DOT's Draft GPS/LTE Interference Study 'Vague Waste,' LightSquared Says

deadline for comments for its draft test plan on establishing criteria for power limits for transmitters in GPS-adjacent bands, it said in a Federal Register notice Wednesday. DOT isn't developing standards either for GPS receivers or transmitters operating in adjacent bands, but the interference tolerance masks "will be used to assess the adjacent band interference power levels that can be tolerated" by Global Navigation Satellite System receivers, the agency said. The draft test plan gives broad outlines of the study parameters. For example, the categories of receivers operating in the 1559-1610 MHz band to be studied are aviation, cellular, general location/navigation, high precision, timing, networks and space-based receivers. The details of the test procedure are being developed, but the testing is expected to take up to nine days, DOT said. "Instead of developing a plan to enable technological advancement and spur spectrum innovation, the DOT is proposing to set limits on spectrum use by promoting the continued use of outdated filter technology in receivers," the LightSquared spokeswoman said. This latest plan follows a 2012 DOT testing plan aimed at setting up "the framework for definition of the processes and assumptions that will form the basis for development of the GPS adjacent-band compatibility for GPS civil applications," she said. "It has taken DOT almost four years to propose a vague study that is absent procedures or timelines and will not answer the critical question of whether wireless broadband would cause any actual harm to the accuracy of GPS devices." Roberson and Associates is doing a LightSquared-commissioned study of the scope and degree of L-band LTE network interference to GPS, and results are due this fall. That plan has faced criticism from the GPS industry as being redundant to the DOT planning effort (see 1508250070).