6 ms·

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 t

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)
    - DannyBee 5y ago
      200 is already crazy large. Super crazy. The original request from Boeing was only 100 These altimeters are dangerously defective if they need a 400mhz guard band. That is nuts
      - indrora 5y ago
        you're actually looking at the intersection of three problems: * LTE is very noisy (it has echos in its sidebands for up to 100Mhz) * low-frequency LTE is *loud* -- punch through mountains loud. * These altimiters are doing the RF equivalent of looking for a needle in a haystream While FCC Part15 says "accept any/produce as little as possible", much of this comes down to the physics of RF.
  - berkut 5y ago
    I've read it's multiple concerns: https://www.faa.gov/5g https://www.faa.gov/5g https://www.airlines.org/5g-frequently-asked-questions/ https://www.airlines.org/5g-frequently-asked-questions/ In Europe, the power output seems to be ~2.5 time lower, there's a bigger frequency separation in Europe, the 5G towers are placed further away from approaches, and the antennas have to point downwards.
  - gormandizer 5y ago
    C-Band in the US is rolling out in 2 phases, the first uses spectrum from 3.7 to 3.8 GHz. The second - in roughly two years - adds the remaining 3.8 to 3.98 GHz. So for the first two years the spectrum used by C-Band 5G in the US is essentially the same as in most of the rest of the world. https://www.commscope.com/blog/2021/maximizing-c-band-deployments-with-commscope/ https://www.commscope.com/blog/2021/maximizing-c-band-deploy...
  - Terry_Roll 5y ago
    Doesnt this show that some country's dont plan ahead that much or different elements of Govt are too disconnected to work cohesively? Still, this chatter will no doubt give some loon some ideas on how to bring down a plane or mess around with the flight patterns at busy airports.
    - kolanos 5y ago
      > Doesnt this show that some country's dont plan ahead that much or different elements of Govt are too disconnected to work cohesively? This can be a feature, not necessarily a bug. There are plenty of examples of government central planning and cohesion going very wrong.
    - MomoXenosaga 5y ago
      Radio spectrum was decided somewhere in the 1950s and as I understand it the US military owns most of it. It's difficult to plan ahead for future technology.
      - Terry_Roll 5y ago
        Oh I dont know, I think other countries seem to be making less of a hash of it, compared to the US. And does it really matter if the US Mil own the spectrum? Thats like me saying the UK Govt owns the spectrum, they should still both be subjected to the court of law, if the laws are fit for purpose in the first place!
- kyrra 5y ago
  I thought that AT&t and Verizon offered to do lower power towers near airports. The story from November seems to say as much. https://www.theverge.com/2021/11/24/22801008/verizon-att-midband-5g-c-band-lower-power-six-months https://www.theverge.com/2021/11/24/22801008/verizon-att-mid...
- RNCTX 5y ago
  All cell phone towers seem to be aimed toward the ground. I've flown a GA aircraft all around the lower 48, and only get a cell phone signal briefly when flying directly over a cell tower.
  - Fatnino 5y ago
    Naturally. Why would a cell carrier want to expend energy beaming signal into space? That said, you do get the occasional misaligned antenna or weird bounce off terrain that gets you signal midflight for a minute.
    - barcoder 5y ago
      How easy is it to report those type of issues?
      - krisoft 5y ago
        What do you like to report? That cell signal was available somewhere?
      - dylan604 5y ago
        make a phone call, and let the big data folks raise eyebrows when they see the elevation the call was made.
  - jcalvinowens 5y ago
    It's really regional. I get 5 bars pretty much anywhere below 5000ft in the bay area.
    - _moof 5y ago
      Yep, I get signal up to about 3000' AGL where I am.
      - supernova87a 5y ago
        Well, given that the possible range to a cell tower is about 35 km / 20 mi (max, an absolute limitation of how the GSM/timing is done), it's very plausible that even if cell broadcast antennas are generally pointed down + flat with the horizon, you're gonna get some signal from some antenna in the distance.
Spooky23 5y ago
tedunangst 5y ago
The US seems stuck in a holding pattern of "two more weeks, two more weeks" without addressing any of the potential workarounds like power, directional antennas, or even blackout zones. From what I've read, the airlines and FAA haven't really put forward any proposals for compromise, like leaving towers off near airports. It's always no 5G anywhere until they've had more time, as if the planned 5G deployment came as a total surprise. Or why can't the towers be turned off in bad weather only?
- houseofzeus 5y ago
  My read is either the FAA or the airlines or both want money re-allocated from the FCC spectrum sales or the carriers (or both) to retrofit their dated equipment.
  - deleted 5y ago
    [deleted]
  - LocalH 5y ago
    So the airlines are cheap bastards, got it
- themaninthedark 5y ago
  Maybe key people are out with Covid?
- RNCTX 5y ago
  Shouldn't be surprising to hear that the FAA doesn't really do anything with this stuff. They appoint a corporate-filled board of avionics companies to do all of the work for them, and then rubber stamp what those companies want.
- bin_bash 5y ago
  yeah as someone that isn't following this super closely it feels like the airlines are on their back foot and unprepared. These radios are days away from being turned on permanently and they haven't done any smoke testing? Why weren't they working with the telecoms 12 months ago to run trials? I'm not sympathetic to the airlines right now.

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)
  - DannyBee 5y ago
    200 is already crazy large. Super crazy. The original request from Boeing was only 100 These altimeters are dangerously defective if they need a 400mhz guard band. That is nuts
    - indrora 5y ago
      you're actually looking at the intersection of three problems: * LTE is very noisy (it has echos in its sidebands for up to 100Mhz) * low-frequency LTE is *loud* -- punch through mountains loud. * These altimiters are doing the RF equivalent of looking for a needle in a haystream While FCC Part15 says "accept any/produce as little as possible", much of this comes down to the physics of RF.
- berkut 5y ago
  I've read it's multiple concerns: https://www.faa.gov/5g https://www.faa.gov/5g https://www.airlines.org/5g-frequently-asked-questions/ https://www.airlines.org/5g-frequently-asked-questions/ In Europe, the power output seems to be ~2.5 time lower, there's a bigger frequency separation in Europe, the 5G towers are placed further away from approaches, and the antennas have to point downwards.
- gormandizer 5y ago
  C-Band in the US is rolling out in 2 phases, the first uses spectrum from 3.7 to 3.8 GHz. The second - in roughly two years - adds the remaining 3.8 to 3.98 GHz. So for the first two years the spectrum used by C-Band 5G in the US is essentially the same as in most of the rest of the world. https://www.commscope.com/blog/2021/maximizing-c-band-deployments-with-commscope/ https://www.commscope.com/blog/2021/maximizing-c-band-deploy...
- Terry_Roll 5y ago
  Doesnt this show that some country's dont plan ahead that much or different elements of Govt are too disconnected to work cohesively? Still, this chatter will no doubt give some loon some ideas on how to bring down a plane or mess around with the flight patterns at busy airports.
  - kolanos 5y ago
    > Doesnt this show that some country's dont plan ahead that much or different elements of Govt are too disconnected to work cohesively? This can be a feature, not necessarily a bug. There are plenty of examples of government central planning and cohesion going very wrong.
  - MomoXenosaga 5y ago
    Radio spectrum was decided somewhere in the 1950s and as I understand it the US military owns most of it. It's difficult to plan ahead for future technology.
    - Terry_Roll 5y ago
      Oh I dont know, I think other countries seem to be making less of a hash of it, compared to the US. And does it really matter if the US Mil own the spectrum? Thats like me saying the UK Govt owns the spectrum, they should still both be subjected to the court of law, if the laws are fit for purpose in the first place!
kyrra 5y ago
I thought that AT&t and Verizon offered to do lower power towers near airports. The story from November seems to say as much. https://www.theverge.com/2021/11/24/22801008/verizon-att-midband-5g-c-band-lower-power-six-months https://www.theverge.com/2021/11/24/22801008/verizon-att-mid...
RNCTX 5y ago
All cell phone towers seem to be aimed toward the ground. I've flown a GA aircraft all around the lower 48, and only get a cell phone signal briefly when flying directly over a cell tower.
- Fatnino 5y ago
  Naturally. Why would a cell carrier want to expend energy beaming signal into space? That said, you do get the occasional misaligned antenna or weird bounce off terrain that gets you signal midflight for a minute.
  - barcoder 5y ago
    How easy is it to report those type of issues?
    - krisoft 5y ago
      What do you like to report? That cell signal was available somewhere?
    - dylan604 5y ago
      make a phone call, and let the big data folks raise eyebrows when they see the elevation the call was made.
- jcalvinowens 5y ago
  It's really regional. I get 5 bars pretty much anywhere below 5000ft in the bay area.
  - _moof 5y ago
    Yep, I get signal up to about 3000' AGL where I am.
    - supernova87a 5y ago
      Well, given that the possible range to a cell tower is about 35 km / 20 mi (max, an absolute limitation of how the GSM/timing is done), it's very plausible that even if cell broadcast antennas are generally pointed down + flat with the horizon, you're gonna get some signal from some antenna in the distance.

Spooky23 5y ago

tedunangst 5y ago

The US seems stuck in a holding pattern of "two more weeks, two more weeks" without addressing any of the potential workarounds like power, directional antennas, or even blackout zones. From what I've read, the airlines and FAA haven't really put forward any proposals for compromise, like leaving towers off near airports. It's always no 5G anywhere until they've had more time, as if the planned 5G deployment came as a total surprise. Or why can't the towers be turned off in bad weather only?

houseofzeus 5y ago
My read is either the FAA or the airlines or both want money re-allocated from the FCC spectrum sales or the carriers (or both) to retrofit their dated equipment.
- deleted 5y ago
  [deleted]
- LocalH 5y ago
  So the airlines are cheap bastards, got it
themaninthedark 5y ago
Maybe key people are out with Covid?
RNCTX 5y ago
Shouldn't be surprising to hear that the FAA doesn't really do anything with this stuff. They appoint a corporate-filled board of avionics companies to do all of the work for them, and then rubber stamp what those companies want.
bin_bash 5y ago
yeah as someone that isn't following this super closely it feels like the airlines are on their back foot and unprepared. These radios are days away from being turned on permanently and they haven't done any smoke testing? Why weren't they working with the telecoms 12 months ago to run trials? I'm not sympathetic to the airlines right now.