About the SA Blog Network



Opinion, arguments & analyses from the editors of Scientific American
Observations HomeAboutContact

Will 4G Interfere with GPS? Wireless Firm LightSquared Denies the Charge

The views expressed are those of the author and are not necessarily those of Scientific American.

Email   PrintPrint

The U.S. has been widely criticized in recent years for falling behind other developed countries in its deployment of high-speed wireless networks. The current dustup involving LightSquared, Bloomberg News and several government agencies provides some clues as to the complexity of the problem.

LightSquared is proposing to build a high-speed nationwide 4G LTE (long-term evolution) network and lease capacity on that network to different wireless carriers, including Sprint Nextel Corp. LightSquared and Sprint subsequently signed a 15-year deal in July through which LightSquared will invest billions of dollars to build and operate Sprint’s wireless network. The 4G LTE network will operate on the L-Band spectrum that LightSquared has licensed from the Federal Communications Commission (FCC).

Therein lies a big part of the problem. Because the L-Band is adjacent to the portion of the electromagnetic spectrum used by global positioning system (GPS) services, some purveyors and users of this service fear that LightSquared’s 4G network will interfere with GPS used by consumers, businesses and even the military. The 4G networks being rolled out by carriers such as Verizon and AT&T do not operate near the  GPS spectrum and so are not at issue here.

In addition to the FCC’s monitoring the situation, the National Telecommunications & Information Administration (NTIA), a Department of Commerce agency that oversees airwaves use, requested a test to determine whether LightSquared’s 4G wireless service interfered with GPS receivers.

Bloomberg News reported on Friday that thus far 75 percent of the GPS devices tested had experienced interference from LightSquared’s 4G network.

The report incensed LightSquared Chairman and CEO Sanjiv Ahuja. On Monday he wrote a letter (pdf) to Ashton Carter and John Porcari , the deputy secretaries of the departments of Defense and Transportation, respectively, demanding an investigation into skewed information he claims was leaked to Bloomberg News. Carter and Porcari are also chairs of the National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT), the executive-branch advisory group in charge of running the tests.

Ahuja claims that portions of internal analyses of ongoing tests were selectively disseminated in order to “damage LightSquared’s reputation, spread false information in the marketplace, and prejudice public opinion against LightSquared before a full and complete analysis of the testing results had been presented.”

Ahuja disputes the incomplete results that were presented by Bloomberg, which reported that the PNT found that 69 of 92 of receivers tested “experienced harmful interference” at the equivalent of 100 meters from a LightSquared base station. Ahuja countered by saying, “To achieve that level of threshold of failure, the leaked internal analysis assumes that the power levels of LightSquared networks are 32 times greater than the power levels at which LightSquared will actually operate.” Ahuja claims that realistic information was not used in the analysis of the test results. “Based on our review of Bloomberg News’ reporting, the leak was based on an incomplete, selective, and slanted analysis of the data of the testing of general location/navigation devices,” according to Ahuja.

“LightSquared’s own analysis shows that the vast majority of general location/navigation will experience no interference from LightSquared’s network,” Ahuja adds.

The NTIA acknowledges that the testing of LighSquared’s network is not yet complete. The current phase of testing focused on GPS receivers found in mobile phones and personal/general-navigation GPS and was completed by November 30. The NTIA has received the data from this stage of testing but has not yet analyzed the results, says Moira Vahey, an agency spokeswoman. The second phase of NTIA testing will focus on GPS receivers used for high-precision and timing applications.

Whereas Bloomberg reported that results of the NTIA tests would be revealed at an agency meeting on Wednesday, Vahey says they will not be issuing a policy recommendation until all testing is complete. The agency has not yet stated a timeline but is working to address the issues promptly and conclusively, she adds.

Image a taxi ride in Kyoto (aided by a GPS) courtesy of Paul Vlaar, via Wikimedia Commons

Larry Greenemeier About the Author: Larry Greenemeier is the associate editor of technology for Scientific American, covering a variety of tech-related topics, including biotech, computers, military tech, nanotech and robots. Follow on Twitter @lggreenemeier.

The views expressed are those of the author and are not necessarily those of Scientific American.

Rights & Permissions

Comments 8 Comments

Add Comment
  1. 1. JamesDavis 7:09 am 12/13/2011

    I wouldn’t care to bet “$10,000.00″ (Oh! wait. I can’t make that wager because the religious conservatives have beat me to it.), that Verizon and AT&T is behind this shady scare operation. Verizon and AT&T have been trying to get rid of Sprint ever since Sprint came out with the “first” “in your pocket” cell phone.

    Link to this
  2. 2. MikeB 9:58 am 12/13/2011

    I’m not sure I see the reason for all this hue and cry. Either Lightsquared’s bandwidth will interfere with GPS or it will not, and the only way to find out if it will be a problem when fully operational is to make it fully operational. If it does bugger up GPS signals public reaction from the Pentagon, aviation industry and private users will be so great — and litigation so extensive — that Lightsquared will be shut down and out of business in a matter of hours.

    If the company’s investors want to take that chance, let ‘em.

    Link to this
  3. 3. Eddie74 11:30 am 12/13/2011

    No-one is testing the detrimental Environmental effects of MW radiation on birds, insects, & animals by the increasing over-all intensity & field strength of Radio Wave energy all across the RF spectrum.. If you know anything about “wave length” you will notice that the shorter the wave length – the more “in-tune” the insect or the bird size matches the power pulse of the RF energy.. We all absorb a portion of the broadband radio frequency energy.. Don’t believe this,? – then go touch the antenae of your radio.. Bugs & Birds feel this excessive RF Energy as well.. You will too when the “Silent Spring” finally wipes out all life around you except for You & Your 4G Cell Phone.. So talk your self to an early 4G death, but first read “The Silent Spring” by Rachel Carlson..

    Link to this
  4. 4. mwagner17 5:21 pm 12/13/2011

    This is the same nonsense that the airlines use to get us to turn off our electronic devices. Today’s communcations are digital. It takes a lot more than random analog signals to interfere with professional grade communications equipment (airline communications gear) – let alone military grade gear (GPS).

    You cannot prove a negative so these alarmist warnings persist. (You remember that claims that the LHC at CERN would destroy the Earth with a microscopic black hole?)

    The point is that you CAN prove a positive and if such interference were possible, it could very easily be reproduced in the lab under controlled circumstances.

    Link to this
  5. 5. Piume 5:56 am 12/14/2011

    GPS system is vastly benifesal for communication. Thnks for the invent of such divise.

    Link to this
  6. 6. Hel-n-highwater 9:55 pm 12/16/2011

    So look up Light Squared and the founder… He serves Bangaladesh and Pakistan. Dumasazil or however you spell dumb _ _ _ in German. He is a Muslim and if our Homeland Security doesn’t protect us from these people using our capitalism against us, our military will be compromised when the GPS is most needed. Like the Commies used to say, a capitalist will sell you the rope to hang them. Al Quaida is based in Pakistan and it is not just a bunch of illiterate suicide bombers but educated in the USA citizens of the Middle East.

    Link to this
  7. 7. TimmyTim 3:29 pm 12/19/2011

    In Response to JamesDavises comment above “Verizon and AT&T is behind this shady scare operation”. I don’t think they are, but if I were AT&T or Verizon I would be mighty ticked off about how LightSquared managed to get control of spectrum that was basically worth almost nothing due to the restrictions in place on its use then got the rules changed to suit themselves.

    There are so many groups against this I am really shocked that this horrible idea hasn’t gone off in a corner to die. Most people have no idea how many uses there are for GPS in America today.

    -Consumer devices, probably the most obvious, including providing location services to 911 if you make an emergency call
    -Aviation, the FAA has been planning to overhaul the US Air navigation system by utilizing GPS to not have to rely so much on the manual routing of planes we do today
    -Land Surveying and Geomatics, these folks need precision GPS in order to find property features and do surveying, utility inventory, etc.
    -Timing, most of the precision timing used in the US today is provided by GPS. Practically every cell site, and every telephone company central office typically has 2 GPS clocks (they are so critical they have a spare, they are that important).

    The best analogy I can come up with for LightSquared’s business model is that it’s almost like they are planning to start a car rental business, but they are going to build their rental inventory by stealing the cars they need. It’s really easy to start a business when you don’t have to concern yourself with all the costs of the externalities…

    Link to this
  8. 8. rickofudall 8:14 pm 12/19/2011

    When LightSquared first proposed its network it was to be satellite based with ground station enhancement so they were issued the bandwidth that is internationally reserved for satellite communication. Then they decided that the system would be ground based with satellite enhancement. There proposed signal strength is 800 BILLION times what the GPS constellation transmits so they claim that it’s the GPS receivers that are at fault. Every test done, no matter where they put their transmissions in the frequency spectrum, has shown interference. We, the taxpayers, have spent billions on the GPS system and it is integrated into almost every aspect of daily life and the national defense. LightSquared made a bet they could buy the FCC Chairman and lie, cheat, and steal there way to a fortune along the way and got caught.

    Link to this

Add a Comment
You must sign in or register as a member to submit a comment.

More from Scientific American

Email this Article