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LightSquared Says GPS Tests Were Rigged
itwbennett writes "Would-be cellular carrier LightSquared claims that the company's LTE network was set up to fail in GPS interference tests. 'Makers of GPS (Global Positioning System) equipment put old and incomplete GPS receivers in the test so the results would show interference, under the cover of non-disclosure agreements that prevented the public and third parties from analyzing the process,' LightSquared executives said on a conference call with reporters Wednesday morning."
>old and incomplete GPS receivers
I'm not an expert in the deployment of GPS, but is this not what we would consider a real-world test? Why should they be set up to pass the test, by only testing the latest deployments of GPS?
Don't you test, in order to understand previous unknowns or to flesh out previously unforeseen scenarios?
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If this is fraud on the GPS companies' part or the testing authority's part then there should be hell to pay.
If this is sour grapes then LightSquared just libeled the companies involved.
If, on the other hand, "old and incomplete equipment" tests were a required part of the test for good reason, then LightSquared is a bit late in its complaints - it should've made these complaints well before testing happened, and its current statement should've started off with "As we said before the tests were run, testing for old and incomplete equipment is not a valid test...."
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
Garmin GPS-12 13(?) years old.
Nagivo 3100, closing on 4 years old.
In addition, many GPS receivers in general aviation aircraft are _significantly_ more expensive than domestic units, and are not replaced merely because the battery wears out.
What possible motive do the GPS manufacturers have for rigging the tests? If modern, properly-configured GPS units don't recieve interference, then why would they care? I read the article expecting some important link, like Garmin having an alliance with Verizon, but there was no mention of that.
In fact if anything, GPS makers would enjoy selling modern units to customers with older units that no longer work because of LightSquared.
Sorry, but it's just too much of a stretch to believe in this conspiracy. I think LightSquared are simply desperate to get the FTC to give them their waiver. Their business is royally screwed without it.
"A week in the lab saves an hour in the library"
A lot of aircraft GPS receivers are quite old. It can cost 10-20K$ to put a certified receiver in a light aircraft, so pilots will keep their existing equipment as long as possible. Changing the requirements on interference resistance might require very expensive re-certifications of these receivers.
So LTE needs a federal license which requires proof that their network transmissions do not interfere with GPS receivers. Well, lets see, apparently the GPS equipment worked when the LTE network wasn't on and when it was turned on the GPS had issues. So what LTE is saying is that everyone with old GPS receives has to upgrade them because their network causes issues with them so that they can get a FCC license in order for their network to be deployed everywhere. Are they assuming that people buy all new electronics every year? I mean especially testing this on a military base, when I was in the military I used computers that were designed before I was born. I have a 30 year old television myself, if LTE decides to make a network that stops my television from working isn't that their problem. The whole purpose of the FCC license is to ensure that someone doesn't put new equipment into use that will stop the use of old equipment. Okay, maybe not the only purpose, but that one is at least important.
So LTE's network failed in real world conditions and they are blaming GPS manufactures for that failure. I don't think they have a case because the GPS manufactures likely did not go back in time and put in circuits to stop their equipment from running if they detected LTE's network. It's probably a good thing it wasn't raining either or they would have to sue God for conspiring against them.
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According to TFA, the vendors
deliberately chose obsolete and niche GPS devices that would show the most interference ... The tests also included receivers that were tested without interference filters that normally would be included in a complete device for consumers
If true, the use of units without filters may be enough to invalidate the tests. It would be similar to testing a microwave for radiation leakage, with the door removed.
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1) GPS manufacturers are not a direct competitor to a wireless networking company. If Verizon or AT&T were complaining they might have a case.
2) GPS was there first.
3) Clearly the Lightsquared hardware is spitting out a harmonic which could be fixed but would probably make the devices much more expensive to produce.
4) Lightsquared has been trying this case in the court of public opinion by running full page newspaper ads instead of dealing with the technology issues.
5) Lightsquared has been making huge political donations and receiving government grant funding which makes the whole thing stink like old fish.
All I can say to LightSquared is ... (sarcasm on) "Right...." (off)
This company is *done* unless they can find a way to lower their required power or move their spectrum away from GPS. They are fighting for their very existence and it's getting down to the wire so they are saying *anything* in an attempt to keep things going. The test was rigged eh? Guess physics did you in guys, no need to rig the test.
Had you asked an RF engineer you could have saved yourself a pile of cash trying to fight this issue. If the FAA didn't do this idea in because it would make Airborne navigation using GPS unreliable (and thus end the practice), the DOD's arguments should win the day. Further, the FACT that the consumer use of GPS would surely be impacted (if not totally disabled) for miles around their transmitters regardless of what they do should nail the coffin shut.
I guess, to be fair, with the FCC buying tickets to the Broadband over Power Lines (BPL) circus, the chance that they'd buy into this sideshow was worth a try. However, the game is over guys.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
LS is full of it. I used to do testing of this nature for the Navy. I know many of the people who would have done this testing for the USAF. Never in 6 years of working in that field did we ever require a contractor who had submitted equipment for test to do so with no knowledge of what the test would be. They are blowing smoke to cover their asses in the hope that "the right people" won't know any better.
The spectrum bleeds so there will be interference, though it remains to be seen how much.
Falcone is certainly paying fof his chance to get Light squared going.
http://www.bloomberg.com/news/2011-09-20/house-republicans-ask-white-house-for-records-of-falcone-contact.html
But that's business as usual.
However the claim is that the Lsquared signals are a "billion times greater in strength" than GPS, and I know my modern GPS unit seems to have trouble locking on at times.
http://www.insidegnss.com/node/2498
Lsquared seems like a great opportunity for rural areas to get high-speed Internet and maybe it's time we updated our GPS satellites again, but from my perspective after what I have read from multiple sources I am going to go with Light squared will cause issues with commercial GPS and the motivation on Lsquared's part is being the only provider in the area, charging a higher fee for access, and not having to lay cable and other infrastructure thereby reducing deployment and maintenance cost, in other words a large profit margin, and the only problem is they have to destroy the GPS infrastructure already in place.
"If any question why we died, Tell them because our fathers lied."
For surveyors, GPS basestations + roamers used for surveying are in the $10,000+ dollar range, and you don't replace them every few years.There's always going to be significant amounts of "old" (and old in terms of the 2-year churn for mobile phones) GPS equipment being used by the folks who need extremely high levels of accuracy.
Here is good info on the issue:
http://www.forbes.com/sites/danielfisher/2011/12/21/falcones-lightsquared-faces-enemies-on-all-sides/
Prove anything by multiplying Huge Number times Tiny Number
it's not about filters, nor is it about "GPS listens outside its band"
GPS receivers have "wide open" front ends and always have for good engineering reasons:
1) Spectrum planning ensured that there's no high power signals in adjacent bands (i.e. the adjacent band is also for satellite signals)
2) "brick wall" filters are heavy, expensive, large, and have bad effects on the inband signals (see, e.g. any digital audio application since CDs started being sold 30 years ago). Your cellphone has GPS that is as small as it is partly because you can use a fairly wide open front end that doesn't require a lot of filtering.
3) GPS signals are below the noise floor, allowing use of 1 bit ADCs in receivers, reducing cost and complexity in receivers.
There's quite a bit of arguing about what is an appropriate propagation model from L2 terrestrial transmitter to GPS victim. L2 would like to use a conventional communication model. GPS folks would like to use a jammer/interference model. The difference isn't in the "mean power" but is in where the outliers are. For comm, your concern is that your worst case low power deviation is still high enough that you can "close the link" (i.e. not drop the call). For interference, your concern is that the worst case high power deviation is still low enough that it doesn't interfere with your link. The problem is that in urban environments, the distribution isn't uniform and is highly skewed (lots of reflecting surfaces and multipath.. distance isn't as big a factor as just the number of bounces). There's lots of deviations below the mean, but small ones, and relatively few deviations above the mean, but they are huge (e.g. "hot spots"). We're talking 15-20 dB difference between the 5% low end and the 5% high end
There's also arguing about what "performance degradation" is acceptable. L2 would like to claim that 6-8 dB is ok, while GPS industry would like to use 1dB. That's because communications uses error correcting codes and such, and can tolerate dropouts and degradation. GPS is more like radar, and relies on measuring the timing of the signal, and doesn't have as much in the way of error correction or error tolerance, so they've historically used the radar standard of 1dB degradation. The GPS industry is a bit stretching here, because with new receiver designs (which might consume more power and be bigger) they could probably deal with the worse interference environment. But that's a 10-20 year kind of project.
So the tests were fair, with published test criteria, and only now, a week from their deal with Sprint expiring (after a 30 day reprieve) they're starting to raise these questions.
Besides nobody ever flew into a mountian because they didn't have a clear LTE signal.
For every benefit you receive a tax is levied. - Ralph Waldo Emerson
With the Laws of Physics Against Them, they have decided to turn to Public Relations a tried and true way to overcome conservation laws.
Missing from the discussion is why this happened to begin with. The Federal Communications Commission was created with the explicit mission to avoid allocation problems like this with the electromagnetic spectrum. This is not the first time they've screwed up like this. In the late 1980s we installed a SCADA sytem on 928.8 MHz. A year after we were up and running, high power paging showed up on 929.03 MHz. You could light a neon bulb with the energy we were getting from our Master receiver antenna.
Our remotes were transmitting with 5 watts and the paging systems were transmitting with over 3 kW ERP. Our receivers had been optimized for sensitivity, not selectivity. But even with the state of the art receivers designed for selectivity, we were still getting clobbered. Only with massive effort did we overcome this problem.
The FCC screwed up because they don't do their homework any more. Even back then, engineers were being relegated to the broom closet while attorneys and political hacks took charge. Applicants were being told to hire consultants to suggest available frequencies, do interference studies and to submit the consultant's work with their license application. Tell me there wasn't a conflict of interest even then!
For all I know things are still like that today. LS probably paid for a consultant who told them what they and the FCC commissioners wanted to hear.
This is why we can't have nice things. We need an FCC to keep this from happening. And instead of an FCC, we get political hacks of both flavors who don't know a damned thing about the state of the art or even what the radio spectrum is.
Nearly fifty percent of all graduates come from the bottom half of the class!
They bought spectrum that was cheap because it was designated for satellite to ground transmission, then they demanded it be redesignated for ground transmission
they have no claim against the FCC, what they did would be like buying up some cheap land that was zoned to be used for parks/rec centers then whining that they cannot open a nitroglycerin factory next to the city park
Snowden and Manning are heroes.
There is always some leakage of the local oscillator through the other mixer port. There may also be some leakage of the downconverted intermediate frequency (IF).
In my youth I made a "police detector" using this principle. It worked quite well.
The PNT government website has the complete test results for the first round of testing here:
http://www.pnt.gov/interference/lightsquared/
Look for "Final Report of FCC-Ordered Working Group"
I'd expect you'll find the test report for the second test to be available at the same site, once it is released.
~1500 watts was the official LS broadcast power for its towers, until after the parameters for the second round of tests were finalized.