospheric signal delays were corrected by the Saastamoinen and Klobuchar models, respectively.

    [Click on an image to enlarge it.]

    Precision and Accuracy

    Two of the most important GNSS performance parameters are the precision and accuracy of the coordinate solution. FIGURE 3 shows topocentric coordinate differences with respect to the reference trajectory and clock-error time series of the receiver driven by its internal quartz oscillator, estimated without RCM. This is typical for almost all end users. The (linearly detrended) receiver clock error exhibits values between roughly −100 and +200 nanoseconds, which is typical for a quartz oscillator.

    The noise of the coordinates is in the range of 20–25 centimeters in the horizontal components and about 50 centimeters in the up-component, respectively. Furthermore, certain coordinate offsets are visible due to remaining systematic effects such as ionospheric delay and orbit errors. We could attribute these effects thanks to repeated analysis runs with different correction models such as precise IGS final orbits or by forming the ionosphere-free linear combination. Hence, the assessment of the accuracy of the results is difficult since it chiefly depends on the applied correction models, and it is less influenced by receiver clock modeling.

    Without use of RCM, the three receivers connected to the CSACs show similar behavior in the coordinate domain. However, the clock residuals become very small compared to those of the internal oscillator and amount to only a couple of nanoseconds at most. As an example, FIGURE 4 depicts the results for CSAC A. Even over a relatively short period of time of approximately eight minutes, this oscillator shows a significant frequency drift, which we have to account for in RCM. Note that this is also true for the device’s oven-controlled crystal oscillator (OCXO) post-filtered signal.

    When applying RCM, as expected, no changes in the time series of the north and east coordinates occur, but a strong decrease of the up-coordinate residuals is clearly visible. The noise level is up to 20–30 centimeters. Due to the applied polynomial clock model, the clock residuals are also reduced. Thanks to the increasing number of epochs/observations contributing to the estimation of the clock parameters, the course of these residuals gets smoother over time. Furthermore, spikes in the up-coordinate time series at around minutes five to seven caused by sudden signal obstructions are almost eliminated thanks to RCM. Also, when applying RCM, there are no improvements in the horizontal components, but the scatter of the up-coordinates is decreased in the range of 48 percent (CSAC B) to 58 percent (CSAC A).

    Our second RCM approach based on an existing extended Kalman filter clock model shows comparable results. The most obvious difference to a sequential least-squares approach is that the spikes in the up-coordinate and clock residual time series at around minutes five to seven are not smoothed as strongly.

    Reliability and Integrity

    Reliability and integrity are very important GNSS performance parameters, especially for real-time and safety-of-life critical applications. In general, we distinguish between internal and external reliability, which are both measures for the robustness of the parameter estimation against blunders in the observation data. Thereby, good reliability makes it easier to identify and remove gross errors and outliers in GNSS data analysis.

    Internal reliability is calculated in terms of so-called minimal detectable biases (MDBs) of the GNSS observations. These values determine lower bounds for gross observation errors so that these can still be detectable. External reliability describes the influence of these MDBs on the parameter estimates. In our experiments, we found reductions in the size of the MDBs of up to 16 percent.

    As a consequence, the vertical protection level — a measure of integrity — is also improved.

    Positioning with 3 Satellites

    Generally, GNSS positioning requires at least four satellites in view to solve the equation system for the four unknowns. This can become a severe restriction in difficult environments such as urban canyons. Taking benefits of an oscillator of high accuracy, with known and predictable frequency stability, enables positioning using only three satellites. This approach enhances GNSS continuity and availability, and is called clock coasting.

    Thanks to the stability of CSACs, the GNSS observations are corrected by an additional receiver clock term, which is computed from the latest clock-coefficient estimates. To show the effects of this method, we generated two artificial partial satellite outages so that only observations on only three satellites remain. The latter were chosen in such a way that typical situations in an urban canyon were simulated; that is, only satellites with high elevation angles were visible to the receiver.

    The resulting coordinate and clock time series are depicted in FIGURE 5. When coasting through periods with only three satellites available, the horizontal coordinates become approximately two to three times noisier (1–2 meters). Due to the poor observation geometry, an additional offset of about 1 meter is induced in the north component during the first partial outage. However, the noise of the up-coordinate is only slightly increased in both of the outage periods, although a significant drift is visible during the first one. Most likely, this is because the coefficients used for clock coasting are only based on 60 epochs up until that time. During the second partial outage this drifting behavior vanishes independently of the satellite geometry. Due to the fact that the clock time series are linearly detrended and a linear clock polynomial is applied, the corresponding residuals shown in FIGURE 5 equal zero during the coasting periods.

    The presented approaches for RCM and clock coasting are applicable in multi-GNSS positioning and timing data analysis, too, where we also have to consider inter-system biases. Thanks to the high temporal stability of these biases, they can be modeled by a polynomial in the same sense as the receiver clock error.

    [Click on an image to enlarge it.]

    FIGURE 3. Topocentric coordinate deviations with respect to the reference trajectory and clock errors. The receiver is driven by its internal oscillator. No receiver clock modeling was applied in a sequential least-squares adjustment. Note the different y-axis scales.
    FIGURE 3. Topocentric coordinate deviations with respect to the reference trajectory and clock errors. The receiver is driven by its internal oscillator. No receiver clock modeling was applied in a sequential least-squares adjustment. Note the different y-axis scales.

    FIGURE 4. Topocentric coordinate deviations with respect to the reference trajectory and clock errors for a receiver connected to the CSAC A signal. The results without receiver clock modeling are depicted in black and blue. The results applying a quadratic polynomial for clock modeling in a sequential least-squares adjustment are shown in red.
    FIGURE 4. Topocentric coordinate deviations with respect to the reference trajectory and clock errors for a receiver connected to the CSAC A signal. The results without receiver clock modeling are depicted in black and blue. The results applying a quadratic polynomial for clock modeling in a sequential least-squares adjustment are shown in red.

    FIGURE 5. Topocentric coordinate deviations with respect to the reference trajectory and clock errors. The receiver is connected to CSAC B. The solution is obtained from a sequential least-squares adjustment with clock coasting from minutes one to two and five to seven.
    FIGURE 5. Topocentric coordinate deviations with respect to the reference trajectory and clock errors. The receiver is connected to CSAC B. The solution is obtained from a sequential least-squares adjustment with clock coasting from minutes one to two and five to seven.

    Spoofing Detection

    Jamming and spoofing of GNSS signals have become major threats to GNSS positioning and timing. Although these authentication issues have been well known since the beginnings of GPS, they have become more severe in recent years due to the greatly increased number of applications that rely on (highly) accurate GNSS positioning and timing.

    Experiment

    A spoofing attack’s goal is for the signal tracking loops of a target receiver to acquire the spoofing signal, and then pull its navigation solution away from the authentic position. So as not be detected by the target receiver, the common delay of the spoofing signals — which will be absorbed by the receiver’s clock-error estimate — must not deviate significantly from the receiver’s authentic clock error. This means that the injected delay has to be as small as possible so that it cannot be separated from the typical random frequency (and thus time) fluctuations of the oscillator driving the receiver.

    To simulate a spoofing attack, we set up an experiment consisting of two GNSS receivers, one driven by its internal quartz oscillator, and one connected to CSAC B, both recording the same GNSS signals via a signal splitter. The input signal of the latter comes from an active coaxial switch, which allows us to switch between two different antennas in less than 1 second. Both antennas in our measurement configuration were mounted on tripods. However, one antenna was connected to a commercial GNSS repeater, which generates an additional delay, and its output signals were transmitted via cable to the coaxial switch (see FIGURE 6). When switched to the antenna without the repeater, the receivers recorded authentic signals. When switched to the repeater, they recorded spoofed signals. The location of the repeater antenna ranges from 2 to 25 meters away from the authentic antenna, thereby introducing different delays — in addition to the repeater delay — into the signal processing of the two receivers. We assume that a short delay of about 2 meters (7 nanoseconds) is more difficult for receivers to detect than a delay of about 25 meters (83 nanoseconds).

    Whenever the signal path is switched from the authentic antenna to the repeater antenna, this should result in a jump in the clock-error time series. Combined with the known frequency stability of the receivers’ oscillators, we can establish a hypothesis test for the significance of such a clock-error jump.

    For each new location of the repeater antenna, the measurement procedure was the same. We recorded authentic and spoofed data four times alternating for two minutes with a data rate of 1 Hz.

    FIGURE 6. Measurement configuration of a spoofing detection experiment.
    FIGURE 6. Measurement configuration of a spoofing detection experiment.

    Results

    FIGURES 7 and 8 show the original clock-time offsets for two different locations of the repeater antenna as recorded by the receivers, and the corresponding predicted clock states from the Kalman filter. The jumps in each clock-error time series are more or less clearly visible, especially in the case of the 2-meter distance. For the latter, the hypothesis test of the temperature-controlled crystal oscillator (TCXO) always accepts the alternative in favor of the null hypothesis; that is, from a statistical standpoint, no spoofing attack is detectable. This is because of the small signal delay attributable to the measurement geometry, which cannot be properly separated from random time deviations caused by the TCXO’s low frequency stability. On the contrary, even for this short distance between the spoofing and authentic antennas, every start and end of the four spoofing attacks were detected.

    As an example, FIGURE 8 shows the results for a larger distance (around 14 meters). In this case, all spoofing attacks can be properly detected by both the TCXO- and the CSAC-controlled receivers. The seven-times-increased distance ensures that even the low-cost TCXO inside the receiver combined with a sophisticated receiver internal clock estimation is capable of spoofing detection by monitoring its clock states.

    Conclusions

    In this article, we have proposed a deterministic approach for receiver clock modeling in a sequential least-squares adjustment by applying a linear or quadratic clock polynomial whose coefficients are updated each consecutive epoch. As a prerequisite, an individual characterization of the frequency stabilities of three miniaturized atomic clocks was carried out with respect to the phase of an active hydrogen maser showing an overall good agreement with manufacturers’ data.

    A real kinematic experiment was carried out with two chip-scale atomic clocks, and typical code-based GPS navigation solutions were computed. We showed that the precision of the up-coordinate time series are improved by up to 58 percent, depending on the clock in use. Furthermore, internal and external reliability were significantly enhanced. Additionally, it was shown that our algorithm is capable of coasting through periods of partial satellite outages with only three satellites in view. This increases availability and continuity of GNSS positioning with poor satellite coverage caused by high shadowing effects or multipath, for example.

    Finally, we investigated the benefits of an atomic clock in spoofing detection and showed first results. Our approach, based on a Kalman filter and a hypothesis test, enhances the detectability of a spoofer when using a CSAC instead of the receiver’s internal oscillator, especially in the case of small signal delays injected by the spoofing device, which helps to identify a sophisticated spoofer very quickly.

    Manufacturers

    We used two different CSACs: a Jackson Labs (jackson-labs.com) LN (CSAC A) and a Microsemi Quantum SA.45s (CSAC B). For the kinematic experiment, we used four JAVAD GNSS Delta TRE-G3T receivers connected to a NovAtel 703 GGG antenna via an active signal splitter. The local reference station consisted of a Leica (leica-geosystems.us) AX1202GG antenna connected to a Leica GRX1200+ GNSS receiver. A JAVAD Delta TRE-G3T was used in the spoofing experiment.

    Disclaimer

    The authors do not recommend any of the instruments tested. It is also to be noted that the performance of the equipment presented in this article depends on the particular environment and the individual instruments in use.

    Acknowledgments

    This article is based, in part, on the paper “Benefits of Chip Scale Atomic Clocks in GNSS Applications” presented at ION GNSS+ 2015, the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation, held Sept. 14–18, 2015, in Tampa, Florida.

    The authors would like to thank Andreas Bauch and Thomas Polewka, who are both with PTB, for their support during execution and analysis of the clock comparisons, and Achim Hornbostel from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt) for discussions on spoofing experiments.

    We also thank IGS and its participating agencies for their GNSS products, which were a valuable contribution to our case study.

    Our work was funded by the Federal Ministry of Economics and Technology of Germany.

    Further Reading

    • Authors’ Conference Paper

    “Benefits of Chip Scale Atomic Clocks in GNSS Applications” by T. Krawinkel and S. Schön in Proceedings of ION GNSS+ 2015, the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation, Tampa, Florida, Sept. 14–18, 2015, pp. 2867–2874.

    • Chip-Scale Atomic Clocks and GNSS Applications

    “Reducing the Jitters: How a Chip-Scale Atomic Clock Can Help Mitigate Broadband Interference” by F.-C. Chan, M. Joerger, S. Khanafseh, B. Pervan and O. Jakubov in GPS World, Vol. 25, No. 5, May 2014, pp. 44–50.

    “Time for a Better Receiver: Chip-Scale Atomic Frequency References” by J. Kitching in GPS World, Vol. 18, No. 11, Nov. 2007, pp. 52–57.

    • Time, Frequency and Clocks

    “A Historical Perspective on the Development of the Allan Variances and Their Strengths and Weaknesses” by D.W. Allan and J. Levine in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 63, No. 4, April 2016, pp. 513–519, doi: 10.1109/TUFFC.2016.2524687.

    Time – From Earth Rotation to Atomic Physics by D.D. McCarthy and P.K. Seidelmann, published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2009.

    “Special Issue: Fifty Years of Atomic Time-Keeping: 1955 to 2005,” Metrologia, Vol. 42, No. 3, June 2005.

    The Measurement of Time: Time, Frequency and the Atomic Clock by C. Audoin and B. Guinot, published by Cambridge University Press, Cambridge, U.K., 2001.

    The Science of Timekeeping by D.W. Allan, N. Ashby and C.C. Hodge, Hewlett Packard (now Agilent Technologies) Application Note 1289, 1997.

    “The Role of the Clock in a GPS Receiver” by P. Misra in GPS World, Vol. 7, No. 4, April 1996, pp. 60–66.

    “Time, Clocks, and GPS” by R.B. Langley in GPS World, Vol. 2, No. 10, Nov./Dec. 1991, pp. 38–42.

    • Clock Modeling

    Feasibility and Impact of Receiver Clock Modeling in Precise GPS Data Analysis by U. Weinbach, Ph.D. dissertation, Gottfried Wilhelm Leibniz Universität Hannover, Hannover, Germany, Wissenschaftliche Arbeiten der Fachrichtung Geodäsie und Geoinformatik der Leibniz Universität Hannover, Nr. 303, and Deutsche Geodätische Kommission bei der Bayerischen Akademie der Wissenschaften, Reihe C, Dissertationen Heft Nr. 692, 2013.

    “Time and Frequency (Time-Domain) Characterization, Estimation, and Prediction of Precision Clocks and Oscillators“ by D.W. Allan in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. UFFC-34, No. 6, Nov. 1987, pp. 647–654, doi: 10.1109/T-UFFC.1987.26997.

    “Relationship Between Allan Variances and Kalman Filter Parameters” by A.J. van Dierendonck, J. McGraw and R.G. Brown in Proceedings of the Sixteenth Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting, Greenbelt, Maryland, Nov. 27–29, 1984, pp. 273–292.

    • Spoofing

    “GNSS Spoofing Detection: Correlating Carrier Phase with Rapid Antenna Motion” by M.L. Psiaki with S.P. Powell and B.W. O’Hanlon in GPS World, Vol. 24, No. 6, June 2013, pp. 53–58.

    “Assessing the Spoofing Threat” by T.E. Humphreys, P.M. Kintner, Jr., M.L. Psiaki, B.M. Ledvina and B.W. O’Hanlon in GPS World, Vol. 20, No. 1, January 2009, pp. 28–38.

  • Are you experienced? Tell us about jamming, spoofing, RF interference encounters

    We talk a lot about — and publish a lot of technical articles about — GPS/GNSS jamming, spoofing and unintentional RF interference in GPS World magazine and on this website. Clearly it is an emerging and potentially huge problem. How much of it goes on right now?  Tell us very briefly (10 seconds it will take) if You are experienced with these incidents.

    One week only! Final results will be collected on October 18 and published in the November issue of the magazine.

    Answer now, and you’ll be entered in a drawing to win a $50 gift card. Go to env-gpsworld-integration.kinsta.cloud/septpoll now!

  • Automotive abstract: INS to protect against GNSS spoofing

    Automotive abstract: INS to protect against GNSS spoofing

    iongnss16_manickam

    Using Tactical and MEMS Grade INS to Protect Against GNSS Spoofing in Automotive Applications

    By Sashidharan Manickam and Kyle O’Keefe PLAN Group, Department of Geomatics Engineering, University of Calgary

    This paper analyzes the GNSS signal authentication limits in using different grades of IMU (Tactical and MEMS) to detect errors in combination with different grades of GNSS receiver (Geodetic grade and Automotive). To test these combinations, a tightly-coupled 23 state navigation Kalman Filter is implemented with a constant velocity dynamics model for the position, velocity, attitude and clock states and first-order Gauss-Markov processes to model the 12 sensor errors.

    Presented at ION GNSS+, September 2016.

  • Vulcano weapon system to fire with Rockwell Collins NavFire GPS

    Rockwell Collins is bringing its NavFire Precision Positioning Service (PPS) GPS to Leonardo-Finmeccanica’s Vulcano family for naval and artillery applications.

    NavStrike military GPS offers high performance GPS for tightly coupled GPS/INS integrations.
    NavStrike military GPS offers high performance GPS for tightly coupled GPS/INS integrations.

    Derived from the field-proven 12-channel NavFire Precise Positioning Service GPS receiver, Rockwell Collins’ NavStrike military GPS offers high performance GPS for tightly coupled GPS/inertial navigation system (GPS/INS) integrations.

    “We have customized the NavFire receivers for the particular caliber of the ammunition, and provided full support to the customer during and after the firing trials,” said Claude Alber, vice president and managing director, Europe, Middle East and Africa for Rockwell Collins. “In the end, our product perfectly matched the demanding performance requirements of our customer.”

    The NavFire GPS includes the Selective Availability Anti-Spoofing Module (SAASM) to allow decryption of precision GPS observations through over-the-air rekeying. The positioning information is used by the guidance system of the projectile.

    Nearly 30 years ago, Rockwell Collins assisted the U.S. Air Force in developing GPS technology and that legacy continued when the company created the world’s first all-digital miniature GPS receiver under contract with DARPA. Over the years, Rockwell Collins has produced more than 50 GPS products and delivered more than 1 million GPS receivers for commercial avionics and government applications. This recent GPS contract continues this legacy to create leading edge military navigation solutions.

  • Spoofing, Detection, and Navigation Vulnerability

    Sponsored by: NavCom
    Broadcast date: Thursday, September 18, 2014
    Moderator: Alan Cameron, Group Publisher, GPS World and Geospatial Solutions
    Speakers: Todd E. Humphreys, Director, Radionavigation Laboratory, University of Texas; Mark L. Psiaki, Professor, Sibley School of Mechanical and Aerospace Engineering, Cornell University
    Summary: The threat of deceptive signal spoofing is a key element of cyber-crime and cyber-terrorism. The ongoing effort, vital to defense, government security, and all forms of navigation and tracking, to differentiate between real and fake GNSS signals gets an up-close and personal look from two leading researchers in the field, Mark L. Psiaki and Todd E. Humphreys. Our speakers will also expand the topic to address other vulnerabilities of navigation, collision avoidance, and timing systems, for example, weaknesses in aviation’s ADS-B protocol and the vulnerability of automotive radar systems.

  • AF Space Command holds wargame focused on resilience

    Air Force Space Command began its 10th Schriever Wargame May 19 at Maxwell AFB, Montgomery, Ala.

    The Schriever Wargame (SW 16), set in the year 2026, explores critical space issues and investigates the integration activities of multiple agencies associated with space systems and services.

    The objectives of SW 16 center on identifying ways to increase the resilience of space that includes our intelligence community, civil, commercial and Allied partners; exploring how to provide optimized effects to the warfighter in support of coalition operations; and examining how to apply future capabilities to protect the space enterprise in a multi-domain conflict.

    The Air Force announcement did not include specific mention of GPS jamming and spoofing, but these and related cyberthreats could reasonably be expected to appear in the pantheon of cyberspace competition.

    The SW 16 scenario depicts a peer space and cyberspace competitor seeking to achieve strategic goals by exploiting those domains. Scenarios will focus on the European Command Area of Responsibility. They will also include a full spectrum of threats across diverse operating environments to challenge civilian and military leaders, planners and space system operators, as well as the capabilities they employ.

    The Schriever Wargame team will conduct SW 16 on behalf of Air Force Space Command, headquartered in Colorado Springs, Colorado. Approximately 200 military and civilian experts from more than 27 commands and agencies around the country will participate in the Wargame.

    U.S. commands and agencies participating in SW 2016 include: Air Force Space Command, Army Space and Missile Defense Command, Naval Fleet Cyber Command, the National Reconnaissance Office, Executive Agent for Space Staff, Air Combat Command, Office of the Secretary of Defense, U.S. European Command, U.S. Strategic Command, Defense Information Systems Agency, the Intelligence Community, National Aeronautics and Space Administration, Office of Homeland Security, Department of Transportation, Department of State and Department of Commerce.

  • New Spirent Test Framework Evaluates Threats to GPS, GNSS

    New Spirent Test Framework Evaluates Threats to GPS, GNSS

    GNSS Interference Detector System.
    GNSS Interference Detector System.

    Spirent Communications has announced a Robust PNT Test Framework that evaluates GPS and GNSS security vulnerabilities for positioning, navigation and timing (PNT) systems.

    Threats to GNSS and related PNT applications are more orchestrated and coordinated, with the motivation to disrupt or cause financial loss. The technology to disrupt GPS has also become much more accessible, resulting in GPS vulnerability gaining attention at hacker conventions.

    Spirent’s GSS100D Detector, developed in collaboration with Nottingham Scientific Ltd, enables detection, characterization and analysis of real GNSS threats.
    Spirent’s GSS100D Detector, developed in collaboration with Nottingham Scientific Ltd, enables detection, characterization and analysis of real GNSS threats.

    The Robust PNT Test Framework will be used by technology, system and application developers where PNT is critical. Spirent’s framework enables threats to be detected in the field, taken into the lab and re-synthesized along with GPS and other GNSS signals. In addition, Spirent’s threat intelligence library of actual and typical threats provides a wide range of GNSS segment errors and spoofing attacks, as well as space weather and other vulnerabilities for preventive troubleshooting.

    “Spirent wants to move beyond talking about the increase of GNSS vulnerabilities and offer a pragmatic approach to enable informed decision making when it comes to evaluating the impact of vulnerabilities,” said John Pottle, marketing director of Spirent’s Positioning Technology Division. “Through our Robust PNT Test Framework Spirent is pulling everything together to enable users to readily audit systems and take practical steps to improve resilience.”

    Spirent’s New GSS100D Detector, developed in collaboration with Nottingham Scientific Ltd., enables detection, characterization and analysis of real GNSS threats.

    The Robust PNT test framework is being demonstrated on the Spirent booth at ION GNSS+ 2015 this week.

    Spirent’s Robust PNT Test Framework.
    Spirent’s Robust PNT Test Framework.

  • Inexpensive Hack Spoofs GPS in Smartphones, Drones

    Researchers at Qihoo 360, a Chinese Internet security firm, say they have found a way to make a GPS emulator that can falsify the location of smartphones and in-car navigation systems, reports Forbes. The system is inexpensive compared to expensive, sophisticated GPS emulators that can cost thousands of dollars.

    Qihoo’s researchers hacked a Tesla Model S in 2014, taking control of the car’s lock, horn and flashing lights.

    Qihoo lead researcher Lin Huang is the first Chinese woman to present at the yearly hacker conference Defcon, held in Las Vegas on Aug. 6-9. Huang said her team used common software-defined radio (SDR) tools to create their module and software. They also used open-source software found on Github that had come from researchers at a Chinese university, along with their own code.

    The SDR tools used include HackRF, described by Forbes as the $300 wireless Swiss army knife for hackers. The small board can move between radio frequencies, and read and transmit to a broad range of radio frequencies. On smartphones, the attack targets navigation signals delivered at the chipset level, on both Apple or Android smartphones.

    Huang suggests that chipset manufacturers consider introducing new software that can better detect GPS spoofing.

    One potential target of such spoofing is a drone., which could be commandeered by the spoofer and taken into restricted airspace. Alternatively, it’s possible to make drones believe they’re in a no-fly area.

    The Qihoo team demonstrated such attacks using the free and open source GNU Radio, among other tools, to alter the GPS coordinates on a DJI Phantom 3. In a video at Forbes,  filmed from a drone-mounted camera, the hackers force a UAV to crash land.

    The researchers said the weaknesses could be fixed by DJI and other drone makers, but they would have to do so at the GPS chip level, meaning any drones already out there are unlikely to receive an update.

  • A WINS for Warfighters

    A WINS for Warfighters

    The current WINS form factor (left) sits beside a prototype for the future incarnation.
    The current WINS form factor (left) sits beside a prototype for the future incarnation.

    The Evolution of the Warfighter Integrated Navigation System

    A new device is being developed to enable foot soldiers to find their exact location in GPS-denied situations. If satellite signals are blocked by heavy jungle canopy, or because of enemy interference, soldiers — and Headquarters — will still know where they are with the Warfighter Integrated Navigation System (WINS).

    WINS will be a compact, wearable navigation device capable of operating either as a standalone system or networked to distribute position location information to other soldier platforms. WINS will extend positioning capability for soldiers in environments where GPS is not available, reducing the effect of GPS interference and enabling integrity monitoring for trusted position reporting.

    The technology behind WINS is being developed at the U.S. Army’s Communications Electronics Research Development and Engineering Center (CERDEC) labs. “WINS will be not just one technology; it’s a soldier-worn multi-sensor source incorporating information from GPS, inertials, vision-aided navigation, RF ranging, etc.,” explained John DelColliano, chief for CERDEC’s PNT Branch, which falls under CERDEC’s Command, Power and Integration Directorate (CP&I).

    “All these will tie in to making a more robust navigation system, so if you’re in a situation where GPS fails, you can have other things to back you up.” For instance, inertial sensors will calculate an offset from the last-known GPS location using footsteps taken, speed, acceleration and time.

    “The bottom line is that the soldier, without having to do any extra work on his own, will have a navigation system on his person that will provide him with a solution that he can count on when he needs it,” DelColliano said.

    WINS is expected to help eliminate dependence on vulnerable commercial receivers. It will improve positioning in GPS-degraded environments, enduring some jamming and providing positioning indoors and in urban areas. It will enable soldier-based cooperative engagements and provide trusted dismounted soldier position through integration with Selective Availability Anti-Spoofing Module (SAASM) GPS receivers and redundant navigation sensors.

    “CP&I’s PNT branch has worked on these individual technologies for many years, but we’ve always had the vision of an integrated solution,” DelColliano said. “That’s where we are today. It makes the most sense for what the soldier is going to need in the battlefield.” With a WINS-equipped solder, DelColliano said, “We’ll be able to know where he is and at what time, and we’ll be able to track if something happened to him. This capability will also enable our forces to be more mobile and maneuverable. It allows the commander and HQ to see where each squad is.”

    As part of a technology demonstration program at Fort Dix, N.J., WINS is being developed under an incremental build process as researchers consider what functionality should be incorporated. The engineering specifications for WINS are expected to be transferred to Program Executive Office, Intelligence and Electronic Warfare & Sensors by 2017, and from there eventually be made available to soldiers.

    Future WINS capabilities

    The final version of the WINS will have the following capabilities:

    • Military GPS for a protected signal and anti-jam capability on the soldier.
    • Inertial measurement unit for soldiers to track their location.
    • RF ranging using a radio or radio-like device to communicate between soldier-worn nodes and determine the range between soldiers, computing positions through triangulation relative to GPS.
    • Vision-aided navigation using the same kind of camera as in a cell phone, which is ideal for SWaP-C (size, weight and power compliance), to help navigate by tracking the soldier’s motion through an environment.
    • Network-assisted navigation and GPS.
    • Chip-scale atomic clock.

  • All GNSS Attend, But Galileo Gets the Spotlight

    Tim Reynolds
    Tim Reynolds

    First and foremost, let’s give a big hand to Adam and Anastasia, the two Galileo FOC satellites that were successfully launched on March 27. Following the not-so-successful Galileo launch in August, it was imperative that this go smoothly.

    Although the Double-A launch occurred after the conclusion of this year’s Munich Satellite Navigation Summit, anticipation of the event set the context for the entire convocation. The summit is a fixture on the European and global GNSS calendar. It is always intense, often spectacular and sometimes leaves one with contradictory feelings. This year it took place March 24-26 and sought to determine the future of PNT, encouraging delegates to look into the crystal ball and predict developments.

    If we go by the number of times these words were repeated during the three days of the summit, the future will hinge around compatibility and interoperability. The multi-constellation GNSS is already here. The elephant in the room remains, as always, interference, but here integration of alternative sensors and signals should hold the key to continuous and possibly resilient operations.

    As usual the summit kicked off with a high-level plenary in the imposing Allerheiligen-Hofkirche (Court Church of All Saints) in the Residenz München, the Bavarian royal palace. The welcoming speeches and presentations were interspersed with some pleasant jazz, and the atmosphere was relaxed.

    Into the Crystal Ball

    Matthias Petschke, director of EU Satellite Navigation Programmes at the European Commission, admitted that 2014 had been difficult, but he was looking forward to 2015. Clearly the deployment of the Galileo infrastructure — especially the space segment — was critical, and the March 27 launch was very much on his mind. However, he expressed confidence that the launch would be fine and that satellite production was, and would remain, on schedule. In the long view, he stated: “We will make it for 2020,” signifying full operational capability (FOC).

    He also talked about stimulating global markets to foster uptake of Galileo and EGNOS, and this was discussed by Carlo des Dorides, executive director of the European GNSS Agency (GSA). The ground infrastructure is very much in place and preparing for the Galileo exploitation phase. A significant milestone in that process would be finding the right partner to lead Galileo operations for the next ten years. A tender was now in process to find that organization or consortium. Des Dorides described the process as a competitive dialogue with the emphasis on finding a partner who can inspire new ideas and provide innovative solutions. The contract is big, worth around 1 billion euros.

    Carlo des Dorides, Executive Director of the European GNSS Agency (GSA), discusses the 1 billion euro tender, now in process to find the organization or consortium to lead Galileo operations for the next ten years. Photo: GSA
    Carlo des Dorides, Executive Director of the European GNSS Agency (GSA), discusses the 1 billion euro tender, now in process to find the organization or consortium to lead Galileo operations for the next ten years. Photo: GSA

    He also emphasized the successes for EGNOS in the year. Almost 180 airports now benefit from EGNOS-enabled approaches and more than 70 percent of “GNSS-enabled” farmers in EU use the EU’s SBAS.

    Johann-Dietrich Wörner, chairman of the German Aerospace Centre (DLR) — and the nominated next Director-General of ESA – highlighted the growing dependence of critical services on GNSS. In this context multiple systems were not a question of competition; it was all about redundancy and safety. Multi-GNSS improves availability, accuracy and reliability.

    The view from the United States was given by Harold “Stormy” Martin, Director, National Coordination Office for Space-Based Positioning, Navigation, and Timing in Washington, D.C. The GPS fleet was now 30 strong in orbit including four successful launches in 2014 and he stated the 2014 averaged user range error to be 70 cms — the best ever — and improving year on year.

    One major upcoming trend is a realization that there’s a need to establish a U.S.-wide backup coverage for GPS outage due to natural or man-made interference. The U.S. is currently assessing alternatives with a decision likely in summer 2015.

    There was a particularly warm welcome from the audience for Michael Khailov, deputy head of Roscosmos and co-ordinator for GLONASS. Last year the Russians were conspicuous by their absence at the Munich Summit, but for 2015, despite the intervening local difficulty in Ukraine, they were back in force. Khailov claimed that the sustainable development of the world depends on GNSS. On more esoteric ground he stated that GLONASS had maintained stable operations in 2014 and three more satellites had bene launched. Further launches would depend on operational circumstances. The user domains for GLONASS were continuously expanding. Continuing the summit text he said that it was better [working] together than separately — in fact separately often doesn’t work at all and therefore we must continue to promote interoperability and the Munich Satellite Summit is a good forum for this.

    Jianyun Chen of the China Satellite Navigation bureau also took up the theme of all GNSS together. Sixteen Beidou (pronounced — for the avoidance of doubt — as ‘bay-doe’) had been launched since 2007 and the Chinese had been in discussion with Russia to ensure full interoperability with GLONASS. This process will be repeated with GPS and Galileo.

    GNSS Updates

    One of the idiosyncrasies of the Munich Summit is its very discreet signage. If you don’t know where it is — and specifically the correct side door that brings you up two floors to the main Max Joseph Saal venue — it is highly likely you’ll miss it! But once you are in it is two full-on days of updates on systems and discussions on a vast range of topics that impinge on the development and implementation of GNSS around the world.

    Discreet signage. Photo: GSA
    Discreet signage. Photo: GSA

    The first two session of the summit proper gave updates on the GNSS systems in operation and under development as well as the regional and augmentation systems. Much of the material was slightly more detailed versions of presentations at the plenary but a few news snippet emerged.

    “Stormy” Martin said that a modified battery charge control had been implemented that would extend operational life for some of the fleet by one or two years. He also reiterated the improving accuracy performance of GPS which was now much better that its published standards. He predicted that the first GPS III would be available for launch in 2016 and said that GPS was improving every day.

    Eric Chatre from the European Commission reiterated that Galileo was still expecting to start early services in 2016 with full operational capability in 2020. He expected 18 satellites to be launched by 2018. The new Ariane 5 launcher will enable the launch of four satellites at one time and the first launch with this system would be in 2016. In terms of the ground segment only one station in the Pacific was yet to be established.

    Sergey Karutin of Roscosmos talked about a four-fold accuracy improvement for GLONASS with the use of new clocks and the introduction of new CDMA signals that will improve accuracy and access. According to Dongfeng Yu of the China Satellite Navigation Office the BeiDou constellation is moving from “regional to global, active to passive” and is aiming for global coverage by 2020.

    U.S. SBAS developments were covered by Deborah Lawrence of the Federal Aviation Administration (FAA). The Wide Area Augmentation System (WAAS) now has 100 percent coverage for LPV200 in CONUS. More than 41,000 runway ends are now included, and she predicted full completion in 2016.

    Jean-Marc Pieplu of the GSA talked about EGNOS status. The next system release (2.4.1) should be published in Q3 2015 and will include a significant input on ionospheric corrections. Further service evolution includes a plan to declare LPV 200 in Q4 this year and EGNOS coverage will be extended to 72 deg North and ensure full coverage of the 28 EU member states.

    The Russian Augmentation system SDCM performs at 0.8 metre accuracy according to Grigory Stupak of JSC / Russian Space Systems. He noted new validated SDCM ground stations had been established in Antarctica and Brazil and stated that global exploitation was a key objective for SDCM as its satellite coverage was very wide. GLONASS and GPS together could ensure complete coverage. He also indicated that work was in hand for SDCM SBAS service certification for LPV 200 and he called for providers of all WAAS to work closely together.

    2020 Vision

    After lunch we were offered the chance to hear some expert views on the future of GNSS and PNT with Prof Vidal Ashkenazi of Nottingham Scientific Limited asking for their vision of GNSS in 2020. By that year there should be 100-120 GNSS satellites in orbit, multi-constellation receivers would be the norm, but what would be the new applications and what were the challenges?

    Jamming and spoofing would still be issues. Pierre Bouniol of Thales thought that in civil aircraft receivers would probably incorporate jamming indicators by 2020 to inform users when signals may be compromised. For Stuart Riley of Trimble the key was integration of other sensor signals to bridge any GNSS signal outage. Gang Mao of Unicore Communications Inc. in China considered multiple frequencies to be a big help in reducing the threat of jamming. Nigel Davies of QinetiQ agreed saying there were a host of technical solutions but key for success would be solutions that use low power, are low cost and feature high usability. He also noted that safety certification of receivers for use in driverless vehicles would be required and this challenging application would need the provision of robust continuous navigation — and sub-metre accuracy.

    The future market for GNSS was also discussed in a session that unveiled the GSA’s 4th Issue of its comprehensive GNSS Market Report. With almost four billion GNSS devices used worldwide and all regions experiencing growth, GNSS represents an unprecedented business opportunity. Over the past 15 months the GSA’s team of market monitoring experts has taken a close look at all aspects of the GNSS marketplace with analysis of both hardware and software market opportunities, technology trends and future developments.

    Gian-Gherardo Calini, Head of Market Development at GSA, gives highlights of the comprehensive GNSS Global Market report. He will deliver this information in an April 16 webinar hosted by GPS World. Photo: GSA
    Gian-Gherardo Calini, Head of Market Development at GSA, gives highlights of the comprehensive GNSS Global Market report. He will deliver this information in an April 16 webinar hosted by GPS World. Photo: GSA

    The top-line results were presented by Gian-Gherardo Calini, Head of Market Development at GSA. GNSS is one of the few growing markets in the world showing 12.7 percent CAGR. It is a very attractive market with volumes and revenues driven by mass market segments: the dominant two being Location-based services and transport applications. This latest edition includes information a new market segment: Timing and Synchronisation. One area that is not included is security and government applications. Mr Calini indicated that this information has been collected by the GSA team but as it is essentially for users of the Public Restricted Service (PRS) it was not included in the open report.

    Although the report is very much “Galileo flavored,” its findings are of great importance and value to whole GNSS community and will be the subject of a GPS World webinar with Mr Calini and myself on 16 April. You can register — free — for this informative global perspective now.

    A panel discussion followed and covered a range of topics and applications from aviation to agriculture. Again the consensus was that chips would become multi-constellation and quickly. Philippe Prats of STMicroelectronic outlined automotive applications from insurance applications to advanced driver assistance systems (ADAS).

    The role of government mandates in establishing markets was seen as positive. The e911 mandate in the states had provided the seed for GPS integration into smartphones. Similarly authentication was also seem as a significant future market driver.

    Multi frequency was also showing on industry’s radar and in a couple of years will be a reality thought Philippe Prats with the main motivation being better accuracy. Frank van Diggelen of Broadcom highlighted the recent GPS World feature demonstrating cm accuracy on a smartphone.

    Legal Issues

    A dedicated session on legal issues was not the best attended part of the conference, which is a shame as it had some serious points to raise and highlighted a gap that is opening up between our technical abilities in GNSS and the legal basis for its use. The Munich Summit is to be commended for its commitment to providing a platform for these issues every year; they are often ignored elsewhere.

    Oliver Heinrichs, a partner at BHO Legal in Cologne, emphasised the need to establish a firm regulatory framework and to ensure that any decisions did not cross World Trade Organisation (WTO) provisions and the General Agreement on Tariffs and Trade (GATT). In particular the idea of mandating a specific GNSS for applications such as emergency response systems in cars may well be incompatible with WTO rules.

    Amedeo Arena of Universitá degli Studi di Napoli Federico II in Naples noted that all GNSS players were members of the WTO and considered that GNSS services and their trade was definitely “caught by the GATTs” so no favouritism for ‘home’ systems should be allowed.

    Another area of controversy is automated vehicles. In discussion after the session I learnt that current international conventions governing the use of motorised vehicles require a human supervisory role at all times. There will need to be some fundamental legal groundwork done before the first driverless vehicles will be allowed out on the road for real.

    These are legally complex issues and certainty will only come from test cases. Talking of complexity Aleksey Bolkunov of the Russian Federal Space Agency revealed that the legal, regulatory and standardisation measures governing GLONASS and GNSS in Russia consisted of more than 900 documents originating at various different levels of the state. This clearly gave great scope for “regulatory collisions” and he is involved in work to develop a single regulatory framework that should eliminate the remaining barriers to GNSS use in Russia.

    Emerging Applications

    Peter Grognard of Galileo Services chaired a final session of the day on emerging applications. Bruno Bougard of Septentrio saw dependable accuracy as key to emerging markets. He thought high precision driven by surveying was becoming more and more mainstream. For autonomous driving the challenge was to provide cost-effective, dependable accuracy at 10-30cm that was safe, reliable, and always available. This would require multi GNSS, multiple signals, highly integrated sensors and transparent and open augmentation.

    For Neil Gerein of Novatel the mantra is “Accuracy, availability, assurance.” Users needed availability to their PNT solutions at all times. He also saw future applications integrating GNSS with inertial sensors and correction systems for high accuracy without the need for a base station.

    or Neil Gerein of Novatel the mantra is “Accuracy, availability, assurance." Photo: GSA
    or Neil Gerein of Novatel the mantra is “Accuracy, availability, assurance.” Photo: GSA

    Lionel Garin of Qualcomm Inc talked about ADAS. Safety was paramount and he foresaw the need for rigorous design and certification procedures similar to that required for the aviation market. Fortunately the industry has lots of expertise here. Philip Mattos of u-blox UK argued that a volume market is in femtocell and small cell synchronisation in mobile networks where GNSS is the lowest cost solution.

    Tom Stansell praised geometry as the most important and unique ingredient supplied by multi constellation GNSS. And the second most important ingredient was interoperability. He doubted users would care where their signals originated and devices would still be generically described as ‘GPS’ into the future. Application growth will be stimulated by the better geometry supplied by multi-GNSS constellations. When the E6 signal became available he predicted that 10cm accuracy would enable reliable lane keeping for ADAS.

    And Galileo will supply E6 for free said Ignacio Fernandez Hernandez from the European Commission. Ignacio works on the Galileo Commercial Service design and outlined some significant differentiators of the European system including its broad signal for high accuracy and better multipath resilience, more stable clocks and improved ionospheric modelling compared to GPS.

    Lionel Garin sounded a note of caution at the end of the session when he noted that multi constellation ability was good, but he was not sure what was actually gained beyond two, or perhaps three, constellations.

    GNSS for Weather

    The final day of the conference saw a few fragile heads courtesy of the previous evening’s Summit Space Night 2015 sponsored by Airbus Defence & Space, which took place at the Filmcasino am Hofgarten close to the conference venue. And the first session, chaired by Oliver Montenbruck from the DLR, certainly required a clear focus as we were taken through the use of GNSS in space geodesy, space navigation and reflectometry.

    Roland Pail from the Technical University, Munich described results from the satellite gravity missions GRACE and GOCE that looked at mass transport processes on our dynamic Earth. A particularly sobering animation showed the extent of ice mass loss from Greenland over the past decade. But what is role of gnss here? The ability to give precise positioning of the satellites and the fact that the satellite orbits carry information on the gravity field.

    Atmosphere sounding using GNSS radio occultation allows precise atmospheric profiles with global coverage in all-weathers. Jens Wickert of the Helmholtz Centre Potsdam said that since 2006 these high vertical resolution profiles had been making a significant impact on the world’s weather forecasting including improved hurricane forecasts. It was also a bias free technique for observing global temperature change. With a multi-GNSS future new missions could be planned as more signals would reduce noise. Combining GNSS and reflectometry could enable accurate tsunami detection from space. Similarly Prof Antonio Rius from Barcelona was using reflected GNSS signals to determine data on the surface of the sea such as surface roughness, extent of sea ice and early warning of a tsunami.

    Stefan Sassen of Airbus Defence & Space described the LION GNSS navigation receiver for MEO and LEO platforms. The unit was qualified since 2014 and now 50 were on order. LION is highly flexible with multi-frequency, multi-constellation and multi-antennae configurations possible. It was accurate enough for autonomous orbit raising (a few kms) and or station keeping (to within 100cm).

    Finally Manfred Sust of RUAG Space GmbH said that space borne gnss receivers were true enabling technologies for Earth Observation missions as precise orbit determination was key to capturing sharper images.

    Alternatives

    The second session of the day returned to the practical issues around possible alternative or complementary PNT (APNT) systems. As GNSS becomes ubiquitous many terrestrial PNT systems are being decommissioned (LORAN, VOR), but the potential vulnerability of GNSS signals to interference is highlighting the need for backup. The challenge being to balance functionality and cost in the search for “plan ‘B’ for GNSS” as chairman Michael Meurer from DLR described it.

    The FAA’s Deborah Lawrence reiterated her plans for scoping and implementing a backup system to cope with a GPS outage in the US. The FAA is currently engaging with stakeholders to define what the minimum operational target for a GPS outage should be to set the basis for procurement activity. The timeline for a final investment decision was now December 2018.

    For Europe Gerhard Berz of Eurocontrol thought there were many potential APNT in place and the topic was in the SESAR 2020 research programme. He thought existing DME could potentially do the job in Europe as it had good coverage, but the challenge is to get good geometry and coverage at low altitudes, in remoter areas and over water.

    Prof Per Enge of Stanford University “put the moose on the table” and pointed to the 978 and 1030 ranging frequencies as an existing system that could be used for positioning. But how accurate was it? Airborne experiments had shown good agreement with GPS positioning with an accuracy of around 100m and in turns 300m, which was good enough in an emergency. Further tests using a UAV at spider infested Camp Rogers had demonstrated APNT in flight with 50m error. The UAV itself was specifically developed to navigate using APNT while looking for GNSS jammers.

    Wouter Pelgrum of Ohio University discussed the relative merits of eLORAN, which has high power – and therefore difficult to jam – and beyond line of site accuracy of less than 10m, and alternatives such as collocation of pseudolites with mobile phone cell towers. This could also enable high accuracy indoors positioning applications. He believed that APNT will need to be context specific and there was no single solution.

    Belabbas Boubeker of the DLR discussed modular APNT concepts while Nick Ward of the UK’s General Lighthouse Authorities indicated there was no coordinated policy on resilient PNT in the European maritime sector at present but his authority and others were exploring the possibility of using eLORAN as a commercial enterprise. Nine transmitters were operational in Europe and the service had been declared in 2014.

    Michael Hoppe of Fachstelle der WSV für Verkehrstechniken said resilient PNT was a core element of e-navigation for waterways. A combination of techniques such as medium frequency RF, AIS and eLoran could give good accuracy in areas of highest traffic. First results of trials were encouraging.

    Processing Power

    The final session of the Summit to grab my full attention was chaired by Frank van Diggelen of Broadcom. He led a wide ranging debate on GNSS receiver architecture trends and more generally the future of chip design and fabrication: are we approaching the end of Moore’s law and if so — what next?

    Recently “The balance of power has moved back onto the GNSS chip” to enable lower device power use. To highlight current developments Frank described a couple of Broadcom products: the Broadcom 4773 “location hub” that is at the heart of the Samsung Galaxy 6 “super smart phone” and the 4774 that can access signals from all four GNSS constellations and will be shipping in early 2016 on new smartphones.

    In fact earlier this year the 4774 was used to make a first fix using signals from four different GNSS constellations (with signals from one each of GPS, GLONASS, Galileo and BEIDOU satellites) and a significant event in terms of our multi-constellation future.

    Greg Turetzky of Intel talked about the benefits and challenges for GNSS in advanced silicon processes. He noted that Intel is now shipping 14nm technology and plans were in hand for the next two generations (10nm and 7nm). Moore’s law has been a great enabler for modern society. If automobiles had taken a similar development in the same timeframe we would all be driving cars with a maximum speed of some 300 000 km/hour that cost us around 4 cents to buy!

    The big challenge for GNSS architecture was to take advantage of the smaller geometries while greatly reducing standby power. The integration of multiple radio sources to provide a single location solution was key giving ubiquitous location capability that will improve the experience of every mobile product.

    Looking into his crystal ball, Peter Anderson of Integrated Navigation Systems in the UK saw that integrating signals from complimentary technologies and sensors would be important but would lead to a greater demand for digital processing. He predicted that multiband receivers would become standard in consumer devices. He also pointed out that the worst potential source of GNSS jamming for a smartphone was the phone itself! The move to dual frequency would be helpful here.

    An overview of the Chinese XIHE system for seamless outdoor and indoor location was given by Dongkai Yang of Beihang University. This Beidou Innovative application provides a LBS system based on gnss and mobile communication networks to give a “fusion of communication and positioning for indoor positioning”. The system is being demonstrated in four areas in China in shopping malls. The target for positioning accuracy in the system is for less than 3 metres indoors and less than 1 metre outdoors.

    Franz Kreupl of Munich Technical University gave a sobering view of “life after silicon” – essentially it looks like there isn’t one. He outlined the limits to silicon technology such as tunnelling current and predicted some further progress could be made in reducing interconnect sizes and via circuit design. But new candidate materials for semiconductor electronics from carbon nanotubes to widely hailed 2-D materials graphene and MoS2 all suffer major issues that seem to make them non-starters.

    But do we need to keep on miniaturizing? Norbert Schuhmann of Fraunhofer IIS in Nuremberg thought that technology downscaling would have an end in terms of the physics, but especially in terms of reasonable cost. He thought 7nm and 2020 was the end point for the physics but that in fact 28nm should be seen as the actual last node in Moore’s law as from then scaling has no longer also been the path for cost reduction. He saw silicon on insulator technology and monolithic 3-D integration as possible paths forward, but the technology sweet spot — and well suited for GNSS — was 55nm and a format that was already extensively used in automotive applications.

  • Bill Supports eLoran as GPS Backup

    A bi-partisan group of legislators led by Congressman John Garamendi (D-Calif.) has introduced a bill that would require the U.S. Secretary of Defense to establish a backup for GPS within three years using eLoran.

    The National Positioning, Navigation, and Timing Resilience and Security Act of 2015, H.R. 1678, was co-sponsored by Congressmen Duncan Hunter (R-Calif.), Peter DeFazio (D-Ore.), and Frank LoBiondo (R-N.J). Garamendi is the ranking member of the House Transportation and uInfrastructure Subcommittee on the Coast Guard and Maritime Transportation.

    H.R. 1678 would require the secretary of defense, in coordination with the commandant of the Coast Guard and the secretary of transportation, to establish and sustain a reliable, land-based positioning and navigation system that will complement and backup America’s GPS for military and civilian uses by using eLoran.

    eLoran is the government’s existing and underused long-range navigation system infrastructure. The backup system would step in when GPS signals are corrupted, degraded, unreliable, or otherwise unavailable. A terrestrial-based system, eLoran wouldn’t be affected by atmospheric interruptions such as solar storms, or jamming or spoofing aimed at GPS.

    The bill directs the secretary of defense to incorporate the expertise and contributions of the private sector to quickly establish  system architecture, as well as build and operate the system.

    “GPS is much more than a LCD screen on your dashboard. It’s a technology used for much of our nation’s critical infrastructure and by almost every major industry in America, as well as the military, law enforcement, and first responders,” Garamendi said in a press release. “We are increasingly reliant on the precision, navigation, and timing services that GPS provides. From land navigation on cell phones to a timing source for our national infrastructure, we need a reliable backup system to GPS.”

    Garamendi said the bill would make the nation’s geopositioning infrastructure more resilient to “threats both natural and nefarious.” “A backup system could also reach places that GPS currently cannot, such as inside many buildings. This would help first responders and law enforcement more effectively protect the public,” he added.

    Other members of Congress are expected to sign on as co-sponsors after Congress returns from its spring recess, according to Dana A. Goward, president and executive director, Resilient Navigation and Timing Foundation.

    The eLoran PNT system would use enhanced long-range signals (eLoran) from 19 towers around the country, each with approximately a 1,000-mile range providing overlapping fields from which a device can derive its location. The back-up system would use the remaining Loran infrastructure and provide a secure and reliable cybersecurity insurance policy, said the press release.

    The U.S. atomic clock, accurate to one second in 300 million years, also serves as the base timing source for this backup GPS capability. This exceeds the timing needs of modern cell phones, creating an infrastructure backbone that is prepared to handle the evolution of consumer and industry electronic communications in the years ahead, the press release said.

    The bill sets out numerous requirements for the system, saying that it shall:

    • Be wireless, terrestrial, and wide area
    • Provide a precise, high-power 100 kilohertz signal
    • Be resilient and extremely difficult to disrupt or degrade
    • Be able to penetrate underground and inside buildings
    • Take full advantage of existing, unused Loran infrastructure
    • Work in concert with and complement any other similar positioning, navigation and timing systems, including eLoran.

    Since 2004, the federal government has recognized that the absence of a reliable backup system for GPS is a glaring economic and security threat to the United States, and has reaffirmed its interest in developing an eLoran as a reliable, land-based backup for GPS signals, the press release said.

    In January, the United States Army began soliciting information for eLoran receivers for the warfighter, either stand-alone or integrated with GPS, for use in Army and other Department of Defense maritime, aviation, or vehicular platforms, and for position and timing.

    The United Kingdom began using eLoran in October 2014 to protect its shipping lanes, which carry 95 percent of UK trade, in case of GPS signal loss.