C-Band 5G dates and controversy.

Rufus

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I’m not a telemetry expert. However, my job does require me to stay current with any industry trends or federal regulations that affect future use within the ISM bands.

To keep it really fundamental, your garage door opener is a radio and your neighbor’s drone is a radio. So why can’t you crash his drone with your garage? Different frequencies in different bandwidths with different encryption. This was all established and has been regulated. It’s been over 30 years since you heard cross talk on your home phone. This is why. Telemetry and encryption and explicit messaging have been standardized and this is just a distraction.
Its not just a distraction and can happen when they both share some of the same frequency band...which IS the case with 5g and radar altimeters.

Its real easy to sit in your armchair and dismiss any safety concerns.
Its a bit different when safety is directly affected
 

bumnote

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The airlines and pilots complained about this before the frequencies were sold in 2016...no one listened. Pilots and airlines have been raising concerns over this for years. When the phone companies point to Europe's 5G rollout...they conveniently forget to mention the HUGE difference in signal strength between the two.
The phone companies also didn't provide the final data until either right before or right after Christmas...which I'm sure is purely coincidental.

Frankly I'm kinda surprised the phone companies did this. One single crash is a PR nightmare...late night hosts cracking "can you hear me now" jokes over pictures of smoldering wreckage...Lily the AT&T girl in an "Airplane!" spoof...
Then there's the lawsuits.
This was pretty stupid of them.
 

SRHmusic

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Also it’s important to acknowledge that in order for the aircraft navigation devices to be approved and decertified for flight use they had to be designed such that they were impervious to radio interference.

THIS IS Y2K, just home spun panic.
As I understand it, the prior use of the C band was fixed, point to point, terrestrial links with little chance of causing interference. The altimeter radio standards required what was reasonable in that environment. When the C band was reallocated to mobile services, it changed the assumptions about the RF environment of all the existing equipment.

There is no such thing as "impervious to radio interference." Transmitters always have some amount of unwanted emissions in other bands, and receivers always have some sensitivity to strong signals in other bands. The level of interference between the two systems depends on the combination of emissions from one and sensitivity or rejection in the other, which depend on things like filtering, noise and coupling issues in each system. Improving each of them cost money, complexity, weight, volume, etc. No company would have made altimeter products capable of being compatible with a non existent, future radio system in the adjacent band. And it's not as if they don't have any filtering or rejection, just possibly not enough for the new situation.

One of the concerns is that out of band emissions from 5G transmitters that fall in the altimeter band effectively raise the noise floor of the altimeter receivers, making them inaccurate. (Like looking into a bright light while trying to read the set list in front of you.)

The two industries should have been working together on this particular "coexistence" problem and arrived at an agreed understanding of what, if anything, would need to be done, but it appears they haven't. Or at least there's an ongoing dispute over testing and calculations that the aircraft people did vs the cellular.
 

Killing Floor

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Its not just a distraction and can happen when they both share some of the same frequency band...which IS the case with 5g and radar altimeters.

Its real easy to sit in your armchair and dismiss any safety concerns.
Its a bit different when safety is directly affected
From my "armchair" I can tell you that 5G bandwidth in USA centers at 28GHz and 39GHZ while avionics altimeters use a center frequency of 4,300MHz. If you're not familiar with the units that = 4.3GHz. Not even in the same ballpark as 28GHz. Check your math.

Also, FWIW, it is illegal for any commercial company to manufacture radios for commercial/consumer use that operate within the federally restricted space of 4,200-4,400.

There would also be no patents issued for commercial/consumer radios (cell phones) that operate in restricted bandwidths.

But I enjoy the banter.
 

SRHmusic

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I’m not a telemetry expert. However, my job does require me to stay current with any industry trends or federal regulations that affect future use within the ISM bands.

To keep it really fundamental, your garage door opener is a radio and your neighbor’s drone is a radio. So why can’t you crash his drone with your garage? Different frequencies in different bandwidths with different encryption. This was all established and has been regulated. It’s been over 30 years since you heard cross talk on your home phone. This is why. Telemetry and encryption and explicit messaging have been standardized and this is just a distraction.
If someone transmitted enough noise power directly on channel into either system, or a very high power in an adjacent band, there is a point where the receive signal to noise ratio drops to the point they just wouldn't work. (It's sometimes called receiver de-sense.) Encryption and coding helps, but it's not pure magic. There are limits, and that's why there are standards for out of band emissions. In this case the altimeter band standard is/was different from, and didn't anticipate coexistence with, the mobile communication standards for an adjacent band. Whether there is a real problem or not seems to be the point of contention.
 

SRHmusic

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From my "armchair" I can tell you that 5G bandwidth in USA centers at 28GHz and 39GHZ while avionics altimeters use a center frequency of 4,300MHz. If you're not familiar with the units that = 4.3GHz. Not even in the same ballpark as 28GHz. Check your math.

Also, FWIW, it is illegal for any commercial company to manufacture radios for commercial/consumer use that operate within the federally restricted space of 4,200-4,400.

There would also be no patents issued for commercial/consumer radios (cell phones) that operate in restricted bandwidths.

But I enjoy the banter.
This is a C-band deployment at 3.7 to 3.98GHz, new band (edit - new allocation for this band). The real high frequency bands are also used in 5G. Lots of bands have been reallocated and are in use now.
There's a list here. The C-band is one of the "mid bands" here.
edit2 - And the issue isn't 'directly transmitting' in the altimeter band; it's the interference caused by out of band emissions of the new transmitters and out of band rejection of existing altimeters.
 

Killing Floor

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As I understand it, the prior use of the C band was fixed, point to point, terrestrial links with little chance of causing interference. The altimeter radio standards required what was reasonable in that environment. When the C band was reallocated to mobile services, it changed the assumptions about the RF environment of all the existing equipment.

There is no such thing as "impervious to radio interference." Transmitters always have some amount of unwanted emissions in other bands, and receivers always have some sensitivity to strong signals in other bands. The level of interference between the two systems depends on the combination of emissions from one and sensitivity or rejection in the other, which depend on things like filtering, noise and coupling issues in each system. Improving each of them cost money, complexity, weight, volume, etc. No company would have made altimeter products capable of being compatible with a non existent, future radio system in the adjacent band. And it's not as if they don't have any filtering or rejection, just possibly not enough for the new situation.

One of the concerns is that out of band emissions from 5G transmitters that fall in the altimeter band effectively raise the noise floor of the altimeter receivers, making them inaccurate. (Like looking into a bright light while trying to read the set list in front of you.)

The two industries should have been working together on this particular "coexistence" problem and arrived at an agreed understanding of what, if anything, would need to be done, but it appears they haven't. Or at least there's an ongoing dispute over testing and calculations that the aircraft people did vs the cellular.
By the way, you are correct. No radio is impervious to interference. But some radios (altimeters, missile guidance systems, long wave navigation for examples) are designed to be robust enough to withstand well in excess of common tolerance.

1 - Look at it this way, airlines were aware of this transformation for several years.
2 - Manufacturers of avionics are not represented as the chief complainers.
3 - The federal approval and licensing of 5G occurred with rigor and diligence to account for all concerns.

Bottom line, 5G has been politicized by endless conspiracy theory and this is another one in line.
And airplanes have been taking off and landing within comm range of 5G towers for over 4 years in some markets.
 

SRHmusic

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By the way, you are correct. No radio is impervious to interference. But some radios (altimeters, missile guidance systems, long wave navigation for examples) are designed to be robust enough to withstand well in excess of common tolerance.

1 - Look at it this way, airlines were aware of this transformation for several years.
2 - Manufacturers of avionics are not represented as the chief complainers.
3 - The federal approval and licensing of 5G occurred with rigor and diligence to account for all concerns.

Bottom line, 5G has been politicized by endless conspiracy theory and this is another one in line.
And airplanes have been taking off and landing within comm range of 5G towers for over 4 years in some markets.
I think a concern here is the legacy equipment. Aircraft have very long service life. Also there is the concern of on-channel interference in the altimeters from out of band emissions by the 5G systems, which could affect newer systems, too. Yes, they should have had this sorted out by now - FCC announced reallocation in 2016, auction in 2020, I think? And yes, I would love to see what the avionics suppliers have to say and haven't found anything direct like that. (Links, anyone?)

Hmm... part of a 5G conspiracy? Well, there are some very serious people in these industries. Some of the engineering reports, comments and a technical annex are at the links below. Decide for yourself, I guess. The CTIA has good points about possible errors and lack of transparency in the air industry study. The CTIA also says things like 'there are no reported incidents elsewhere,' but anecdotes or lack of evidence is hardly a robust analysis, given the differing details of frequencies, power levels, antenna angles, buffer zones, etc. in other countries, and given the importance of aircraft actually knowing their altitude, eh? Well the s**t is hitting the fan, so hopefully they get their heads together!

 

Killing Floor

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I think a concern here is the legacy equipment. Aircraft have very long service life. Also there is the concern of on-channel interference in the altimeters from out of band emissions by the 5G systems, which could affect newer systems, too. Yes, they should have had this sorted out by now - FCC announced reallocation in 2016, auction in 2020, I think? And yes, I would love to see what the avionics suppliers have to say and haven't found anything direct like that. (Links, anyone?)

Hmm... part of a 5G conspiracy? Well, there are some very serious people in these industries. Some of the engineering reports, comments and a technical annex are at the links below. Decide for yourself, I guess. The CTIA has good points about possible errors and lack of transparency in the air industry study. The CTIA also says things like 'there are no reported incidents elsewhere,' but anecdotes or lack of evidence is hardly a robust analysis, given the differing details of frequencies, power levels, antenna angles, buffer zones, etc. in other countries, and given the importance of aircraft actually knowing their altitude, eh? Well the s**t is hitting the fan, so hopefully they get their heads together!

OK, good info. Calling back to the comment regarding "very serious people in these industries..." this is valid. Equally valid is the lack of concern from the military (every branch utilizes aircraft) and the lack of concern from the manufacturers of commercial avionics.

If you've been in a hospital for any reason you know that you are not permitted to use your mobile phone because it can interfere with critical life saving devices. You also know that the doctor is calling you with updates from her cell phone in the hospital. You also know that medical devices are so heavily fortified against "disruptive" interference because of the incredibly high risk of litigation. Now multiply that times 100 if an aircraft crashes. God forbid, if a plane falls from the sky because of cell towers it is the legal responsibility of the manufacturer of the avionics because they are the ones who have certified the robustness of their gear before the FAA. All radio devices from your handheld AM receiver to your microwave oven to your cell phone to navigation systems to all capture signals from other sources.
The difference here is that the altimeters in the conspiracy theory are were not designed to operate on dual band of 4,300 MHz and 28GHZ.

But here's the best and most hilarious part....

The free broadband that is blasted across the airports is mostly in the lower 5,000 MHz bandwidth, much closer to the bandwidth used by altimeters. Yet this raises absolutely no concerns because it's named WiFi instead of 5G. If the industry rebranded 5G as Mobile Broadband this would no longer be a concern.
 

tap4154

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I think it comes down to three points. In America we allocated frequencies much closer to the avionics frequencies, many of our cell towers put out a much more powerful signal than overseas, and during the past two years the airlines and FAA have had their hands full with other issues.

It seems to me a simple solution would be to change the allotted 5G frequencies to be a little further away from the avionics frequencies.
 

getbent

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This thread is funny because it illustrates the change matrix and process that any major change requires. There are announcements of a need to change. Then planning, then timelines, then more planning and money allocations for the change (and the ripple effect adjustments as needed) and the time keeps rolling...

with 5G they had the tin foil component too(and some other timing issues) and as the day draws closer, folks take it more seriously than they had, they realize they have shortcomings and they announce them.

The change group has to posture that they are moving forward so that they eventually CAN move forward and the stragglers hustle to get in line.

This is all shared with a breathless media who consume and expel it to masses who mostly flunked math and like the guy at lowe's last night pronounce it 'wee fee' who are mostly currently not flying but assume that all airplanes will fall from the sky.

Then it gets postponed, the stragglers get their stuff fixed and the change occurs. Until then, everything (and I mean everything) will continue to work as it has worked. No one is threatened, it is not harming anyone and some potential values are shifted in tiny ways.

But this 'mess' confirms for the folks who need messes everytime there is change that they are right. For the people who don't care much about messes and who find change just another thing to do, it amounts to nothing.

but, it is something to talk about, I suppose.
 

Blrfl

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If you've been in a hospital for any reason you know that you are not permitted to use your mobile phone because it can interfere with critical life saving devices.

People in my family have had a pretty solid string of hospital stays. The last place I remember there being restrictions was in the cardiac ward where they were using wireless telemetry, and that was about 20 years ago.

The free broadband that is blasted across the airports is mostly in the lower 5,000 MHz bandwidth, much closer to the bandwidth used by altimeters. Yet this raises absolutely no concerns because it's named WiFi instead of 5G. If the industry rebranded 5G as Mobile Broadband this would no longer be a concern.

It raises no concerns because WiFi isn't in the ballpark or even the same sport.

WiFi operates on a 100 MHz slice starting at 2.4 GHz and a 150 MHz slice starting at 5.725 GHz. Neither of those bands is anywhere close to C-band 5G, which is a 500 MHz slice starting at 3.7 GHz. The bottom 100 MHz of that band is where the altimeters live.
 

imwjl

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From my "armchair" I can tell you that 5G bandwidth in USA centers at 28GHz and 39GHZ while avionics altimeters use a center frequency of 4,300MHz. If you're not familiar with the units that = 4.3GHz. Not even in the same ballpark as 28GHz. Check your math.

Also, FWIW, it is illegal for any commercial company to manufacture radios for commercial/consumer use that operate within the federally restricted space of 4,200-4,400.

There would also be no patents issued for commercial/consumer radios (cell phones) that operate in restricted bandwidths.

But I enjoy the banter.
By understandable coincidence - roll out day - our Verizon tech rep just sent me a status report as of today. There are mostly 1 but up to 3 cities in 26 states with C-band turned on.

I side with anyone saying the airlines, avionics makers and FCC are slow and dullards compared to the tech leaders. None of them work with the competition that the major tech companies have. By that I mean speed, delivery and the overall quality of their business and products.

The concerns some have are real but a lot of the noise also seems to be from civil aviation where a lot of that is welfare for the well off. The truly important airports in my area are where the telecom firms are holding off and have consideration.

My thoughts were aircraft like the med flight helicopters have good reasons for concern. I expected an associate who's a med fight and Army reserves helicopter pilot to weight in but haven't heard anything.
 

Killing Floor

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It raises no concerns because WiFi isn't in the ballpark or even the same sport.
Point is 5G centers at 28GHz and 39 GHz, that is 2 orders of magnitude remote from C-Band (4.3 GHz). The 2 systems of concern here (5G and C) are stratospherically different. My point is if a pilot (not the actual engineers of the avionics) wants to worry about a radio interfering with his/her approach there are millions of devices whose signals the plan glides through that are much closer to C without actually being in that band.
Point is 4G and 3G are closer to the center of C. It's a physics issue, you can't solve it with philosophy.
 

Jim_in_PA

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That's true, 'Floor...the concern that the airlines have is that there is minimal separation between the radio altimeter gear's frequency bands and the C-Band 5G cellular bands. It's less than what's in place in Europe, for example. Base station antenna power and "aim" is different near airports in the European space, too. It would have been nice if all the parties involved did testing a couple of years ago for sure.
 

Blrfl

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Point is 5G centers at 28GHz and 39 GHz, that is 2 orders of magnitude remote from C-Band (4.3 GHz). The 2 systems of concern here (5G and C) are stratospherically different.

"G" is a marketing term that refers to successive generations of the airside interface to handsets. It's not tied to a frequency; you can run it anywhere you can get a license and equipment. The size of the allocation determines capacity to carry data. There's low-bandwidth 5G being operated right now at 600 MHz. The 28 and 39 GHz allocations happened because you have to go up that high to find enough open spectrum to run at the kinds of speeds that will download half the Internet while waiting for a latte at Charbucks.

My point is if a pilot (not the actual engineers of the avionics) wants to worry about a radio interfering with his/her approach there are millions of devices whose signals the plan glides through that are much closer to C without actually being in that band.

Close doesn't matter. This isn't horseshoes. Receivers are built with bandpass filters ahead of the first IF stage that rejects most of what isn't in the band it wants to hear and anything left or a result of mixing products is tamped down by filters ahead of successive conversions. Anything close by doesn't register because a good receiver is engineered to be deaf anywhere else. If receivers weren't designed that way, nothing would work. It's a well-solved problem.

This isn't like LightSquared where the concern was an insufficient guard band between the service they proposed and GPS L1. The FCC took what was a primary allocation for altimeters and licensed others to intentionally radiate in the same band where the altimeters' receivers are listening. The physics says that has a lot of potential for that to go wrong.

I'll pose this question: Would you put your family on a plane knowing that there was potential for a safety-critical instrument to not work or, worse, give incorrect answers?
 

SRHmusic

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Point is 5G centers at 28GHz and 39 GHz, that is 2 orders of magnitude remote from C-Band (4.3 GHz). The 2 systems of concern here (5G and C) are stratospherically different. My point is if a pilot (not the actual engineers of the avionics) wants to worry about a radio interfering with his/her approach there are millions of devices whose signals the plan glides through that are much closer to C without actually being in that band.
Point is 4G and 3G are closer to the center of C. It's a physics issue, you can't solve it with philosophy.
See the FCC 5G band list linked above. There are different types of 5G services planned in many bands, including at the low end of C band, 3.7 to 3.98GHz (which the FCC callls a mid band in that list), 220MHz below the 4.2GHz radio altimeter band.
 

Killing Floor

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I'll pose this question: Would you put your family on a plane knowing that there was potential for a safety-critical instrument to not work or, worse, give incorrect answers?
Asked and answered. We flew quite safely on a 737 Max over spring break, March 2021. They reentered service March 11. So we can communicate fairly let me assure you I have no fear of flying and I typically fly 2-3 times per week and I will be flying tomorrow and Friday.

I quite understand how radio amplifiers and filters work. And again I kindly ask why is the military not concerned? Aren't their airmen precious cargo? Why aren't manufacturers concerned? Are they not at the greatest risk of litigation?
I'll call attention to the fact that to date, no legal team representative of a US commercial passenger or cargo airline has expressed concerns.
 

Killing Floor

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See the FCC 5G band list linked above. There are different types of 5G services planned in many bands, including at the low end of C band, 3.7 to 3.98GHz (which the FCC callls a mid band in that list), 220MHz below the 4.2GHz radio altimeter band.
Liked because 4G has been operating equally near the C band for 7+ years.
 




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