LightSquared has formally presented the company’s modified spectrum plan to the Federal Communications Commission, a plan it says will solve the GPS interference issues in its original launch plan.Read more here. The document apparently does not include extensive test results based on the revised spectrum plan LightSquared now is touting, so it isn’t clear that the test results settle much of anything.

In the detailed report to the FCC, the company said it would use a new block of spectrum that is further away from the GPS frequencies and thus will cause less interference. The company has said that this would reduce interference for 99.5 percent of GPS devices in service. To mitigate interference among the remaining devices, LightSquared said it would work with the GPS community to resolve the issues.Read more here .

But the degree of testing at the new proposed frequencies apparently have not been subjected to the same level of testing as the original plan.

LightSquared also argues that the interference in the original plan is caused by the GPS device manufacturer’s decision over the last eight years to design products that depend on using spectrum assigned to other FCC licensees.

Some will find that an odd, perhaps desperate argument. The clear burden of proof is on the new proposed user of spectrum, not the users already using spectrum. Had the GPS system threatened to cause interference, it also would have been asked to demonstrate that there was not such interference. And all spectrum users shown to be infringing can be disciplined for willful violations.

GPS industry interests still are not mollified by the new plan. “The FCC technical working group report conclusively shows that LightSquared’s proposed operations defy the law of physics, and therefore simply will not work,” says the “Coalition to Save Our GPS.” Read more here.

“The only real solution to the LightSquared interference problem is to move out of the MSS band altogether,” the Coalition argues, still convinced that the new plan will pose the danger of a “severely crippled” GPS system. LightSquared maintains that only about 200,000 mobile phones would still face some interference issues under the new plan. But the Coalition says there is no way to know at this point whether other non-phone devices would be affected.

“The FCC working group report only scratches the surface of the widespread disruption LightSquared’s proposed operations would cause,” the coalition says. “There are 500 million GPS receivers in use in the U.S. alone” and “these receivers in turn are embedded in tens of thousands of complex systems, from aviation navigation systems to law enforcement dispatch, and millions of pieces of complex equipment ranging from agricultural combines to snowplows for precision guidance.”

“While we know that these systems will be interfered with, we have frighteningly little idea of the magnitude of the consequences of interference, other than it will be truly extraordinary in scale,” the Coalition maintains. The new interference estimates are “guesswork,” the Coalition says.

The United States Global Positioning System Industry Council (USGIC), which participated in the FCC Working Group, says in its own report that after briefly examining the new LightSquared spectrum plan, “there was some reduction in the interference effects on GPS receivers and GPS‐dependent applications was both expected and observed.”

“There is no question, however, that many types of GPS receivers and GPS‐dependent applications will suffer harmful interference from LightSquared’s operations in the lower channel, even when transmission power is limited to one‐tenth the authorized limit that was used in the testing,” USGIC says.

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