4G Broadband May Jam GPS

Faulty GPS receivers... by Anonymous Coward · 2011-02-09 02:36 · Score: 1

is faulty.

A clever marketing stunt... by fuzzyfuzzyfungus · 2011-02-09 02:38 · Score: 0

This should really help move 4G gear in countries that the US and/or NATO bloc show signs of disapproval toward... And possibly even make subscription free GPS substantially less usable in 4G coverage areas, where those lazy consumers really should have signed up for a $100/month 4G data plan with telco provided location services by now...

Somebody in engineering just earned themselves a scapegoating in front of the FCC.

Somebody in marketing just earned themselves a nice fat bonus.

Frequencies? by lcreech · 2011-02-09 02:39 · Score: 4, Informative

All the GPS satellites transmit on the same frequency, 1.575ghz for L1 and 1.227ghz for L2. The only variance from this is Doppler shifts from the user to satellite perspective.

Re:Frequencies? by Anonymous Coward · 2011-02-09 02:48 · Score: 2, Interesting

That is not the only variance. One frequency contains no information. To carry a signal it must be modulated, which adds line width.
Re:Frequencies? by Anonymous Coward · 2011-02-09 03:33 · Score: 1

Yes, but don't forget L5 (1176.45) and L2c, as well as GLONASS and GALILEO also in that same band.
And in any case, those frequencies are modulated with a pseudo random sequence at 10 MHz, making the signal 20 MHz wide. An interferer at 1565 will be a problem, so that 4G transmitter better meet its spectral mask requirements with a vengeance. The pretty casual Part 15 style 40dB down sort of requirement probably won't hack it. GPS received signal power is in the -110dBm range, so that 1 watt cellphone (+30dBm), needs to have spurs down by only 140 dB to avoid interference... piece of cake, eh?... well.. you'll get a few tens of dB isolation because the cellphone antenna is separated from the GPS antenna in your car by a few meters. For the GPS in the phone, it's easy.. turn of the transmitter when making a GPS measurement.
Re:Frequencies? by caluml · 2011-02-09 03:51 · Score: 1

What about Morse code? You can use a single frequency, and convey information by simply switching it on and off.

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Re:Frequencies? by Chrisq · 2011-02-09 04:01 · Score: 1

What about Morse code? You can use a single frequency, and convey information by simply switching it on and off.
Which will create a sideband. Very small and narrow for the normal rate of Morse code, but present none the less.
Re:Frequencies? by Anonymous Coward · 2011-02-09 04:09 · Score: 0

"simply switching it on and off" is modulating the carrier.
Re:Frequencies? by Anonymous Coward · 2011-02-09 04:22 · Score: 0

That's only if you use Frequency Modulation. You can also use Amplitude Modulation and Phase Modulation.
Re:Frequencies? by fxkr · 2011-02-09 05:31 · Score: 1

Amplitude modulation
Re:Frequencies? by icebike · 2011-02-09 05:41 · Score: 1

But will the chatty Cathy standing to your left STFU long enough for you to get fix on your Google Maps? Eventually there will be a 4G phone every 2 meters.

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Re:Frequencies? by jpmorgan · 2011-02-09 06:08 · Score: 1

Sorry, go back to your fourier transforms. AM might not be modulated by design, but it does have signal bandwidth.
Re:Frequencies? by timeOday · 2011-02-09 06:50 · Score: 1

What about Morse code? You can use a single frequency, and convey information by simply switching it on and off.

OK, how often do you want to switch in on or off? If you go too slow, you won't be able to send many characters each second, but if you go too fast, even the slightest distortion to the signal (e.g. passing through a wall) will blur out the signal.
Also, what if somebody else wants to send morse code too? How will the receiver know whose dots and dashes they're hearing? I guess maybe you could switch at different speeds to distinguish them. Although if you go at speeds too close together, it will become difficult to tell which is which.
Oh, wait, this is starting to sound a lot like where we started by transmitting on different "frequencies."
Re:Frequencies? by Obfuscant · 2011-02-09 07:27 · Score: 1

That is not the only variance. One frequency contains no information.

That is not correct. L1 carries C/A and P codes, L2 carries P.
Re:Frequencies? by Anonymous Coward · 2011-02-09 07:37 · Score: 0

That is not the only variance. One frequency contains no information.
That is not correct. L1 carries C/A and P codes, L2 carries P.
Almost complete.
L1 carries CA, P and M, L2 carries P and M.
Re:Frequencies? by Anonymous Coward · 2011-02-09 07:45 · Score: 0

m-code is ~40 MHz wide.
Re:Frequencies? by drerwk · 2011-02-09 07:54 · Score: 2

Look up FourierTransform. A signal of finite length; say a dot or dash, can not be represented by a single frequency. The only way to have a carrier at a single frequency is for that signal to exit over all time. Certainly you can get a narrow band of carrier if you have a longing signal, but as hinted elsewhere, in order to convey an increasing amount of information you have to make your dot and dashes ever shorter, which in turn increases your bandwith both of information and of carrier.
Re:Frequencies? by Anonymous Coward · 2011-02-09 10:05 · Score: 0

Damned pedants. You would be more useful if you provided a link to a GPS primer instead.
Re:Frequencies? by kybred · 2011-02-09 10:41 · Score: 1

All the GPS satellites transmit on the same frequency, 1.575ghz for L1 and 1.227ghz for L2. The only variance from this is Doppler shifts from the user to satellite perspective.
Same frequencies, but each satellite has a unique modulation code that generates its spread spectrum output.
Re:Frequencies? by Eudial · 2011-02-09 11:00 · Score: 1

You don't even need Fourier transforms. You can illustrate this happens with kindergarten level trigonometry. Let the carrier be C(t)=sin(kt) and the amplitude modulation be a simple oscillatory modulation given by A(a,b,t)=a cos(ft) + b sin(ft)
Then as
sin(x)cos(y) ~ sin(x-y) + sin(x+y)
sin(x)sin(y) ~ cos(x-y) - cos(x+y)
you get a modulated signal
C(t)A(a,b,t) = a sin(kt-ft) + a sin(kt+ft) + b cos(kt-ft) - b cos(kt-ft)
As this is simple multiplication, you can build arbitrary functions out of a sum of of different A-functions as a Fourier series.

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Re:Frequencies? by X0563511 · 2011-02-10 12:35 · Score: 1

"kindergarten level trigonometry"
Really now... I thought our education system wasn't doing as best it could, but surely you're exaggerating?

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For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...

Acquiring satelites... by Anonymous Coward · 2011-02-09 02:41 · Score: 0

It already takes our Garmin about 15-20 minutes to get connected whenever we plug it in. Twenty minutes filled with explicative-ladden rantings, as my copilot hates being lost and out of control. I had better avoid 4G devices, or risk giving the man an aneurism.

Re:Acquiring satelites... by bemymonkey · 2011-02-09 04:18 · Score: 1

Time to upgrade. Devices with AGPS usually get a fix within 10 seconds or less...
Re:Acquiring satelites... by rhook · 2011-02-09 07:57 · Score: 1

My smart phone gets a fix in under 3 seconds.
Re:Acquiring satelites... by CompMD · 2011-02-09 08:02 · Score: 1

An aviation panel-mount model? Talk to your avionics shop tech, make sure the software is up to date. And don't listen to the idiots that talk about AGPS and their smartphones, I have far more knowledge than they do about GPS...
Re:Acquiring satelites... by bemymonkey · 2011-02-09 08:18 · Score: 1

That's because it's one of those fantabulous devices I mentioned... you know, the ones with AGPS.

FCC approved this? by gblackwo · 2011-02-09 02:42 · Score: 0

That would be a pretty big screw up by the FCC. So that would pretty much destroy what is left of the already dwindling GPS market. I mean, I saw stand-alone GPS devices becoming niche products, but I never thought the government would help their demise. So who should/will sue whom?

Re:FCC approved this? by gblackwo · 2011-02-09 02:44 · Score: 2, Interesting

Just to specify, that was all assuming that the study isn't crap, and that properly designed GPS receivers could infact be affected.
Re:FCC approved this? by by+(1706743) · 2011-02-09 02:54 · Score: 1

Airplanes (commercial and private) utilize GPS for navigation -- and according to TFA, one such device experienced "Loss of Fix in Open Sky" 5.6 miles from the transmitter.
Re:FCC approved this? by LWATCDR · 2011-02-09 02:55 · Score: 1

dwindling GPS market?
Stand along GPSs maybe getting smaller and smaller but that is because GPS is in every cell phone and most cars on the planet. Throw in Boats and Aircraft and you have booming market for GPSs just not standalone.

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Re:FCC approved this? by AB3A · 2011-02-09 03:10 · Score: 4, Informative

Feh. It wouldn't be the first time these dimwits at the FCC screwed up. I remember installing 928.8... MHz SCADA (you know, the telemetry that runs your water, electricity, gas...) and it worked great. About nine months later, the FCC allowed 929 MHz paging. In a very short span of time we had enough energy coming down the antenna line to light a neon bulb. They were licensed for 3 kW ERP. Our remotes were licensed for 5 W + some gain from a small Yagi.
The master receivers went deaf from the continuous blast of high powered paging traffic. A Cavity filter can't do much to get rid of strong signals only 200 kHz away at 900 MHz.
Yeah, the FCC screwed up. They had no knowledge of the state of the art of receivers. We bought receivers engineered for sensitivity, not strong signals, because at the time, there were no other significant strong signal sources on that band. The state of the art took a while to catch up. We ended up solving the problem by re-licensing our channels for horizontal polarization. The pager stuff remained vertical. We got 20 dB of immunity from them and that was enough.
And to the jerkwads at the FCC who thought this was acceptable: DO YOU LIKE WATER? DO YOU LIKE ELECTRICITY? DON'T DO THIS TO US!
spit...

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Nearly fifty percent of all graduates come from the bottom half of the class!
Re:FCC approved this? by GooberToo · 2011-02-09 03:16 · Score: 3, Interesting

You're right. The report is likely to be bogus.
If this is true it means the up and coming cash cow and one of the largest payola maker for representatives is now default for US. Yes, that means UAVs are now unsafe for operation. That also means IFR aviation traffic in inclement weather is many cases is now impossible. It means the entire GPS and navigation markets have been destroyed.
Simply put, if in fact there is any proof that GPS can be compromised by 4G deployment, the FCC will be forced to move 4G to another frequency. Period.
Can you imagine headline, "FCC sued for string of airliner crashes - negligent homicide charges filed against head." And that's just the tip of the iceberg.
No bones about it. *IF* its even remotely true, 4G would be forced to change. Otherwise both safety of the masses and economic damage is just too massive to ignore. Not to mention the possibility of criminally negligent charges.
Re:FCC approved this? by 0123456 · 2011-02-09 03:28 · Score: 1

Airplanes (commercial and private) utilize GPS for navigation -- and according to TFA, one such device experienced "Loss of Fix in Open Sky" 5.6 miles from the transmitter.
Lots of systems use GPS for accurate timing. Servers synced to NTP from a GPS receiver, for example.
Re:FCC approved this? by GooberToo · 2011-02-09 03:37 · Score: 2

and according to TFA
The data point is best completely ignored. Outages like that do periodically occur and are well documented. Furthermore, they have occurred long before 4G was deployed. Such a failure could have been anything from wiring problem, faulty antenna, or even a software glitch.
But, it says it happened 5.6 miles from the transmitter, it almost certainly means the article is completely confused. Which if true, means GPS IS NOT BEING JAMMED. PERIOD. For them to be that close to a transmitter means they are in space, which simply isn't likely. Likely, they are talking about WAAS, which is not GPS in of itself. Rather, WAAS is ground based signal correction/enhancement which is used to increase GPS accuracy; but GPS still works without it.
If in fact 4G interferes with WAAS, expect the FCC force 4G to new frequencies as without WAAS, some GPS IFR aviation approaches can not be legally or safely performed. Simply put, air safety and speed is likely to trump high speed wireless broadband. Worst case this means some approaches may become obsoleted and unlikely to affect anyone else other than pilots.
Re:FCC approved this? by countertrolling · 2011-02-09 04:01 · Score: 1

The FCC is too busy policing the airwaves for porn to be tied down with such droll technical matters.

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For justice, we must go to Don Corleone
Re:FCC approved this? by commodore6502 · 2011-02-09 04:06 · Score: 1, Insightful

>>>That would be a pretty big screw up by the FCC.
The FCC has been screwing-up a lot lately. Like the claim "all you need is a digital-to-analog converter box". They forgot to tell the people, per the FCC's own engineering specs, that you also need the antenna raised to 20 feet height. DTV power levels were too low to penetrate into homes unless you live within 15 miles of the transmitter.
They also screwed-up Digital radio when they specified 1% power levels would provided acceptable range. Later they changed the 1% to 10%, due to many complaints.
And the FCC also approved Internet Gadgets to broadcast on the TV Band without requiring a license. i.e. Right over top of existing ABC, CBS, NBC, PBS, et cetera stations. Brilliant move FCC.
So yeah this G4 and GPS frequency overlap is just another in a long list of FCC frak-ups.

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Re:FCC approved this? by ndege · 2011-02-09 04:09 · Score: 2

Dude, your GPS receiver is 14 seconds off!
People who use GPS for accurate timing need to be aware that GPS doesn't account for leap-seconds. As such, GPS is ahead of UTC by about 14 seconds. You can read more about the problem here.
It gets more complicated, however, as some receivers correct for this. You can read more about the correction here.

Some have wondered how accurate the time display is on Garmin GPS receivers such as G-12XL, G-II+, and the G-III. Here is an answer provided by Garmin Engineering. This also explains why the GPS can be locked for awhile and still differ from UTC by 11 or 12 seconds. (This answer applies to other brands of GPS receivers as well.)
Start of Garmin quote>
Provided the unit has collected current leap second count from the navigation message, (current leap second difference from GPS time is only broadcast once in a 12.5 minute Nav. message), or current leap second has not changed since the last time the unit collected this variable, the time displayed on the front of the unit should be accurate to within 1 second of UTC.
>end of Garmin Quote
Joe Mehaffey comments:
This means that IF your GPS does not have (or does not save) the leap second offset from last time it was operated, your time may be off by perhaps 12 seconds until the complete NAV MESSAGE is received by the GPS. Jack and I have observed that "typically" Garmin GPS receivers display time which is delayed from about 1/2 to 1 second behind UTC. Lowrance GPS receivers are usually between 1 and 2 seconds delayed behind UTC. In both cases, this is a result of the display driver subroutine having low priority as the "GPS internal clock" is within a few nanoseconds of correct.
Similarly, the NMEA time output on the serial link is typically delayed a second or two depending on various factors.

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Re:FCC approved this? by by+(1706743) · 2011-02-09 04:16 · Score: 1

But, it says it happened 5.6 miles from the transmitter, it almost certainly means the article is completely confused. Which if true, means GPS IS NOT BEING JAMMED. PERIOD. For them to be that close to a transmitter means they are in space, which simply isn't likely. Likely, they are talking about WAAS, which is not GPS in of itself.
They were talking about distance from the (simulated) Lightsquared 4G transmitter, not the GPS satellites. Airplanes are very often within 5.6 miles of a cell tower, and with "40,000 high-power transmitters close to the GPS frequency, across the United States," you can bet that airplanes will routinely be much closer to the real transmitters (especially near cities/airports).
Re:FCC approved this? by ColdWetDog · 2011-02-09 04:49 · Score: 1

The FCC is too busy policing the airwaves for porn to be tied down with such droll technical matters.
Nipples or electricity - the choice is clear.

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Faster! Faster! Faster would be better!
Re:FCC approved this? by countertrolling · 2011-02-09 06:06 · Score: 1

For them, nipples and electricity...

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For justice, we must go to Don Corleone
Re:FCC approved this? by dslbrian · 2011-02-09 06:08 · Score: 1

But, it says it happened 5.6 miles from the transmitter, it almost certainly means the article is completely confused. Which if true, means GPS IS NOT BEING JAMMED. PERIOD. For them to be that close to a transmitter means they are in space, which simply isn't likely. Likely, they are talking about WAAS [wikipedia.org], which is not GPS in of itself. Rather, WAAS is ground based signal correction/enhancement which is used to increase GPS accuracy; but GPS still works without it.
No they are talking about distance to the terrestrial 4G transmit tower. As a vehicle (car or plane) approaches the tower the GPS device loses signal. This effect is real - essentially a powerful enough off-channel signal can saturate the front-end LNA in the GPS receiver and block the on-channel signal. I've had to deal with this before on GSM front-end designs (it's been a while but IIRC blocker specs may be in the GSM spec, I forget). Essentially the front-end SAW filters only provide so much off-channel attenuation, and the LNA is always more wideband than the narrow desired receive channel, so if you have a strong enough signal (say a giant tower transmitting a high level signal) on a close off-channel band you can easily saturate the LNA and kill the on-channel signal.
Re:FCC approved this? by davester666 · 2011-02-09 06:27 · Score: 1

Just great. Now you've got me thinking about electrified nipples.

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Re:FCC approved this? by MozeeToby · 2011-02-09 06:29 · Score: 1

That also means IFR aviation traffic in inclement weather is many cases is now impossible.
IFR does not, in any airplane, rely solely on GPS. In fact, in many situations the information from GPS is weighted well below the information from other sources which can be much more accurate. This is especially the case in situations where IFR is the most important, namely approach and departure. If you look at the plates for any airport in the world, STARS (standard approaches) and SIDS (standard departures) are laid out based on localizers and VOR stations, not GPS coordinates and there are plenty of good reasons for that. You don't need to know exactly where you are over the pacific ocean for safe IFR flight, which is about the only place on the planet where you're likely to be flying IFR without having access to navigational aids.
Re:FCC approved this? by Crewdawg · 2011-02-09 07:10 · Score: 1

IFR does not, in any airplane, rely solely on GPS. In fact, in many situations the information from GPS is weighted well below the information from other sources which can be much more accurate. This is especially the case in situations where IFR is the most important, namely approach and departure.
Well this isn't entirely true and neither is the GP. There are more published Instrument Landing System (ILS) runways using Localizer performance with vertical guidance (LPV) than there are traditional CAT I systems. These rely solely on GPS with WAAS. While WAAS are ground based references they require no equipment or changes to the particular airport.
Re:FCC approved this? by CompMD · 2011-02-09 08:04 · Score: 1

The industry report is real and true, I know several of the authors, one of them works down the hall from me.

A little late for these tests? by Anonymous Coward · 2011-02-09 02:42 · Score: 0

Isn't 4G already here in some markets? WTF is the FCC?

Re:A little late for these tests? by firex726 · 2011-02-09 03:05 · Score: 1

I believe those "4G" are meant to denote the 4th generation network; and not actual 4G the standard since it's not been finalized/implemented yet (Last I heard). That's why like every carrier has a 4G network, but use different technologies; there is no standard for them to actually adhere to.
Re:A little late for these tests? by SimonTheSoundMan · 2011-02-09 03:32 · Score: 1

4G is years away, and implementations of prototypes are still in the lab. American operators are advertising 3G as '4G', because they can.
Re:A little late for these tests? by crashumbc · 2011-02-09 03:50 · Score: 1

And also because the definition of 4G hasn't been finalized, and has been changed many times. Current 4G networks meet the "earlier" specs. from what I understand...

What about all the other RF noise? by the_raptor · 2011-02-09 02:44 · Score: 4, Informative

Don't worry about bandwidth overlap (guaranteed to happen with some poorly designed transmitters and antennas) worry about all the other electronic devices which aren't meant to transmit RF but blast it out all over the bands.

I have recently got into amateur radio and some bands are locally unusable due to something as simple as a transformer power supply blasting out many watts of RFI.

The slow death of radio bands to RFI is like the "death" of stargazing due to light pollution.

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CINC, 4th Penguin Legion

Re:What about all the other RF noise? by Anonymous Coward · 2011-02-09 03:37 · Score: 0

"The slow death of radio bands to RFI is like the "death" of stargazing due to light pollution."
Good analogy, and I second that.
Re:What about all the other RF noise? by Anonymous Coward · 2011-02-09 04:14 · Score: 1

You need to learn about receiver desense. Then you will see that this could be a problem. This is from someone who has been into amateur radio for over 25 years, not someone who recently got into it.
Re:What about all the other RF noise? by ndege · 2011-02-09 04:22 · Score: 1

> Good analogy, and I second that.
Agreed! However, can you convert this into a car analogy? ;)

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Re:What about all the other RF noise? by Anonymous Coward · 2011-02-09 05:01 · Score: 1

These are good points -- however "adjacent channel interference" can be a problem even without bandwidth overlap due to a phenomenon known as "receiver desense". This means that the receiver has been "desensitized" to the signal it's actually meant to receive due to a stronger transmission that overloads the input RF filter such that the detector gets overloaded by the undesired nearby signal. All RF filters are not perfect and have a "rolloff" characteristic where they reject more of the undesired input signal the further away from the passband the undesired signal is -- but right at the threshold of the passband, the filter doesn't start to reject.
Now, add to this the fact that GPS receivers have to receive signals that are BELOW noise level. Why this is possible is that the GPS transmitters in the satelites use a "gold code" binary sequence in the transmission, and these "gold codes" are known to all GPS receivers, so they are used as a digital filter to pull out the GPS signal out of the noise.
http://en.wikipedia.org/wiki/Gold_code/
So the fact that there's a 4G network on an adjacent channel is still a problem, even if there is no frequency overlap -- because GPS receivers can still be overloaded by the "nearby" (in frequency) signals from that 4G band.
If an anecdotal example helps, think back to listening to FM radio and hearing a powerful station come through even though it's off frequency. That's receiver desense.
Re:What about all the other RF noise? by Cwix · 2011-02-09 05:02 · Score: 2

Umm..
The slow death of a relaxing Sunday drive is due to assholes with SUVs?
(Probably more to the price of gas, but whatever.)

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You are entitled to your own opinions, not your own facts.
Re:What about all the other RF noise? by Anonymous Coward · 2011-02-09 06:10 · Score: 0

Too bad. I guess now you'll have to turn your router off for a minute when you want to get its global coordinates.
Re:What about all the other RF noise? by thegarbz · 2011-02-09 09:34 · Score: 1

A small powersupply is less of a concern than a widely adopted standard with high power transmitter basestations. We have similar issues with the TETRA 2-way radio standard. Sure it's spec says it's 25kHz bandwidth for TETRA V1, and our government license gives us just that, a 25kHz chunk of the 800MHz spectrum in which we can blast 40watt which is enough to pickup the tower on the otherside of the city. However, looking at the actual signal coming out, due to all the fancy modulation and whatnot the actual spectrum used is closer to 45kHz.

Sounds minor here but the same principles apply. These are licensed devices capable of pretty high power outputs in their standard configuration operating outside of beyond their licensed band. Though there's no known reports of governments cracking down on TETRA users, there's a lot of engineers who seem to think that in reality what is speced and what is happening breaches the communication laws of many countries.

So yes your transformer powersupply may put out a few mW of RF, however a) it shouldn't if it complies with the FCC regulations, and b) it's nothing compared to a multitude of high power basestations operation over an entire city spewing out garbage into another band. Personally I hope the article is FUD, just because two systems operate in adjoining frequencies doesn't mean they will interfere if they have been designed correctly.
Re:What about all the other RF noise? by Anonymous Coward · 2011-02-09 11:40 · Score: 0

You should track down these devices and report them to the FCC.

Not a problem by Anonymous Coward · 2011-02-09 02:45 · Score: 0

Samsung took care of this for me already. I have a Samsung Galaxy S. The GPS doesn't work for shit.

Harmonics and Modulation by Onuma · 2011-02-09 02:48 · Score: 2

Depending on the type of bandwidth and modulation within those specific carriers (specifically at or very near 1559 MHz), they could be interfering with each other.

Using a more highly-compressed modulation type (ie qpsk or 8psk vs. bpsk) with viable harmonic filtering should eliminate any "side lobes" and therefore interference at low power levels. Filtering at the satellite and/or cell tower side should also be present, further eliminating possible treading across bands.

This sounds like a problem between frequency management, poor choices of modulation, excessively wide bandwidth on carriers, and simple bandpass-style filtering. Certainly not difficult to overcome, but one of these technologies is going to have to budge in the correct direction, and I doubt GPS will be the one to do so.

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Re:Harmonics and Modulation by vlm · 2011-02-09 03:06 · Score: 1

Don't forget phase noise on both transmitter and receiver.

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"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
Re:Harmonics and Modulation by cats-paw · 2011-02-09 03:11 · Score: 1

The FCC regulates the emissions into GPS bands, like any other allocated frequency band.
Just because the 4G allowable band extends right up to it, doesn't mean you will be able to use those frequencies.
Having a transmitter that's "spilling" over due to PA distortion or some other problem would preclude you from using those frequencies if you can't stay under the emission limits.
So technically they shouldn't be any more of a problem than any other transmitter, WHICH HAS BEEN PROPERLY TESTED.
The fact is that stuff is going to get an FCC sticker which doesn't meet requirements.

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Absolute statements are never true
Re:Harmonics and Modulation by Anonymous Coward · 2011-02-09 04:10 · Score: 0

You can make a wireless signal as spectrally efficient as you like (e.g. excessive pulse shaping with PSK, build shaping directly into the modulation a la CPM, etc.), but it will never come close enough to a "brickwall" to completely alleviate the adjacent band interference problem (though OFDM might come close). There is no guard band in this case. Even for a cellular signal with nice (say -50dBc) sidelobe attenuation, the power disparity between a strong interfering signal and the desired, weak GPS signal will often (if you believe TFA) be large enough to cause problems for GPS reception.
I found the broadcaster quote about the "looking to see which GPS equipment needs filtering so that they don't look into our band" puzzling. He seems to be implying that they're going ahead with the 40,000 transmitter deployment come hell or high water, and that newer GPS units will simply have to be designed with improved interference rejection. Umm, what about the millions of existing GPS units that are already in the wild?????
Re:Harmonics and Modulation by kybred · 2011-02-09 10:35 · Score: 1

This isn't just interference from adjacent signals. A big part of the problem is the huge difference in power levels between a GPS signal (received signal about -130 dBm) and a high power terrestrial transmitter a few miles away. The high power signal will swamp the GPS receiver's front end and play havoc with its AGC.
From a GPS World article:

The consumer GPS device began to be jammed at a power level representing a distance of 3.6 miles (5.8 kilometers) from the simulated LightSquared transmitter. The consumer device lost a fix at 0.66 miles (1.1 kilometers) from the transmitter.
The Federal Aviation Administration (FAA)-certified aviation receiver began to be jammed at a distance of 13.8 miles (22.1 kilometers) and experienced total loss of fix at 5.6 miles (9.0 kilometers) from the transmitter.
The bottom line is that if this goes through, GPS receivers will get more expensive due to the additional filtering, and existing receivers will operate in a degraded mode.

Obama to plug 4G on Thurs by olsmeister · 2011-02-09 02:51 · Score: 0

Well, Obama just mentioned in SOTU that he wants to expand 4G out to 98% of the U.S. He'll be giving a speech on Thursday to plug it.

Re:Obama to plug 4G on Thurs by commodore6502 · 2011-02-09 04:16 · Score: 1

>>>expand 4G out to 98% of the U.S.
That's foolishness. There's simply not enough room in the radio spectrum to have everyone using internet via 4G (plus already-existing radio, television, emergency services). Maybe if the users were throttled to 500k each, then it would work, but not otherwise.
WIRED internet is the only way we'll ever get people to 3000k minimum speed (per FCC specs) (and as the Japanese have done with their VH-DSL).

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Information wants to be expensive AND wants to be free. So you have Value vs. Cheap distribution fighting each other.
Re:Obama to plug 4G on Thurs by olsmeister · 2011-02-09 05:36 · Score: 1

I tend to agree. If everyone tried to hop on a 4G network and start streaming Netflix in HD, it would go down faster than a Thai hooker.

Break out your paper maps and compasses by PolygamousRanchKid+ · 2011-02-09 02:54 · Score: 1

It's time to learn old fashioned orientation again! When driving on car trips as a child, when we got lost, my father would always ask, "Where's the sun?" This to figure out in what direction we were traveling. He grew up on a large, remote ranch, so he learned this skill from my grandpa. Now if some other broadcaster starts sending something that interferes with the Earth's magnetic field . . . the rest of us will be in big trouble.

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Schroedinger's Brexit: The UK is both in and out of the EU at the same time!

Re:Break out your paper maps and compasses by Anonymous Coward · 2011-02-09 03:05 · Score: 0

Yeah!
Orienting is just what we need when flying 300 pax in the clouds at 30,000'
The prelim tests by aviation GPS companies show interference at 8 mi from one of these 4G base stations and complete nav failure within 5 mi.
Purrfect
Re:Break out your paper maps and compasses by ColdWetDog · 2011-02-09 04:56 · Score: 2

It's time to learn old fashioned orientation again! When driving on car trips as a child, when we got lost, my father would always ask, "Where's the sun?" This to figure out in what direction we were traveling. He grew up on a large, remote ranch, so he learned this skill from my grandpa. Now if some other broadcaster starts sending something that interferes with the Earth's magnetic field . . . the rest of us will be in big trouble.
I'll just mention that to the Alaska Airlines pilots who are shooting GPS assisted landings into Juneau and Ketchikan (next to mountains) or Sitka (where the airport hangs out over the ocean AND abuts the mountains). I'm sure they still carry their sextants in their flight bags.

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Faster! Faster! Faster would be better!
Re:Break out your paper maps and compasses by jpmorgan · 2011-02-09 06:22 · Score: 1

Zero-visibility landings use ILS, not GPS, which is broadcast from a calibrated ground transmitted next to the runway. ILS operates at ~110MHz.
In general we've been using radio navigation in aircraft long before GPS became widely available. Lookup VOR and NDB. GPS is useful for aircraft navigation, since it lets you take more direct routes than strictly following the VOR/NDB defined airways. If GPS became useless, it would make air travel more expensive (and less fuel efficient), but planes aren't going to be dropping out of the sky or crashing into mountains.
Re:Break out your paper maps and compasses by elijahmm · 2011-02-09 08:31 · Score: 1

Check the FAA's next gen initiative and look at the new WAAS GPS approaches. Many airports now have precision approaches (can't see anything until 200 feet above the ground) based on GPS alone. A certified WAAS GPS installation is considered legal for primary instrument navigation in IMC (instrument meteorological conditions). Translated? You loose the GPS signal at a critical point in flight and it DOES mean crashing into mountains, the ground, etc.
Re:Break out your paper maps and compasses by Anonymous Coward · 2011-02-09 11:12 · Score: 0

I'm sure they still carry their sextants in their flight bags.
You make a funny, but if the *don't* still carry them, it hasn't been for very long.
Re:Break out your paper maps and compasses by Daa · 2011-02-09 16:23 · Score: 1

there are no more NDB stations left in the USA and the FAA is working on turning off the VOR stations as soon as they finally get the WAAS GPS based nexgen navigation system working. The whole idea of the Nexgen Navigation system is to stop flying on airways defined by VORs and move to flying directly from point to point navigating by GPS only.. i predict a huge fight between the FAA and the FCC

Issues in guatemala by Anonymous Coward · 2011-02-09 03:09 · Score: 0

This is also happening in Guatemala City for the general car owners with gps installed. http://www.prediosguatemala.com/ [www.prediosGuatemala.com]

Not all 4G by Anonymous Coward · 2011-02-09 03:19 · Score: 1

Note that this is not all 4G as that term is more a marketing term than a technical term. This is a specific band granted to a specific company (Lightsquared) so if it really is an issue, it will be easier to revoke as it doesn't effect currently established 4G networks (Verizon LTE, Sprint WiMAX, TMobile or AT&T HSPA+).

Re:Not all 4G by Anonymous Coward · 2011-02-09 05:04 · Score: 0

I agree 100%, there is nothing to worry about here and this story is actually quite misleading. 4G means 4th Generation of wireless broadband technology with higher speeds than the previous generation and there are no specific set frequencies that it absolutely must run on.
Re:Not all 4G by amRadioHed · 2011-02-09 05:20 · Score: 1

The concern isn't how Lightsquared will affect other 4G services, the concern is how it will affect GPS service.

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We hope your rules and wisdom choke you / Now we are one in everlasting peace
Re:Not all 4G by SrJsignal · 2011-02-09 05:26 · Score: 2

You fail to understand the issue. Lightsquared's transmitters could screw up GPS service for EVERYONE. The FCC waived their own rules to allow this, rollout. If you RTFA (I know I know, this is slashdot) you would see the large distances a single transmitter can jam GPS devices at.
Re:Not all 4G by Svartalf · 2011-02-09 05:35 · Score: 1

Heh... That's what I thought was going on.

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I am not merely a "consumer" or a "taxpayer". I am a Citizen of the State of Texas
Re:Not all 4G by Zouden · 2011-02-09 06:03 · Score: 1

Do you really think that Lightsquared will be allowed to continue if their transmitters are found to interfere with GPS? The FCC will revoke their license in a heartbeat. That might result in a lawsuit from Lightsquared but the rest of us will forget about it and get back to using our GPS-enabled 4G phones.

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"A week in the lab saves an hour in the library"
Re:Not all 4G by MikeBabcock · 2011-02-09 16:41 · Score: 1

There aren't a lot of regulations on GPS but I hope you're right.
From the inverse situation: FCC on GPS regulation

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- Michael T. Babcock (Yes, I blog)

This isn't a problem with 4G by Anonymous Coward · 2011-02-09 03:23 · Score: 1

This isn't a problem so much with 4G as it is with low-end GPS receivers. Most of the mass-market GPS receivers have poor filtering of the bands around the GPS frequencies (this makes the hardware cheaper). They had done this under the assumption that those bands near the GPS frequencies would never be utilized.

Now enter 4G in the surrounding frequencies. There isn't a problem with 4G spilling over into the other frequencies, but with the GPS receivers being sensitive in frequencies that they shouldn't be.

What about good ol' Loran C by Anonymous Coward · 2011-02-09 03:35 · Score: 0

We could always turn on Loran-C again, its much harder to jam. Eloran could be built into GPS recievers as a backup. If a 4g cellphone could jam GPS what about the military? A gps guided missle aint no good if someone can jam it with a cellphone.

This just in... by Erich · 2011-02-09 03:40 · Score: 3, Insightful

FM Radio could interfere with television broadcast channels 5 and 6, or aircraft navigation, since they're right next to each other!

AM Radio could interfere with aircraft beacons, since they're right next to each other!

Please. We've been allocating spectrum for things for a long time. Interference can be monitored and controlled. Do you really think that mobile telephone companies would put up with broadcasters puking all over their spectrum? Or vice versa? Or either putting up with amateur radio interference?

Or, perhaps worst of all, do you think the Hams would put up with someone interfering with their spectrum? They can triangulate secret government projects accidentally using their shortwave spectrum.

Yes, interference happens from all sorts of places. You'll likely find that devices in your adjacent spectrum are less likely to interfere than other sources of interference.

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-- Erich

Slashdot reader since 1997

Re:This just in... by caluml · 2011-02-09 03:54 · Score: 1

Interference can be monitored and controlled.
I suspect that the tiny signals received from from the satellites, and the lack of any sort of decent antenna in most GPS devices mean that it wouldn't take much to cause problems.

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Get your own free personal location tracker
Re:This just in... by Anonymous Coward · 2011-02-09 03:57 · Score: 0

The problem is not the same as for television or mobiles at all. The problem with the GPS signal is that it is incredibly weak compared with terrestrial based transmissions. A typical consumer GPS antenna will typically acquire down to around -160 dBm, so anything near the relevant frequency will have an effect.
Re:This just in... by cadeon · 2011-02-09 04:26 · Score: 3, Informative

>>AM Radio could interfere with aircraft beacons, since they're right next to each other!
These intentionally overlap. Back in the day, AM radio stations were just as useful at navigation as proper NDBs. You can tune in and listen to most of the AM band using your aircraft's (very old) ADF.
Re:This just in... by CaptainChuck · 2011-02-09 19:53 · Score: 0

There are two concepts of free space radio communications that must be understood to appreciate the gravity of the problem with LightSquared's currently proposed system. Radio signals lose strength as the square of the distance. GPS satellites are some 10,000 miles up. That puts GPS signals at a disadvantage of 10 billion to one over a cell tower a mile away, and LightSquared are proposing to build 40,000 of them. That represents a 100 decibel difference in signal strength. Can you hear the rustle of leaves over the roar of a jet? The other factor is the closeness of the frequencies as a percentage of the frequencies, as well as the bandwidths involved. Tune in the strongest station on your AM dial, then try to get a station 100 miles away up or down 20 kHz. Broadcast band DXers (long distance reception hobbyists) use precisely aimed loop antennas to null out nearby stations. Unfortunately that trick won't work for practical GPS navigation receivers.

Not all 4G by Zouden · 2011-02-09 03:40 · Score: 4, Informative

Contrary to what the headline and summary implies, "4G" doesn't always use 1500Mhz. In fact, I'd never heard of a 1500Mhz cellular network until now. Apparently a startup called "Lightsquared" has bought that patch of spectrum and wants to roll out an LTE network. No other 4G network is in that frequency range. For example, Verizon's LTE network is at 700Mhz and Sprint's Wimax network is 2500Mhz.

So, really, this is no concern to anyone but Lightsquared. Either there's no interference and they can go ahead with their rollout, or there is interference and the FCC has to step in. In either case, the other 4G networks are unaffected.

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"A week in the lab saves an hour in the library"

Bad for Aircraft by SirBitBucket · 2011-02-09 03:42 · Score: 1

As a pilot I would be concerned about GPS degradation (we get reports of it). This could lead to a number of issues with aircraft navigation, especially for pilots flying VFR with handheld units that do not have RAIM. (The FAA says those are for situational awareness only, but that is frequently abused.)

Re:Bad for Aircraft by Anonymous Coward · 2011-02-09 05:36 · Score: 0

Raim is for calculated loss of service due to satellite coverage, not interfering ground stations
Re:Bad for Aircraft by elijahmm · 2011-02-09 07:28 · Score: 1

It's far worse than you think. GPS degradation, jamming, loss of fix, etc. will completely destroy the FAA's next gen plan since it's based on GPS as primary navigation. LORAN is dead, the NDB network is unmonitored and unmaintained, and new ILS installations few and far between. WAAS GPS is the primary avenue being used for expanding low precision approaches throughout the nation's air transport network (which is considered part of the emergency response system). Due to the FAA's decisions to retire the old ground based navigation systems in favor of GPS this is a huge concern and worst case could put people's lives in danger.
Re:Bad for Aircraft by SirBitBucket · 2011-02-09 07:47 · Score: 1

Well, yes... this is just poor planning o the FAA's part.I don't trust GPS to always be available. Of course your ADF can still be used to listen to AM radio (or find your way to a good radio tower...)
Re:Bad for Aircraft by elijahmm · 2011-02-09 08:24 · Score: 1

yup, that's the main thing I use it for. Listening to traffic reports and laughing at the people stuck in traffic as I fly by.

Geocaching by SiaFhir · 2011-02-09 03:45 · Score: 2

This could be somewhat worrisome to us urban geocachers. It's gonna be harder to use the multi-billion dollar military satellite network to find that little tupperware container.

Bad News! by brunokummel · 2011-02-09 04:20 · Score: 1

Can you imagine how chaotic the eletromagnetic spectrum will be when the Bieber's 6G Fever hits off ??

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What is best in life? To crush your enemies, to see them driven before you and to hear the lamentations of their women.

Military use trumps all by CaseyB · 2011-02-09 04:43 · Score: 3, Insightful

I would stress too much about this. Anything that has even a remote chance of interfering with the US military's use of GPS is never going to be deployed. Period.

Re:Military use trumps all by Anonymous Coward · 2011-02-09 10:36 · Score: 0

Mod parent "Funny". Like any large organization, the US military has a long history of utter cock-ups. This sort of facepalm would hardly rate.
(Which is definitely not to say everyone in the US mil is a fuckup, or that this sort of thing wouldn't get sorted eventually, but to say it'd never be deployed... heh, yeah. Good one.)
Re:Military use trumps all by Anonymous Coward · 2011-02-09 11:24 · Score: 0

Or, as soon as it starts interfering in any meaningful way, it's gonna' get rapidly un-deployed...
Re:Military use trumps all by coolsnowmen · 2011-02-09 18:11 · Score: 1

The military uses "m" codes which are supposedly more resistant to jamming. With the exception of the nation guard, they shouldn't really care about how bad gps is in the US. In fact, wouldn't it be better for fighting Terrorism if there was no more GPS!
Re:Military use trumps all by Anonymous Coward · 2011-02-10 07:30 · Score: 0

Not really - the primary military use of GPS is outside the US, obviously; whereas Lightsquared's spectrum allocation is only in US and Canada.
Re:Military use trumps all by Anonymous Coward · 2011-02-10 19:11 · Score: 0

The military can still use their encrypted L2 band at 1.2 Ghz. This affects only the unencrypted "civilian" L1 band.
Besides, it's not like the US military is going the bomb the US soon, and other countries are going to jam GPS anyway.

Garmin & Trimble Tests released, doesn't look by Anonymous Coward · 2011-02-09 05:07 · Score: 0

This system does in fact affect GPS receivers from the big names in GPS navigation. Initial tests by Garmin and Trimble show at least 0.6 to 5 miles away from a transmitter tower a GPS receiver will loose the ability to lock onto a signal reliably. With jamming and degiration present at 3.5 to 14 miles. It is not just a Garmin/Timble problem, this will affect ALL companies GPS receivers.

With at least 36,000 transmitters planned for the US this will affect you if you use GPS for navigation. That is on average one transmitter for every 82 square miles at launch, with more to come. In urban environments there will obviously be more transmitters placed along major roadways and in congested city environmental where GPS is already hard to receive.

Even WAAS grade aviation GPS receivers which are required to be more sensitive are susceptible, this poses risks for pilots using the system to fly and passengers traveling aboard aircraft navigating with GPS. These GPS receivers are certified to FAA approved levels and are designed to tolerate high levels of interference. Additionally it will affect the service and reliability of the FAAs next-gen ADS-B system that is scheduled to replace radar by 2020 since air traffic control will be dependent on the aircraft telling it where it is using GPS. (look at Wikipedia on ADS-B for more details)

Please URGE the FCC and congress to push back against LightSquared, protect our valuable GPS resources.

Here is GPS Worlds Article:
http://www.gpsworld.com/gnss-system/news/data-shows-disastrous-gps-jamming-fcc-approved-broadcaster-11029

Letter to the FCC from Garmin and Trimble:
http://www.gpsworld.com/gnss-system/signal-processing/lightsquared-jamming-report-11030

FCC proves its incompetence once again by Anonymous Coward · 2011-02-09 05:09 · Score: 0

Here we go again. The FCC, in its zeal to provide moneymaking opportunities for political friends, throws engineering and science out the window. Should we think that Garmin and the GPS industry are just whining? I own one of the GPS receivers mentioned in the Garmin report, and I know that there are millions like it in the US. The FCC's casual attitude toward RF interference has once again raised its ugly, incompetent head. FCC does these idiotic things more and more often, excusing them in terms of "deregulation". Out goes the baby with the bath-water!

Am I the only person... by ewhenn · 2011-02-09 05:30 · Score: 0

Am I the only person who read that and hoped it would be more of the other way around? Got some disruptive douchebag slapping away on her cellphone near you? Turn on your GPS and toss it in your pocket.

Re:Am I the only person... by Anonymous Coward · 2011-02-09 06:49 · Score: 0

Your GPS receiver doesn't transmit signals, it only receives them from satellites.
Re:Am I the only person... by Anonymous Coward · 2011-02-09 07:32 · Score: 0

Because then there'll be two disruptive douchebags?
If what they're doing is really a violation of social norms, ask them to stop -- and if asking them to stop makes you look like an asshole, it's a good clue that you're the one with the misperception of social norms, and resorting to covert signal jamming will just make you a ballsless asshole.

Garmin's analysis is poor by Anonymous Coward · 2011-02-09 05:52 · Score: 0

The QPSK signal is jamming the GPS from spectral regrowth bleeding into the GPS band, caused from amplifier nonlinearities, baseband filtering, and phase noise. Problem is they don't list the actual re-growth density at GPS. So saying their QPSK signal is the same as LightSquared's is like comparing apples to oranges.

It's a conspiracy! by marciot · 2011-02-09 07:29 · Score: 2

The GPS manufacturers and 4G companies are colluding to get us all to buy new GPS devices and GPS-enabled phones with better band-pass filters!

MOD PARENT UP by CompMD · 2011-02-09 08:13 · Score: 1

I'm a pilot, and an engineer who designed some of the equipment in the panel of my aircraft. This idiocy at the FCC scares the crap out of me when you consider the NextGen ATC system the FAA is rolling out. This will lead to loss of situational awareness for pilots and air traffic controllers resulting inevitably in death, just so someone can say OMG i HAVE TEH FOUR GEES.

Re:MOD PARENT UP by elijahmm · 2011-02-09 08:37 · Score: 1

I could not agree more. The FCC has been running into the FAA far too frequently (such as the ELT issue last year). Maybe it's time to start developing transmitter agnostic navigation systems that use ANY transmitter (ground or space) to triangulate position based on a database and an initial known position. Isn't this basically the way LORAN worked but with a specialized set of towers? Like you I'm a pilot and while I did not design the equipment in my panel I did install it all myself (with the help of a radio repair station and an A&P).
Re:MOD PARENT UP by CompMD · 2011-02-09 10:47 · Score: 1

Being transmitter agnostic is a problem because various ranging technologies have different implementations. Sure, you could conceivably use information from three VORs to accomplish this, but the accuracy would probably only be good to 1/10 nm. AM radio stations are handy navaids if you know where they are and you have an ADF. I could fly most of the way from Kansas City to Chicago by tuning the ADF to 720kHz. However, this doesn't tell you where you are, and no new aircraft come equipped with an ADF these days. None of this technology can provide the precision or accuracy of GPS. I'm just keeping my fingers crossed for GPS/Galileo/GLONASS receivers.
Nice job installing your own avionics! I should clarify I had a fair bit of help...since my employer manufactures avionics. :)

GPS World article by kybred · 2011-02-09 10:23 · Score: 1

GPS World has a good write-up on this.

On January 26, the FCC waived its own rules and granted permission for the potential interferer to broadcast in the L Band 1 (1525 MHz—1559 MHz) from powerful land-based transmitters. This band lies adjacent to the GPS band (1559—1610 MHz) where GPS and other satellite-based radio navigation systems operate.

4G LTE supports lots of frequency bands by billstewart · 2011-02-09 11:40 · Score: 1

Wikipedia LTE Article lists a bunch of different frequency bands used by LTE (and other cellular standards), and this L1 band isn't in there. So while GPS interference problems may affect this particular carrier's frequency band, it's not going to affect the widely announced plans for 4G* LTE or HSPA+, and it doesn't look like it affects the current 4G* WiMax carriers either.

Of course, I'll be really annoyed if these guys interfere with my el-cheapo car GPS, or my cellphone's GPS, and I'll be really annoyed if they start interfering with airplane GPS systems (if I had to worry about my car falling out of the sky or crashing into mountains, I'd have more serious problems than just GPS...)

* Defining your product as "nth-Generation Wireless" is a marketing-slogan issue, and it was hubris for the carriers and equipment makers who declared their products to be the standard in the first place, so I'm not going to argue about whether LTE or WiMax or NewerShinierRadio is real 4G or not. The stuff that the major carriers and handset makers are deploying in the next year or two doesn't interfere with GPS, which is what matters, not what label they attach to it, so it's not going to cause sky-is-falling problems or create no-fly zones around your local cellular tower, even though there are probably Marin County residents panicking about it as we speak.

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Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks

Nearby Frequencies Support Common Radio Hardware by billstewart · 2011-02-09 11:44 · Score: 1

I don't know anything about this company's equipment except what I've read in the article today, but if they do have approval to use a radio band next to GPS and can do so without interfering with it, it's likely that equipment for that data service can use the same radio hardware as they'd use for receiving GPS signals, with just software-defined-radio or similar tuning technology to let handsets do both with less hardware, instead of needing a cellular radio and also a GPS radio.

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Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks

ALL our eggs in one basket, PLEASE by Anonymous Coward · 2011-02-09 12:03 · Score: 0

Up until last year we had a backup at least some of the functionality of GPS http://en.wikipedia.org/wiki/Loran_C
In an act of political expediency it was turned-off and intentionally rendered impractical to restore.

Discussion of the implications and context is left as an exercise fro the slashdotters

Nice blinders you've got there by Anonymous Coward · 2011-02-09 14:54 · Score: 0

GPS signal strength is down around -160dBw. TV receivers don't have to deal with signals anywhere near that weak, nor do beacon trackers. At neg 160, you want/need a damn low noise floor.

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