Presentation on theme: "Interference, a Threat!? Chris Rizos. What is Interference? GPS signal Noise RF Interference - jamming, unintentional RFI, multipath GPS Signal RF Interference."— Presentation transcript:
Interference, a Threat!? Chris Rizos
What is Interference? GPS signal Noise RF Interference - jamming, unintentional RFI, multipath GPS Signal RF Interference Environmental noise
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
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
CORS Infrastructure… Permanent high-grade GPS Rx: low multipath antenna comms & control box, to NCC UPS secure installation Rx backup?
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.
Global IGS Infrastructure… redundancy Multitude of geoscience apps…but robust & not RT
Global Commercial WADGPS… Fugro’s Omnistar … Navcom’s Starfire
National CORS … geodesy Plus stns in SW Pacific, Antarctica, Macquarie Is., etc
National CORS… navigation Part of global free-to-air DGPS network…
Regional Coverage… GPSnet
Local Coverage… SydNet Support local RTK operations, expand to other parts of NSW…
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
Interference to one CORS impacts 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? Protecting the CORS Infrastructure …
Research Challenge … a project of the CRC for Spatial Information 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 Use CORS infrastructure as “sentinels”. Project objectives:
What is Affected by RFI? Receiver Operations … AGC LNA Filters Code Tracking Loops Carrier Tracking Loops
Which Observables are Affected? Signal Quality (C/No) Tracking Error Correlator Output Power Pseudorange Measurements PVT Accuracy
GPS Receiver and RFI Analysis Radio Frequency Front End Antenna Navigation Data Processing Output GPS Signal Acquisition & Tracking
Progress on Characterisation of RFI… TABATABAEI, A., DEMPSTER, A.G., & BARNES, J., Characterization of interference effects on GPS signal carrier phase error and pseudo-range. Spatial Sciences Conference, Melbourne, Australia, September, , CD-ROM procs. TABATABAEI, A., 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, September. TABATABAEI, A., & DEMPSTER, A.G., A novel approach in detection and characterization of CW interference of GPS signal using receiver estimation of CNo. IEEE/ION PLANS, San Diego, California, April. TABATABAEI, A., DEMPSTER, A.G., THAN, N.T., & BARNES, J., An application of post-correlation GPS receiver interference detection and characterization. Symp. on GPS/GNSS (IGNSS2006), Surfer’s Paradise, Australia, July.
1) Experiment Setup2) Real-World Data
RFI in Sydney … last week SBS TV Tx NordNav frontend sampling (spectrum)
Next? Building a Detection Rx Key resource: “Namuru I” FPGA-based Rx
Localisation Using CORS Network? Could CORS network be used to localise GPS interference/jamming sources?
Antenna Array Multi-RF Front-end A/D Conversion RFI Source Location DSP Interference Localiser Test-bed TOA AOA RSS Detection/Reference Station Hardware Interference Source What about synchronised, geographically dispersed detection Rxs ? - either AOA or TOA
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…