How The FCC Plans To Destroy GPS – A Simple Explanation
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What they're trying to do is balance the legitimate right that one user has to a piece of spectrum, with the legitimate right that a lot of users have to some that's adjacent. They'd be looking at nothing but an endless series of lawsuits if they told LightSquared that they couldn't use their spectrum (which they have a license to), particularly since LightSquared has a proposal which -- yes, on paper, but what's on paper matters -- says they'll not interfere with GPS.
It looks much more like the FCC is giving LightSquared an opportunity, either to show that they can make the system workable, or to come up with enough rope to hang themselves, one way or the other. If LightSquared can't resolve the interference issues, then the FCC will have a much better case for an enforcement action than they currently do. (Although an enforcement action might require a rule change, because it's not clear that they would actually be in violation of the rules; front-end overload is typically the receiver's problem, not the transmitter's.)
I'm all for spectrum users being vigilant, and perhaps GPS users need an organization analogous to the ARRL (which protects the Amateur Radio spectrum, and successfully defeated the shitty BPL implementations that were kicking around a few years ago) to nip these things in the bud. But the conspiracy-theorizing is a bit rich.
GPS does have a group that protects it's users - I believe it's called the USAF.
Using two frequencies makes the military receivers more robust, and also lets them do some clever ionospheric distortion cancellation that you can't do with one channel. (Basically they get the benefits of WAAS without actually needing to receive the WAAS signal.)
That said, neither the FAA or the military are going to tolerate any significant degradation of GPS, domestically or otherwise.
BTW, I'm not a pilot, but I work for a government aerospace contractor, so I have some experience in this.
Since this thread sprung up I've wondered what might be impacted by a GPS failure.
As far as BIS info, it's not something I've followed closely, but we're talking things like every plane, tank, and infantryman now (soon?) has gps and information on the location of all friendly forces is automatically shared so you cut down friendly fire.
Apparently caf has more info on milspec GPS than I do, I thought that it required the same main band as civilian, and just used additional military bands to increase precision, but apparently it can function fully independently (not really surprising when you think about it). At least that gives you a little info on some of the troubles of failure of military GPS, as unlikely as that is.
This specific problem definitely wouldn't affect our aircraft simply because they would be at such a high altitude. Even if it was a problem, the military also has a some pretty impressive anti-jamming capability.
So there are enforcement people out there. They just don't happen in the middle of a superbowl broadcast.
They unfortunately do not have nearly enough officers to really do anything particularly effective, but if you are really egregiously bad about your spectrum abuse, to the point where you generate complaints from other users, they do sometimes pull licenses.
The only interaction with them I have any sort of knowledge of is secondhand; a friend of mine spent months trying to get the local power company to fix a bad transformer on the street that was failing internally and creating a lot of noise, pretty much from DC well up into the HF. (And I suspect it was making some pretty ugly AC waveforms.) They wouldn't do anything, and he eventually got one of the FCC Enforcement Bureau people involved.
You have to be a very "squeaky wheel" to get any sort of attention to a complaint, though; my friend had what amounted to a fairly serious engineering study of the failing transformer, done with parabolic antennas and spectrum analyzers, so that the FCC guy didn't really have to do a whole lot. (Presumably he verified things, but I don't know for sure.)
[1] http://www.gpsworld.com/gnss-system/news/data-shows-disastro...
This sounds a lot more like the FCC not entirely understanding the ramifications of what they approved and/or a company trying to take advantage of licensing loopholes which have unforeseen consequences.
Yes, the FCC fucked up here but it isn't time to bring out the tin foil hats yet.
This would be like the FDA accidentally approving a new drug that gave everyone in a 1 block radius cancer.
The funny part is, some times, that's how the FDA does work. That's how we wound up with all those depression drugs that were only as effective as a placebo.
Aviation, both general and commercial, relies increasingly on GPS integrated avionics to navigate the rigidly defined airspace that instrument rated pilots refer to as "the system."
GPS has become so prevalent that the decades old method of navigation using VOR (VHF omnidirectional frequency) radials is going the way of that which came before it, ADF ("Automatic" Direction Finder).
Even the smelly old 1965 Piper Cherokee I fly sometimes has a Garmin GPS unit in it. The guy that taught me to fly has a 1947 Cessna 140 with a GPS unit. It's become ubiquitous in general aviation and is a de-facto requirement in commercial aviation.
GPS isn't going anywhere because it's too crucial to one of the major facets of the national transportation system.
http://licensing.fcc.gov/cgi-bin/ws.exe/prod/ib/forms/report...
Wait until a couple airliners go missed on RNAV GPS approaches in low IFR conditions (visibility < 1 mile or cloud ceilings at less than 500 feet). The airlines will raise hell, the FAA will get involved and that'll be all she wrote.
As for the airlines, they are so heavily regulated that they might think twice about filing official comments on stuff like this without permission. No doubt FAA and FCC are talking about this even if it's not official. Their offices are only a few blocks away.
"The results are even worse for the aviation GPS. The FAA has essentially discontinued support for the old LORAN electronic navigation system in favor of GPS, and now LightSquared has proposed a system that essentially disables GPS in exactly the areas aviation needs it most."
The author is agreeing with you in that it would be a disaster for both commercial and non-commercial.
Was the article modified since you posted your comment?
Basically I was that guy on the internet I complain about.
http://www.fcc.gov/Daily_Releases/Daily_Business/2011/db0209...
(I've never heard of a good reason to block cell phone transmissions. It always seems to come down to trying to enforce some vision of politeness via technical means, which doesn't take considerate cell phone usage into account at all.)
You could (presumably) attempt to fix this with technology. It might even work for a while, but when it breaks, someone could very easily die. And they'd have died of someone else's dislike for cell phones, which is not a good reason.
The only real problem is GPS equipment manufacturers intentionally cut corners and costs by FAILING to implement proper bandpass filters.
When the LightSquared towers get turned on, and customers who bought incorrectly designed garbage from the likes of Garmin, the result will be simple: The equipment makers will get sued in massive class action law suits for selling broken equipment. And yes, the manufacturers deserved to be sued for cutting corners on bandpass filters and selling junk since THEY HAVE ALWAYS KNOWN the adjacent spectrum frequencies could be used at any time.
Regardless, it's generally the responsibility of the receiver to ignore signals in another part of the same band, and this is a different band entirely. Perhaps some receivers are built as cheaply as possible and don't have the best filters. If they all break, well, their customers should know not to trust that brand again. Any other policy amounts to no one ever being able to establish new radio service on its own part of the spectrum, on the theory that some other defective other equipment might fall over.
Personally, I think it's far more interesting the prospect of having a network of 20,000 steerable-beam transmitters approved for 15KW ERP each at 1.5GHz. 300MW is about half the output of a typical electrical power plant. If those were networked that could make one hell of an antisatellite weapon, phased-array radar illuminator, or maybe even an SDI-type directed energy weapon.
If the military isn't behind this, well they should be. <conspiracy theory>Maybe that's why the FCC is fast tracking it so much.</conspiracy theory>
The receiver is not required to be overengineered to cope with transmissions vastly more powerful than expected - that's why limits on broadcast power exist in the first place.
I suppose it would be reasonable for an engineer to assume a receiver is not going to end up within a few KM of a 15 KW transmitter at those frequencies.
40,000 of 15KW transmitters on the ground may be another matter.
1. They can repurpose existing infrastructure with just a software change 2. Nobody has to pay for much out of their own budget or build it in anyone's back yard 3. Nobody has to declare it under any treaties or such 4. The system can receive as well as transmit 5. It's engineered and tested for continuous operation. There may even be excess capacity available almost for free 6. The system is massively redundant and supplies its own power and backup generators 7. More is better 8. Why not? 9. If it saves one child... 10. ... 11. Profit!
and so on. Just tossing out wild ideas here.
If only Nikola Tesla were alive to see this plan, he would certainly approve.
http://en.wikipedia.org/wiki/GPS_signals#Frequencies_used_by...
Galileo changed the frequency to be slightly different to GPS to allow selectively blocking one or the other - but it's still close enough for this to interfere.
Lets think of it as you trying to eavesdrop on a meeting.
You have your ear pressed on a big thick wooden door that lets very little sound through, you are attempting to hear so you have everything around you very quiet and try your best to hear that very faint sound of your boss talking about the companies plan to fire everyone. Now your co-worker just a cubicle down is on the phone and instead of keeping it down is talking very loudly. It doesn't matter how hard you try to listen for the sound from inside the meeting all you can hear is your co-worker.
Now think of your boss in the meeting as the GPS satellites and your co-worker as this new company.
Unfortunately when it comes to transmitting power, the more you have of it the more likely you are to overpower other signals. This is the same issue that FM transmitters have as mentioned in the article.
Unless we put better band filters on GPS devices and attempt to filter out a very high power signal GPS is going to get lost in the signal that is being transmitted from the ground.
See, e.g., http://gpsinformation.net/main/gpspower.htm