Lightsquared and GPS system

Yea lets remove the biggest improvement to aviation just as it gets cheap enough for everyone to afford.

Lets go back to 4 course's and see how many people die too.

I think its a huge risk to safety.
 
It's an RF land-grab. Lightsquared is hoping for someone to hand them alternate spectrum to "save" GPS.

A tactic that started with Nextel, and worked.

It will continue to happen until the FCC starts getting real about not putting things right up against each other that aren't truly compatible.

GPS, in the end, has much much more money into lobbyists than Lightsquared, and FCC won't let it stay.

They may hand Lightsquared some prime spectrum somewhere else to appease them. Or they could finally get tough on people who plan this kind of silliness.

Lightsquared's RF engineers know full well what they're doing...
 
The reason I asked if this was a Chicken Little scare was I had hear about a month ago that Light Squared had agreed to back off on this but the link I included was dated 21AUG. So is this 'old news' or has Lightsqaured not really backed off?
 
I heard from a friend the other day that her DoD office, which had stayed out of this figuring that AOPA/EAA/NATA/NBAA/FAA/Airlines/Hikers/Truckers/EverybodyelsewhoreliesonGPS would have killed it, got a directive by the NSC to send formal comments to the FCC on the issue.

Apparently the FCC is not ready to put this a$ide yet.
 
Richard said:
The reason I asked if this was a Chicken Little scare was I had hear about a month ago that Light Squared had agreed to back off on this but the link I included was dated 21AUG. So is this 'old news' or has Lightsquared not really backed off?
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In the same breath LS claimed that GPS receiver users and manufacturers are to blame for any issues caused by transmissions in LS's allotted bandwidth. And I haven't seen any believable testing results demonstrating the lack of interference with existing receivers from their latest proposal to increase the guardband from 4MHz to 23MHz. That might work but it wouldn't surprise me to learn that many aircraft GPS receivers are still affected. Finally LS continues to suggest that their "voluntary" spectrum reduction is a temporary measure to tide things over until all the existing receivers are replaced with ones that can deal with their interference with the original 4 MHz separation in a couple years.
 
What I can't figure out is why the spectrum wasn't protected to begin with... GPS is really a foundation technology that so much else is built on. I know that DOD "hijacked" the spectrum way back when, but still...
 
TMetzinger said:
What I can't figure out is why the spectrum wasn't protected to begin with... GPS is really a foundation technology that so much else is built on. I know that DOD "hijacked" the spectrum way back when, but still...
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It was protected. The L band including GPS and the spectrum that LS purchased was allocated for space based transmission. That's why LS needed/needs a waiver from the FCC to broadcast on those frequencies from the ground.
 
The "DoD" mentions in this thread, that would be via NTIA, correct? I haven't looked at the public comments lately to see what NTIA had to say, but I will be surprised if they've been on the sidelines until now. Holy crap.

I can't believe how distinctly lazy it is to "hope the other groups take care of it" in this case... they should have filed their complaints along with everyone else.

If there's one thing I've learned from my time volunteering for spectrum management duties in Amateur Radio, which are far less important than this, it's that you don't "wait around and see what happens" in spectrum management. You take action immediately upon reports of interference, and you investigate immediately, and if interference is suspected or expected due to design, you give the coordinated users priority.

Forgive me if I expect better from the pros than volunteers... sheesh...
 
bartmc said:
Little bit of sky is falling but Lightsquared has some friends in high places backing them. And yeah their probably just fishing for a handout.

http://www.fiercebroadbandwireless....ind-way-allow-lightsquared-operate/2011-08-22

Especially if you read their whining and complaining. and "not our fault" mentality.

http://www.lightsquared.com/press-r...ts-nationwide-wireless-broadband-plan-to-fcc/

One thing is sure, it will get ugly.
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What they are saying sounds reasonable to me though - the GPS industry dropped the ball pretty badly here.
 
The GPS industry responded to the market which wants their GPS receiver to work indoors, in basements, all sorts of places the (relatively) weak signals from orbit normally shouldn't be heard.

Their receivers have been this sensitive for a long time now. Lightspeed just figured out a way to hamstring the FCC who hadn't thought it through and put a bigger guard-band around the GPS service.

IMHO, the fact that it's a band not intended for terrestrial transmitters means the real screw-up here was in ever even entertaining the idea or granting test permission for a high-power terrestrial transmitter in that spectrum at all. They could have put those transmitters in a more appropriate band and built a dual-receiver radio for their service.

They just didn't want to spend the money -- easier to trigger interference, and cross fingers -- and hope they win the same spectrum lotto that Nextel did. Hiring lawyers and lobbyists is a lot cheaper than spectrum these days.
 
SkyHog said:
What they are saying sounds reasonable to me though - the GPS industry dropped the ball pretty badly here.
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I can't tell if you're trolling, being sarcastic or serious? They bait and switched what they were going to do then cried like a 10 year old that didn't get their way.
 
According to an article in AWS&T a few weeks back, the LS signals remain within allotted frequencies, but blocks out important weak GPS signals transmitted outside of the allotted band.

Apparently, the GPS satellite builders were a little sloppy, and the receiver builders worked with what they had. I don't honestly know the facts, but the vitriol from some public spokespeople is infantile and insane.

It will be interesting to see how it pans out.

LS shouldn't necessarily be allowed to impair the operation of the signal even if they are right, but if they invested a lot of money developing the infrastructure for legitimate business purposes in good faith, they may be rightfully entitled to compensation for losses.
 
bartmc said:
I can't tell if you're trolling, being sarcastic or serious? They bait and switched what they were going to do then cried like a 10 year old that didn't get their way.
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I'm actually serious. If GPS bleeds into a separate range of frequencies that LS owns, and GPS devices rely on that, then basically GPS is stealing bandwidth. My understanding is that the reason GPS doesn't have the filters installed is because they are actively using bandwidth that they don't own.

That's pretty bad, if true, and my understanding is that it is.

If I'm wrong, and GPS is operating only within its bandwidth and LS is trying to bleed over, then I take it back. But if both technologies are operating within their own bandwidth, there should be no problems.
 
SkyHog said:
What they are saying sounds reasonable to me though - the GPS industry dropped the ball pretty badly here.
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The GPS industry presumed (and rightly so) that all emissions in the L-band around GPS would also be satellite based. The RF engineers built filters that would sensitive to the GPS L-band signal and filter non-GPS signals of roughly the same strength.

GPS signals are pathetically weak; like really really really weak. The received signal strength is spec'd at -151 dBw, which is roughly 8*10^-16 watts.

It is not possible to build a filter that will pass the GPS band and exclude a band next to it that is carrying signals that are trillions of times more powerful.
 
SkyHog said:
I'm actually serious. If GPS bleeds into a separate range of frequencies that LS owns, and GPS devices rely on that, then basically GPS is stealing bandwidth. My understanding is that the reason GPS doesn't have the filters installed is because they are actively using bandwidth that they don't own.

That's pretty bad, if true, and my understanding is that it is.

If I'm wrong, and GPS is operating only within its bandwidth and LS is trying to bleed over, then I take it back. But if both technologies are operating within their own bandwidth, there should be no problems.
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GPS is transmitting well within its own bands and doesn't bleed into LS's band. Its the other way around. LS is bleeding into GPS.

Everything was hunky-dory when LS was going to use satellites in that band, because the signal strengths would be roughly the same. When they went to terrestrial transmitters that changed the whole game (and quite frankly the FCC dropped the ball by even considering allowing that).
 
SkyHog said:
I'm actually serious. If GPS bleeds into a separate range of frequencies that LS owns, and GPS devices rely on that, then basically GPS is stealing bandwidth. My understanding is that the reason GPS doesn't have the filters installed is because they are actively using bandwidth that they don't own.

That's pretty bad, if true, and my understanding is that it is.

If I'm wrong, and GPS is operating only within its bandwidth and LS is trying to bleed over, then I take it back. But if both technologies are operating within their own bandwidth, there should be no problems.
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Appears to me their original design called for a seat at the bench, they were granted that then they changed their mind and wanted the entire bench to themselves. They had plenty of money and engineers, this wasn't some sort of surprise, they knew what was going to happen. IIRC the original plan called for only satellite based transmissions then they swapped over to the ground towers after the fact. They have enough money and interest to make me semi-scared. There's a lot of money on the line, don't be surprised when you get that letter about the GPS in your plane "only" needing a 1AMU filter that probably won't work well. I've just been waiting on the USDOD to step in and put the brakes on it.
 
You've got it.

I'm going to steal a link here that is actually for a different type of discussion (analog vs. digital signals), to give a visual look for those that learn visually...

http://utahvhfs.org/analog_dstar_spectrum1.gif

The signal on the left is an analog signal, the one on the right is a specific type of digital signal.

Don't worry about that right now. What you want to notice from this picture is that all transmitted RF signals have a center frequency (see that little point that touches the top of the screen on each signal) and "skirts"... all that stuff flowing down to either side.

Okay, remember those little men you cut out of paper in an accordion? Duplicate that left side picture and line 'em all up in a row on a big wide graph, left to right. (For the moment let's pretend those don't overlap or arrive at the receiver at different strengths... they all look exactly the same.)

Now take your copy machine and make one of those blobs 10X bigger (not an accurate number for the Lightsquared case, but close enough for the visual demonstration here) and put it equidistant to the last small one on the right side.

Where do the "skirts" from that big "mountain" go? They cover up a whole bunch of the signals on the right side of your receiver's passband.

Make sense?

The person that said Lightspeed is "operating in good faith" most RF engineers disagree with. The reason is... they KNEW their stronger signals from the terrestrial stations would do this.

What they're trying to do is jump through a loophole that defines this stuff like this, converted into "visual terms" from the picture...

If you mountain stays within X power levels (height of the mountain) and your "knee" in the graph is X number of dB down by X amount of frequency away, you're legal.

This is where the FCC botched, not just once (not protecting the GPS spectrum adequately since they've obviously also known how sensitive GPS receivers have been since GPS deployment by the military long before the public even knew about it), but they REALLY botched it when they granted Lightspeed the test licenses to even fire up those "giant mountains" right next to GPS.

Lightspeed knew they were trying to get away with it before anyone noticed. Unfortunately the folks who were supposed to notice, somehow didn't, and the first folks to really see it were the GPS receivers going blank. Unwanted interference.

I'm just a layman, not a pro and I'm amazed the pros missed this. There's a lot of things one could infer about what's going on at the FCC from seeing them make this gaffe, not the least of which is that they're undergoing a "brain drain" of traditional analog RF engineers for various socio-economic and political reasons.

Just for kicks... here's a report I sat on a committee in 2007 where we discussed where to put the "relatively new" digital radio systems in Amateur Radio spectrum in Colorado. Some of the folks on the committee are also pros in their "day jobs", and others are simply technologically interested Amateurs who volunteered to come up with policy. If a bunch of "dumb" Amateurs can do this... certainly FCC should be able to for the size of their budget. It says something about their priorities.

The first report: http://www.ccarc.net/images/CCARC-Spectrum%20Committee%20Report-%20Rev%203.pdf

Which led to the second report: http://www.ccarc.net/images/Second%20Spectrum%20Use%20Report-VHF.pdf

The issue above is not really "resolved" three years later. VHF spectrum in the Colorado Front Range is still jammed full. However, as things have gone on and off the air "naturally" some spectrum has been "carved" for digital systems over time and a few VHF digital systems are in operation.

In the case of GPS... it's not moving, and it's not going anywhere... so Lightsquared jammed up against it (pun intended, I guess), with high-powered terrestrial transmitters, just doesn't work from a purely technical standpoint.

Now that FCC already issued the temporary licenses, they painted themselves in a legal corner. That's the other problem going on here, as well as "influence" by big money supporters on both sides.

Ultimately -- in my opinion -- our government has shown throughout my lifespan that solid engineering takes a back seat to money interests, so that push-pull is at the core of this problem.

But I definitely disagree with the idea that Lightsquared "acted in good faith". They did not -- unless their RF engineers got their degrees from a Cracker Jack box. They knew, did the calculations showing they'd hammer GPS, kept those findings to themselves, and the execs decided to roll the dice. FCC helped them by granting them the test licenses terrestrially, who knows why?

Bad move. It set precedent that FCC was even interested in letting them try something that was easily known would be a real-world problem. My guess: A clerk somewhere looked up a set of procedures and followed them blindly, like any giant bureaucracy, without any knowledge of RF Engineering. A paper-pusher got FCC into the mess they're in, and now they'll try to get out by using the same "larger mountain" technique the RF spectrum interlopers are using, but their "mountain" will be paperwork... and committees... and more paperwork... and more.

Taxpayers have little idea about how expensive this will all be, that it could have been avoided, and will write it off as "the FCC doing their job" instead of being angry that FCC has gotten this whacked that they miss such obvious stuff and then spend years and tons of money cleaning up the mistake.

I never thought I'd see Nextel get a deal, but they did. Lightsquared probably will too. FCC could stop the whole thing by simply revoking the licenses and saying "no", but the lawsuits will fly at that point. Lightsquared is out to make money, either with their RF data system, or in court.

Now that FCC opened Pandora's box, they have to tread lightly... allow the "tests" to continue, control the conditions, document six-ways-from-sideways the effects of the transmitters, and then carefully cancel the test licenses and say "no" very gently. But they'll still get sued. As will the manufacturers of the "too sensitive" GPS receivers.

It's going to keep a lot of RF engineers and lawyers in a lot of money for a long time.
 
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TMetzinger said:
I heard from a friend the other day that her DoD office, which had stayed out of this figuring that AOPA/EAA/NATA/NBAA/FAA/Airlines/Hikers/Truckers/EverybodyelsewhoreliesonGPS would have killed it, got a directive by the NSC to send formal comments to the FCC on the issue.

Apparently the FCC is not ready to put this a$ide yet.
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DoD has not stayed out. They have been involved at a very early time with the Congress and FCC to deal with this issue. Your friend is mistaken.

Here is a letter from March of this year that is public from the DoD to the FCC

http://static.arstechnica.com/OSD03393-11.pdf
 
That letter is awesome if you understand Government-lawyer-speak...

"understand the importantance of a thorough and equitable process"... We're about to beat you to death with a bureaucratic process so large you'll wonder what you were thinking.

"DoD and DOT were not sufficiently included"... so FCC asked us to write this note to know that they have bought us, their friends, Guido and Vinnie, along to help.

"regarding how differing technical viewpoints from federal and private sector manufacturers and users will be reconciled"... By the way, we brought our own unpublished rulebook. We'll be using that.

"An exchange of all pertinent technical and operational information is also crucial to ensure the effectiveness of interference mitigation solutions." - We're firing up the printing presses now for the first list of questions and forms to fill out. (Implied... it's going to be huge.)

"[Signature blocks]" - Love, Vinnie and Guido. Don't call us, we'll call you. (And we're ****ed... is implied.)
 
kontiki said:
According to an article in AWS&T a few weeks back, the LS signals remain within allotted frequencies, but blocks out important weak GPS signals transmitted outside of the allotted band.
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I doubt that the LS signals don't have sidelobes in GPS bands. Nobody builds filters that good.
 
Bob Noel said:
I doubt that the LS signals don't have sidelobes in GPS bands. Nobody builds filters that good.
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Antenna have sidelobes. You mean out of band emissions (OOBE). All services have OOBEs and it is how those are dealt with and specified in the regulations that are the issue here.
 
gismo said:
It was protected. The L band including GPS and the spectrum that LS purchased was allocated for space based transmission. That's why LS needed/needs a waiver from the FCC to broadcast on those frequencies from the ground.
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But what would stop LS from using the spectrum from space and still causing problems? Were there strict limits on transmission power and such?
 
ScottM said:
DoD has not stayed out. They have been involved at a very early time with the Congress and FCC to deal with this issue. Your friend is mistaken.

Here is a letter from March of this year that is public from the DoD to the FCC

http://static.arstechnica.com/OSD03393-11.pdf
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I didn't say DOD stayed out, I said her DOD OFFICE stayed out of the discussion. I got the impression they dealt with things that were normally classified.
 
TMetzinger said:
But what would stop LS from using the spectrum from space and still causing problems? Were there strict limits on transmission power and such?
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I don't know, but the inverse square law probably helps a lot, and the power available is going to be limited by what they can gather from a solar panel.
 
SkyHog said:
I'm actually serious. If GPS bleeds into a separate range of frequencies that LS owns, and GPS devices rely on that, then basically GPS is stealing bandwidth. My understanding is that the reason GPS doesn't have the filters installed is because they are actively using bandwidth that they don't own.

That's pretty bad, if true, and my understanding is that it is.

If I'm wrong, and GPS is operating only within its bandwidth and LS is trying to bleed over, then I take it back. But if both technologies are operating within their own bandwidth, there should be no problems.
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Nick, GPS transmitters (the satellites) don't "bleed into" into the spectrum that LS owns, and normal GPS reception doesn't require any of LS's spectrum either. The problem is that adjacent channel rejection filtering with a 4 MHz guard band is simply impractical when the emissions needing to be filtered out is a hundred million times stronger at the receiver. LS claims that the mfg's dropped the ball by going with cheap filters that aren't up to the job is pure BS, most of the GPS units sold in the last several years are capable of rejecting transmissions on LS's frequencies as long as the signal strength of the adjacent channel is limited to about 100 times the strength of the GPS signal at the same antenna. The waiver that the FCC foolishly granted to LS would allow LS to transmit from the ground on those frequencies with the same or greater power than what's allowed from space. Signal strength falls off at the square of the distance between the transmitting and receiving antennas. With a GPS SV near the horizon it's something like 12000-13000 miles away. One mile from a LS ground station operating at the same power as the GPS transmitter the signal strength is 140-170 million times weaker than the interfering LS signal. Real filters do not pass everything at 1.5 GHz and block everything .004 GHz lower, instead there's a slope on the plot of attenuation vs frequency and the slope of a filter that could actually be built today simply isn't steep enough to knock 100+ million time stronger signal down to a tolerable level.

So LS's claim that GPS is "stealing" their bandwidth is a huge exaggeration and/or distortion of the facts. The facts are that LS bought spectrum that was designated for space based transmitters at power levels similar to the GPS transmitters then paid off the FCC to allow the same frequencies to be used from the ground. This is the RF version of someone buying a lot in the middle of a residential community and paying off the zoning board to rezone the land so it can be used for a steel mill. And their latest proposal amounts to an agreement to not operate the mill between 10 PM and 7 AM for a couple years until all those nearby homeowners can soundproof their walls and roofs at their own expense using materials yet to be developed in order to sleep at night.
 
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TMetzinger said:
But what would stop LS from using the spectrum from space and still causing problems? Were there strict limits on transmission power and such?
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Yes. AFaIK all FCC spectrum allocation comes with limits on effective radiated power. But an even bigger issue is the limited power available in space on a continuous basis and (more importantly) the huge drop in signal strength at 10,000 mile distances.
 
ScottM said:
Antenna have sidelobes. You mean out of band emissions (OOBE). All services have OOBEs and it is how those are dealt with and specified in the regulations that are the issue here.
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And from a technical perspective it's far easier to filter out of band emissions at the transmitter than a receiver. With a transmitter you can simply increase the power into the filter to mitigate any in-band losses and any noise added by the filter is miniscule in relation to the intended signal. On the receive side, whatever is lost in the filter is unrecoverable and the tiniest bit of noise will affect the reception noticeably because it's strength is much closer to the extremely weak GPS signal.
 
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I agree it's a ploy to get new spectrum, and I think there has already been contact on the international level. Personally, I'm fine with that. We need both services to work correctly and harmoniously. If that means we open up some new spectrum, we do it. That raises the question though, "Do we have it to open?". I wish you could talk Scott....
 
I can see a real benefit to reopening the discussion of proceeding with the robust and well-designed eLoran standard to reactivate the Loran system, upgrade its capabilities (at very low cost), and avionics manufacturers can incorporate Loran receivers in future iterations of their navigators.
 
Henning said:
I agree it's a ploy to get new spectrum, and I think there has already been contact on the international level. Personally, I'm fine with that. We need both services to work correctly and harmoniously. If that means we open up some new spectrum, we do it. That raises the question though, "Do we have it to open?". I wish you could talk Scott....
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It won't matter in this case. They can't pull the satellites down and change the transponders.

(Although I must admit I hadn't even looked to see if they already have on-orbit assets or not. If not, the game they're playing is even more obvious... "Give us spectrum so we know how to build our birds.")

Generally, the answer is no. There isn't any unaccounted-for spectrum at all. In reality, there's some underutilized spectrum in every major band. L-band, I'd have to go look. But it's pretty full.

It's really just an incompatible use. Terrestrial vs. Satellite.

Lightsquared just wants non-shared nationwide spectrum which is neither cheap nor plentiful.

Line up at the government auctions and plunk down your cash like everybody else...

There were blocks of spectrum that did *not* sell at the last big auction... They had goofy restrictions on them including a requirement to build a specific type of national Public Safety radio system. The radio manufacturers said, "Nope. We're not playing." They knew that local agency budgets control local Public Safety systems and they're not going to buy gear on a national system that covers outside their jurisdiction. Didn't make any sense.

So there's spectrum. Whether or not Lightsquared can utilize it is the question. And prior to that, I'd say the message that this method of back-door loophole spectrum grabs is going to get used to send a huge message... "Don't try it."

But it'll be in Court for years...
 
When the Feds auction off spectrum, is it actually sold, or just leased? In other words, once the buyer plunks down the money, do they own it in perpetuity, with the Feds getting no more revenue from it?
 
Palmpilot said:
When the Feds auction off spectrum, is it actually sold, or just leased? In other words, once the buyer plunks down the money, do they own it in perpetuity, with the Feds getting no more revenue from it?
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That is a very complex answer.

Spectrum seems to always be owned by the government, with the auctions leasing parts of that spectrum. But then the ownership of the lease gets to be an interesting issue.

On an auction of a few years ago the FCC awarded a license to a company that went bankrupt before it was able to deploy their equipment. The FCC was going to reauction that license since NextWave had not paid for them, but in the bankruptcy proceeding the company listed that license as an asset and resold it. Lots of court battles ensued and the company was able to keep the license and then use it as an asset. The spectrum sat unused for a while as a result.

http://en.wikipedia.org/wiki/NextWave
 
Thanks. I'm glad to hear that it's a lease and not an ouright sale, because if it were the latter, I would say that the taxpayers were getting a raw deal.
 
Palmpilot said:
Thanks. I'm glad to hear that it's a lease and not an ouright sale, because if it were the latter, I would say that the taxpayers were getting a raw deal.
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My understanding they work it like mineral leases.
 
Scott works in the industry...he has a good handle on the leasing thing.
 
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