The future of GPS

Hopefully we have dodged the bullet and this post can be marked up as "paranoia"

Potential threat of GPS disablement!   I know this has been an ongoing issue for a while. A company called LightSquared has been trying to build a cellular network that interferes with GPS.  You don't hear much in the news about it these days, but it seems that maybe the threat has not completely gone away yet.

Although LightSquared was denied the frequencies after building out much of a network and had to file for bankruptcy, they are still petitioning the government to try to get a deal that would allow them to use some of the frequency's that are a little further from the GPS frequency. And apparently some venture capitalists seem the think that somehow the network could be resurrected and salvaged.  Still there is a strong resistance from the Airforce, Trimble, and others, but I am worried that the power of big money could prevent this threat to the GPS system from going away.

Does anybody have an updated status on this issue?

When I hear about problems with GPS inaccuracies and runaways, I wonder if testing of the lightsquared network might be going on, or similar cellular interference could be a factor.

Interference on GPS and other links we use in out UAV's bring to mind the concern as it already applies with existing RF sources in our environment.   There is a spot I would love to do a fly around getting some nice video, but a cell tower and some other towers sits on the top of the hill that I want to video, along with various other frequencies such as 2 meter, 70cm, GPRS an cellular services from Sprint, AT&T and maybe others.  Probably not a good place to fly!

Anyway, the LightSquared technology is referred to in some articles as LTE, I know that LTE is been deployed around the country, so it doesn't seem to be the same LTE that light squared plans to deploy is it?  as far as I can tell, so far they have been blocked from deploying the GPS blocking technology and lets hope they continue to be blocked!


Here is the latest thing I can find on it right now on the position of the FCC:

Anyway, hopefully, like I said: we have dodged the bullet..

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  • Well said Dan, and exactly correct on all counts.  

  • @frederic,

    While I'm not specifically familiar with who may have held licenses to that spectrum previously, the issue here is space-based vs. terrestrial use.  The spectrum was licensed for space-based transmissions which (by their nature) do not present the same challenges to GPS receivers.  GPS receivers were designed to handle that environment.

    What is the value of those licenses?  Well, you can provide service via satellites.  There is a lot of value in that, and that's what LS purchased the rights to use.  The problem is that they then wanted to provide services from terrestrial transmitters.

    So LS managed to get a conditional waiver from the FCC for terrestrial transmitters.  IMO, the FCC should have never granted that in the first place.  But in any case, LS did not comply with the conditions of the waiver (they couldn't, short of changing the laws of physics), and the FCC revoked it.

    So nobody was prevented from operating according to the rules for the spectrum they paid for.  But LS made the assumption that they could operate outside the rules (or get them modified).  And that was indeed unreasonable.

  • @Dan

    I see your point. so what I do not get is that another company had license to some of those frequencies, so what is the value of that license if when operating strictly in the space you have a licence for you are prevented to do so because third parties made some assumptions on what you would be doing? even if those assumptions were as you said not unreasonableas as I am sure they were at the time. acquiring a company that has right to some frequencies and making the assumption that you will be able to operate within that band does not seem to be an unreasonable assumption either?

  • Admin


    Well said, that is exactly What LS did. Now the guys who put their money are neither engineers nor users of important service like GPS , all they care about is their money and the much bigger returns , in fact they were fooled by the LS's marketing/investors meeting I guess and now they have no choice but to forget the invested

    " Millions" or to put in more money to salvage the lost cause., Mark my word , they will prove to be fools when they invest more money :))

  • @frederic,

    The filtering requirements on GPS receivers were based not on "assumptions" about the adjacent frequency bands, but the fact that these frequencies were reserved for satellite-based transmissions.  More selective filtering does require more hardware and cost, and there was nothing unreasonable about the way GPS receivers were engineered given how the frequencies were allocated.

    LightSquared was given permission to test with these bands with the explicit requirement that they NOT interfere with GPS.  The "discovery" you speak of that LS's transmitters screw over GPS receivers was not a surprise to anyone with the slightest clue about RF engineering.  In fact, given the laws of physics, it was the only possible outcome.  Of course LS tried to play the whole thing off as a political issue, and because the FCC has a hard time keeping politics and reality separated, they almost got away with it.

    So I reject your suggestion that LS spent money "in good faith".  They did not.  The only way LightSquared could have possibly succeeded was by trickery or fraud.  They might as well have been selling perpetual motion machines.  And those people who invested in LS (or continue to do so) are fools who need to learn when to listen to engineers instead of shady businessmen.

  • I find it hard to be sympathetic to Lightsquared, as their behavior was unacceptably aggressive and dismissive of reality.  If they spent a lot of money without doing due diligence on the engineering side, which all indications are so, then they deserve exactly what they got.  GPS was designed quite a while ago, and the signal strength is not much, so having terrestrial applications in a nearby band is simply bad planning.  

  • in fact it seems that most of the current GPS receivers have been designed assuming that the frequency band next to theirs was free, which lowers the complexity and cost. when lightsquared acquired access to their frequency ( for which they paid a lot of money, even acquiring a company that had some rights on some chanels ) the gps industry "discovered" that any activity there would "jam" their receivers and lobbied to remove lightsquared license. the implication of stopping the GPS service is such that of course there was no way for lightsquared to survive even if they demosnstrated with some GPS vendors that frequency compliant receivers were not jammed by lightsquared signals. whatever money has been invested and spent "in good faith" on that project is lost "for the greater good"

  • They will continue to be blocked, their BS about GPS being "outdated" flew like a lead turkey.  Too much of the economy relies on GPS, so until it's replaced with something else (which I don't see happening with the next decade at least, given the cost of the aviation grade units and current investment), anybody attempting to do something that messes up GPS will be hammered.  

  • Admin

    You can dodge the bullet for only so long   !!  , ,  I thought the idea was completely shut down/discarded after company  went turtle !! ?    I remember wondering about why in the hell would LTE want to use the same freq as GPS for a terrestrial network when I first read about some time back :(.   and I don't remember  reading a decent answer for that either.

  • Very Interesting/informational Video thanks for sharing!

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