GPS Adjacent-Band Compatibility Assessment
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Demand for commercial spectrum to support broadband wireless communications has led the government to consider repurposing various radio frequencies, including the satellite communications bands next to GPS.
In 2012, the National Executive Committee for Space-Based Positioning, Navigation, and Timing proposed to draft new GPS spectrum interference standards to inform future proposals for non-space, commercial use of the bands adjacent to the GPS signals. Learn more
The Department of Transportation's (DOT) approach to this task is to develop power limit criteria for transmitters in the bands near GPS. DOT prepared a GPS Adjacent-Band Compatibility Assessment Plan providing a framework for the development of the criteria.View assessment plan, Dec 2012 (500 KB PDF)
The plan identifies the processes to (a) derive power limit criteria to ensure new adjacent-band applications do not disrupt current GPS services and (b) determine similar levels needed for future GPS equipment using modernized and interoperable GNSS signals. These processes will be used to develop and specify adjacent-band transmitter power limits needed to protect GPS/GNSS signals for civil applications.
DOT began testing GPS/GNSS receivers in April 2016 pursuant to the final test plan published in March 2016. Device testing took place at the U.S. Army Research Laboratory at the White Sands Missile Range (WSMR) facility in New Mexico. All GPS device manufacturers had an opportunity to participate in the testing.View test plan, Mar 2016 (500 KB PDF)
A second round of testing occurred in July 2016 at Zeta Associates in Fairfax, Virginia, and MITRE Corporation in Bedford, Massachusetts. The goals of the additional lab testing were:
- (1) Receiver characterization for comparison with results obtained in April at the anechoic chamber at the U.S. Army Research Laboratory;
- (2) Evaluation of Out Of Band Emission (OOBE) interference at prescribed and proposed levels with Long Term Evolution (LTE) uplink and downlink signals;
- (3) GPS/GNSS signal acquisition characterization; and
- (4) Antenna characterizations.
Anechoic chamber test setup
- September 2016 presentation to CGSIC (821 KB PDF)
- Federal Register announcement of July testing
- Federal Register announcement of April testing
- DOT announcement of April testing
- Non-disclosure agreement (PDF)
- Draft test plan (426 KB PDF)
- Public comments on draft test plan (regulations.gov)
October 2016 Workshop
The U.S. Department of Transportation hosted its fifth workshop on the GPS Adjacent Band Compatibility Assessment effort on Friday, October 14, 2016, in Washington, D.C.
The purpose was to discuss the results from testing of various categories of GPS/GNSS receivers to include aviation (non-certified), cellular, general location/navigation, high precision and networks, timing, and space-based receivers. The workshop also included a discussion on the development of use-case scenarios for these categories.
October 2015 Workshop
DOT hosted a fourth workshop on October 2, 2015, to discuss the draft test plan and provide an opportunity for questions prior to the close of the comment period.
March 2015 Workshop
DOT hosted a third workshop on March 12, 2015, at Aerospace Corporation, El Segundo, CA, to continue discussions of the GPS Adjacent Band Compatibility Assessment. The workshop focused on the following topics: (i) Identification of GPS and Global Navigation Satellite System (GNSS) receivers to be considered for testing that are representative of the current categories of user applications; and (ii) discussion of a GPS/GNSS receiver test plan.
December 2014 Workshop
DOT hosted a second workshop on December 4, 2014, at Aerospace Corporation, El Segundo, CA, to continue discussions of the GPS Adjacent Band Compatibility Assessment. The workshop focused on the following topics: (i) GPS "use case" information, with emphasis on non-government applications; (ii) identification of current GPS receivers which are representative of the current categories of GPS applications and which should be considered for testing; and (iii) feedback on the GPS Adjacent Band Compatibility Assessment program implementation plan presented during the September 2014 workshop.
September 2014 Workshop
On September 18, 2014, DOT hosted a workshop in Cambridge, MA, to discuss implementation of the Adjacent-Band Compatibility Assessment Plan. Discussion focused on the various implementation steps, including development of GPS receiver use cases, identification of representative GPS receivers, and development of a test and analysis program.
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