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4G Network 'Will Create GPS Dead Zones Across the US'What would you rather have—a superfast data connection on your cellphone, or a reliable GPS signal to pinpoint your location? If a plan to install a network of base stations for the new 4G mobile wireless protocol goes ahead, it may mean you can have one but not the other.

GPS satellites transmit their navigation signals in the range 1559 to 1610 megahertz. Telecoms firm LightSquared of Reston, Virginia, has long communicated with its satellites using low-power signals in the adjacent frequency band, from 1525 to 1559 MHz, part of the "L band". Despite the closeness of the frequencies, satnav receivers have so far operated without any interference problems.

But in January, the US Federal Communications Commission (FCC) gave preliminary approval to a plan by LightSquared to build 40,000 new 4G base stations on the ground. These stations would broadcast much stronger signals in the 1525 to 1559 MHz range, to link to cellphones.

Based on lab simulations of the new transmissions, Scott Burgett and Bronson Hokuf, engineers with satnav manufacturer Garmin International in Olathe, Kansas, say this will seriously damage GPS reception. In a report to the FCC last month, they say that overlaps between the two systems are inevitable, and that this "will result in widespread, severe GPS jamming [and] will deny GPS service over vast areas of the United States".

Jeff Carlisle of LightSquared says it is the GPS receivers, not his company's base stations, that are at fault. "The issue is that some GPS receivers may be able to see into the L band where we operate," he told New Scientist.

The stakes are high. By 2015, LightSquared expects to spend $6 to $8 billion to complete the network, which promises to bring download speeds of 5 to 10 megabits per second to cellphone users. Meanwhile, over a billion GPS receivers are in use worldwide.

LightSquared has until 25 February to submit a plan to the FCC for working with the GPS industry and federal agencies to analyse interference issues; a final report detailing a solution is due by 15 June. LightSquared wants all future tests to be performed with real transmitters rather than simulators.

Government tests appear to confirm earlier tests done by the GPS industry: LightSquared's proposed mobile broadband network disrupts GPS devices in the area. The data is given more weight by the impartiality of the testing, but wasn't a surprise: LightSquared's spectrum block is right next to that used by GPS receivers.

All GPS devices tested were affected, but some more than others. The government's tests were overseen by the National PNT Engineering Forum, a federal advisory group of engineers. Some devices simply saw signal strength degrade. Others were completely disabled. For example, the tests found that GM's OnStar system saw a "significant degradation of service" on most receivers tested.

A separate FAA-commissioned study found that "GPS operations below 2000 feet [of elevation] would be unavailable over a large radius of metro (areas)" for aircraft. Meanwhile, James Kirkland, vice president and general counsel of GPS maker Trimble Navigation said, "It will cause interference. It will cause devastating interference. There is not a solution here. In our view it's time to stop squandering resources on this and find alternative spectrum for them."

An alternative spectrum block would move LightSquared's operations away from that of GPS receives, eliminating the interference. The FCC gave LightSquared preliminary approval for the network in January pending interference tests.

Sabre wrote:Well, this makes it "official": Gov't Tests Confirm LightSquared Interference with GPS

Government tests appear to confirm earlier tests done by the GPS industry: LightSquared's proposed mobile broadband network disrupts GPS devices in the area. The data is given more weight by the impartiality of the testing, but wasn't a surprise: LightSquared's spectrum block is right next to that used by GPS receivers.

All GPS devices tested were affected, but some more than others. The government's tests were overseen by the National PNT Engineering Forum, a federal advisory group of engineers. Some devices simply saw signal strength degrade. Others were completely disabled. For example, the tests found that GM's OnStar system saw a "significant degradation of service" on most receivers tested.

A separate FAA-commissioned study found that "GPS operations below 2000 feet [of elevation] would be unavailable over a large radius of metro (areas)" for aircraft. Meanwhile, James Kirkland, vice president and general counsel of GPS maker Trimble Navigation said, "It will cause interference. It will cause devastating interference. There is not a solution here. In our view it's time to stop squandering resources on this and find alternative spectrum for them."

An alternative spectrum block would move LightSquared's operations away from that of GPS receives, eliminating the interference. The FCC gave LightSquared preliminary approval for the network in January pending interference tests.

A separate FAA-commissioned study found that "GPS operations below 2000 feet [of elevation] would be unavailable over a large radius of metro (areas)" for aircraft.

The US Department of Commerce's telecommunications division has released an assessment of problems that the LightSquared 4G service might create for commercial and government Global Positioning System services (GPS), and the conclusion isn't pretty. LightSquared's deployment of wholesale LTE "poses a significant potential for harmful interference" to commercial and government GPS, the National Telecommunications and Information Agency's Lawrence Strickling wrote in his introduction to the report.

Sabre wrote:First the test were done by the industry, now by the government...

US: LightSquared 4G would have "severe operational impact" on GPS

The US Department of Commerce's telecommunications division has released an assessment of problems that the LightSquared 4G service might create for commercial and government Global Positioning System services (GPS), and the conclusion isn't pretty. LightSquared's deployment of wholesale LTE "poses a significant potential for harmful interference" to commercial and government GPS, the National Telecommunications and Information Agency's Lawrence Strickling wrote in his introduction to the report.

When are they just going to say NO to this?!?!