A new study presented to the FAA last week is adding fuel to the debate over the proposed expansion of broadband communications by a company called LightSquared, a plan that has drawn extensive concern from the aviation community about potential interference with GPS reception.
The study, conducted by the non-profit RTCA, confirmed what many critics have warned for months: LightSquared’s plan to make broadband transmissions on a frequency band adjacent to that used by GPS will cause significant interference with GPS reception.
After testing and reviewing the performance of four aircraft GPS receivers, members of a RTCA Special Committee concluded that, “the current LightSquared terrestrial authorization would be incompatible with the current aviation use of GPS.”
The authors of the report maintained that LightSquared’s plan would not only cause widespread disruption of GPS-based operations throughout the United States, but would completely wipe out reception in some areas. “Given the situation in the high altitude U.S. East Coast scenario, GPS-based operations will likely be unavailable over a whole region at any normal aircraft altitude,” the report said.
The study also implied that LightSquared’s plan would probably cause even greater interference with non-aviation receivers, since they lack the six-decibel safety cushion employed in receivers used for aviation purposes.
“From an aviation perspective, LightSquared upper channel operation should not be allowed,” the authors recommended. While they said certain changes could allow LightSquared’s system and GPS to co-exist, they maintained further research is necessary to determine appropriate frequency limits.
The FAA requested the RTCA study after the Federal Communications Commission (FCC) granted LightSquared a waiver to install up to 40,000 ground stations throughout the United States earlier this year. The move sparked the formation of the Coalition to Save Our GPS, as well as a letter to the FCC signed by 33 senators urging the commission to withdraw the waiver. The FCC has responded that it will allow LightSquared's plan to move ahead only if the GPS interference issues are addressed.
