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GPS Interferer
MrUmbra
A company called Lightsquared has recently received permission from the FCC to operate thousands of high power terrestrial transmitters on a frequency that's adjacent to GPS:

FCC Grants Go-Ahead to Potential Interferer with GPS Signal | GPS World

Consequently, there will be potential impairment of GPS reception. Miniaturized GPS receivers are susceptible to overload because they have insufficient filtering for out of band signals.

Garmin has performed laboratory testing confirming a serious issue:

Data Shows Disastrous GPS Jamming from FCC-Approved Broadcaster | GPS World

Tens of millions of susceptible GPS devices are in daily service. This is going to be interesting.

--- CHAS
MrUmbra
I came upon this graphic that nicely illustrates how the Lightsquared network could impair GPS reception. It was presented to the FCC by John Deere Co; marketers of an augmented GPS positioning service that's commonly in use in agriculture. GPS corrections, calculated from a network of ground monitoring stations, are delivered by Inmarsat via a geosynchronous satellite.

The original FCC waiver authorized Lightsquared license to operate without technical analysis of effects on satellite navigation. When the DoD and FAA learned of that, they persuaded FCC to require testing. Subsequently, FCC ordered a Lightsquared managed working group to assess possible impacts.

With good reason, skeptics contend that process is flawed.

--- CHAS
Attached Images
deere.png  
Marvin Hlavac
Chas, thanks for posting the graph. It nicely illustrated why the GPS-only receivers are less susceptible to this interference than the newer receivers that are capable of using also other networks.
MrUmbra
I told you this would be interesting. The latest developments:

Testing organized by Lightsquared didn't bode well for them. As predicted, most test devices showed performance degradation when subjected to the proposed network signals.

The original band plan proposes two network channels; a low channel and a high channel. Radio Technical Commission Aeronautics performed an analysis indicating the high channel, closest to GPS, is totally incompatible with aviation navigation. Testing suggests the low channel might be usable but additional investigation would be required to quantify its effects upon the installed base of avionics equipments.

Additionally, most high accuracy receivers employed by land surveyors and scientific users failed.

Consequently, Lightsquared has modified its network roll-out agenda proposing to initially activate only the low channel. That plan provides enough spectral separation from GPS allowing filters of practical design. JAVAD, a small company specializing in precision GPS, has presented technical information claiming they have solved the interference problem.

Unfortunately for Lightsquared, no filters or other solutions permiting operation on their upper channel have be demonstrated. But they remain insistent about turning it on in a few years when they would need it to maintain 4G network standards. Coalition to Save our GPS has petitioned FCC to emphatically deny them use of that spectrum citing the uncertainty that its use presents.

What does all this mean to Laptop GPS navigators? There's another round of testing in progress focusing on the effects of the lower channel upon cell phones and personal navigators. Perhaps the results will be published by year's end.

Attached is the filter plan from Dr. Javad Ashjaee's very technical presentation at:

http://www.pnt.gov/advisory/2011/11/ashjaee.pdf

--- CHAS
Attached Images
javad-filter.jpg  
Marvin Hlavac
<joke>
This could be good for the economy. New GPS equipment with better filters would need to be manufactured, some old units could perhaps be saved by modifying them with new filters... :-)
</joke>
MrUmbra
Well, the testing of mobile phones and personal navigators is complete. Tests were conducted with low channel signals.

Unfortunately for Lightsquared and its proponents, a majority of the personal devices were adversely affected. Interestingly, GPS receivers in phones worked.

Evidently, the FAA concurrently conducted tests that revealed the LTE low channel signal also degrades GPS dependent terrain avoidance systems. Of course, no government official wants to be found complicit after a perfectly operating airplane flies into a mountain top .. aircraft navigation remains Lightsquared's major nemesis.

So after several rounds of compatibility testing, EXCOM, the committee that advises the President about GPS policy, has concluded there is no reasonable scenario that allows Lightsquared to operate within the next several years. No additional testing is warranted.

http://tmfassociates.com/blog/wp-content/uploads/2012/01/EXCOM-Memo-to-NTIA-Jan13.pdf

Certainly Lightsquared cannot agree. Their retort .. attack the committee and the ethics of its members.

Government Committee

That's a last act of desperation. They've been spinning bogus arguments attempting in vain to blame the GPS industry for their problems.

It's time for Lightsquared to just go away.
SpadesFlush
Good news for GPS users!

It seems that the FCC wants Lightsquared to go away, too. See http://www.nytimes.com/2012/02/15/business/media/fcc-bars-airwave-use-for-broadband-plan.h...ml?_r=1&ref=business
Ken in Regina
For the record, Lightsquared is simply responding to huge public demand for LTE (the real 4G cellular data protocol, not the phoney baloney stuff that is currently being peddled as "4G") and planned to use spectrum sold to them by the government for exactly that purpose.

Lightsquared is not the only villain in this piece. One has to portion out much of the blame to the FCC who should have known better to start with.

...ken...
Boyd
So Ken - just for the sake of argument - do you feel that such a lawsuit against the FCC is justified, since much of the blame belongs to them?

LightSquared Looks to Lawyers to Overcome FCC's Decision - WSJ.com


LightSquared Looks to Lawyers
...........

The lawyers are investigating the merits of a potential suit against the Federal Communications Commission, which this week rejected LightSquared's plan for a broadband network, and the Global Positioning System industry. GPS companies and Defense Department officials have argued that LightSquared's signal could interfere with their networks.
Ken in Regina
So Ken - just for the sake of argument - do you feel that such a lawsuit against the FCC is justified, since much of the blame belongs to them?

LightSquared Looks to Lawyers to Overcome FCC's Decision - WSJ.com
Since I can't know the exact contents of the lawsuit I can't give a straight answer to that, Boyd.

But as a general response, yes, I think it may be justified.

The FCC is the controller of what can and cannot be used in the various bands of the radio frequency spectrum. That is, it defines and approves what you can do in various bands. So it knew in advance and agreed, at least in principle, to LTE use in that band by the simple act of selling licenses to LightSquared for that use. A company like LightSquared would never have begun serious product development if the FCC had not sold them the necessary licenses.

So it's not out of the question that LightSquared may have a good legal basis to sue the FCC for some form of relief. In this case it could easily be construed that the FCC used them, intentionally or through negligence, to do the research to determine feasibility of LTE in this band.

The basis for this would be that many experts in the field were hollering at the FCC about interference issues almost the instant LightSquared announced their product development plans.

So, it's not like the FCC was not warned immediately after the sale of the spectrum. And, further, it should be really easy to demonstrate that the FCC should have been able to see this themselves without having to have it shoved in their faces in this fashion.

And, finally, at worst the FCC could easily be seen as culpable by allowing the development to go on as long as it did before finally pulling the plug, given that all of the necessary evidence to stop it was in front of them much earlier.

Please understand that I'm not trying to be an apologist for LightSquared. I don't believe there is any grounds for allowing them to continue to try to use their licenses if there is any chance at all of GPS being screwed up.

I'm simply saying that the FCC pretty much screwed the pooch by selling licenses to use spectrum so close to the GPS frequencies without doing a lot more homework. And then made it worse by not taking the concerns of experts seriously enough, soon enough. So it would not be unreasonable to ask the FCC to, for instance, buy those licenses back. And maybe pay LightSquared something for being the R&D guinea pigs for the applied research that the FCC might have otherwise contracted to someone BEFORE selling those licenses.

Just sayin'...

...ken...
Boyd
Some good food for thought - thanks. Naturally I didn't expect you to comment of the actual lawsuit.

I was not following this saga at the very beginning, but had the impression that Lightsquared purchased the frequencies for the intended purpose of space-based communications, then later revealed that the terrestrial network would be the focus. Maybe that's a wrong assumption on my part however.

While the FCC did take a long time to actually rule, the writing has been on the wall for quite a long time - especially as the political aspects of the story came to light. Seems to me that Lightsquared had a responsibility to mitigate the damage and cut their losses, but they stubbornly fought on.

When I think of Falcone, I have this mental image of the scene from Citizen Kane where he is confronted by Boss Geddys who threatens to release the details of Kane's illicit affair..

If it was anybody else, I'd say what's going to happen to you would be a lesson. Only you're going to need more than one lesson. And you're going to get more than one lesson.
SpadesFlush
Stay tuned. There is enough money at stake to support lawsuit, perhaps even a frivolous one.
Ken in Regina
Yes. And that's the driver here. Demand for high speed wireless bandwidth is high and climbing. There is a huge amount of money for those who can provide that bandwidth earliest.

That's why nobody in the business world would expect a company like LightSquared to do anything other than what they did. And will likely do. Their major investors have a lot to lose and even more to gain. That makes LightSquared's behaviour absolutely predictable. And completely justifiable in the eyes of their investors. Whether we like it or not.

...ken...
MrUmbra
Actually, the FCC did not sell Lightsquared its spectrum. The spectrum came down to them with the SkyTerra satellite. I'm not sure if SkyTerra just changed its name or if they are separate entities but the satellite license, along with its terrestrial base station authorization, does go back to at least 2004. Then, Mobile Satillite Ventures held the license.

Lightsquared spent a lot of money preparing to deploy its network and serve 260 million potential users in accordance with conditions set by the FCC. If they can establish they were encouraged by the government to do this in exchange for expedited licensing considerations, then maybe they have a legal case to sue for financial loses. That certainly appears to be what transpired.

Otherwise, FCC might make its argument that it denied Lightsquared its license after review of interference data. Ruling in the 'public interest' is what they are tasked by Congress to do.

--- CHAS



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