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LightSquared deals with continued GPS interference  (Source:
U.S. officials say no additional testing is needed to prove the existence of harmful interference

A recent government study found that the LightSquared Inc. wireless service interrupted 75 percent of global-positioning system (GPS) receivers.

LightSquared Inc. is a company looking to offer a wholesale 4G LTE wireless broadband communications network with satellite coverage in the United States. It was founded by Philip Falcone and has had interference issues for years now. Just this year alone, interference concerns were raised by the National Telecommunications and Information Administration (NTIA), USAF Space Command, and the U.S. GPS Industry Council.

Now, a test conducted by the U.S. government has shown that 69 of 92 (75 percent) of receivers experienced "harmful interference" at the equivalent of 100 meters from a LightSquared base station. It was deemed that millions of GPS units were incompatible with the LightSquared service, and it could affect cars, planes, boats and tractors.

The test was performed from October 31 to November 4 for the National Space-Based Positioning, Navigation and Timing (PNT) Systems Engineering Forum, which advises policy makers about GPS issues. The Department of Defense and the Federal Aviation Administration took part in the testing, as well as companies like Garmin Ltd., Trimble Navigation Ltd., Deere & Co., and General Motor Co.'s OnStar unit.

"LightSquared signals caused harmful interference to majority of GPS receivers tested," said U.S. officials in a draft prepared for the review of the LightSquared proposal. "No additional testing is required to confirm harmful interference exists."

LightSquared has proposed that it operate at a reduced power than the levels used during the testing. With low power usage, LightSquared believes its services would only affect 10 percent of devices.

Sources: Business Week, SlashGear

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RE: 10% ???
By Solandri on 12/12/2011 5:35:44 PM , Rating: 4
What you're missing is that if the GPS folks had played by the rules and used proper filtering in the first place, this wouldn't be an issue. But when GPS began there was no LightSquared, so they cheaped out on the filters since there was nothing there to filter.

No. The spectrum owned by LightSquared was originally used by Inmarsat to communicate with satellites. The satellite signals were about as weak as GPS signals. And the ground station broadcasts to satellites were highly directional. Other bands in that spectrum were reserved for amateur communications to satellites, so again, a similar type of use.

GPS receivers were designed with filters adequate to remove this low level of noise at those frequencies. In 2004 LightSquared got permission from the FCC to repurpose the spectrum for land-based cellular data services. Essentially, the FCC gave them permission to blast away at those frequencies at energy levels thousands of times higher than originally allowed, omnidirectionally instead of pointed straight up. This is what's causing the interference with GPS. The GPS receivers at the time were designed to filter out the FCC-mandated maximum level of noise from those adjacent frequencies. It's the FCC (at LightSquared's behest) which raised those maximums far beyond levels where existing equipment can cope.

Also, many electrical engineers in the industry have come forward to state unequivocally that the frequencies are so close and LightSquared's proposed broadcast signal strengths so high that it is literally impossible to filter it out so that there is no degradation of GPS service. The units which fared well in the test are probably bigger units with better antennas and more power for electronic filtering and signal processing. If LightSquared's project goes live, you can probably kiss the GPS in your phone goodbye.

RE: 10% ???
By knutjb on 12/13/2011 1:01:34 AM , Rating: 2
The units which fared well in the test are probably bigger units with better antennas and more power for electronic filtering and signal processing. If LightSquared's project goes live, you can probably kiss the GPS in your phone goodbye.
What about those in cars, boats, or worse yet aircraft. Changing these kind of standards in such a rushed manner is dubious at best but prevent drilling for oil or running a pipeline without an extra decade just to make sure it's safe. Hmm....

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