Spirent Communications plc is offering a solution that enables the civil aviation industry to evaluate the growing threat of GNSS interference, jamming and spoofing.
The new GSS200D Interference Detector was developed as part of Spirent’s partnership with Nottingham Scientific Limited.
Spirent’s GSS200D interference detector.
As skies and airports become more congested, there is increasing pressure on airports to be safely accessible at all times — which cannot be achieved by relying solely on non-precision approaches with high minimums or on today’s expensive and rigid ground-based infrastructure such as ILS (Instrument Landing Systems).
Ground-Based Augmentation System (GBAS) and instrument approach procedures based on Satellite Based Augmentation Systems (SBAS), such as Localizer Performance with Vertical Guidance (LPV) and Required Navigation Performance (RNP), provide Air Traffic Management with flexible, cost-effective alternatives while providing equivalent operational performance.
For example, the European Geostationary Navigation Overlay Service (EGNOS) launched the LPV-200 service in Europe that enables aircraft approaches without the need for visual contact with the ground until a height of only 200ft. above the runway.
With this service, accessibility, sustainability, efficiency and safety of the landing are greatly improved, especially in bad weather conditions.
Spirent’s new GSS200D solution monitors the radio bands used by EGNOS, as well as other GNSS augmentation systems such as the Wide Area Augmentation System (WAAS) or the GPS Aided Geo Augmented Navigation system (GAGAN), to ensure awareness of interference that could compromise positioning information.
Since local interference near the runway in the GNSS bands could degrade position accuracy or lead to a total loss of the navigation service, it is critical to continuously monitor and understand the RF environment and level of interference around airports.
The GSS200D collects quantitative data on interference allowing assessment of the risks, so that robust mitigation plans can be created. The new Spirent solution has been trialed at a number of European airports, and has collected numerous interference signatures from both unintentional man-made interference and intentional jamming.
“As more airports begin to use GNSS-based instrument approach procedures, they need to know what could be affecting their GNSS signals,” said Martin Foulger, general manager of Spirent’s positioning business. “With this latest solution we can detect interference in the key radio bands, based on levels defined by the United Nations International Civil Aviation Organization and European Organisation for Civil Aviation Equipment. This enables the aviation industry to gain a much better understanding of the electronic environment, helping to avoid dangerous situations going forward.”
For more information on Spirent’s GNSS testing solutions, visit the website. To learn how to test receivers of GPS, Galileo and other GNSS, download Spirent’s latest eBook.
Topcon Positioning Group is offering a local positioning system (LPS) for concrete paving. The LPS Paving System is designed to provide a stringless paving solution in conditions when GNSS signals are blocked or unavailable.
It uses multiple Topcon PS series robotic total stations — tracking two prisms mounted to the concrete paver — for steering and elevation control.
“This robotic-based system does not encounter sensor outages from bridges and tight paving lanes, including sound walls and active traffic on a mainline project, which could be a problem using GPS,” said Brian Lingobardo, Topcon 3D road construction systems manager.
The LPS system uses the new MC-i4 receiver with LongLink for local communications between the robots.
“Multiple robots can be setup ahead of time for seamless transitions and without the need to stop to switch total stations. Often a contractor needs to minimize stoppage to achieve tight ride specifications on projects such as tollways,” Lingobardo said.
“The robots provide very accurate data to the paver’s control system and in turn the results are very impressive,” said Lingobardo.
Bordelon Marine, providers of vessel services to operators in the Gulf of Mexico and around the world, has selected acoustically aided inertial navigation technology from Sonardyne Inc., Houston, for its new ultra-light intervention vessel (ULIV) Brandon Bordelon.
The dual Ranger 2 Pro DP-INS systems, the highest specification available, will be used to track remotely operated underwater vehicles (ROVs)during inspection, repair and maintenance activities and provide an independent position reference for the vessel’s Marine Technologies Class 2 dynamic positioning system.
Specialized vessels such as the Brandon Bordelon conventionally rely on GNSS and ultra-short baseline (USBL) acoustics as their primary sources of dynamic positioning reference data.
However, a vessel’s station-keeping capability can be compromised in the event that the USBL is affected by thruster aeration or noise and the GNSS signal is simultaneously interrupted. The latter is particularly common around equatorial regions and during periods of high solar radiation.
Sonardyne’s Ranger 2 Pro DP-INS system addresses this operational vulnerability. It aids vessel positioning by exploiting the long term accuracy of Sonardyne’s Wideband 2 acoustic signal technology with high integrity, high update rate inertial measurements. The resulting navigation output has the ability to ride-through short-term acoustic disruptions and is completely independent from GNSS.
The Brandon Bordelon was delivered at the end of 2015 and is under a 60-day contract with Tidewater Subsea. Designed to support complex inspection, repair and maintenance operations, the vessel features a high-capacity deep-water crane, infrastructure for two work-class ROVs and a large, reconfigurable back-deck area.
In addition to the system’s deep water positioning performance and safety benefits, DP-INS has been proven to deliver valuable time and cost savings for vessel owners. It does not need a full seabed array of transponders to be installed and calibrated before subsea operations can commence.
For most subsea tasks, positioning specifications can be met with only one or two transponders deployed on the seabed. Additionally, as the system needs only occasional aiding from the acoustics, transponder battery life is substantially increased and the need to task an ROV to deploy and recover transponders for servicing is reduced.
The equipment supplied to Bordelon Marine included Sonardyne’s ship-mounted inertial navigation sensor and two HPT 7000 acoustic transceivers. The HPTs have been installed on the Brandon Bordelon through-hull deployment poles and are optimised for tracking and dynamic positioning in ultra-deep water.
Wes Bordelon, President/CEO Bordelon Marine said, “Equipping the Brandon Bordelon with Sonardyne’s Ranger 2 DP-INS, reflects our commitment to providing high-tech, high-spec equipment on our fit-for-purpose Stingray vessels and ensuring our fleet is safe, efficient and cost-effective.
“Ranger 2 DP-INS is a mature, field proven technology that addresses operators’ need for a robust, independent DP reference that provides an update rate and accuracy on par with GNSS,” said Ralph Gall, Technical Sales Manager at Sonardyne in Houston. He added, “The Brandon Bordelon joins a significant fleet of vessels which depend upon our acoustically-aided inertial technology for safer and more efficient dynamic positioning operations.”
A Proactive Approach for More Efficient Spectrum Use
In my vision of the future of GNSS, I see a pressing need to manage radio-frequency spectrum more efficiently. This will drive the creation of official standards for GNSS receivers, and better design of those receivers with better filters at lower cost, to protect against out-of-band and near-band interference. This in turn will enable user to undertake widespread monitoring and reporting of in-band interference, and create the freedom for many technologies to explore wider and more productive use of all bands of the radio-frequency spectrum.
Spectrum Management
As a consequence of unprecedented technological development on all fronts and in many fields, the radio-frequency spectrum is very congested. All countries, and the United States in particular, must find ways to use this spectrum more efficiently. Licenses for spectrum bands are very expensive, and special interest groups do all they can to secure ownership of any part of the spectrum and to prevent others from competing with them. There is an intense struggle going on, both behind the scenes and in the public arena; it has been called “the spectrum wars.” These involve big companies, very high stakes, politicians, and special interest groups. The Federal Communications Commission (FCC) seems caught, powerless, in the crossfire between these powerhouses.
GNSS Interference
GNSS interference exists everywhere and comes from many different sources, identified and unidentified, intentional or unintentional. The 1-dB effect on GNSS of the proposed LightSquared signal is negligible compared to what already exists. The reason that the LightSquared plan encountered so much opposition was not because of its effect on GNSS. It was because of its effect on the competing business models of large companies and special interest groups.
With the tools that we have created and embedded in our receivers, everyone can easily see that widespread interference already exists in most places, especially in cities, and that interferences can easily be monitored and automatically reported. It seems no organization has ownership of regularly monitoring interferences on these bands and taking corrective actions. This is partly because the tools to easily monitor and report interferences did not exist earlier.
GNSS Receivers
Current GNSS receivers on the market and in use around the world rely on inadequate designs. The technology does in fact exist to overcome out-of-band interference problems such as LightSquared and many others commonly encountered in today’s congested radio-frequency environment. There is no reason to prohibit others from using bands near GNSS; this just makes spectrum use inefficient. Continued shipping of inadequate, inefficient receivers by current manufacturers only increases and compounds the problems encountered by users.
There are standards for manufacturing countless industrial goods — for example, something as ordinary as car tires or — but there is no standard for building GNSS receivers that will be used in critical applications.
So far, the FCC has been silent on this topic, and has not established guidelines for GNSS receivers that are used in critical applications. The civilian users of GNSS, such as the U.S. National Geodetic Survey, the U.S. Geological Survey, the Federal Aviation Administration, and so on, have criteria for all sorts of little equipment, but there is no criteria for GNSS receivers that they claim are so important for their job.
Instead of taking the proactive and productive approach of putting filters into the receivers that they use, these organizations advocate keeping spectrum bands adjacent to GNSS off-limits to other users. Manufacturers do not see any reason to make better receivers while such a powerful lobby protects them.
Interference monitoring and reporting is strongly desirable for places such as GNSS reference stations, or for users to see the interferences before they start a jog that they are tracking on their GPS-enabled personal training device — just as pilots check the weather before they take off.
Special Interest Groups, Politics, and Blind Followers
The problem that LightSquared encountered was that its proposal impacted the business models of special interest groups. Although we — that is, JAVAD GNSS in presentations before the FCC in Washington DC — showed that other interferences exist in cities, the FCC did not care, and GNSS magazine editors did not care. They just blindly followed what the special interest groups had planned for them.
Brad Parkinson, in his article “PNT for the Nation: Three Key Attributes and Nine Druthers” in the October issue of GPS World, did not even hint at guidelines for building GNSS receivers. This is similar to formulating guideline on how to build and clean the roads while having no guidelines on how to build tires that are going to ride on the roads.
In Parkinson’s long list of recommendations, there was no mention at all that we need to build better GNSS receivers and be able to monitor interferences. There are guidelines and standards for how build every little item, but none for GNSS receivers that are claimed to be so essential for our security and prosperity.
Military GPS receivers do not have protection against even one particular type of interference such as that posed by LightSquared — and the suggested approach was to bomb such interferences, which most admit that of course cannot be done. This is a bad attitude. The cost of a filter in a receiver is almost nothing. A precision bomb costs millions if you factor in development costs, and deployment and delivery puts the full cost even higher.
The case is similar for GNSS receivers used in commercial airplanes. Instead of pushing for a better GNSS receiver design, the FAA simply hopes that interference does not happen.
Conclusion
These are my predictions — and my strongest possible recommendations — for the future of GNSS.
The FCC will create standards for GNSS receivers.
GNSS manufacturers will be forced to build better receivers.
GNSS users will benefit from better receivers at a lower cost.
Interference monitoring and reporting will become a desirable feature of GNSS receivers.
Bands near the GNSS spectrum will be freed for more efficient use by all types of productive technology.
I am proud to be a part of the efforts to make these happen, against all odds.
Javad Ashjaee received his Ph.D. in electrical engineering from the University of Iowa. He was chairman of the Computer Engineering Department, Tehran University of Technology, 1976-1981. He began his GPS engineering career at Trimble Navigation, 1981–1986. Founder and president of Ashtech Inc., 1986–1995, the company that produced the first integrated GPS-GLONASS receivers; founder and CEO of Javad Positioning Systems, 1996–2000, which he sold to Topcon Corporation. He founded JAVAD GNSS in 2007, and is currently president and CEO. In 2010, the company introduced the integrated geodetic receiver TRIUMPH-VS, with a GNSS Interference Analyzer, capable of tracking current and next-generation signals of GPS, GLONASS, QZSS, and Galileo signals. In 2011, the company introduced a LightSquared-compatible GNSS receiver.
