Would-be LTE network operator LightSquared is claiming tests that found its satellite-based LTE network interfered with GPS signals were rigged, with GPS “industry insiders” colluding with government officials to craft tests that LightSquared was guaranteed to fail, then conducting those tests behind closed doors.
Last month, tests conducted by the National Space-Based Positioning, Navigation, and Timing Systems Engineers Forum (PNT) found that some three quarters of GPS devices it tested experienced harmful interference when operating within 100 meters of one of LightSquared’s terrestrial base stations. The idea behind LightSquared’s network is to sidestep the need to build out a ground-based broadband network by relaying signals between stand-alone ground stations by satellite. The issue with the design is that the frequencies LightSquared plans to use for that communication are adjacent to frequencies used by GPS receivers. Where GPS signals are very low powered, LightSquared’s transmissions are high-powered, leading to ongoing concerns they will overwhelm GPS reception.
LightSquared now maintains that government-conducted tests that found its technology interferes with a wide range of GPS units were performed in secret—so there’s no way for independent experts to verify the results—and that GPS makers cherry-picked devices for the tests (including several obsolete and niche-market products) that were almost certain to fail. LightSquared argues that the lack of transparency in the tests highlights how “GPS industry insiders” are out to hobble LightSquared, and that the testing regimen didn’t reflect the reality of the GPS market.
The results of the tests have not been released to the public, and companies participating in the tests—including LightSquared—are barred by non-disclosure agreements from discussing the specifics. LightSquared indicated it has learned what devices were used in the testing, but can’t reveal the information due to similar agreements.
Based on the results of the tests, the PNT Executive Committee concluded that LightSquared’s network cannot be made compatible with existing GPS. Although a second round of testing for high-precision gear had been scheduled, the committee recommended no additional testing be conducted.
Before LightSquared can begin operating its network, it needs approval from the Federal Communications Commission that all GPS interference issues have been resolved. LightSquared is seeking a waiver from that requirement. The company has taken several steps to try to mitigate its network’s potential impact on GPS, including shifting initial services to new frequencies farther away from the GPS band, and offering an inexpensive technical workaround that would enable makers of GPS receivers to successfully shield their devices from interference.