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U.S. FAA clears 45% of commercial plane fleet after 5G deployed

159 points by neom 5y ago

sokoloff 5y ago
Note that the adjacent band interference concern is with radio altimeters, not sensitive pressure altimeters. (The article makes this clear later, but not on the first mention of altimeter.)
- largbae 5y ago
  While your statement is true, this does not diminish the importance of radar altimeters: the barometer is not specific to the landing site terrain like radar is, but rather related to distance above sea level. In low visibility, radar is the only way to tell how close to touchdown you are.
  - mlindner 5y ago
    This isn't really true. Before landing an aircraft gets the pressure altitude of the airport and sets their altimeters with that as a reference before landing. It's a very common procedure. These are updated regularly.
    - snuxoll 5y ago
      While it’s true the barometric pressure is included in the ATIS information every plane will get before landing, pilots also rely heavily on GPWS callouts when landing and those are provided by radio altimeter and not the barometric one. It’s not an issue to land without them, and some approaches and emergency checklists require you turn them off to allow other messages to be announced without GPWS callouts taking priority - but it’s ideal to have them for sure.
    - p_l 5y ago
      Radar altimeter is used for low-visibility approach collision avoidance and for triggering events in last few meters on AUTOLAND-equipped planes (this is rarer in USA but common for example in UK airports). The main glide slope is managed with barometric altimeter, sure, but that one lacks the detailed resolution of the radar altimeter and can't detect ground - it can only follow the difference from specific pressure according to standard model atmosphere.
Victerius 5y ago
US airlines warn C-Band 5G could cause 'catastrophic disruption' https://www.engadget.com/us-airlines-warning-letter-211919932.html https://www.engadget.com/us-airlines-warning-letter-21191993...
- mlindner 5y ago
  Better title "US airlines warn government ineptness in slow approval of regulations could cause 'catastrophic disruption'". This is a regulatory failure not a technological one.
JohnJamesRambo 5y ago
Has anyone ever had awesome lte and said “I need more bandwidth” on their phone? Idk I just don’t see the need for 5g but I’m definitely not a phone power user.
- girvo 5y ago
  Yes, but only in the context of tethering a more powerful device personally.
- kevml 5y ago
  Having a mobile hotspot has allowed me to work just about anywhere I want to. The more bandwidth the better!
- LeoPanthera 5y ago
  I'm going to guess that you have home broadband internet that is reasonably fast and reliable.
  - snowgrove 5y ago
    But that’s just it. How is 5G-based rural broadband a significant improvement on LTE-based service?
    - vel0city 5y ago
      More customers being able to be served from the same number of towers with better per-customer performance. One challenge in rural broadband deployments is there are only so many good locations for the carrier to actually stick antennas. Maybe a water tower or two, you might get lucky and have some tall radio tower at the edge of town. So then all the customers in the area are essentially sharing a single tower, all needing to point their CPE to that one point. You can only slice the tower up into some number of sectors and once you hit that point the tower is saturated. Every additional customer is now diminishing the service for every other customer. Having better spectral efficiency per sector means you can service more customers, have better service per customer, or even both depending on how you balance it.
Aloha 5y ago
I am highly skeptical that we need additional 5G spectrum. We're not even fully using the spectrum that has already been auctioned.
- username190 5y ago
  Carriers are not currently using the spectrum that they gained in Auction 107, because of the issues that this article mentions. Their agreement with the FAA has given Verizon and AT&T the go-ahead to begin operations on this spectrum tomorrow (outside of existing FCC-approved test sites, which have been operating for months). Which spectrum are you referring to that carriers have purchased and not deployed, if not 3.7–3.9 GHz?
mrhands556 5y ago
——
- kbaker 5y ago
  "Passengers should check with their airlines if weather is forecast at a destination where 5G interference is possible," the FAA said Sunday. It only affects landing in bad weather.
  - supernova87a 5y ago
    Really, they're going to ask passengers and airlines to publish and follow up to find out if this is gonna be an issue on their particular flight? Passsengers should also be sure to look up all the latest airworthiness directives and advisory circulars for the plane and engine type they're going to fly as well. And get the crew medical reports just to be sure. Hell, maybe passengers should just as well check that the aircraft manufacturers haven't modified any critical safety systems that the FAA should've been regulating.
    - deleted 5y ago
      [deleted]
supernova87a 5y ago
From the most barebones news articles I read about the topic (and in this country they generally all are), this has already been rolled out in other countries to no great issue? Here it's a turf/jurisdictional spat between FAA and FCC over not having gotten all the approvals through the desired channels in time for rollout? Although, I guess papers like this detail the issue more carefully: https://ecfsapi.fcc.gov/file/7021340930.pdf https://ecfsapi.fcc.gov/file/7021340930.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-In...
- mdasen 5y ago
  The FAA has noted that in other countries there were mandates for lower power levels for 5G and that the antennas be pointed down toward the earth so that they interfered less. https://www.faa.gov/5g https://www.faa.gov/5g Lower power levels and a downward tilt on the antennas would mean less range for C-Band networks so carriers would rather not do that - especially in the US where the population is much more suburban and rural than Europe. It's possible that C-Band won't interfere even at higher power levels and even without downward antenna tilts. However, other countries have mandated greater permanent restrictions on C-Band than the US's temporary 6-month measures.
  - ajmurmann 5y ago
    AFAIK it's not the power level, but 5G in the US has a sightly higher spectrum range that's closer to that of the radio altimeters. Finland apparently even uses power levels that are do high that they'd be illegal in the US without any problems. Source: https://www.lightreading.com/5g/why-does-5g-only-pose-a-problem-for-us-airplanes/d/d-id/774629 https://www.lightreading.com/5g/why-does-5g-only-pose-a-prob...?
    - mdasen 5y ago
      The FAA doesn't cite that concern on their page, but having a 200MHz buffer in the US rather than a 380MHz buffer is a difference. As noted in the article you posted, Canada is requiring antenna down-tilting nationwide as well as exclusion zones around airports. EDIT: "an exclusion band is allowed ±10% around the band, within which the HIRF levels are very low—for radar altimeters, this spans 3.78–4.84 GHz" https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-In... So, in Europe, their C-Band ends at 3.8GHz and barely enters the range. In the US where we're going to 3.98GHz, we're well into that range. It looks like Korea's band ends at 3.7GHz which is outside the range (and definitely by 3.8GHz which is where band N78 ends; the US is using Band N77 which ends at 4.2GHz, but we've only licensed spectrum to 3.98GHz)
mmaunder 5y ago
As a reminder, Turkish Airlines flight 1951 crashed in 2009 due to a faulty radio altimeter which set the autothrottle to idle before they touched down. This isn’t hot air or some sort of power struggle between FCC and FAA. Radio altimeter interference is a big deal.
- mlindner 5y ago
  We have GPS now combined with lots of other instruments. I'm not even sure radio altimeters are even used on many aircraft anymore.
  - anamexis 5y ago
    GPS surely is not used for instrument landings, and especially not for altitude.
    - supernova87a 5y ago
      >> GPS surely is not used for instrument landings, and especially not for altitude. It is. And increasingly so in fact, as it allows more airports that don't have the resources to install and maintain ground-based equipment to have previously unavailable approaches. https://www.flyingmag.com/everything-you-need-to-know-about-rnav-gps-approaches/ https://www.flyingmag.com/everything-you-need-to-know-about-... However, it doesn't fall into exactly the same class as ILS approaches.
      - lisper 5y ago
        Instrument rated pilot here. A GPS LPV approach is essentially the same as an ILS [edit for clarification: a category 1 ILS]. It’s true that an LPV approach is classified as non precision but in practice an LPV approach is pretty much indistinguishable from a cat 1 ILS, which is classified as a precision approach.
        ketzo 5y ago
        Hm, that's interesting to me. Is it just regulators (FAA I guess?) falling behind the times? Or is the GPS version really not adequate for some use case that is only satisfied by ILS (not sure what that is but I assume it's the "gold standard" landing approach?)
FloatArtifact 5y ago
How about make free Wi-Fi mandatory at all planes above a certain passenger count? Minimizes but does not eliminate the issue.
- anamexis 5y ago
  The 5G cells in question aren’t for the people on airplanes, they’re providing service in the area of the airport.
mlindner 5y ago
Why is this only a problem in the U.S. if 5G is already active in China and many European countries. Obviously airplanes aren't falling out of the sky in those places. Seems like much ado about nothing. If anything this appears to be a FAA/FCC-induced problem where aircraft are being blocked from flying from over-zealous regulation.
- anamexis 5y ago
  Here’s a good overview why: https://www.barrons.com/amp/articles/5g-europe-airlines-51641398766 https://www.barrons.com/amp/articles/5g-europe-airlines-5164...
- p_l 5y ago
  Different frequency allocations in different countries. Nearly nothing uses the frequencies FCC wants to enable at given powers and rules.
- account4mypc 5y ago
  i'm not an expert, but it seems like other countries use lower power levels compared to what the FAA wants to use. https://www.bbc.com/news/business-60042178 https://www.bbc.com/news/business-60042178 also, and this is just my opinion, but the absence of plane crashes does not mean it's safe! some faulty things exist for years before anything happens and/or the issue is noticed.
manacit 5y ago
Some background here, if it's useful. This has been ongoing for quite some time, and has a lot of nuance to it, IMO. The following is my summary as a layperson. I've tried to quote sources wherever possible. - The FCC, which is the government agency that has ultimate control over permitting what goes on in the nation's airwaves, proposed to make additional frequencies available for mobile phone use in 2018: https://www.fcc.gov/document/37-42-ghz-public-notice-opening-gn-docket-no-18-122 https://www.fcc.gov/document/37-42-ghz-public-notice-opening... - This was going to be done by "repacking" satellite communications in the C-band (3.7 GHz to 4.2 GHz) freeing up spectrum to be used by cell carriers. - Boeing encouraged this in late 2018, mentioning that the FCC should give a 100MHz "guard band" to prevent interference with radar altimeters, which operate in the 4.2-4.4 GHz range: https://ecfsapi.fcc.gov/file/121184623679/Boeing%20C-band%20NPRM%20Reply%20Comments%2012%2011%202018%20final.pdf https://ecfsapi.fcc.gov/file/121184623679/Boeing%20C-band%20... - The FCC implemented a 220MHz "guard band" based on studies with radar altimeters, leaving more than double the guard Boeing requested. This was based on studies to evaluate any interference using this frequency (https://arstechnica.com/tech-policy/2021/11/faa-forced-delay-in-5g-rollout-despite-having-no-proof-of-harm-to-aviation/3/ https://arstechnica.com/tech-policy/2021/11/faa-forced-delay... is a good summary, there is a lot to read here). - The FCC auctioned these 280MHz of airwaves (3.7 - 3.98 GHz) last year in FCC Auction 107, garnering $81,168,677,645 in gross winning bids. As there is a delay for the incumbent spectrum users to clear their usage, ATT and Verizon were only granted the use of a combined 120MHz of spectrum in limited areas, spanning the 3.7GHz to 3.82GHz range. - Verizon and AT&T, the largest winners, have sought to deploy the spectrum they paid for in concert with the FCC rules. Specifically, this is the "lower" part of the overall winnings, which leave a minimum of ~400MHz between the top end of the broadcast frequency and the bottom end of altimeter operation. - Airline carriers and the FAA came in at the 11th hour and asked the carriers and the FCC to halt their deployment, asking for more time to be able to study whether this was safe. After a lot of back and forth, Verizon and AT&T have agreed to some power reductions around airports and runways, and voluntarily delayed the rollout of broadcasting on these frequencies twice - most recently at the beginning of the year. - The FAA has so far cleared the altimeters in ~45% of the commercial fleet: https://www.cnbc.com/2022/01/17/us-faa-clears-45percent-of-commercial-plane-fleet-after-5g-deployed.html https://www.cnbc.com/2022/01/17/us-faa-clears-45percent-of-c... Where we are now is a bit of a battle of regulators, airlines, and the cell operators that spent a significant amount of money on spectrum and capital expenditure (radios, antennas, etc) to deploy that spectrum. The FCC has cleared the use of the airwaves, but the FAA insists that not all altimeters can avoid being interfered with, and are now issuing requirements that may ban the use of these instruments in cases where they otherwise would have been necessary. This may result in landings that may not be able to happen, causing diversions, etc. The carriers and the FCC insist that over 40 countries are using this spectrum (which appears to be true) with various restrictions. In Japan, for example, there is a significantly smaller guard band of 100MHz, though the transmit power level is much lower than it will be in the USA. The carriers have voluntarily agreed to adopting restrictions around airports that roughly mirror that of France. At this point, it's unclear what happens next. I am sure I am missing a lot here (why are altimeters sensitive to broadcasts happening 400MHz away from them? are they?), and there seem to be valid concerns and issues on both sides. Ultimately, this is largely looks like embarrassing game of cat/mouse between the FCC, FAA, cell carriers and airlines.
mgraczyk 5y ago
I don't know anything about the specifics of how things got to where they are, just an outsider watching this regulatory mishap unfold. That being said ... It's quite interesting to me that the FAA may end up grounding planes rather than carriers delaying a rollout of 5G. This seems to say a lot about society and government priorities in the US. (personally I don't know enough to make an informed value judgement here, but as a technology worker I'm biased toward preferring more and better internet at the cost of harming other sectors)
- p_l 5y ago
  Ultimately you have two separate agencies that can't block each other except by appealing to higher authority. With FAA not being able to block the rollout, the only way of fulfilling their mandate is to ground planes.
- houseofzeus 5y ago
  For perspective, elsewhere in the world it's already been rolled out - in some cases with less buffer than is proposed in the US. The carriers have already delayed their rollout multiple times and the FAA still hasn't been able to prove there is an impact, rather they keep issuing defensible statements that it could have an impact despite having had years to work on this.
bunnie 5y ago
As a small time hardware maker who spends an inordinate amount of my limited resources trying to meet FCC rules, I find this infuriating. Whenever I complain about how outdated and ineffective the FCC is, the literal pushback I get is "but what about airplanes and satellites". To which I say, touche', we should all do our part to make sure we have safe airports and open channels for satellites and astronomy. Reading through a Link posted by @supernova87a (https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-In...) I have two take-aways: 1. The spectrum involved is valued in excess of $4.6bb 2. Most 5G deployments will create in excess of 100x (20dBm) the allowable interference for radar altimeters From the report, page 18 (SC-239 study results): HUGE AMOUNT OF SCENARIOS INVOLVED Every base station configuration produces harmful interference both from 5G fundamental emissions in the 3.7–3.98 GHz band and 5G spurious emissions* in the 4.2–4.4 GHz band, across virtually all operational scenarios and relative geometries between the aircraft and base station. 5G user equipment (mobile phones) that may be operating onboard aircraft were also found to exceed the safe interference limits for Usage Categories 2 and 3. I find it increasingly difficult not to be cynical about the role of the FCC with respect to public safety issues with a lapse like this. If I shipped a product into the US that had a radar altimeter interference profile like this, I'd be fined and sued into the ground a hundred times over, and I'd accept that fine and outrage because I personally couldn't live with being responsible for any planes literally falling out of the sky because they thought the ground was in the wrong place on account of my product's interference. But apparently, with enough lobbyists and money, it's an acceptable risk. It's hard for me to take the rest of the FCC's rules seriously, when they act as just another rent-collecting agency at the beck and call of lobbyists whose sole mandate is to create market barriers against small startups and imported goods, with little regard to actual safety, science, or modern technology... edit - formatting
- deleted 5y ago
  [deleted]
- mdasen 5y ago
  Verizon, AT&T, and T-Mobile spent nearly $100B for their C-Band spectrum (including relocation costs). I think that creates a lot of pressure for them to be allowed to put them to use. I'm not saying it should, just that it does. I think the US wants to be a 5G leader and it sees delays as potentially sacrificing that leadership. This might not be a real concern, but people complain anytime the US isn't the #1 in something and blame everything from politicians to capitalism. At the same time, it seems reasonable to believe that companies that have access to new 5G capabilities (speed, capacity, latency) will be able to develop and gain marketshare in new services. If American companies are going to develop the next generation of NewThings, playing around with the capabilities and limits of 5G networks in the real world will be an important part of that. We've seen different countries with different scenarios. European countries that have nearly twice the guard band; countries that are mandating down-tilts; countries that have strict power limits; countries that don't have as strict power limits and are comfortable with the risk. Personally, I don't understand why we didn't go with a phased approach. Set low power levels and a downward-tilt mandate. Ease the restrictions month by month and measure the real-world interference. Sure, maybe it means that C-Band networks aren't quite as good as they could be for 6 months, but I think predictable goals and timelines based on real-world data would satisfy cell carriers (who at least state they're confident that there will be no issue). > 5G user equipment (mobile phones) that may be operating onboard aircraft were also found to exceed the safe interference limits for Usage Categories 2 and 3. In some ways, this is what I'm more worried about. People have a smug sense that their phone can't interfere with planes and that regulations around cell phone use on planes are just BS. While the FAA/FCC will be able to enforce restrictions on cell carriers, it's going to be impossible to enforce it on users in-flight. You can't effectively make sure that devices are in airplane mode. Flight attendants can't see the indicator on my device (or lack thereof) when quickly walking up and down the aisles. If C-Band causes interference with radio altimeters, I can see the FAA and FCC adding exclusion areas around airports, mandating antenna down-tilts and lower power levels in certain areas, and other mitigations. I think it's reasonably easy to get AT&T and Verizon to implement those and reasonably easy to check compliance. They might fight it, but it's still reasonably easy. I think if C-Band phones cause interference, it's going to be a problem since we simply won't be able to police everyone on planes.
drmpeg 5y ago
For those who want to do a deep dive, here's the altimeter test data. https://ecfsapi.fcc.gov/file/12070826325320/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%201.pdf https://ecfsapi.fcc.gov/file/12070826325320/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/12070826325320/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%202.pdf https://ecfsapi.fcc.gov/file/12070826325320/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/1207722514473/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%203.pdf https://ecfsapi.fcc.gov/file/1207722514473/AVSI%20AFE76s2%20... https://ecfsapi.fcc.gov/file/1207722514473/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%204.pdf https://ecfsapi.fcc.gov/file/1207722514473/AVSI%20AFE76s2%20... https://ecfsapi.fcc.gov/file/12072133610936/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%205.pdf https://ecfsapi.fcc.gov/file/12072133610936/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/12072133610936/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%206.pdf https://ecfsapi.fcc.gov/file/12072133610936/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/1207848621283/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%207.pdf https://ecfsapi.fcc.gov/file/1207848621283/AVSI%20AFE76s2%20... https://ecfsapi.fcc.gov/file/1207848621283/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%208.pdf https://ecfsapi.fcc.gov/file/1207848621283/AVSI%20AFE76s2%20... https://ecfsapi.fcc.gov/file/12221132030652/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20II%20Part%201%20of%202.pdf https://ecfsapi.fcc.gov/file/12221132030652/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/12221132030652/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20II%20Part%202%20of%202.pdf https://ecfsapi.fcc.gov/file/12221132030652/AVSI%20AFE76s2%2...
- dhimes 5y ago
  Thank you. In all these discussions what's curiously overlooked is exactly what the testing revealed.
bbulkow 5y ago
The only real question, imho, is why this wasn't understood when the frequency was auctioned. If we needed more guard band, we needed more guard band. If antennas point to the sky, don't use the close frequencies. Any answers?
- houseofzeus 5y ago
  The information provided at the time indicated 100 Mhz buffer would be enough, which the FCC doubled. Now the FAA are saying that in fact even 200+ Mhz buffer outside of the frequency that was ever allocated for this purpose is not enough for some altimeters.
malwarebytess 5y ago
I'm unable to understand whether this is something to genuinely be worried about, or if it's red tape. It sounds kind of hysterical, sort of like programmers worrying about cosmic rays. Is this something that's deeply improbable and insignificant, or is it something that is guaranteed to happen eventually even though it is unlikely?
- foxfluff 5y ago
  > is it something that is guaranteed to happen eventually even though it is unlikely? No. If you have an instrument operating at 4.3GHz and it suffers interference from radios operating at 3.9GHz, it indicates inadequate filtering. That's a design issue, not an event with a statistical chance of happening no matter what.
EMM_386 5y ago
For most here, this will be familiar, but what this is affecting is the radar altimeter. You've probably seen the videos where the system will do an audio countdown "100, 50, 40, 30, 20, 10, retard, retard" [Airbus]. That system is critically important in zero-vis triple-autopilot landings. You don't want cell phones screwing that phase up. https://youtu.be/UV_vWtAJIow?t=142 https://youtu.be/UV_vWtAJIow?t=142
- onphonenow 5y ago
  You don't want to be using a radar altimeter that can't handle a 200 Mhz guard band at 20 feet. That is seriously messed up on.the plane MFG front, not cell phone front.
  - BenjiWiebe 5y ago
    This is what I can't figure out. 200Mhz is a large guard band, and it isn't hard to design filters for that at all. Now, single digit khz filters at RF frequencies, that's difficult. But not 200Mhz! I guess the radio altimeter manufacturers just figured, "there's a large guard band, why play it safe and put in filters", or what?
    - meepmorp 5y ago
      The odd part is that Boeing originally proposed a 100MHz guard band. It's literally twice the headroom a major manufacturer suggested for this purpose.
      - onphonenow 5y ago
        Even weirder, the critical phase of all this is generally during airport approach and landing so at pretty low altitudes. In terms of reception if you can't design something to tell you if you are 100 / 50 / 20 feet off the ground with a 200Mhz guard band ON BOTH SIDES that is insane (600Mhz total bandwidth to tell me if I'm 20 feet off the ground??). If you are ham these bandwidth needs are just nuts. And this has been 10 years in the making. The FCC must just be rolling their eyes - why didn't FAA do something earlier. We have coverage during landing phase with a localizer and glideslope as well, plus RNAV / WAAS enhanced GPS options etc etc + the mark 1 eyeball. Somehow in the last year the US has just become helpless to solve problems. Hard to beleive folks flew across the ocean with no GPS or moving map etc etc.
fnord77 5y ago
I'm baffled why 5G was approved and deployed before there were safety verifications with aircraft
coldcode 5y ago
The only opinions that matter in the end is the pilots', I want to hear from them. Are you willing to fly a loaded jumbo into an airport with a flaky altimeter during a zero visibility landing? Airline and manufacturing execs and the FAA/FTC are not risking their lives every day (although it might be eye opening if they would be willing to all cram into a plane and land in a thunderstorm at an airport with 5G towers at the end of the runway).
- _moof 5y ago
  Pilots don't know anything about RF beyond "VHF is line-of-sight" and "use HF over the ocean." I'm inclined to listen to their (our) concerns but we don't have some special understanding of the underlying technical issues.
dhimes 5y ago
Here's the list of the 50 airports with 5G buffer zones. At least the Feds will be eating their own dog food: Neither Reagan National nor Dulles are on the list (nor is Baltimore-Washington International, for that matter). Edit: The link is a pdf. https://www.faa.gov/sites/faa.gov/files/2022-01/50%20Airports%20with%205G%20Buffer.pdf https://www.faa.gov/sites/faa.gov/files/2022-01/50%20Airport...
- dhimes 5y ago
  Update: Reagan National apparently doesn't have a tower nearby, so it doesn't need to be on the list.
kjellsbells 5y ago
Honestly I still dont quite get it. The FCC allocated 3.7 to 3.98Ghz for cellular wireless. Then there is 20Mhz of guard band to 4.0GHz. Then there is satelite from 4.0 to 4.2GHz. And then, finally, the altimeter fequency band from 4.2 to 4.4GHz. So the two uses appear quite far apart in the frequency domain. Do signals get sent out on the wrong frequency or something? What does it mean to interfere? And, assuming something bad is happening, why?
- bbulkow 5y ago
  Yeah, and more importantly, was the equipment designed to exist with that much guard band? And isn't the cell equipment specified to throw off only a certain amount of harmonics, or whatever the out of band noise would be? This seems like without either a massive engineering mistake or a tempest in a teapot?
- kloch 5y ago
  It does seem like an overreaction to me but there is a big difference in cell towers and satellite uplinks/downlinks Radio towers (sites) have widely varying quality control of their tenant's installations. Other transmitters can mix and amplify signals from other carriers without well designed and maintained RF filtering on each and every antenna. The more transmitters at a site the more carrier frequencies that can contribute to the mixing, and the more opportunities for poor or broken RF filters. At some busy sites there is almost nothing you can do to prevent this. Anything on the tower that acts like a diode can cause mixing, even without being amplified by another transmitter. This usually just harms other receivers at the site however. But an airplane flying close by could theoretically be affected depending on how close it is.
  - NovemberWhiskey 5y ago
    >It does seem like an overreaction to me but there is a big difference in cell towers and satellite uplinks/downlinks N.B. as far as I know, the portion of the C-band that's in question was allocated for satellite downlinks; uplinks were over 6GHz. With that in mind, there is indeed a Big Difference between a satellite in orbit radiating downwards, and a 5G beam forming installation on the ground potentially radiating upwards.
account4mypc 5y ago
Seems like: - downside of delaying 5g is slightly longer download speeds (?) - downside of interference is planes might crash (!) why not just give the FAA all the time it wants
- reaperducer 5y ago
  why not just give the FAA all the time it wants For the same reason we allow multiple private companies in multiple countries to pollute the skies with (eventually) millions of satellites: Sacred, holy, internet. Without which all human civilization could crumble to dust and blow away.

159 points by neom 5y ago

Note that the adjacent band interference concern is with radio altimeters, not sensitive pressure altimeters. (The article makes this clear later, but not on the first mention of altimeter.)

largbae 5y ago
While your statement is true, this does not diminish the importance of radar altimeters: the barometer is not specific to the landing site terrain like radar is, but rather related to distance above sea level. In low visibility, radar is the only way to tell how close to touchdown you are.
- mlindner 5y ago
  This isn't really true. Before landing an aircraft gets the pressure altitude of the airport and sets their altimeters with that as a reference before landing. It's a very common procedure. These are updated regularly.
  - snuxoll 5y ago
    While it’s true the barometric pressure is included in the ATIS information every plane will get before landing, pilots also rely heavily on GPWS callouts when landing and those are provided by radio altimeter and not the barometric one. It’s not an issue to land without them, and some approaches and emergency checklists require you turn them off to allow other messages to be announced without GPWS callouts taking priority - but it’s ideal to have them for sure.
  - p_l 5y ago
    Radar altimeter is used for low-visibility approach collision avoidance and for triggering events in last few meters on AUTOLAND-equipped planes (this is rarer in USA but common for example in UK airports). The main glide slope is managed with barometric altimeter, sure, but that one lacks the detailed resolution of the radar altimeter and can't detect ground - it can only follow the difference from specific pressure according to standard model atmosphere.

Victerius 5y ago

US airlines warn C-Band 5G could cause 'catastrophic disruption' https://www.engadget.com/us-airlines-warning-letter-211919932.html https://www.engadget.com/us-airlines-warning-letter-21191993...

mlindner 5y ago
Better title "US airlines warn government ineptness in slow approval of regulations could cause 'catastrophic disruption'". This is a regulatory failure not a technological one.

JohnJamesRambo 5y ago

Has anyone ever had awesome lte and said “I need more bandwidth” on their phone? Idk I just don’t see the need for 5g but I’m definitely not a phone power user.

girvo 5y ago
Yes, but only in the context of tethering a more powerful device personally.
kevml 5y ago
Having a mobile hotspot has allowed me to work just about anywhere I want to. The more bandwidth the better!
LeoPanthera 5y ago
I'm going to guess that you have home broadband internet that is reasonably fast and reliable.
- snowgrove 5y ago
  But that’s just it. How is 5G-based rural broadband a significant improvement on LTE-based service?
  - vel0city 5y ago
    More customers being able to be served from the same number of towers with better per-customer performance. One challenge in rural broadband deployments is there are only so many good locations for the carrier to actually stick antennas. Maybe a water tower or two, you might get lucky and have some tall radio tower at the edge of town. So then all the customers in the area are essentially sharing a single tower, all needing to point their CPE to that one point. You can only slice the tower up into some number of sectors and once you hit that point the tower is saturated. Every additional customer is now diminishing the service for every other customer. Having better spectral efficiency per sector means you can service more customers, have better service per customer, or even both depending on how you balance it.

Aloha 5y ago

I am highly skeptical that we need additional 5G spectrum. We're not even fully using the spectrum that has already been auctioned.

username190 5y ago
Carriers are not currently using the spectrum that they gained in Auction 107, because of the issues that this article mentions. Their agreement with the FAA has given Verizon and AT&T the go-ahead to begin operations on this spectrum tomorrow (outside of existing FCC-approved test sites, which have been operating for months). Which spectrum are you referring to that carriers have purchased and not deployed, if not 3.7–3.9 GHz?

mrhands556 5y ago

——

kbaker 5y ago
"Passengers should check with their airlines if weather is forecast at a destination where 5G interference is possible," the FAA said Sunday. It only affects landing in bad weather.
- supernova87a 5y ago
  Really, they're going to ask passengers and airlines to publish and follow up to find out if this is gonna be an issue on their particular flight? Passsengers should also be sure to look up all the latest airworthiness directives and advisory circulars for the plane and engine type they're going to fly as well. And get the crew medical reports just to be sure. Hell, maybe passengers should just as well check that the aircraft manufacturers haven't modified any critical safety systems that the FAA should've been regulating.
  - deleted 5y ago
    [deleted]

supernova87a 5y ago

From the most barebones news articles I read about the topic (and in this country they generally all are), this has already been rolled out in other countries to no great issue? Here it's a turf/jurisdictional spat between FAA and FCC over not having gotten all the approvals through the desired channels in time for rollout? Although, I guess papers like this detail the issue more carefully: https://ecfsapi.fcc.gov/file/7021340930.pdf https://ecfsapi.fcc.gov/file/7021340930.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-In...

mdasen 5y ago
The FAA has noted that in other countries there were mandates for lower power levels for 5G and that the antennas be pointed down toward the earth so that they interfered less. https://www.faa.gov/5g https://www.faa.gov/5g Lower power levels and a downward tilt on the antennas would mean less range for C-Band networks so carriers would rather not do that - especially in the US where the population is much more suburban and rural than Europe. It's possible that C-Band won't interfere even at higher power levels and even without downward antenna tilts. However, other countries have mandated greater permanent restrictions on C-Band than the US's temporary 6-month measures.
- ajmurmann 5y ago
  AFAIK it's not the power level, but 5G in the US has a sightly higher spectrum range that's closer to that of the radio altimeters. Finland apparently even uses power levels that are do high that they'd be illegal in the US without any problems. Source: https://www.lightreading.com/5g/why-does-5g-only-pose-a-problem-for-us-airplanes/d/d-id/774629 https://www.lightreading.com/5g/why-does-5g-only-pose-a-prob...?
  - mdasen 5y ago
    The FAA doesn't cite that concern on their page, but having a 200MHz buffer in the US rather than a 380MHz buffer is a difference. As noted in the article you posted, Canada is requiring antenna down-tilting nationwide as well as exclusion zones around airports. EDIT: "an exclusion band is allowed ±10% around the band, within which the HIRF levels are very low—for radar altimeters, this spans 3.78–4.84 GHz" https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-In... So, in Europe, their C-Band ends at 3.8GHz and barely enters the range. In the US where we're going to 3.98GHz, we're well into that range. It looks like Korea's band ends at 3.7GHz which is outside the range (and definitely by 3.8GHz which is where band N78 ends; the US is using Band N77 which ends at 4.2GHz, but we've only licensed spectrum to 3.98GHz)

mmaunder 5y ago

As a reminder, Turkish Airlines flight 1951 crashed in 2009 due to a faulty radio altimeter which set the autothrottle to idle before they touched down. This isn’t hot air or some sort of power struggle between FCC and FAA. Radio altimeter interference is a big deal.

mlindner 5y ago
We have GPS now combined with lots of other instruments. I'm not even sure radio altimeters are even used on many aircraft anymore.
- anamexis 5y ago
  GPS surely is not used for instrument landings, and especially not for altitude.
  - supernova87a 5y ago
    >> GPS surely is not used for instrument landings, and especially not for altitude. It is. And increasingly so in fact, as it allows more airports that don't have the resources to install and maintain ground-based equipment to have previously unavailable approaches. https://www.flyingmag.com/everything-you-need-to-know-about-rnav-gps-approaches/ https://www.flyingmag.com/everything-you-need-to-know-about-... However, it doesn't fall into exactly the same class as ILS approaches.
    - lisper 5y ago
      Instrument rated pilot here. A GPS LPV approach is essentially the same as an ILS [edit for clarification: a category 1 ILS]. It’s true that an LPV approach is classified as non precision but in practice an LPV approach is pretty much indistinguishable from a cat 1 ILS, which is classified as a precision approach.
      - ketzo 5y ago
        Hm, that's interesting to me. Is it just regulators (FAA I guess?) falling behind the times? Or is the GPS version really not adequate for some use case that is only satisfied by ILS (not sure what that is but I assume it's the "gold standard" landing approach?)

FloatArtifact 5y ago

How about make free Wi-Fi mandatory at all planes above a certain passenger count? Minimizes but does not eliminate the issue.

anamexis 5y ago
The 5G cells in question aren’t for the people on airplanes, they’re providing service in the area of the airport.

mlindner 5y ago

Why is this only a problem in the U.S. if 5G is already active in China and many European countries. Obviously airplanes aren't falling out of the sky in those places. Seems like much ado about nothing. If anything this appears to be a FAA/FCC-induced problem where aircraft are being blocked from flying from over-zealous regulation.

anamexis 5y ago
Here’s a good overview why: https://www.barrons.com/amp/articles/5g-europe-airlines-51641398766 https://www.barrons.com/amp/articles/5g-europe-airlines-5164...
p_l 5y ago
Different frequency allocations in different countries. Nearly nothing uses the frequencies FCC wants to enable at given powers and rules.
account4mypc 5y ago
i'm not an expert, but it seems like other countries use lower power levels compared to what the FAA wants to use. https://www.bbc.com/news/business-60042178 https://www.bbc.com/news/business-60042178 also, and this is just my opinion, but the absence of plane crashes does not mean it's safe! some faulty things exist for years before anything happens and/or the issue is noticed.

manacit 5y ago

Some background here, if it's useful. This has been ongoing for quite some time, and has a lot of nuance to it, IMO. The following is my summary as a layperson. I've tried to quote sources wherever possible. - The FCC, which is the government agency that has ultimate control over permitting what goes on in the nation's airwaves, proposed to make additional frequencies available for mobile phone use in 2018: https://www.fcc.gov/document/37-42-ghz-public-notice-opening-gn-docket-no-18-122 https://www.fcc.gov/document/37-42-ghz-public-notice-opening... - This was going to be done by "repacking" satellite communications in the C-band (3.7 GHz to 4.2 GHz) freeing up spectrum to be used by cell carriers. - Boeing encouraged this in late 2018, mentioning that the FCC should give a 100MHz "guard band" to prevent interference with radar altimeters, which operate in the 4.2-4.4 GHz range: https://ecfsapi.fcc.gov/file/121184623679/Boeing%20C-band%20NPRM%20Reply%20Comments%2012%2011%202018%20final.pdf https://ecfsapi.fcc.gov/file/121184623679/Boeing%20C-band%20... - The FCC implemented a 220MHz "guard band" based on studies with radar altimeters, leaving more than double the guard Boeing requested. This was based on studies to evaluate any interference using this frequency (https://arstechnica.com/tech-policy/2021/11/faa-forced-delay-in-5g-rollout-despite-having-no-proof-of-harm-to-aviation/3/ https://arstechnica.com/tech-policy/2021/11/faa-forced-delay... is a good summary, there is a lot to read here). - The FCC auctioned these 280MHz of airwaves (3.7 - 3.98 GHz) last year in FCC Auction 107, garnering $81,168,677,645 in gross winning bids. As there is a delay for the incumbent spectrum users to clear their usage, ATT and Verizon were only granted the use of a combined 120MHz of spectrum in limited areas, spanning the 3.7GHz to 3.82GHz range. - Verizon and AT&T, the largest winners, have sought to deploy the spectrum they paid for in concert with the FCC rules. Specifically, this is the "lower" part of the overall winnings, which leave a minimum of ~400MHz between the top end of the broadcast frequency and the bottom end of altimeter operation. - Airline carriers and the FAA came in at the 11th hour and asked the carriers and the FCC to halt their deployment, asking for more time to be able to study whether this was safe. After a lot of back and forth, Verizon and AT&T have agreed to some power reductions around airports and runways, and voluntarily delayed the rollout of broadcasting on these frequencies twice - most recently at the beginning of the year. - The FAA has so far cleared the altimeters in ~45% of the commercial fleet: https://www.cnbc.com/2022/01/17/us-faa-clears-45percent-of-commercial-plane-fleet-after-5g-deployed.html https://www.cnbc.com/2022/01/17/us-faa-clears-45percent-of-c... Where we are now is a bit of a battle of regulators, airlines, and the cell operators that spent a significant amount of money on spectrum and capital expenditure (radios, antennas, etc) to deploy that spectrum. The FCC has cleared the use of the airwaves, but the FAA insists that not all altimeters can avoid being interfered with, and are now issuing requirements that may ban the use of these instruments in cases where they otherwise would have been necessary. This may result in landings that may not be able to happen, causing diversions, etc. The carriers and the FCC insist that over 40 countries are using this spectrum (which appears to be true) with various restrictions. In Japan, for example, there is a significantly smaller guard band of 100MHz, though the transmit power level is much lower than it will be in the USA. The carriers have voluntarily agreed to adopting restrictions around airports that roughly mirror that of France. At this point, it's unclear what happens next. I am sure I am missing a lot here (why are altimeters sensitive to broadcasts happening 400MHz away from them? are they?), and there seem to be valid concerns and issues on both sides. Ultimately, this is largely looks like embarrassing game of cat/mouse between the FCC, FAA, cell carriers and airlines.

mgraczyk 5y ago

I don't know anything about the specifics of how things got to where they are, just an outsider watching this regulatory mishap unfold. That being said ... It's quite interesting to me that the FAA may end up grounding planes rather than carriers delaying a rollout of 5G. This seems to say a lot about society and government priorities in the US. (personally I don't know enough to make an informed value judgement here, but as a technology worker I'm biased toward preferring more and better internet at the cost of harming other sectors)

p_l 5y ago
Ultimately you have two separate agencies that can't block each other except by appealing to higher authority. With FAA not being able to block the rollout, the only way of fulfilling their mandate is to ground planes.
houseofzeus 5y ago
For perspective, elsewhere in the world it's already been rolled out - in some cases with less buffer than is proposed in the US. The carriers have already delayed their rollout multiple times and the FAA still hasn't been able to prove there is an impact, rather they keep issuing defensible statements that it could have an impact despite having had years to work on this.

bunnie 5y ago

As a small time hardware maker who spends an inordinate amount of my limited resources trying to meet FCC rules, I find this infuriating. Whenever I complain about how outdated and ineffective the FCC is, the literal pushback I get is "but what about airplanes and satellites". To which I say, touche', we should all do our part to make sure we have safe airports and open channels for satellites and astronomy. Reading through a Link posted by @supernova87a (https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-In...) I have two take-aways: 1. The spectrum involved is valued in excess of $4.6bb 2. Most 5G deployments will create in excess of 100x (20dBm) the allowable interference for radar altimeters From the report, page 18 (SC-239 study results): HUGE AMOUNT OF SCENARIOS INVOLVED Every base station configuration produces harmful interference both from 5G fundamental emissions in the 3.7–3.98 GHz band and 5G spurious emissions* in the 4.2–4.4 GHz band, across virtually all operational scenarios and relative geometries between the aircraft and base station. 5G user equipment (mobile phones) that may be operating onboard aircraft were also found to exceed the safe interference limits for Usage Categories 2 and 3. I find it increasingly difficult not to be cynical about the role of the FCC with respect to public safety issues with a lapse like this. If I shipped a product into the US that had a radar altimeter interference profile like this, I'd be fined and sued into the ground a hundred times over, and I'd accept that fine and outrage because I personally couldn't live with being responsible for any planes literally falling out of the sky because they thought the ground was in the wrong place on account of my product's interference. But apparently, with enough lobbyists and money, it's an acceptable risk. It's hard for me to take the rest of the FCC's rules seriously, when they act as just another rent-collecting agency at the beck and call of lobbyists whose sole mandate is to create market barriers against small startups and imported goods, with little regard to actual safety, science, or modern technology... edit - formatting

deleted 5y ago
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mdasen 5y ago
Verizon, AT&T, and T-Mobile spent nearly $100B for their C-Band spectrum (including relocation costs). I think that creates a lot of pressure for them to be allowed to put them to use. I'm not saying it should, just that it does. I think the US wants to be a 5G leader and it sees delays as potentially sacrificing that leadership. This might not be a real concern, but people complain anytime the US isn't the #1 in something and blame everything from politicians to capitalism. At the same time, it seems reasonable to believe that companies that have access to new 5G capabilities (speed, capacity, latency) will be able to develop and gain marketshare in new services. If American companies are going to develop the next generation of NewThings, playing around with the capabilities and limits of 5G networks in the real world will be an important part of that. We've seen different countries with different scenarios. European countries that have nearly twice the guard band; countries that are mandating down-tilts; countries that have strict power limits; countries that don't have as strict power limits and are comfortable with the risk. Personally, I don't understand why we didn't go with a phased approach. Set low power levels and a downward-tilt mandate. Ease the restrictions month by month and measure the real-world interference. Sure, maybe it means that C-Band networks aren't quite as good as they could be for 6 months, but I think predictable goals and timelines based on real-world data would satisfy cell carriers (who at least state they're confident that there will be no issue). > 5G user equipment (mobile phones) that may be operating onboard aircraft were also found to exceed the safe interference limits for Usage Categories 2 and 3. In some ways, this is what I'm more worried about. People have a smug sense that their phone can't interfere with planes and that regulations around cell phone use on planes are just BS. While the FAA/FCC will be able to enforce restrictions on cell carriers, it's going to be impossible to enforce it on users in-flight. You can't effectively make sure that devices are in airplane mode. Flight attendants can't see the indicator on my device (or lack thereof) when quickly walking up and down the aisles. If C-Band causes interference with radio altimeters, I can see the FAA and FCC adding exclusion areas around airports, mandating antenna down-tilts and lower power levels in certain areas, and other mitigations. I think it's reasonably easy to get AT&T and Verizon to implement those and reasonably easy to check compliance. They might fight it, but it's still reasonably easy. I think if C-Band phones cause interference, it's going to be a problem since we simply won't be able to police everyone on planes.

drmpeg 5y ago

For those who want to do a deep dive, here's the altimeter test data. https://ecfsapi.fcc.gov/file/12070826325320/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%201.pdf https://ecfsapi.fcc.gov/file/12070826325320/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/12070826325320/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%202.pdf https://ecfsapi.fcc.gov/file/12070826325320/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/1207722514473/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%203.pdf https://ecfsapi.fcc.gov/file/1207722514473/AVSI%20AFE76s2%20... https://ecfsapi.fcc.gov/file/1207722514473/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%204.pdf https://ecfsapi.fcc.gov/file/1207722514473/AVSI%20AFE76s2%20... https://ecfsapi.fcc.gov/file/12072133610936/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%205.pdf https://ecfsapi.fcc.gov/file/12072133610936/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/12072133610936/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%206.pdf https://ecfsapi.fcc.gov/file/12072133610936/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/1207848621283/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%207.pdf https://ecfsapi.fcc.gov/file/1207848621283/AVSI%20AFE76s2%20... https://ecfsapi.fcc.gov/file/1207848621283/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20I-Part%208.pdf https://ecfsapi.fcc.gov/file/1207848621283/AVSI%20AFE76s2%20... https://ecfsapi.fcc.gov/file/12221132030652/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20II%20Part%201%20of%202.pdf https://ecfsapi.fcc.gov/file/12221132030652/AVSI%20AFE76s2%2... https://ecfsapi.fcc.gov/file/12221132030652/AVSI%20AFE76s2%20Report%20-%20ITMs%20Vol%20II%20Part%202%20of%202.pdf https://ecfsapi.fcc.gov/file/12221132030652/AVSI%20AFE76s2%2...

dhimes 5y ago
Thank you. In all these discussions what's curiously overlooked is exactly what the testing revealed.

bbulkow 5y ago

The only real question, imho, is why this wasn't understood when the frequency was auctioned. If we needed more guard band, we needed more guard band. If antennas point to the sky, don't use the close frequencies. Any answers?

houseofzeus 5y ago
The information provided at the time indicated 100 Mhz buffer would be enough, which the FCC doubled. Now the FAA are saying that in fact even 200+ Mhz buffer outside of the frequency that was ever allocated for this purpose is not enough for some altimeters.

malwarebytess 5y ago

I'm unable to understand whether this is something to genuinely be worried about, or if it's red tape. It sounds kind of hysterical, sort of like programmers worrying about cosmic rays. Is this something that's deeply improbable and insignificant, or is it something that is guaranteed to happen eventually even though it is unlikely?

foxfluff 5y ago
> is it something that is guaranteed to happen eventually even though it is unlikely? No. If you have an instrument operating at 4.3GHz and it suffers interference from radios operating at 3.9GHz, it indicates inadequate filtering. That's a design issue, not an event with a statistical chance of happening no matter what.

EMM_386 5y ago

For most here, this will be familiar, but what this is affecting is the radar altimeter. You've probably seen the videos where the system will do an audio countdown "100, 50, 40, 30, 20, 10, retard, retard" [Airbus]. That system is critically important in zero-vis triple-autopilot landings. You don't want cell phones screwing that phase up. https://youtu.be/UV_vWtAJIow?t=142 https://youtu.be/UV_vWtAJIow?t=142

onphonenow 5y ago
You don't want to be using a radar altimeter that can't handle a 200 Mhz guard band at 20 feet. That is seriously messed up on.the plane MFG front, not cell phone front.
- BenjiWiebe 5y ago
  This is what I can't figure out. 200Mhz is a large guard band, and it isn't hard to design filters for that at all. Now, single digit khz filters at RF frequencies, that's difficult. But not 200Mhz! I guess the radio altimeter manufacturers just figured, "there's a large guard band, why play it safe and put in filters", or what?
  - meepmorp 5y ago
    The odd part is that Boeing originally proposed a 100MHz guard band. It's literally twice the headroom a major manufacturer suggested for this purpose.
    - onphonenow 5y ago
      Even weirder, the critical phase of all this is generally during airport approach and landing so at pretty low altitudes. In terms of reception if you can't design something to tell you if you are 100 / 50 / 20 feet off the ground with a 200Mhz guard band ON BOTH SIDES that is insane (600Mhz total bandwidth to tell me if I'm 20 feet off the ground??). If you are ham these bandwidth needs are just nuts. And this has been 10 years in the making. The FCC must just be rolling their eyes - why didn't FAA do something earlier. We have coverage during landing phase with a localizer and glideslope as well, plus RNAV / WAAS enhanced GPS options etc etc + the mark 1 eyeball. Somehow in the last year the US has just become helpless to solve problems. Hard to beleive folks flew across the ocean with no GPS or moving map etc etc.

fnord77 5y ago

I'm baffled why 5G was approved and deployed before there were safety verifications with aircraft

coldcode 5y ago

The only opinions that matter in the end is the pilots', I want to hear from them. Are you willing to fly a loaded jumbo into an airport with a flaky altimeter during a zero visibility landing? Airline and manufacturing execs and the FAA/FTC are not risking their lives every day (although it might be eye opening if they would be willing to all cram into a plane and land in a thunderstorm at an airport with 5G towers at the end of the runway).

_moof 5y ago
Pilots don't know anything about RF beyond "VHF is line-of-sight" and "use HF over the ocean." I'm inclined to listen to their (our) concerns but we don't have some special understanding of the underlying technical issues.

dhimes 5y ago

Here's the list of the 50 airports with 5G buffer zones. At least the Feds will be eating their own dog food: Neither Reagan National nor Dulles are on the list (nor is Baltimore-Washington International, for that matter). Edit: The link is a pdf. https://www.faa.gov/sites/faa.gov/files/2022-01/50%20Airports%20with%205G%20Buffer.pdf https://www.faa.gov/sites/faa.gov/files/2022-01/50%20Airport...

dhimes 5y ago
Update: Reagan National apparently doesn't have a tower nearby, so it doesn't need to be on the list.

kjellsbells 5y ago

Honestly I still dont quite get it. The FCC allocated 3.7 to 3.98Ghz for cellular wireless. Then there is 20Mhz of guard band to 4.0GHz. Then there is satelite from 4.0 to 4.2GHz. And then, finally, the altimeter fequency band from 4.2 to 4.4GHz. So the two uses appear quite far apart in the frequency domain. Do signals get sent out on the wrong frequency or something? What does it mean to interfere? And, assuming something bad is happening, why?

bbulkow 5y ago
Yeah, and more importantly, was the equipment designed to exist with that much guard band? And isn't the cell equipment specified to throw off only a certain amount of harmonics, or whatever the out of band noise would be? This seems like without either a massive engineering mistake or a tempest in a teapot?
kloch 5y ago
It does seem like an overreaction to me but there is a big difference in cell towers and satellite uplinks/downlinks Radio towers (sites) have widely varying quality control of their tenant's installations. Other transmitters can mix and amplify signals from other carriers without well designed and maintained RF filtering on each and every antenna. The more transmitters at a site the more carrier frequencies that can contribute to the mixing, and the more opportunities for poor or broken RF filters. At some busy sites there is almost nothing you can do to prevent this. Anything on the tower that acts like a diode can cause mixing, even without being amplified by another transmitter. This usually just harms other receivers at the site however. But an airplane flying close by could theoretically be affected depending on how close it is.
- NovemberWhiskey 5y ago
  >It does seem like an overreaction to me but there is a big difference in cell towers and satellite uplinks/downlinks N.B. as far as I know, the portion of the C-band that's in question was allocated for satellite downlinks; uplinks were over 6GHz. With that in mind, there is indeed a Big Difference between a satellite in orbit radiating downwards, and a 5G beam forming installation on the ground potentially radiating upwards.

account4mypc 5y ago

Seems like: - downside of delaying 5g is slightly longer download speeds (?) - downside of interference is planes might crash (!) why not just give the FAA all the time it wants

reaperducer 5y ago
why not just give the FAA all the time it wants For the same reason we allow multiple private companies in multiple countries to pollute the skies with (eventually) millions of satellites: Sacred, holy, internet. Without which all human civilization could crumble to dust and blow away.