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4G Broadband May Jam GPS
mferrare noted some rumblings that 4G Broadband may jam GPS. There's a slew of technical bits in an report (PDF). 4G broadband frequencies (1525-1559MHz) are next door to GPS frequencies (1559-1610MHz). Test results won't be out until June.
is faulty.
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.
Just to specify, that was all assuming that the study isn't crap, and that properly designed GPS receivers could infact be affected.
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
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.
What else can happen when an unstoppable force collides with an immovable object?
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.
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.
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
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.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
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.
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...
Nearly fifty percent of all graduates come from the bottom half of the class!
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.
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+).
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.
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.
4G is years away, and implementations of prototypes are still in the lab. American operators are advertising 3G as '4G', because they can.
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.
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.
-- Erich
Slashdot reader since 1997
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.
"A week in the lab saves an hour in the library"
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.)
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.
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...
The FCC is too busy policing the airwaves for porn to be tied down with such droll technical matters.
For justice, we must go to Don Corleone
>>>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.
Information wants to be expensive AND wants to be free. So you have Value vs. Cheap distribution fighting each other.
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.
Sig Return: 204 No Content
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).
>>>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).
Information wants to be expensive AND wants to be free. So you have Value vs. Cheap distribution fighting each other.
Time to upgrade. Devices with AGPS usually get a fix within 10 seconds or less...
Can you imagine how chaotic the eletromagnetic spectrum will be when the Bieber's 6G Fever hits off ??
What is best in life? To crush your enemies, to see them driven before you and to hear the lamentations of their women.
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.
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.
Faster! Faster! Faster would be better!
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.
For them, nipples and electricity...
For justice, we must go to Don Corleone
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.
Just great. Now you've got me thinking about electrified nipples.
Sleep your way to a whiter smile...date a dentist!
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.
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.
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!
My smart phone gets a fix in under 3 seconds.
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...
The industry report is real and true, I know several of the authors, one of them works down the hall from me.
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.
That's because it's one of those fantabulous devices I mentioned... you know, the ones with AGPS.
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.
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.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
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.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks