How Europe Rolled Out 5G Without Hurting Aviation (cnn.com) 120
gollum123 shares a report from CNN: Major international airlines are canceling flights to the United States over aviation industry fears that 5G technology could interfere with crucial onboard instruments. But it's business as usual in Europe, where the latest generation of high speed mobile networks is being rolled out without a hitch. Why is there a potential problem in the United States, but not Europe? It comes down to technical details.
Mobile phone companies in the United States are rolling out 5G service in a spectrum of radio waves with frequencies between 3.7 and 3.98 GHz. The companies paid the US government $81 billion in 2021 for the right to use those frequencies, known as the C-Band. But in Europe, 5G services use the slower 3.4 to 3.8 GHz range of spectrum. The aviation industry is worried that US 5G service is too close to the spectrum used by radar altimeters, which is between 4.2 and 4.4 GHz. Europe does not face the same risk, according to the industry, because there is a much larger buffer between the spectrum used by radar altimeters and 5G.
There are other differences in how 5G is being rolled out, according to the US Federal Aviation Administration (FAA). Other countries are using lower power levels, restricting the placement of 5G antennas near airfields and requiring them to be tilted downward to limit potential interference with aircraft. In France -- cited by telecom carriers such as AT&T and Verizon as an example of 5G and aviation working seamlessly together -- the height of a 5G antenna and the power of its signal determine how close it is allowed to a runway and the flight path of an aircraft, according to a technical note from France's National Frequency Agency (ANFR). Antennas around 17 major French airports are also required to be tilted away from flight paths to minimize the risk of interference, the agency's director of spectrum planning and international affairs, Eric Fournier, told CNN.
Mobile phone companies in the United States are rolling out 5G service in a spectrum of radio waves with frequencies between 3.7 and 3.98 GHz. The companies paid the US government $81 billion in 2021 for the right to use those frequencies, known as the C-Band. But in Europe, 5G services use the slower 3.4 to 3.8 GHz range of spectrum. The aviation industry is worried that US 5G service is too close to the spectrum used by radar altimeters, which is between 4.2 and 4.4 GHz. Europe does not face the same risk, according to the industry, because there is a much larger buffer between the spectrum used by radar altimeters and 5G.
There are other differences in how 5G is being rolled out, according to the US Federal Aviation Administration (FAA). Other countries are using lower power levels, restricting the placement of 5G antennas near airfields and requiring them to be tilted downward to limit potential interference with aircraft. In France -- cited by telecom carriers such as AT&T and Verizon as an example of 5G and aviation working seamlessly together -- the height of a 5G antenna and the power of its signal determine how close it is allowed to a runway and the flight path of an aircraft, according to a technical note from France's National Frequency Agency (ANFR). Antennas around 17 major French airports are also required to be tilted away from flight paths to minimize the risk of interference, the agency's director of spectrum planning and international affairs, Eric Fournier, told CNN.
Planning (Score:4, Interesting)
Without even reading the story and just looking at some of the highlights, it sounds like the Europeans took a more pragmatic approach and thought in advance of deployment details.... I mean, planning ahead seems like such a easy thing, why did we not think ahead ourselves....?
That is definitely a head scratcher.
Re:Planning (Score:4, Informative)
Canada too. Both Europe and Canada have had 5G deployed for several years with no incident.
On another note, it sounds like radar altimeters are pretty shite.
Re: (Score:2)
Radar altimeters are excellent, and function exceedingly well to prevent specific kinds of landing accidents since they became widely used.
Re:Planning (Score:5, Insightful)
Radio devices that cease to function because someone is transmitting 400 MHz out of their band are not excellent.
Re:Planning (Score:5, Informative)
From things I've read and put together:
Europe is using 3.4 to 3.8 GHz
US is using 3.7 to 3.98 GHz
The radio altimeters use 4.2 to 4.4 GHz
So the spacing in Europe is 400 MHz, which is fine, but in the US it's 220 MHz
The other thing is, apparently, the US radio/antenna setups are up to 2 times as powerful as those used in Europe and the antenna are installed in vertical positions in the US vs they're tilted away from any finals/flight paths in Europe.
So it's not an apples-to-apples comparison when someone says "well Europe did it, so it's all fine!"
On top of that, the AT&T spokesperson quote of "We are frustrated by the FAA's inability to do what nearly 40 countries have done, which is to safely deploy 5G technology without disrupting aviation services, and we urge it do so in a timely manner" (Megan Ketterer, an AT&T spokesperson)
What? The FAA isn't deploying 5G, the wireless carriers are with the backing of the FCC. If anything, you should be asking why your own companies (and by extension the FCC) cant' deploy 5G without interrupting aviation services. I've seen reports where the concerns from the FAA were forwarded to the FCC for quite a while now, but...
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If the radar altimeters licensed between 4.2 GHz and 4.4 GHz *actually* require nothing else doing from 3.8 to 4.8 GHz, then declare that in the regulation, call that the radar altimeter band, and don't sell rights anywhere in that range.
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If the radar altimeters licensed between 4.2 GHz and 4.4 GHz *actually* require nothing else doing from 3.8 to 4.8 GHz, then declare that in the regulation, call that the radar altimeter band, and don't sell rights anywhere in that range.
Either that, or plan far enough in advance that the airlines have more than ample time to replace the equipment in question. Three years seems like a long time, but in aviation terms it really isn't. I still think they should have got their shit together and replaced them by now, but I realize what I want (everyone involved to be competent) is not realistic.
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Sure, there are exclusion zones around airports too. All reasonable compromises the FAA could have implemented, except for the frequency thing, which the FCC should have been on top of.
Some further research also suggests that only about half of airliners have radio altimeters that can't operate properly within their allocated band. Want to guess who makes them?
So the cock up seems to be a joint effort between the FCC, FAA and a subset of equipment manufacturers who the FAA and FCC should have sent back to t
Re: Planning (Score:2)
You can interpret that indeed as a harder technical challenge for the US carriers. Or you could say the more conservative approach of the EU was what needed to be done to keep flying without all the handle.
Probably a side effect of being with so many different countries and having to take each other into account all the time.
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From things I've read and put together:
Europe is using 3.4 to 3.8 GHz
US is using 3.7 to 3.98 GHz
The radio altimeters use 4.2 to 4.4 GHz
So the spacing in Europe is 400 MHz, which is fine, but in the US it's 220 MHz
The spacing in the US is also zero for intermodulation products from the 5G transmitters which land directly in the radio altimeter band, which no filtering will remove.
Re: Planning (Score:5, Interesting)
how do you figure "our government"?
ATT and sprint over in europe knew what to do so it would avoid interfering with planes.
When they got back to the states the same companies are like F it. Since they didn't say we couldn't aim it a planes, were going to aim it at planes.
You would think the companies rolling this stuff out would have enough self preservation to duplicate what they did in Europe instead of progressing the way they did.
Why is it never the companies fault and regulation bad?
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In aviation you will find that a lot of stuff is based on very old designs that have not been updated because they work and updating requires expensive certification. Being simple also makes them easier to maintain and cheaper.
Radar altimeters are a great example. They use a very simple system where they sweep through a range of frequencies, and measure the difference between the frequency being transmitted and the one coming back. Electrically it's very easy to do without any complex filtering or expensive
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From the list of affected aircraft, it looks like the old ones are fine. MD-11's? No problem. 787s on the other hand....
Essentially every radio device modulates its signal in some way, which involves occupying some bandwidth. The US radio altimeter allocation is 200 MHz wide. That's not narrow. Anyway, a radio device that stops functioning because of interference from outside its spectrum allocation is shite. Such a thing shouldn't have ever been approved.
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>Anyway, a radio device that stops functioning because of interference from outside its spectrum allocation is shite. Such a thing shouldn't have ever been approved.
Not sure that's right. The altimeter sounds to me more like a multi frequency radar than a device that locks onto a frequency and discards others.
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That sounds like a description of how a (Doppler) radar relative speed detector works, not a distance measuring device.
Unless ... no, even if you were looking for a resonance frequency picked out by your (rather leaky) cavity between the aircraft and the ground, that would give a signal intensity that
Re:Planning (Score:5, Interesting)
It's not that they "stop working", you doofus.
No, it's actually worse than that. They work improperly and produce erroneous output. You WISH they would "stop working" because that's better than lying to you in every case. Congratulations, you just put a hole in your foot. I hope you enjoyed it, I know I did.
And yes, 200-400Mhz out-of-band signals can totally cause enough interference when you're taking about precision devices operating at over 4Ghz.
Sure, if those supposedly precision devices have a sloppy-ass filter that doesn't do the job it should be doing, specifically preventing interference from adjacent bands. I've heard the arguments that the former use of those bands made it irrelevant, and those arguments are stupid because frequency reallocation has always been a thing.
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Sure, my wifi craps out every time a plane goes over or someone in the area uses a cell phone. Sucks. Wait... no it doesn't.
Radar altimeters have both a pretty wide operating band and also very wide guard bands, and apparently that's *still* not sufficient.
Also, apparently Airbus, older Boeing and McDonnell Douglas (lol) planes have no problem. So I guess I should have said "it seems newer Boeing radar altimeters are kind of shite."
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I see that physics education whereever you are is fucking horrible and didn't even teach you that power of transmission matters, if you genuinely think that a weak signal from a radar altimeter is anywhere strong enough to jam your indoors wifi.
That makes discussing the topic that you know nothing about and go off brand loyalty instead rather pointless.
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Try using a filter that blocks out the sun's light and I you shouldn't have a problem. It isn't that there can be interference by adjacent bands rather it is a problem of not having adequate filter on both the 5G and radar transmissions and inadequate filters on the in plane instruments.
That having been said it also wouldn't hurt to modify installations of 5G towers around airport like they have done in Europe.
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You can, but costs associated with it will have to be born by the clientele. Also such filters commonly reduce accuracy of observations.
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And probably far cheaper to replace than the cost of additional 5G tower sites to cover a narrower bandwidth of spectrum.
Look, I love traveling internationally. I love flying. I have a shit ton of frequent flyer miles. But I do feel the aviation industry gets far too generous access to public resources.
Right now, there is an airplane jet engine roaring overhead is literally the only sound I can hear. And I'm not living right next to an airport. In my city millions of people are subjected to constant jet
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Actually, you've prompted me to check. Ohhh, the nearest coverage is only 25 miles away! That's really going to encourage me to replace my 5-yo phone with one costing 3-5 times as much.
Probab
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Because the US Government officials saw an opportunity to make more short term money (either directly though the sale itself or indirectly via lobbyists) by selling slightly more of the radio frequencies than was appropriate or safe to the mobile operators at the inconvenience of existing users of adjacent frequencies. The existing users just happened to be the aviation and satellite operators causing operational issues for the latter and safety issues for the former and neither of which can easily do anyt
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The aviation industry was asking the FCC to delay the spectrum auction as well way back in 2020 when the auction was announced. It's been going the whole time.
https://www.aopa.org/news-and-... [aopa.org]
They proposed some mitigation strategies, including having industry help fund upgrading the entire fleet of aircraft with the newest radar altimeters which should be more immune to the interference. (Radar altimeter technology hasn't changed in decades, so it's not unusual to have planes flying around with older units
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That is definitely a head scratcher.
Not really. Several organizations and a lot of individuals screwed up massively in the US. At the same time, this works without a problem in the rest of the world. So much for "technological leadership".
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We *DID* get it right. There's a whole 220MHz separation between the highest frequency the telcos bought and are licensed to operate on, and the lowest frequency the airlines bought and are licensed to operate on. That is a huge gap which is more than enough to prevent interference... IF both sides had bought decent, compliant, gear.
The issue is that some crooked airline execs decided to pad their quarterlys by buying cheap, dodgy kit that illicitly operates outside its licensed spectrum... essentially sq
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We *DID* get it right. There's a whole 220MHz separation between the highest frequency the telcos bought and are licensed to operate on, and the lowest frequency the airlines bought and are licensed to operate on. That is a huge gap which is more than enough to prevent interference... IF both sides had bought decent, compliant, gear.
The gap is irrelevant when the intermodulation products from the transmitter are inside the channel to be protected.
inbound filter? (Score:1)
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Aviation equipment isn't expensive (or at least, doesn't have to be), and much of it is VERY dated. It's sort of good from a backwards compatibility standpoint - you can buy a 60 year aircraft and the radios, transponders, etc generally will all still be perfectly useful. On the other hand, it can pose problems for things like this, but it is good from a waste standpoint - things in aviation don't get discarded or thrown away at nearly the same rate as general equipment. Usually its serviced, fixed, repa
Radio Altimeters are not critical (Score:2)
Only really useful in the late stages of landing in very bad weather.
But they are backed up by an ILS system, plus GPS and VOR/DME that tells them where they are.
So very occasional outages caused by 5G interference should not be an issue. All instruments can fail occasionally.
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P.S, I should have mentioned the normal altimeter, which when backed up by accurate air pressure readings from the airport are good to within about 100 feet.
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None of the systems you mentioned, including the 'normal altimeter', tell you the most important safety information, which is height above terrain.
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None of the systems you mentioned, including the 'normal altimeter', tell you the most important safety information, which is height above terrain.
They all do if you happen to have a map with you.
Sure, a Radio Altimeter is a good thing to have in bad weather. But the plane is not going to fall out of the sky if, for example, it fails 0.001% of the time.
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It may be a problem if that 0.001% happens usually when a plane is about to land, when it's flying low, with less safety margin, and the radio altimeter data starts getting corrupted since it's closer to the ground / 5G base stations.
I don't think it will be too much of an issue when you have 10000 feet ground clearance. I think it will be an issue when your ground clearance is 100 feet.
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Nobody said the plane was 'going to fall out of the sky'. And I said SAFETY information. A map does not provide safety information. How many planes do you think are flying where somebody is actively looking at their position on a map? I'll tell you: zero.
Safety information includes things like the plane calling out 'TERRAIN! PULL UP!'. This avoids little problems like 'controlled flight into terrain'.
Finally, this claim that the radio altimeter is a 'bad weather' thing is pure bullshit. Pilots (of com
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Finally, this claim that the radio altimeter is a 'bad weather' thing is pure bullshit. Pilots (of commercial aircraft in particular) rely on it on EVERY landing.
While I presume this is true, it doesn't have to be. Laser altimeters are cheap now and could reasonably be used in any fair weather condition — and some of them work in poor visibility conditions, too.
Fair weather conditions (Score:2)
That is a bit like a safety belt that works well except in a crash.
Nobody needs a radio altimeter in good weather. It is when you cannot see the ground.
But like I said, there are other systems for redundancy like ILS, GPS and a map.
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I mean, that would be useful, but people have been flying without that for a long time. The "V" in VFR is "Visual" - look out of the window :).
Modern airplanes were starting to look like a veritable buffet of little gauges though now there's a large trend on newer planes to go towards "Glass cockpits" with all electronic displays condensing info onto only a few screens (with less frequently used info hidden on pages you can access only if needed).
That said, you can quite safely fly on quite few instruments
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Who needs ASI's? The devils work.
My old Tiger Moth had an open cockpit, you could feel the wind in your face, now the speed by the sting (and the angle of attack).
The Wrights never had no ASI. The beginning of the end...
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"you could feel the wind in your face"
And the hail, and engine oil
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It does not feel right to fly without the oil.
But at least it is a mineral oil. In the good old days they used castor oil which made the WW 1 pilots ill!
Re:Radio Altimeters are not critical (Score:4, Informative)
GPS does, and WAAS/GBAS are being designed to support category II/III landings.
Radar altimeters might (with caveats) tell you how high you are above terrain, but they don't tell you how high the terrain a few seconds in front of you is. Nor about that smoke stack.
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None of the systems you mentioned, including the 'normal altimeter', tell you the most important safety information, which is height above terrain.
You can also look out of the window. That's a very good approximation.
(Houses too big? Move the stick backwards...)
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Oh, right. I forgot that planes (especially commercial planes) only fly on cloudless days during the daytime.
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And hence it is useful only for VFR landings.
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"Backed up by [...] GPS and VOR/DME"? Do you have some special TSO-C129 equipment that is approved for approach operations with vertical guidance? ILS can provide a vertical fix like RALTs do, but not those other things.
Yes, many US airports have WAAS approaches published. Not all.
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Only really useful in the late stages of landing in very bad weather.
Which is exactly the issue. If you can't trust your radar altimeter on board, CAT III insturmental landings are basically impossible.
Re:inbound filter? (Score:4, Informative)
As a pilot owner, Im shocked at the claim the aviation equipment does not have to be expensive, every single item used in my aircraft has to have an associated certificate for airworthiness, and the cost is at least 2X what one would expect to pay for a consumer item of similar functionality. Even just servicing an ASI costs $400au.
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Even water bottles certified to be taken into an passenger aircraft (and bought inside the airport) are twice (or more) as expensive as the apparently similar (but not airworthy) thing bought from a supermarket.
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As a pilot owner, Im shocked at the claim the aviation equipment does not have to be expensive, every single item used in my aircraft has to have an associated certificate for airworthiness.
Also a complete paper trail of when/where it was purchased, where/how it was stored, etc.
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The FCC isn't really in the business of stopping anyone from making defective receivers. The FAA on the other hand ought to care about that very much, and apparently they have been missing in action on this subject.
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I think the FAA prefers to play it "Why fix when it's not broken", After all those radio altimeters have been in use for decades and working perfectly fine.
It's just that the environmental EM status quo has changed. I understand new equipment takes years and cost big money to be certified for aircraft use. With that being the case, giving FAA 2,3 years notice of the EM changes may not be enough.
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No equipment is required to have such filters.
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The antenna and amplification circuitry do a good enough job of preventing interferences from other frequencies (or it seems they did a good enough job until now).
If more filtering is required, then you increase complexity by adding filters (additional stages).
You don't want more complexity in aircraft parts.
Also, the issue isn't really the fact that the radio altimeter might not function. The risk is that other systems of the aircraft tied to a malfunction altimeter (or Angle of Attack sensor, as in the 73
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Does the FCC require devices to have inbound filters to prevent interference? Or is expensive aviation equipment exempt from such simple requirements?
Sometimes, but in general no. They may have a requirement that the equipment accept harmful interference, meaning that there can be no claim against an interfering source.
Re:inbound filter? (Score:4, Informative)
This should help [fcc.gov]
Re:inbound filter? (Score:5, Informative)
That is a great reference. It explains the older aircraft use an older type of radar altimeter that sweeps a CW signal up and down the frequency band. As the frequency gets near the lower end of the frequency band, it sees some of the 5G Band C signals and takes a small amount of time to reject those readings.
From that analysis:
Only the most recent altimeters used aboard all new aircraft such as the 787, A350 or A380 have digitally synthesized or reference crystal stabilized modulation. There are well over 10,000 aircraft flying with “open loop” VCO systems in their radar altimeters. These open loop designs are reliable and remain in full production as of this writing.
So the problem is so many older aircraft are using the old swept-CW systems and the airlines don't want to have to replace the equipment with newer models. The older radar altimeters worked well until 5G started using Band C frequencies, so they blame 5G for causing the problems.
This is similar to when the FCC auctioned off the old broadcast TV spectrum and caused all older TVs to stop receiving analog VHS broadcast signals. They gave plenty of warning that older TVs would stop working on a certain date and provided free converter boxes, but they didn't provide free TVs. The airlines had almost three years to prepare for this change and decided to just ignore it.
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Re:inbound filter? (Score:4, Insightful)
The airlines had almost three years to prepare for this change and decided to just ignore it.
Actually, they spent their time, effort, and money lobbying against it, instead of preparing for it. And now this has translated into a delay in 5G rollout, even though we have a whole system in place for regulation of this kind of equipment which says they're in the wrong.
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Actually, they spent their time, effort, and money lobbying against it, instead of preparing for it.
Why should they when Canada and the EU did the equivalent of a "backwards compatible" 5G rollout.
There's a difference between forcing stakeholders to do an upgrade because it is absolutely required, and forcing them to do an upgrade because you fubar'ed your own deployment.
It's only *us* that created this problem. Not Canada, not the EU. *Us.*
So airline companies were totally on the right to spend money in trying to block this (knowing that they can operate with 5G as deployed in the EU.)
Changing eq
Altimeters don't block other wavelengths enough. (Score:4, Interesting)
This 5G issue is an example of the extremely poor quality of the news. The news lacks depth. The news reporters usually don't try to understand the underlying issues.
And, in general, the complexity of new technology is beyond the understanding of people who were born before that technology was created, and who haven't taught themselves new technology.
Re:Altimeters don't block other wavelengths enough (Score:4, Informative)
The main issue: Aircraft radar altimeters have receivers that don't block other wavelengths sufficiently.
Aviation tech moves at a glacial pace. People generally have no idea of just how primitive, obsolete, backwards and badly designed a lot of Aviation tech really is. Aircraft fly around with all kinds of software bugs that cause completely unnecessary problems with ground systems. Bugs that are fixed through updates in the commercial software world within days take years upon years to be installed in aircraft fleets. the result is that developers in ATC centres have to code around these bugs in the aircraft software on an aircraft type and variant basis and try to detect whether some variant of a Boeing or Airbus has spastic software installed simply because it takes forever to certify software updates. Worse yet, when the updates are finally safety certified, the airlines put off installing these fixes for years and years on end because -> profits.
Good explanation of underlying details. (Score:2)
Help people understand underlying details.
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Yes. The bottom line is that too many radar altimeters are defective, are effectively squatting on frequency bands assigned for other uses, and will need to be replaced. This should have been apparent from the beginning.
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I simply don't understand - that's a *huge* amount of gap between services. Do these radar altimeters not use band pass filters at all??
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Of course they do but I think you're overestimating the effectiveness of analog bandpass filters.
The difference between 4.0 and 4.2 is very small.
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What is really amazing is that, with 5G, for the first time in history we have perfect transmitters that emit zero energy outside their band. Truly amazing. Oh, wait, that's not true? You mean the transmitters CAN (and DO) have spurious emissions including in the band that the altimeters use? But yeah, it is entirely the fault of the receivers. Uh-huh.
Re: Altimeters don't block other wavelengths enoug (Score:2)
Almost victim blaming here. But sure it is more complicated. Looks like they played a game of chicken and collided painfully.
No Conclusions (Score:1)
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https://www.rtca.org/wp-conten... [rtca.org]
Boeing (Score:2)
News articles (many of which which repeatedly confuse "5G" with "completely optional use of C-band frequencies for 5G by Verizon and AT&T") have solely indicated Boeing equipment, particularly the 777.
This shouldn't be blamed on "5G" rather than crappy equipment supplied via Boeing, if it can't properly filter out-of-band interference. Even more damning, a 5G signal should look like white noise, not in any way resembling the continuously modulated signals used in radar altimeters as described by Boeing.
3.4 to 3.8 GHz is not slower (Score:5, Informative)
That's more bandwidth (400 MHz) and thus faster than 3.7 to 3.98 GHz (280 Mhz). The association of higher frequencies with faster transfers comes from the availability of more bandwidth at higher frequencies, but the actually allocated and used bandwidth is what matters.
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Interesting, because lots of articles are parroting whatever source said that Europe's band is slower, but they don't give any numbers.
I'd be interested to know what the actual differences are, and why we didn't just allocate a lower end of the band here to avoid an issue while aircraft equipment is upgraded.
Telecoms know how to deploy equipment that is capable of a range like 3.4 to 4.0 GHz but using software switches limit it to using just a part of that, say 3.4 - 3.8 like Europe and then later add 3.8 -
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Basic physics. The higher the frequency, the more data signal can carry.
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That's a myth. The frequency is not a parameter of the channel capacity. The higher the bandwidth, the more data a signal can carry (assuming same SNR). [wikipedia.org]
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This is the standard "you're correct in principle, but technically explanation is different" kind of an argument.
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Basic physics. The higher the frequency, the more data signal can carry.
Sure, but the difference between 3.8 and 4.0 is a negligible gain.
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nb. The big speedup of 5G comes from the range being about 50 times less than 4G, not from a change in frequency.
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It's also fair to note that "5G" isn't a single thing in the first place. The biggest "it's gonna be super fast" claims come from millimetre wave, which is absolutely useless in terms of penetration capability.
For all bits and purposes, "5G" is a marketing buzzword for "generational update for most features of Long Term Evolution technologies which are also now allowed to operate on additional frequencies"
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Absolutely, but the problem is frequency distribution is very rigidly defined in each nation, as spectrum suitable for radio transmissions of any meaningful range, penetrating capability and that can carry a reasonable amount of data at reasonable transmission power and antenna size is very, very constrained.
Which leads to constant tug of war between various users of nearby spectrum bands, resulting in different outcomes for different nations.
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On my planet, 1 MHz bandwidth is 1 Mhz bandwidth. The frequency is utterly irrelevant, Yours must have different laws of physics.
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I think you are drawing improper conclusions from a single tautology. The frequency is definitely *not* irrelevant, but in multiple different ways. (E.g., some frequencies are absorbed by water vapor.) But higher frequencies yield more bits/sec in the absence of noise, etc. I'm not quite sure how beat frequencies might enter into this, but I think it would be a mistake to assume that they don't.
Etc.
I don't have a strong opinion as to which side is correct, but I have a strong opinion that your argument
Re:3.4 to 3.8 GHz is not slower (Score:4, Informative)
You're talking out of your ass, so shut the fuck up. C=B*log2(1+S/N). C is the channel capacity. B is the BANDWIDTH. Note the complete absence of a frequency parameter. Don't disrespect Claude Shannon.
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Consider having someone else reading the statement to you and explaining it. Because for all the kneejerk "you're wrong", the only thing that is wrong is your reading comprehension.
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You of all people to criticise my reading comprehension? You posted a blatantly obvious falsehood, suck it up princess, nobody around here believes a word you say. Explain how 1mhz bandwidth is not 1 mhz bandwidth or shut the fuck up.
Bah 2 5G... (Score:2)
... I can't even good signals with 5G like at my rural nest area. I can sometimes with 1X to 4G LTE. :(
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Why would you? 5G is very short range - about 1000 feet.
(4G is about ten miles...)
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Ugh. 5G sucks then. I want reliability and stability. :(
Spacing (Score:2)
3.8GHz is *not* close to 4.2GHz. 400MHz in the microwave spectrum is a lot of space. You might get a few MHz of frequency shift from doppler effects, but not enough to shift it nearly half a GHz. Even accounting for lousy bandpass filters, the energy leaked that high up would be almost nothing.
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I'm not persuaded without showing me the actual filters used, if any, and info about how the radars work and power levels involved.
For example, if the radars use phase information, simple filters could mess that up. If the radar return is almost down in the noise, splatter from 5G could make it unusable, or a 100dB reduction with the filter might not be enough to counter the 140dB ratio of 5G transmission signal to radar return in band.
On the other hand, it could just be about money. Maybe all the radar s
D.I.E. (Score:2)
FAA D.I.E. appointments and hires will eventually cause many people to die.
Re: (Score:2)
It's the airlines that should be on the hook for a big payout, because FCC regs require that equipment receive interference from equipment which is transmitting within its allocation, even if it is harmful.
Laws are meaningless if we make an exception every time it's economically inconvenient to follow them.
Re: If a plane goes down badly (Score:2)
Re: (Score:2)
And apparently we would rather play Russian roulette with jumbo jets full of people rather than put a few intelligent rules in place.
You mean rules like replacing all the defective-by-design radar altimeters with properly working ones which reject frequencies outside their allocation?
Re: (Score:2)
There are no such 'FCC regs'. What are you talking about? My guess is that you think the altimeters are FCC part 15 devices. They are not. And even part 15 devices have no such requirement. That 'must accept interference' statement is NOT a requirement on the equipment. What it means is that, as the equipment is unlicensed, you have no regulatory protection against interference. In other words, if your use of some part 15 equipment is interfered with, don't complain to the FCC about it.
Of course, non
Re: No one forgot (Score:2)
I pushed the 9-11 button. I shouldnta done that.
Re: (Score:2)
Learn to imagine that a Pilot *might* be looking out of the window and can avoid tall buildings, mountains, etc.
The problem with this is that it confuses autopilots into doing things like deploying landing gear prematurely.
Re: (Score:2)
Because they get to sell a LOT more towers and antennas than before?
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Say what? Everything you said is false. Just like there are no (contrary to the RF 'experts' on slashdot) perfect receivers that can perfectly filter out unwanted frequencies, there are no perfect transmitters that only emit desired frequencies. Spurious emissions are a thing. They are not 'illegal'. They do not cause the FCC to 'shut it down'.
Then we have the claim that radio altimeters are part 15 devices. Wrong again.
Lastly, we have the stupid idea that the FCC somehow regulates receivers, and that