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Interference, a Threat!?

Interference, a Threat!?. Chris Rizos. What is Interference?. GPS signal Noise RF Interference - jamming, unintentional RFI, multipath. GPS Signal. Environmental noise. RF Interference. What types of RFI are there?. Why is RFI a Threat? . Reduces S/N Degraded (or no) measurements

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Interference, a Threat!?

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  1. Interference, a Threat!? Chris Rizos

  2. What is Interference? • GPS signal • Noise • RF Interference - jamming, unintentional RFI, multipath GPS Signal Environmental noise RF Interference

  3. What types of RFI are there?

  4. Why is RFI a Threat? • Reduces S/N • Degraded (or no) measurements • Leads to degraded (or no) positioning accuracy • Can have “knock-on” effect (for multiple users) if GNSS CORS receiver(s) is(are) affected

  5. GNSS Vulnerability to Interference… • Single receiver• low-moderate accuracy applications• denial of service in zone of interference/jamming• geographically isolated consequences• mitigation/augmentation/backup strategies appropriate for user application • CORS network/infrastructure• high accuracy (&/or high integrity) applications• denial of service to ALL users of differential service• impact over wide area (possibly tens/hundreds of kms)• highest level of mitigation to protect CORS, independent of user requirements/concerns

  6. CORS Infrastructure… • Permanent high-grade GPS Rx:• low multipath antenna• comms & control box, to NCC• UPS• secure installation• Rx backup?

  7. CORS Network Infrastructure • Established by civilians beginning in the 1980s. • Initially to support high accuracy positioning apps. • Also provide enhanced accuracy and integrity for some navigation apps. • Established at range of scales … global, national, … and densities … 10s to 1000s km spacing. • Trend for all CORS to operate in real-time. • Increasingly diverse RTK/DGPS applications.

  8. Global IGS Infrastructure… redundancy Multitude of geoscience apps…but robust & not RT

  9. Global Commercial WADGPS… Fugro’s Omnistar …Navcom’s Starfire

  10. National CORS … geodesy Plus stns in SW Pacific, Antarctica, Macquarie Is., etc

  11. National CORS… navigation Part of global free-to-air DGPS network…

  12. Regional Coverage… GPSnet

  13. Local Coverage… SydNet Support local RTK operations, expand to other parts of NSW…

  14. Precision DGNSS Applications … • Machine guidance/ control in mining,construction & agriculture • Robotic navigation • Ports & logistics • Surveying & mapping • Scientific applications Real-time, high accuracy apps are very vulnerable to interruption of CORS service … not just Rx RFI but wireless comms link interference

  15. Protecting the CORSInfrastructure … • Interference to one CORSimpacts many users in zone of service … 10s-100s km • Little or no redundancy, especially for RT operations on land, i.e. for RTK-based apps • RT ops to support machine guidance/control are most vulnerable … alternatives? • How to use CORS network to detect (& localise?) interference/jamming sources?

  16. Research Challenge … a project of theCRC for Spatial Information Use CORS infrastructure as “sentinels”. Project objectives: • Characterise RFI, using SW Rx, simulated & real-world data • Build prototype ‘detection’ Rx • Test on several CORS sites • Study feasibility of using synchronised network of ‘detection’ Rxs for geo-location of RFI sources

  17. What is Affected by RFI?Receiver Operations … • AGC • LNA • Filters • Code Tracking Loops • Carrier Tracking Loops

  18. Which Observables are Affected? • Signal Quality (C/No) • Tracking Error • Correlator Output Power • Pseudorange Measurements • PVT Accuracy

  19. GPS Receiver and RFI Analysis Antenna Output Navigation Data Processing Radio Frequency Front End GPS Signal Acquisition & Tracking Pre-Correlation RFI Detection Post-Correlation RFI Detection

  20. Progress on Characterisation of RFI… TABATABAEI, A., DEMPSTER, A.G., & BARNES, J., 2005. Characterization of interference effects on GPS signal carrier phase error and pseudo-range. Spatial Sciences Conference, Melbourne, Australia, 12-16 September, 1323-1331, CD-ROM procs. TABATABAEI, A., 2006. Statistical inference technique in pre-correlation interference detection in GPS receivers. 19th Int. Tech. Meeting of the Satellite Division of the U.S. Inst. of Navigation, Fort Worth, Texas, 26-29 September. TABATABAEI, A., & DEMPSTER, A.G., 2006. A novel approach in detection and characterization of CW interference of GPS signal using receiver estimation of CNo. IEEE/ION PLANS, San Diego, California, 25-27 April. TABATABAEI, A., DEMPSTER, A.G., THAN, N.T., & BARNES, J., 2006. An application of post-correlation GPS receiver interference detection and characterization. Symp. on GPS/GNSS (IGNSS2006), Surfer’s Paradise, Australia, 17-21 July. www.gmat.unsw.edu.au/snap/new/news2006.htm#pubswww.gmat.unsw.edu.au/snap/about/publications_year.htm

  21. 1) Experiment Setup 2) Real-World Data

  22. RFI in Sydney … last week SBS TV Tx NordNav frontend sampling (spectrum)

  23. Next? Building a Detection Rx Key resource: “Namuru I” FPGA-based Rxwww.dynamics.co.nz/gpsreceiver

  24. Localisation Using CORS Network? CouldCORS network be used to localise GPS interference/jamming sources?

  25. Detection/Reference Station Hardware Antenna Array Interference Source Multi-RF Front-end What about synchronised, geographically dispersed detection Rxs ?- either AOA or TOA A/D Conversion • DSP Interference • Localiser Test-bed • TOA • AOA • RSS RFI Source Location

  26. Network Configuration…

  27. Concluding Remarks… • We must assume jamming/interference will happen…just look for it! • CORS infrastructure (& the increasing user base) must be protected…use CORS sites to detect/located RFI sources? • A number of RFI detection techniques can be refined/developed…just a matter of resources! • Ideal solution is RFI localisation using CORS/sentinel network…this is a challenge, but what an achievement! • UNSW actively engaged in this work…RFI detection/location, multipath studies, GNSS vulnerabilities, ‘intelligent’ Rx tracking, ultra-tight GNSS/INS integration, multi-sensor integration…

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