Testing GNSS Systems and Devices David Pearce Simplifying the - - PowerPoint PPT Presentation

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Testing GNSS Systems and Devices David Pearce Simplifying the - - PowerPoint PPT Presentation

Apr 08, 2024 364 likes •631 views

Testing GNSS Systems and Devices David Pearce Simplifying the integration of Position, Navigation, and Timing technologies into mission-critical systems. High-End Commercial Apps Military / Aerospace Datacenters UAVs

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Testing GNSS Systems and Devices

David Pearce

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  • Military / Aerospace
  • UAVs
  • Electronic Warfare
  • C4ISR

Simplifying the integration of Position, Navigation, and Timing technologies into mission-critical systems.

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  • High-End Commercial Apps
  • Datacenters
  • Robotics/Telematics
  • IDM
  • GIS Data Mining
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Testing GPS Systems & Integration

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4

GNSS Test Methods

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GNSS Test Methods

Simulation Record/ Replay Live Sky True real life constellation replication X X X Repeatable tests X X Replay fixed scenarios ”that has already happened” X X Modify parameters during test X Scenarios that have ”not yet happened” X Simulate events (satellite drop out, change received signal strength, etc) X Simulate multipath X Simulate noise and test sensitivity X Simulate leap second X Test performance with future systems X

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  • Sensitivity
  • Acquisition
  • Tracking
  • Re-aquisition
  • Time to First Fix (TTFF)
  • Location Accuracy
  • Stationary
  • Dynamic
  • Trajectories
  • Time Transfer
  • Leap Second

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Basic Test Cases

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  • 1. Receiver warm-up time
  • 2. Acquisition time
  • 3. Settling time for code and carrier

tracking

  • 4. Navigation data read time
  • 5. Time to compute the navigation

solution

  • 6. Time the retrieve the system time

reference

  • Almanac
  • Orbit and status information for EVERY satellite
  • Each satellite transmits the entire almanac
  • Ionospheric model
  • Leap second information
  • 1/25 of the Almanac data is transmitted in the navigation message
  • Takes 25 complete navigation messages to receive entire almanac (12.5

minutes)

  • Considered valid for 180 days
  • Ephemeris
  • Orbital information for each satellite
  • Each satellite only transmits its own data
  • Considered valid for about 4 hours

Time to First Fix

Almanac Ephemeris Position/Time Cold Start No No No Warm Start Yes No Yes Hot Start Yes Yes Yes Understand cold vs warm vs hot start is critical when generating GPS RF

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  • Time accuracy
  • Leap second handling

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Time Transfer

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  • Multipath
  • Interference
  • Signal fading

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Impairments to GPS

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Test Susceptibility to Jamming and Spoofing

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  • In either case, after detection, there are various mitigation techniques
  • Types of GPS/GNSS Interferers:

What is IDM and GPS Spoofing?

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Interference Detection and Mitigation for improving resiliency of PNT

Accidental / Unintentional Jamming Intentional Jamming (easy to do) Intentional Spoofing (harder to do) Jamming Easy to Detect Spoofing Difficult to Detect!

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  • Interference: radio-frequency signals

that interfere with the ability of the GNSS receiver to extract GNSS signal information from the background noise

  • Jamming: Intentional Interference
  • PPD: Personal Privacy Device

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Jamming & Interference

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Jammer Types

  • Majority of PPD jammers are chirp

jammers

  • GPS L1 Frequency – 1.57542GHz
  • Common Sweep Period – 9us
  • Bandwidth 1kHz (CW) – 44.9MHz, 20MHz

is typical

  • Also available
  • Narrowband Jammers
  • CW Jammers
  • Location Based Jammers

Simulating Jammers

  • CW – choose frequency based on

GNSS constellation

  • Simulates the CW type jammer
  • Noise – set bandwidth around center

frequency

  • Simulates the narrowband jammer
  • Sweep – set sweep time 4µs – 20µs
  • Simulates the chirp jammer
  • All GNSS frequency bands can be

simulated

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Testing Jamming

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  • Receiver alone
  • Example setup:
  • Simulator used for GNSS signals + jamming signals
  • When the jamming signal is applied navigation is lost

Use Case 1: Jamming a Receiver for Navigation

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  • Testing a Geo-PNT (Receiver with IMU + timing outputs)
  • Example Setup:
  • Simulator used as a jamming source with live sky signals
  • When the jamming signal is applied, the IMU allows navigation to continue

Use Case 2: Jamming a Receiver+ IMU for Navigation

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  • Testing a Timing Receiver
  • Monitor the 1PPS signal
  • Using a frequency counter monitor the 1PPS signal of the device-under-test against a stable 1PPS reference
  • 1PPS signal is stable until the receiver is jammed (900 seconds after the start of test)
  • The 1PPS becomes unstable as the receiver tries to overcome the jamming signal

Use Case 3: Jamming a Timing Receiver

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Spoofing requires replicating attributes:

1. TIME SYNC Signal matched to satellite transmission 2. POSITION Accuracy requires real-time tracking of victim location 3. POWER Level controlled in real-time to match receiver

Why is Spoofing so difficult?

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An “perfect” spoofer would be indistinguishable from the Live Sky signal!

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  • Malfunction? Fault?
  • Position drift?
  • Time sync drift?
  • Does it issue an ALERT
  • r does it just FAIL SILENTLY?
  • Which is worse?

Hardening GPS/GNSS Systems

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What happens to your system if GPS/GNSS is spoofed?

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GNSS Simulators

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GNSS: Multi-Frequency, Multi-Constellation

GPS GLONASS Galileo Beidou

SBAS WAAS EGNOS GAGAN MSAS L1/L1C L2/L2C L5 E5 E6

Frequency Bands Constellations

E1 B1 B2 B3 L1 L2 1 2 3 4

Regional

QZSS

L1 L2C L5 L5

IRNSS

Global

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GSG-5/6 Series GNSS Simulators

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Affordable Easy to Use Accurate Powerful

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  • Powerful
  • Up to 64 independent satellite channels
  • GPS L1, L2, C/A, P-Code, P(p-Y), L2C and L5
  • GLONASS L1 and L2
  • Galileo E1 and E5a/E5b
  • Beidou B1, B2
  • SBAS (EGNOS, WAAS, MSAS, GAGAN)
  • QZSS L1 C/A, SAIF, L2C, L5
  • IRNSS L5
  • White noise generation
  • Multipath, interference and jammer simulation
  • Utilizes RINEX navigation data, and optional ALM and e.g. NMEA files as inputs
  • Logs RINEX obervation data, almanac, NMEA and more
  • High accuracy time base
  • Programming interface for automated testing
  • Accurate, variable output level from –65 to –160 dBm, and more

GSG Family of GNSS Simulators

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  • Affordable
  • Modular architecture sets new industry

performance/price standards

  • High performance R&D lab simulator features
  • Priced to support efficient production applications

and use as a common engineering tool

  • Easy to use
  • Create versatile scenarios
  • Full I/O control from intuitive front panel User

Interface

  • GSG StudioView™ PC-based software with Google

Maps interface

  • Remote operation via a web-based interface or via

SCPI commands

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GSG Family of GNSS Simulators

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Vulnerability Test System

GNSS Testing

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  • Simulation allows full testing of systems with integrated an GPS/GNSS

receiver

  • Mission-critical applications require a high degree of operational

validation when transitioning to a new receiver

  • A simulator capable of performing the necessary tests for the application

will greatly simplify the integration of an GNSS receiver

Summary

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