Another round of tests conducted on LightSquared's proposed hybrid satellite network has again reveal interference with GPS devices, said the Department of Defense and Department of Transportation.
LightSquared has been under fire since its June report to the FCC showed that its proposed LTE network posed an interference problem to existing GPS devices. LightSquared can't operate in the band until the FCC is satisfied that interference won't be a problem. LightSquared in recent months has made a number of concessions, including agreeing to temporarily stay out of the upper part of the spectrum that is adjacent to the GPS bands and limiting the power of its base stations.
A round of tests was conducted last month and focused on LightSquared operating in a lower block of frequencies farther from those used by GPS.
"Preliminary analysis of the test findings found no significant interference with cellular phones," the Department of Defense and Department of Transportation said in a statement. "However, the testing did show that LightSquared signals caused harmful interference to the majority of other tested general purpose GPS receivers. Separate analysis by the Federal Aviation Administration also found interference with a flight safety system designed to warn pilots of approaching terrain."
The results were presented to a technical steering group that represents seven federal agencies that make up the Space-Based Positioning, Navigation, and Timing Executive Committee (PNT ExComm). More analysis will happen during the next several weeks and then the National Telecommunications and Information Administration (NTIA) will issue a final report to the FCC.
"We are pleased that the statement issued by the National Space-Based PNT Executive Committee, chaired by the Department of Defense and the Department of Transportation, validates LightSquared's compatibility with the nation's 300 million cellular phones," LightSquared CEO Sanjiv Ahuja said in a statement. "While we are eager to continue to work with the FAA on addressing the one remaining issue regarding terrain avoidance systems, we profoundly disagree with the conclusions drawn with respect to general navigation devices."
Ahuja also reminded those involved that LightSquared has the legal and regulatory authority to use its spectrum for eight years. "The testing further confirmed that the interference issues are not caused by LightSquared's spectrum, but by GPS devices looking into spectrum that is licensed to LightSquared. We have taken extraordinary measures--and at extraordinary expense--to solve a problem that is not of our making. We continue to believe that LightSquared and GPS can co-exist."
LightSquared now faces a round of testing beginning in January.
LightSquared suffered another blow when the U.S. House of Representatives passed legislation that prohibits the FCC from giving "final authorization for LightSquared operations until Defense Department concerns about GPS interference have been resolved."
Meanwhile, in a filing with the FCC, LightSquared proposed that its upper 10 MHz of downlink spectrum (1545-1515 MHz) closest to GPS frequencies not be under the FCC's jurisdiction but rather the PNT ExComm, an executive branch body that helps advise policy makers on issues around GPS. LightSquared previously said it intends to deploy its terrestrial network only on its lower 10 MHz of downlink spectrum (1526-1535 MHz) after tests earlier this year showed crippling interference to GPS receivers in the upper 10 MHz.
In addition to giving oversight of the spectrum to the PNT, LightSquared also proposed that it would eliminate a planned increase in transmission power for its ground-based operations slated for 2017. Additionally, LightSquared said it will delay another scheduled increase in transmission power from 2015 to 2016.
For more:
- see this PCWorld article
- see this InsideGNSS article
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