Inside GNSS Media & Research

JUL-AUG 2018

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Page 22 of 59 J U L Y / A U G U S T 2 0 1 8 Inside GNSS 23 a one (1) dB decrease in Carrier-to-Noise Power Density ("C/N 0 ") (the "1 dB standard") as the appropriate metric for determining whether a GPS receiver has experienced harmful interference." "No empirical, universal and quantifiable alternative to the 1 dB standard exists for evaluating harmful interference into a GPS/GNSS service," wrote Deere. e firm deemed the Roberson and Associates and NASTCN tests "deeply flawed," because they used KPIs — which Deere called inherently sub- jective and unreliable — to evaluate interference. "Reliance on KPIs fails to fully account for the four prin- cipal attributes of GPS/GNSS — accuracy, integrity, continu- ity and availability," said Deere, "and (does) not account for the wide diversity of GPS receivers and use cases. Given the tremendous diversity in GPS/GNSS receiver design and use models, even the broadest, most inclusive test program cannot credibly claim to have harmonized and evaluated end user outputs in a meaningful way against a potentially interfering signal." Garmin agreed saying the "use of any alternative measure based on only user experience will fail to consider the vast number of devices, uses, and environments in which GPS devices are deployed." It also pointed out that its decision not to oppose Ligado's plans was based in part on its testing using the 1 dB standard. e firm said it "negotiated specified periods with reduced power levels to permit time for design of hardened receivers that will be able to tolerate interference at the levels specified in the settlement agreements. at design change process is ongoing and is itself based on ensuring that GPS products are not degraded by more than 1 dB C/N 0 in the presence of Ligado signals. Garmin does not oppose the Ligado Modifica- tion Applications precisely because it has used the 1 dB metric to evaluate its own devices and, on that basis, negotiated the transition period provisions in the agreement." Trimble said the FCC should dismiss Ligado's calls for rejection of the long-established 1 dB standard and the pro- posed alternative use of KPIs. "e 1 dB standard has been consistently applied in a vari- ety of spectrum contexts," wrote Trimble, "but nowhere is it more appropriate than in the context of interference with GPS devices, which receive signals on Earth below the noise floor and where every dB counts in many mission critical applications. Ligado's anecdotal attack provides no basis for abandoning this longstanding U.S. and international standard of harmful interference." Washington, DC, Area December 2018 GNSS Courses December 4-7, 2018, Hyatt Merrifield, VA 557: Inertial Systems, Kalman Filtering, and GPS/INS Integration. Instructors: Dr. Alan Pue and Mr. Michael Vaujin. Immerse yourself in the fundamentals and practical implementations that fuse GPS receiver measurements with strapdown inertial navigation. (Five days) +1-703-256-8900 • 800-628-0885 Contact Carolyn McDonald at The NEW AsteRx-i V GNSS Receiver with IMU ! Your ONE source for GNSS products and solutions +1-703-256-8900 • 800-628-0885 IMU enhanced GNSS positioning with full attitude (heading, pitch, and roll) Quad-constellation, multi-frequency, all-in-view high accuracy RTK receiver AIM+ interference monitoring and mitigation High-update rate, low-latency positioning and attitude Small, light weight Septentrio's NEW dual antenna, multi-frequency receiver with IMU measurements! NavtechGPS introduces ... Contact us for details 346: GPS/GNSS Operations for Engineers and Technical Professionals. Instructor: Dr. Chris Hegarty. For those needing a coordinated, intensive introduction to GNSS concepts, design and operation to enhance skills and become a more productive member of the team. (Four days) December 10-14, 2018, Hyatt Merrifield, VA Two Separate Weeks! 551: Using Advanced GPS/GNSS Signal and Systems, In-Depth Instructor: Dr. John Betz. Develop proficiency with the essential aspects of using GPS / GNSS signals. Drill deep into the signal details to take full advantage of the signals from multiple systems. (Five days) Follow us on Twitter @insideGNSS

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