The US Military will have a quiet word with the FCC Chairman and kill this before it starts. No way they are having signal loss on their GPS bombs and radio kit.
Wireless broadband firm LightSquared has admitted that its original plan would have knocked out most GPS sat-nav kit, but argues that its new plan will only leave 200,000 users lost. Reporting on the results of several months of testing, involving 130 different GPS receivers, LightSquared admits that operating in the …
I bet the military kit has proper filtering. It is sloppy implementation of civilian kit which is the problem.
In fact if we go by the GPS industry logic we should prohibit WiFi because it disallows the mobile phone industry to save 50p on filtering in the 2.5-2.6GHz LTE bands.
Yeah... B*ll*cks... What the FCC needs to do here is to revoke the FCC certificates of compliance on any kit that is affected by adjacent band interference and add adjacent band interference to the GPS test set.
Anything that has been FCC certified will have to carry on working. If not it's the FCC who are liable.
So, in the blue corner we have the telcos and GPS industry both with deep pockets and in the red corner we have a company with a dodgy business model and rapidly dwindling cash reserves...
"[...] contends that LightSquared's estimate of 5 cents per device for better filtering is entirely untested and no better than a guess"
It is an estimate. Therefore it isn't tested. Also, most people would assume that an estimate ~= a guess anyway.
Galileo is a higher bandwidth signal with the same center frequency as gps. That's why the high end galileo ready systems are amongst the ones that are still killed by the revised plans.
This hasn't been mentioned in the FCC reports or even specifically tested because the FCC doesn't care if it is jammed.
And it's an issue with radio filtering, which would make sense, the gps people are really in the wrong here.
Capable rf filtering is a well understood field, and the only reason transmissions which are that far out of band would be causing issues is if they were beig lazy and or ignoring it altogether.
If the FCC decides to shutdown lightsquared I would hope it's only because a large consortium of GPS manufacturers and users decide to reimburse lightsquared for all costs and further agree to license all bands which their designs fail to filter against heretoforth.
I'm goig to go out on a limb here though and guess between the military, FAA, and private industry sectors that lightsquare is going to get shafted, possibly without am admission of guilt on the gps side.
RF filtering is well understood, and one has unavoidable loss when inserting a filter, and this loss is proportional to the amount of rejection in the filter. GPS is always struggling for signal, it is far and away the most sensitive radio receiver you will own, picking signals out from 30dB below the noise. Therefore the SAW filters that have been used up till now in GPS have been on the assumption that there are no strong transmitters nearby - a reasonable assumption for the last 15 years. moving to a better filter will reduce sensitivity, inevitably.
Possibly more of a problem is the transmitter purity from lightsquared, it will be difficult for them to transmit a signal that has a low enough component actually IN the GPS band - this leakage signal cannot be filtered out.
The separation of 30 mhz is not really very much, not at 1500 mhz+
Filtering will not really be that effective at those frequencies, not in space-conscious devices such as gps modules in cellphones and handheld/mobile satnavs.
I very much doubt if any civilian devices will work when in close proximity to the lightsquared kit...close being relative as well.....I note that their scheme to ensure "compatability" is to drop the power and go a few mhz lower in frequency....that will work as long as the gps receivers are not close to a transmitter....
They get quite bandied about, those poor billions, don't they ? The GPS accuses LightSquared to cost the country almost $100 billion (why stop at $96, by the way ?), LightSquared says they'll generate $120 billion so it's fine.
Well no, it is not fine. If you kill 9 people to save 12, I doubt very much that the relatives of the 9 dead will appreciate.
In other news, piracy costs upwards of $1200 billion per year (following my latest guesstimate which is just as reliable as anything Gartner can say on the subject).
Man, thank God we have an economy so robust that it can just go on working despite all those billions going down the drain !
"Well no, it is not fine. If you kill 9 people to save 12, I doubt very much that the relatives of the 9 dead will appreciate."
On the other hand, if a budget strapped city moved funds from the fire department in order to properly fund their EMTs, and that results in 9 extra deaths from fires, but 12 people saved by the EMTs... well, I'd argue that it was the right decision. I'd still argue that even if my house caught on fire; I'd still say it was the right move for the city to take.
To me, this is much closer to the argument here. Assuming the estimates are correct (which I doubt - either from the GPS folks or LightSquared), this is a question of society deciding where to allocate limited resources. You can never save every life, and you can't give everyone access to every possible resource. Instead we have to do our best to balance and make choices.
Note, I don't have a firm personal opinion here, because I don't feel qualified to make that type of determination on the technical merits. As LightSquared tells the story, I'd be 100% behind them. That said, I'm not so certain that RF filtering is nearly so good and capable as they are trying to claim. On the other hand, if it is true that they are not leaking into the GPS spectrum, I do feel that they should be reimbursed for their costs to date by those making the protests. It's not like their plans for this adjoining spectrum have been kept a big dark secret all this time.
In this case I think even an American lawyer would advise you that filing suit against the GPS manufacturer for not building it to standards would be a better bet.
In fact even if it turns out that Lightsquare aren't allowed to deploy then there are all of those thousands of people with sub-standard GPS who should be able to return it to the manufacturer as not being suitable for purpose (Don't know if our colonial friends have an equivalent of the Sale of Goods Act)
Well, since the original poster of this little thread specified "the usual American lawsuit" I will admit to thinking of this particular quip in an American context. If you want to refer to someone filing this particular "American style lawsuit"* over in your particular area (U.K. or otherwise), I can only assume, or at least hope, your court system has it's own way of dealing with such absurdities.
* By which I assume you mean frivolous - which is by no means all of what goes on in our courts, it's just what makes for the most amusing stories.
". But the company reckons its revised plan, announced last week, avoids interfering in all but the most-sensitive GPS kit: which LightSquared pegs at 200,000 devices around the USA. Those are important devices, installed in aircraft to help facilitate instrument landings and in mining operations to guide the drill bit"
So, they're "only" going to be interfering with the GPS units that have the potential to kill the most people at once. And unlike in a car, GPS landings are performed in bad weather when you *can't see the ground*...
...who cares if only a few dozen aircraft crash on instrument approaches. As long as everyone has a faster data connection for their smartphones...
Most of the pilots I know aren't worried about their new $20,000 GPS being useless. I'm sure LightSquared will reimburse them, right?
After all, fast access to Twitter and Facebook is really critical!!!
"This device complies with part 15 of the FCC rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation."
In other words, if you buy a cheap, shitty bit of kit with no shielding and no filtering, don't be surprised if everything from next door's hair dryer to the radio ham down the street causes it to behave funkily.
filtering at 1500 mhz comes with a problem.
The bandwidth of the filters is not narrow enough to shield against very strong signals out-of-band.
I very much doubt if any gps receiver will work within several hundred metres of a strong close out-of-band signal.
After all, the average signal strength from a satellite is -130 dbm ....
Not to worry, it isn't going to be in EU for a while.
With a multi-billion pound gps sat system going up soon (maybe) I doubt that the eu will allow it...
"But the company reckons its revised plan, announced last week, avoids interfering in [with?] all but the most-sensitive GPS kit"
Which is true when using the lightsquared definition of interference.
Most GPS makers consider interference to mean a drop in SNR, lightsquared seem to think it should mean completely fails.
Hmmm, "already spent billions" on reducing interference? Perhaps they have spent money developing the business plan and preliminary hardware. But that's not quite the same thing. More accurate would be "spent money trying to create a business that could be worth billions", but that's hardly likely to garner sympathy.
The "5 cents" would buy a filter that would reduce the signal from other frequencies, but it would also make the receiver less sensitive in the target band and change the phase response. Receiving a GPS signal isn't like building a AM radio with a pencil lead. The data is far below the noise floor. Thermal noise alone creates significant positional uncertainty. Throwing away information by reducing the signal strength is many times worse.
Military GPS receivers do use a different band. But that's in addition to the "civilian" band, not instead of. (They use both the L1 and L2 signal propagation delays combined with the current atmospheric delay model to compensate for the atmospheric lens effect.)
It's what everyone with a little bit of knowledge on signal processing and Fourier transforms knows - wider frequency band will give you more accurate timings and vice versa. GPS is all about timing - you'll simply get less precise GPS with narrower band and there's nothing you can do about it - that's how physics works.
What LightSquare is asking for is reducing precision of civilian GPS. And I don't think FCC should say yes to that.
But the point is, reduced precision only affects people who really care about precision. That is, aircraft landing, and civil engineering in remote locations.
LightSquare is making the case that GPS wasn't designed to give that kind of accuracy, and these people are streching the system.
But that's just an opening argument. The real questions are, will these people be able to use alternative technology? Do they have enough punch to protect their (minority) use of GPS?
The flight industry is conflicted about the use of GPS anyway: they are presently living in fear of the day when some pilot drives his plane with 200 passengers off the edge of a cliff "because the GPS said the road went there", so they are already trying to remind pilots that they can't depend on GPS accuracy. A recent survey found that many pilots are unaware of the effect of GPS satelite dropout, and that their equipment is not reporting drop-out in a clear and effective way.
And remote survey depends on accurate GPS, but if it fails, they will just go back to guessing.
... (which is, of course, precisely nothing), my opinion is that it is LightSquared's problem to sort out. They have come to an existing situation and found that it doesn't suit them. Well, tough luck. They are the new kids on the block, so they have to adapt to it or go and find a new pond to piss in.
(If only we could get the courts in the UK to accept that thinking, it would be really nice).
Anyone using pure civilian GPS for something safety-related should be sacked. Landing planes in fog has been suggested as a use for GPS. Good luck with that- GPS hates fog and similar environmental issues. And geographical surveying? With a ±4m solution? They'd be better with the 'distance' tool in Google Maps.
REAL measurements use multiple, redundant solutions. Aircraft, surveying, ship positioning- all these use much higher quality solutions like DGPS. This was developed when civilian GPS could just about say which country you were in and provides precision better than you can get now with regular GPS. Guaranteed decimetre precision and a much more durable signal.
If GPS requires extended bands to operate in, the people building the devices should have paid for those bands- after all, if the GPS receiver is receiving signals in those bands someone must be transmitting them. By transmitting in licensed spectrum that they don't hold the license for is surely a breach of FCC regs?
It looks like Lightsquared is absolutely in the right here if their story's right.
DGPS is (from what I read) not a standalone system, but rather an augmentation to the existing GPS system. The D in this case stands for "Differential" and refers to the correcting system used by the fixed stations to account for the inherent errors provided by the satellite transmissions. Thing is, those corrections are only good if you have the original signals to begin with--IOW, both of you have to be singing from the same song sheet. So without the acquision of the original GPS signal due to overwhelming interference, so to speak, how would DGPS be able to compensate?
So, I paid for the spectrum within a guidline. . . Spent cash to develop a product that uses it. Then got stopped because a product in a different spectrum cannot handle me using my spectrum that I paid for. . . GPS needs to either buy more spectrum or shut up.
About the only use for GPS units in drilling that I am aware of is for finding where to start drilling from initially. GPS is not accurate enough for drilling, a collision with another well can kill people. The blow out that BP had was not caused by a collision, but a collision could lead to similar consequences. So if somebody is using a GPS to drill, that is something to worry about.
We drill using accurate magnetic sensors in combination with accelerometers and software models to further enhance accuracy. After that gyros are brought in to further confirm accuracy after a certain section has been drilled. Yet still, the further you drill, the more your uncertainty grows (you can't exactly look out the window to see where you are in relation to the well nearby). As you drill further and further, the error margin of error builds up. So why would anybody want to use a technology that is not accurate to start with? Second question is, GPS wont work in my house next to the window, how will it work in drilling underground?
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