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I just read the statement of a company,

"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"

But I don't see any reason to make a rush changing to 5G (except for commerce). I recall recently the outphase of 2G. So there is functional and operating 3G, 4G, LTE services running around, so it isn't a fundamental service (right now), because if these operations are delayed, probably you aren't black outing no one, and in the case of, the 5G devices has 4G/LTE support/fallback at least.

And besides if FAA has requesting a delay in operations starts, at least have the rational doubt about it. As per se, there seems to be some proximity between the frequencies and indeed its a safety measure to avoiding the overlap with the right filters. But this is relative only to the altimeters based on radio waves.

AFAIK, there is no extensive study about the total integrity of the aircraft and control system, and in the case of interference to asset the extent of it.

But it seems that all it rely on the power output antennas, so its hard to measure if there is an issue, but it is reasonable possible.

So is there any paper or document published or ongoing that supports the saying

which is to safely deploy 5G technology without disrupting aviation services,?.

Is so what is the methodology used?

Thanks in advance.

UPDATE I don't want to get outside the scope of the site, but the recent petition from Airlines for America to FAA and FCC, details the aspects about why it is considered dangerous. And the concern is about the altimeter and satellite communications links, (I guess they are referring to gps, internet and navigation services). Under the justifications given, IMHO, its reasonable to provide certain safeguards. I think the main issue has to be with the power of operation of the 5G networks.

While many countries have adopted rules, and some have begun deployment, the allocated frequencies for 5G internationally are generally farther away from the radio frequency band used by radio altimeters. In addition, the permitted power levels are often significantly lower than those authorized in the U.S. Many other countries have also effectively utilized a combination of exclusion zones around airports, lower power levels and directional changes to antennas to mitigate interference. Cited from https://www.airlines.org/5g-frequently-asked-questions/

And this is a point since if the power is too much, this will make render the filters noneffective or inaccurate and under ICAO rules there will be only operations in VFR mode (i.e.: the runway is visible enough to departure and landing). But still there seems to be no more analysis or papers supporting or denying these statements.

riccs_0x
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    This question is not about E&E design is it. – Andy aka Jan 18 '22 at 19:36
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    Aviation SE would probably know more. – DKNguyen Jan 18 '22 at 19:45
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    There may be no rush from the perspective of users, but businesses are always in a rush to create more needs. – DamienD Jan 18 '22 at 20:34
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    Aviation SE has 2 related Qs : https://aviation.stackexchange.com/questions/90898/why-is-the-5g-rollout-a-problem-in-the-usa-but-apparently-nowhere-else and https://aviation.stackexchange.com/questions/91091/what-aircraft-are-susceptible-to-5g-c-band-altimeter-interference –  Jan 18 '22 at 20:36
  • @DamienD , indeed, thats why I noted aside bussines.- – riccs_0x Jan 18 '22 at 21:07

2 Answers2

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Why not make the change - the speeds of the C-band 5G cells approach that of broadband? It's the next evolution. Radar altimeters do operate in C-band - commercial aviation radio altimeters operate in the 4.2-4.4 GHz band, which is separated by 220 megahertz from the C-Band telecommunication systems in the 3.7-3.98 GHz band.

The theoretical risk is that the filters in the altimeters may not be good enough to separate the two bands. And the use of radio altimeters in aircraft is for very low visibility precision approaches, which are fairly rare.

As far as other electronics like cell phones Paragraph (b)(5) of 14 CFR 91.21 leaves it up to the airlines to determine if devices can be used in flight, allowing use of "Any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used.

Larry_C
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    So ... would it be a fair assessment that the manufacturers of radio altimeters have been sloppy with their designs in not using a sufficiently selective front-end/filter - and up until now they've gotten away with it because no-one else was using the adjacent band? I'm assuming here that 5G transmitting equipment *is* well-enough designed that it doesn't 'leak' appreciable energy over into the radio altimeter band though ... – brhans Jan 18 '22 at 20:18
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    No. They designed their filters for the RF environment that existed at the time. Doing more would have been shooting in the dark, with added costs for no good reason. They met their requirements, I assume, and that's good enough. – SteveSh Jan 18 '22 at 20:26
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    Indeed, better frequency domain performance usually implies poorer time domain performance, which you probably don't want in an altimeter. –  Jan 18 '22 at 20:38
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    @user_1818839 not sure how relevant this would be at GHz frequencies vs. human reaction times, though... – DamienD Jan 18 '22 at 20:46
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    @DamienD Well, 2 ns error = 1 foot error, and this is about final approach and touchdown. –  Jan 18 '22 at 20:51
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    @user_1818839 ah yes, I see what you mean! – DamienD Jan 18 '22 at 20:52
  • @Larry_C, then its safe (enough) to make such statements, there are more than only altimeters, and right know there is a transition towards the digital implementation of control and monitoring, in air and in land, as VOR/DME . Thasts why Im asking if there is a study, paper or conducted investigación that supports the afirmation. – riccs_0x Jan 18 '22 at 21:04
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    "They designed their filters for the RF environment that existed at the time." seems a bit like "well yes sort-of, but it was ok back then because no-one was using the adjacent band" ... :P – brhans Jan 18 '22 at 21:05
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    How 'bout "Perfect is the enemy of good enough"? – SteveSh Jan 18 '22 at 21:08
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    @SteveSh - yeah, that's a valid criticism for many engineers ;) - but it still feels like some amount of complacency in not considering that the band next door would some day get allocated and actually used by something. – brhans Jan 18 '22 at 22:14
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    @brhans that's where temporal discounting comes in. I'm sure these engineers didn't sit idle and had other pressing problems to work on. Besides, what if humanity in an alternative future had moved en-masse to gravitational waves for its netflix streaming needs, and left the electromagnetic spectrum blissfully empty for aviation? – DamienD Jan 18 '22 at 22:33
  • @brhans they probably felt that the FCC would help protect the band from interference since the altimeters are a licensed use. – user57037 Jan 19 '22 at 07:22
  • @mkeith - but surely 5G transmitters are now also licensed, and surely the license is conditional on not leaking over into neighboring bands - just as it is for use of the ISM bands for example. It just feels to me like the designers and manufacturers of radio altimeters have been blithely stomping on the neighboring bands(s) for so long now that it's just been taken for granted. It seems like maybe poor planning at the start of the 'radio altimeter age' caused them to not reserve a band as large as is actually required for that purpose... – brhans Jan 19 '22 at 10:06
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    The licensing of 5G is EXACTLY what the controversy is about. Airlines are saying to the FCC (the licensing authority) please don't license 5G at full power near airports because it is going to interfere with our radio altimeters. And the FCC is saying sorry, progress must go on. I don't think the altimeters are stomping on anything. They are the victims in this scenario. It is the FCCs job to manage this. But to a certain extent, when the FCC licenses a device or station or band for a certain usage, it is kind of expected that it will defend that usage against future potential interference. – user57037 Jan 19 '22 at 22:11
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Speculative answer, after following up a comment

They designed their filters for the RF environment that existed at the time.

This reminded me that better frequency domain performance usually implies poorer time domain performance, which you probably don't want in an altimeter.

Consider that, loosely speaking, the separation of 200MHz between 5G and radio altimetry would correspond to 5 ns time domain uncertainty in the round trip time of a radar signal, and that would introduce a 2.5 foot uncertainty in the height measurement.

Now looking at a few references on radar altimetry, this link suggests 2 feet accuracy and this (PDF) suggests 0.75m, or 2.5 feet, both within this ballpark.

So I suspect we are looking at fairly broadband receiver circuitry, not because filter design skills were weak, but to achieve the desired time domain behaviour required for height accuracy for good blind landings. The quote above may actually be reversed ... perhaps the RF environment was designed around 4.3GHz to permit radar altimetry.

The links suggest the actual detection uses FMCW radar, I don't know enough about radar to say anything about its immunity to adjacent band interference or its effect on accuracy.

If so, it's going to take a bit more than tighter filters to clear this up without degrading accuracy.

  • https://www.rtca.org/wp-content/uploads/2020/10/SC-239-5G-Interference-Assessment-Report_274-20-PMC-2073_accepted_changes.pdf – Larry_C Jan 19 '22 at 21:08
  • @Larry_C Thanks, interesting! Seems at least part of the problem is 5G equipment's spurious emissions 400MHz outside its own allotted band... –  Jan 19 '22 at 21:59
  • Also leads to ITU rec M2059 where a receiver bandwidth spec is shown ... (Table 3) "Interference frequency ≤ 4 200 Attenuated at 24 dB per octave to a maximum of 40 dB" Indeed, that's not very selective. –  Jan 19 '22 at 22:47