Re: What do you think about this airline vs 5G brouhaha?

[Mel Beckman]

Geoff,

My understanding is that the FAA and 5G industry has just this week agreed on 
buffer zones around 50 of the impacted 80 US airports:

https://www.8newsnow.com/news/local-news/las-vegas-airport-included-in-5g-buffer-zone/

The 30 airports that are not buffered I think don’t have 5G deployed yet. For 
example, Denver international. The buffer zone is described as “the last 20 
seconds of flight time”, which considering 230MPH (the airspeed limit in Class 
C airspace) as a worst case scenario, would be about a mile and a half.

I fly helicopters, and for helicopter EMS flying, radar altimeters are 
important on the RTB (return to base) leg. So unless the FAA can get buffer 
zones around all the hospital helipads, I think there’s still an issue. There 
wouldn’t be an issue flying to an accident site, because generally outbound EMS 
flights required to have much higher visibility minimums, so I don’t think that 
radar altimeter’s are used in that flight regime.

-mel via cell

On Jan 21, 2022, at 11:52 AM, nano...@mulligan.org wrote:

Jaun says just what I stated previously...  in Europe (and my understanding 
also in Japan) there is an agreement to create a PHYSICAL buffer zone (not just 
an RF spacing) between 5G transmitters and airport.

No such agreement has been made here in the US.  So both the RF spacing and 
physical spacing of 5G in the US is much closer and therefore it is 
disingenuous of ATT and Verizon to claim "well there are no problems in Europe"!

It is not possible to compare the 5G deployment in Europe to the US.

Thanks Mel for finding this video

Geoff


On 1/21/22 12:31, Mel Beckman wrote:
Here’s another video by 767 pilot Juan Brown from his chanel BlancoLirio:

https://youtu.be/aHIFs4EkA0k

He addresses many of the points being claimed by the FCC and 5G industry, in 
particular the reason you can’t compare US 5G with overseas 5G.

-mel via cell

On Jan 21, 2022, at 11:11 AM, Michael Thomas  wrote:


On 1/21/22 10:44 AM, Jay Hennigan wrote:

FAA puts all kinds of restrictions on what equipment is required to perform 
certain maneuvers. You need a localizer, glideslope, etc. for instrument 
landings. Radars are made today that can reject out-of-band interference. If 
FAA simply required a certified radar that filtered out-of-band signals during 
those weather conditions, the airlines would retrofit and private pilots would 
also either retrofit, not fly in those conditions, or divert to land in better 
weather.

It's not an FCC issue, and FAA needs to require equipment capable of safely 
operating within the allocated spectrum.


For commercial airlines is it just old equipment or all equipment that has this 
error? That is, is there actually an off the shelf radio that would solve the 
problem?

Mike

Re: What do you think about this airline vs 5G brouhaha?

[Jay Hennigan]

On 1/21/22 11:10, Michael Thomas wrote:

For commercial airlines is it just old equipment or all equipment that 
has this error? That is, is there actually an off the shelf radio that 
would solve the problem?


I'm not qualified to answer. Avionics needs to go through a testing 
program called TSO.


https://www.faa.gov/aircraft/air_cert/production_approvals/tsoa/

The FAA certainly could require that the radar meet the specs. There are 
several off-the-shelf waveguide filters that are -60dB at 20 MHZ 
out-of-band readily available within that frequency range but a quick 
search doesn't show anything off-the-shelf with the radar band as the 
passband.


It certainly seems that sufficient selectivity within the radar set to 
avoid interference is well within the state of the art and has been for 
some time. Whether FAA has tightened the spec in the last 30-plus years 
is up to them to answer.


--
Jay Hennigan - j...@west.net
Network Engineering - CCIE #7880
503 897-8550 - WB6RDV

Re: What do you think about this airline vs 5G brouhaha?

[Mel Beckman]

Here’s another video by 767 pilot Juan Brown from his chanel BlancoLirio:

https://youtu.be/aHIFs4EkA0k

He addresses many of the points being claimed by the FCC and 5G industry, in 
particular the reason you can’t compare US 5G with overseas 5G.

-mel via cell

On Jan 21, 2022, at 11:11 AM, Michael Thomas  wrote:


On 1/21/22 10:44 AM, Jay Hennigan wrote:

FAA puts all kinds of restrictions on what equipment is required to perform 
certain maneuvers. You need a localizer, glideslope, etc. for instrument 
landings. Radars are made today that can reject out-of-band interference. If 
FAA simply required a certified radar that filtered out-of-band signals during 
those weather conditions, the airlines would retrofit and private pilots would 
also either retrofit, not fly in those conditions, or divert to land in better 
weather.

It's not an FCC issue, and FAA needs to require equipment capable of safely 
operating within the allocated spectrum.


For commercial airlines is it just old equipment or all equipment that has this 
error? That is, is there actually an off the shelf radio that would solve the 
problem?

Mike

Re: What do you think about this airline vs 5G brouhaha?

[Michael Thomas]

On 1/21/22 10:44 AM, Jay Hennigan wrote:


FAA puts all kinds of restrictions on what equipment is required to 
perform certain maneuvers. You need a localizer, glideslope, etc. for 
instrument landings. Radars are made today that can reject out-of-band 
interference. If FAA simply required a certified radar that filtered 
out-of-band signals during those weather conditions, the airlines 
would retrofit and private pilots would also either retrofit, not fly 
in those conditions, or divert to land in better weather.


It's not an FCC issue, and FAA needs to require equipment capable of 
safely operating within the allocated spectrum.




For commercial airlines is it just old equipment or all equipment that 
has this error? That is, is there actually an off the shelf radio that 
would solve the problem?


Mike

Re: What do you think about this airline vs 5G brouhaha?

[Jay Hennigan]

On 1/20/22 13:41, Brandon Martin wrote:

 From the sound of it, at least some of these altimeters were designed 
around the (probably poor) assumption that there would be essentially no 
RF power within half a GHz of them, and that assumption is no longer 
going to be true.  Was that a good design decision?  Probably not, but 
we need to figure out what to do about it.  This is more of an FAA 
problem than an FCC problem since it involves functional device 
performance rather than emissions.


Indeed, it sounds like that is the case, and that's a horrible 
assumption. When the spectrum was originally being allocated, if the 
devices need 1200 MHz of interference-free bandwidth to function they 
should have requested 1200 MHz of spectrum.


The FCC can (and should) attempt to balance the needs of existing users, 
including practical performance of their equipment as deployed, with the 
public good in terms of what has become spectrum that is very valuable 


FCC indeed does take into account practical performance of equipment in 
licensing. Early TV sets weren't very selective, so you wouldn't see 
adjacent VHF channels licensed in the same market. FM broadcast licenses 
need to protect existing stations up to three channels away still, 
despite substantial improvements in FM receivers since the 1950s.


It sounds to me like FAA and the radar designers took a gamble by either:

A: Being capable of designing a radar that could reject out-of-band 
interference but choosing to cut costs and risk safety by using a poorer 
design with less selectivity.


B: Realizing that the state of the art at the time required a +/- 500 
MHZ guard band but not applying for enough spectrum, ignoring the safety 
concerns.


FAA puts all kinds of restrictions on what equipment is required to 
perform certain maneuvers. You need a localizer, glideslope, etc. for 
instrument landings. Radars are made today that can reject out-of-band 
interference. If FAA simply required a certified radar that filtered 
out-of-band signals during those weather conditions, the airlines would 
retrofit and private pilots would also either retrofit, not fly in those 
conditions, or divert to land in better weather.


It's not an FCC issue, and FAA needs to require equipment capable of 
safely operating within the allocated spectrum.


--
Jay Hennigan - j...@west.net
Network Engineering - CCIE #7880
503 897-8550 - WB6RDV

Re: [External] Re: What do you think about this airline vs 5G brouhaha?

[Mark Tinka]

On 1/20/22 20:45, Keenan Tims wrote:



The AOA DISAGREE alert was never intended as an optional feature. 
However either due to a software bug or miscommunication between 
Boeing and their contractor for the avionics package (Collins?), it 
got tied to the optional AoA (value) indicator. This was caught *by 
Boeing* and reported to the contractor, but Boeing instructed them not 
to fix the problem and defer it to a later software update 3 years 
later, and never bothered to notify operators or the FAA about the 
problem.


In my mind, that is still rather negligent and irresponsible, especially 
because in the -MAX, this was more critical considering the level of 
input from the computer to activate MCAS outside of the pilot's control, 
or even knowledge.


Unlikely to be such a big deal in earlier B737 models, where MCAS is not 
used.





Somehow it's even worse this way. I don't think a working DISAGREE 
alarm would have saved the flights, though.


There has been AoA sensor failure in non-MAX B737 aircraft. The 
difference is you don't have MCAS there trying to do its own things.


Of course, had an AoA sensor failure and/or "AoA Disagree" scenario been 
tested and trained for, particularly on the -MAX, it would have been 
fairly obvious to both the Lion Air and Ethiopia crew that 
troubleshooting for a "Runaway Stabilizer Trim" would likely have saved 
their lives. Of course, troubleshooting for a runaway stabilizer with 
MCAS involved also has its nuances, depending on air speed, aircraft 
configuration, e.t.c.


Mark.

Re: What do you think about this airline vs 5G brouhaha?

[Brandon Martin]

On 01/19/2022 03:47, Masataka Ohta wrote:

That's not saturation.

Saturation means a receiver does not have adequate dynamic range.

With digital processing under saturation, effective number of bits
is reduced. That is, some necessary bits are lost, which is not
"everything that's there".


I think we're saying the same thing, but with a different focus.

Yeah, front-end overload will always be a problem if the overload is 
caused by an unwanted signal or if the overload is so severe that it 
causes distortion going into the next stage even if it's just from a 
desired signal.


But even a moderately powerful signal that's outside your band of 
interest by as much as the entire width of the interested band shouldn't 
easily overload your frontend if you designed it reasonably, IMO. 
Obviously the separation at which point you say it's a receiver issue 
vs. a physics issue is something of a judgement call.  Obviously it's my 
problem if my 2.4GHz Wi-Fi receiver is overloaded by the 500kHz 1MW AM 
transmitter next door, but who's fault is it if my low-band cell phone's 
650MHz receiver is overloaded by the 50kW 400MHz UHF TV transmitter half 
a mile away?


IF you had enough dynamic range to receive both your radar reflections 
and the 5G signal as attenuated by your front-end band-pass filter, you 
could use digital tricks (I would think, I Am Not A Radar Engineer, 
though do engineer RF comm systems from time to time) similar to spread 
spectrum to effectively get processing gain on your radar reflection vs. 
that "white noise" 5G signal, but of course none of these devices 
probably do that mostly because they're so old that they predate the 
concept or at least commercial deployment of such techniques which 
didn't become common until around the turn of the century.


From the sound of it, at least some of these altimeters were designed 
around the (probably poor) assumption that there would be essentially no 
RF power within half a GHz of them, and that assumption is no longer 
going to be true.  Was that a good design decision?  Probably not, but 
we need to figure out what to do about it.  This is more of an FAA 
problem than an FCC problem since it involves functional device 
performance rather than emissions.


The FCC can (and should) attempt to balance the needs of existing users, 
including practical performance of their equipment as deployed, with the 
public good in terms of what has become spectrum that is very valuable 
(not just in $$$s but also practicality) bandwidth for wireless 
communications.  That does, to some degree, involve nudging existing 
users to migrate to semi-modern best practices in order to more 
efficiently use their allocation.  They've done this before with e.g. 
reducing bandwidth limits on FM voice in the VHF/UHF "business bands".


--
Brandon Martin

Re: [External] Re: What do you think about this airline vs 5G brouhaha?

[Keenan Tims]

On 2022-01-20 00:49, Mark Tinka wrote:
Furthermore, the AoA "Disagree Alert" message that would need to 
appear on the pilot's display in the case of an AoA sensor failure, 
was an "optional extra", which most airlines elected not to add to the 
purchase order, e.g., Air Canada, American Airlines and Westjet all 
bought the extra feature, but Lion Air didn't.


There were a huge number of failures at Boeing in the MAX/MCAS program; 
it's clear the program if not the whole company was rotten to the core; 
but this isn't quite an accurate characterization of that particular 
failure.


The AOA DISAGREE alert was never intended as an optional feature. 
However either due to a software bug or miscommunication between Boeing 
and their contractor for the avionics package (Collins?), it got tied to 
the optional AoA (value) indicator. This was caught *by Boeing* and 
reported to the contractor, but Boeing instructed them not to fix the 
problem and defer it to a later software update 3 years later, and never 
bothered to notify operators or the FAA about the problem.


Somehow it's even worse this way. I don't think a working DISAGREE alarm 
would have saved the flights, though.


Keenan

Re: What do you think about this airline vs 5G brouhaha?

[Dennis Glatting]

On Wed, 2022-01-19 at 16:37 -0500, Scott McGrath wrote:
> I’m guessing you are not a pilot,  one reason aviation is resistant to
> change is its history is written in blood,    Unlike tech aviation is
> incremental change and painstaking testing and documentation of that
> testing.  
> 

True. True. And true. However, as a pilot you should recognize that many
of the protocols used in aviation (e.g., ADS-B and ACARS) are NOT secure
by any stretch of the imagination [1]. In fact, the CRC used to secure
ACARS messages is initialized with zero - it's in the spec.

It is simple to find spoofing code to program a SDR on the Internet to
confuse aviation systems. Additionally, some of the code and systems
used in  aviation cannot be maintained (e.g., [2]) - because the
original developers have died and no one knows how the code works or the
programming languages. The versions of OpenSSL used to secure some
aviation communications dates back to 2008.

I worked in certification. Certification's goal is to *pass
certification and ship aircraft*. Certification's goal is NOT to
strongly test systems and look for weaknesses outside of certification.
In aviation parlance, strong testing is called "engineering testing."
Engineering testing is considered a cost center. When one of the
relatively newer commercial jests shipped, cost centers were downsized
across the aviation lines.

Whereas one can argue standards are written in blood and go through 
strong processes, the practical result is people are flying under the
perceived safety of 50 year old standards and systems. These standards
are also highly politically influenced, which should make no one
comfortable.


[1]
https://www.researchgate.net/publication/251709004_Security_analysis_of_the_ADS-B_implementation_in_the_next_generation_air_transportation_system

[2]
https://www.zdnet.com/article/a-23-year-old-windows-3-1-system-failure-crashed-paris-airport/




> When that does not happen we get stuff like the 737 Max debacle
> 
> Aviation is the antithesis of ‘Move fast and break things mentality’ for
> a very good reason safety.
> 
> On my flying club’s plane every replacement part comes with a pedigree
> which is added to the plane’s maintenance log upon installation and the
> reason for removing the old one recorded 
> 
> Imagine how much easier our networks would be to maintain if we had
> records down to the last cable tie in the data center.   If there was a
> bug in a SFP+ for instance all of them, when they were installed and by
> who and what supplier they came from was readily available sure would
> make my life easier. 
> 
> The reasoning behind that massive pile of documents (pilot joke ‘a plane
> is not ready to fly until the weight of the paperwork equals the weight
> of the airplane’) is that if a failure is traced to a component all of
> them can be traced and removed from service.
> 
> On a Airbus for instance all the takeoff and landing safety systems are
> tied to the RadAlt.  The EU has strict rules about where the c-band can
> be used as does Japan both use the 120 second rule c-band devices not
> allowed in areas where the the aircraft is in its beginning/ending 2
> minutes of flight.
> 
> So the REST of the world got c-band right the US not so much
> 
> 
> 
> On Wed, Jan 19, 2022 at 10:59 AM Dennis Glatting  wrote:
> > On Tue, 2022-01-18 at 12:29 -0800, Michael Thomas wrote:
> > > 
> > > I really don't know anything about it. It seems really late to be
> > > having 
> > > this fight now, right?
> > > 
> > 
> > I worked in aviation as a technologist. Aviation is resistant to
> > change.
> > Any change. When you fly older aircraft, be aware that the software is
> > old. Very old. As in some of the vendors long ago stopped supporting
> > the
> > software kind of old, assuming the vendors still exist. 
> > 
> > Aviation didn't wake up one day with the sudden appearance of 5G. They
> > knew it was comming. They, aviation themselves, are heavily involved
> > in
> > standards. Aviation had plenty of time to test, correct, and protest.
> > 
> > What aviation now wants is a 5G exclusion zone around airports, or
> > what
> > I sarcastically call "a technology exclusion zone," which tends to be
> > businesses and homes. What is aviation going to do when 6G comes
> > along?
> > A new WiFi standard is implemented? Any other unforeseen future
> > wired/wireless technologies? Or perhaps cell phones should go back to
> > Morse Code for aviation's sake?
> > 
> > 路‍♂️️
> > 
> > 

-- 
Dennis Glatting
Numbers Skeptic

Re: What do you think about this airline vs 5G brouhaha?

[Carsten Bormann]

On 2022-01-19, at 02:39, John Levine  wrote:
> 
> 
> tl;dr while interference is certainly possible in theory, […]

Reminds me of the first few years I had a handheld digital cellphone (GSM).

There was a theoretical possibility that the (up to 2 W) RF pulses from the 
phone could trigger the airbags when calling in a car, which would not have 
been very safe.
This possibility was talked up so much that taxi drivers were screaming at me 
when I used the phone in the car.  
Of course, I ignored them, but it did reduce sound signal/noise a bit during my 
phone calls.

(Obviously, the airbags were designed to take EMI from all kinds of 
walkie-talkies that people used in cars and that often had way more than 2 W.  
But it was a great story that journalists could sell and that “experts” could 
use to boost their egos by getting media coverage.)

Grüße, Carsten

Re: What do you think about this airline vs 5G brouhaha?

[Bryan Fields]

On 1/19/22 10:33 PM, Jay Hennigan wrote:
> On 1/19/22 18:31, Bryan Fields wrote:
>> The narrower the filter is,
>> the higher the loss is. The greater the stopband attenuation is, the more
>> elements required and more ripple is present in the pass band.  Now granted
>> for avionics, this is doable in the thousands of dollars, but older radar
>> altimeters will not have this level of filtering, nor can you slap a filter 
>> on
>> avionics without manufacturer support.
> 
> While the passbands are different in these as they're designed to pass 
> the C-band satellite signals and reject the radar, C-band filters with 
> insertion loss in the 1.4 dB range with 60dB rejection 20 MHz down have 
> been available for quite a while.
> 
> https://cdn.shopify.com/s/files/1/0529/5806/8919/t/9/assets/eBPF-C-Spec-Sheet.pdf

My point was not they are not available, just that you can't take an existing
receiver and slap it in, cuz avionics.  It was really on the FAA to set some
basic receiver performance requirements as the FCC doesn't care about receivers 
:)

>> Further complicating this, radar altimeters in the 4200-4400 MHz band are
>> frequency modulating continuous wave transmitters.   In this configuration 
>> the
>> frequency is not closed loop controlled, it can be anywhere in the 200 MHz
>> band, as it's modulating a free running VCO nominally at 4300 MHz. This is a
>> non-issue as the transmitter is used for the receiver reference, so they are
>> locked to the same free-running oscillator.
> 
> Fair enough, but C-band below 4200 has hardly been a desert all of these 
> years. TD-2 was on mountaintops all over the country pushing a couple of 
> watts into huge KS-15676 horns with something like 39dB of gain. 4400 > and 
> above is also licensed for mobile use.

Those are narrow beams, typically 4 degrees or less half power beam-width in
both planes.

>> Only in recent avionics has the receiver been improved via DSP circuits and
>> FFT to do real time spectral analysis and pick out the right receive signal.
>> The older altimeters out there use simple zero crossing counting to determine
>> the frequency of the strongest signal.  This leaves them open to potential
>> interference by strong near band signals. Exasperating this is the poor
>> filtering on the RF receiver in 99% of altimeters when dealing with wide band
>> signals.
> 
> If that's the case, how have they dealt with the signals from other 
> aircraft in busy airspace that are operating in the same band all of 
> these years?

Law of averages.  Every transmitter is offset from the others.  Since the
transmitter is phase locked to the receiver it forms an effective filter for
similar signals.


> The poor filtering on the receiver is obviously the issue. However, 
> suitable filters have been available for decades, adjacent frequencies 
> have been in use for decades, and it isn't the FCC's fault nor the 
> cellular carriers' fault that FAA has certified crappy receivers for use 
> in mission-critical applications.

Bingo.  This is something that the FAA/IACO should have been testing for and
set requirements for decades ago.

> Somebody using a crystal set to listen to a 1KW AM station 20 miles away 
> isn't going to get very far complaining to FCC about a new 5KW signal 
> 100 kHz below it and a couple of miles away. That the FAA would certify 
> radars with a front-end like a crystal set is the problem.

lol; that's what most pulse radars receivers are!

>> So can this LTE at C band work? Yes.
>> Will it require upgrades to avionics and standards? Yep.
> 
> If the 5G allocation were shared spectrum with the radar altimeters, I'd 
> concede your point. However, it's at least 220 MHz away, over 5% of the 
> actual frequency in use.

5% is nothing when you have no front end filter other than the antenna.

> All of this talk so far is speculation about potential harmful 
> interference. Radar altimeters exist. Cell towers exist. Has anyone 
> gathered any real world data demonstrating actual interference?

Honeywell gave some proof of testing in their comments to the FCC.  There are
others too.

I think the potential for interference here is way over estimated, but the
issue is one of equipment that may be from the 1960's is not robust to
withstand interference in modern times.  This is an issue which must be
resolved prior to widespread deployment.  If it's a FAA certification process
or people having to replace altimeters with modern units, then that should
have been started years ago.

This could be a life safety issue that the FAA and industry didn't address,
but you can't just say "your receiver is worse than a baofeng, it's your
problem, screw your 220 passengers.  The Internet is serious business".  It's
a bit like a protester running in traffic and jumping on your car.  You should
be able to run them over, but at the end of the day it's property damage to a
car vs death to some idiot so it's not legal to run them over.

FAA dropped the ball and 

Re: What do you think about this airline vs 5G brouhaha?

[Mark Tinka]

On 1/19/22 23:57, nano...@mulligan.org wrote:


Scott - a side note to clarify things...

The 737 Max8 problem was NOT due to lack of testing or non-incremental 
changes.  The system was well tested and put through it's paces.  It 
was a lack of proper pilot training in the aircraft and its systems 
and some carriers choosing to NOT purchase specific flight control 
options.


IIRC, one glaring bug in how MCAS received data in the -MAX was that it 
could only take it from one AoA (angle of attack) sensor, despite the 
aircraft actually having two physical ones onboard. That was a massive 
break in Boeing's previous culture of "backup for backup for backup".


Add to that, Boeing's assumption that an AoA failure in the -MAX would 
be backed up by the pilots, who had not been informed about the 
existence of MCAS on the -MAX, to begin with... never mind the lack of 
training on how to deal with it. Despite more than 200 incident reports 
of an AoA sensor failure sent to the FAA, even prior to the -MAX 
shipping, Boeing did not flight-test this scenario.


Furthermore, the AoA "Disagree Alert" message that would need to appear 
on the pilot's display in the case of an AoA sensor failure, was an 
"optional extra", which most airlines elected not to add to the purchase 
order, e.g., Air Canada, American Airlines and Westjet all bought the 
extra feature, but Lion Air didn't.


After the Ethiopia crash, Boeing made "Disagree Alert" a standard 
feature on the -MAX, and would be retrofitted on previously delivered 
equipment.


Boeing had made the decision that the AoA indicator, as well as the 
Disagree Alert" feature were not necessary for the safe operation of the 
-MAX.


I still won't board any flight being operated with a -MAX.

Mark.

Re: What do you think about this airline vs 5G brouhaha?

[Masataka Ohta]

Jay wrote:

    By adding an LC bandpass filter will add to the propogation delay of 
the receiver.  When the round-trip time of the echo at 1000 feet is only 
2 microseconds, that added delay will throw the RA out of calibration. 


Altitude error by the delay is proportional to wavelength of signal
(in this case, 3 inches or so) and shouldn't be so serious.

> Perhaps the calibration circuitry can deal with this added delay.

According to the following patent filed in 1997:

https://patents.google.com/patent/US6008754A/en
Current radio altimeter calibration technology requires
the radio altimeter to be calibrated by adjusting the
length of the cable connecting the radio altimeter to
its antenna during installation.

old altimeters may have some difficulty to fully calibrate the delay.

Masataka Ohta

Re: What do you think about this airline vs 5G brouhaha?

[Scott McGrath]

Um the Lightsquared monster is back stronger than ever however it has a new
name Ligado Networks

Yes we now have something which everyone agrees will hose every civillian
GPS receiver out there.   But hey thats the user’s problem.

I’m glad i know how to use a sextant….   Perhaps someone will come up with
a low priced INS.   The 747 was the last airliner which used a INS.Of
course a improperly initialized INS was responsible for the Korean Air
shoot down incident….

Of course this will also hose our NTP servers and 802.11ad/ay networks and
any other network kit that uses GPS.

On Wed, Jan 19, 2022 at 9:34 PM Bryan Fields  wrote:

> On 1/18/22 9:03 PM, Brandon Martin wrote:
> > One thing the FCC could potentially do to wipe some egg of their
> > collective faces, here, is mandate that transmitters operating in this
> > newly allocated wireless band face additional scrutiny for spurious
> > emissions in the radio altimeter band as well as the guard band between
> > the two services and a similar bandwidth above the radio altimeter band.
>
> The issue is not one of out of band emissions, but rather close but strong
> signals near the receiver pass band.  This can cause compression of the
> first
> RF amplifier stage and de-sensitize the receiver so it cannot hear the
> intended signal.  I won't get into the physics, but it is difficult to
> realize
> an effective filter that will permit 4200-4400 with low loss and attenuate
> everything else starting at 4200 MHz and down.  The narrower the filter is,
> the higher the loss is. The greater the stopband attenuation is, the more
> elements required and more ripple is present in the pass band.  Now granted
> for avionics, this is doable in the thousands of dollars, but older radar
> altimeters will not have this level of filtering, nor can you slap a
> filter on
> avionics without manufacturer support.
>
> Further complicating this, radar altimeters in the 4200-4400 MHz band are
> frequency modulating continuous wave transmitters.   In this configuration
> the
> frequency is not closed loop controlled, it can be anywhere in the 200 MHz
> band, as it's modulating a free running VCO nominally at 4300 MHz. This is
> a
> non-issue as the transmitter is used for the receiver reference, so they
> are
> locked to the same free-running oscillator.
>
> Only in recent avionics has the receiver been improved via DSP circuits and
> FFT to do real time spectral analysis and pick out the right receive
> signal.
> The older altimeters out there use simple zero crossing counting to
> determine
> the frequency of the strongest signal.  This leaves them open to potential
> interference by strong near band signals. Exasperating this is the poor
> filtering on the RF receiver in 99% of altimeters when dealing with wide
> band
> signals.
>
> So can this LTE at C band work? Yes.
> Will it require upgrades to avionics and standards? Yep.
>
> Last time this sort of change out was needed Sprint/Nextel bought every
> major
> public safety agency new radios.  One could plot the decline of Sprint
> stock
> to an uptick in Motorola stock.
>
> This reminds me of the Lightsquared case where they were using adjacent
> spectrum to GPS for low speed data from satellites, and wanted to add in
> repeaters on the ground, or an ATC/ancillary terrestrial component.
> Sirrus XM
> does this, in tunnels and such and it's just the rather low power repeater
> of
> the same signal from the satellite. Lightsquared wanted this the be a high
> power LTE signal, which wouldn't "fill in" their satellite signal but make
> an
> LTE network they would sell access on.  Do to the proximity to the GPS
> bands
> and the rather poor selectivity of the GPS receiver, it would have
> dramatically limited GPS performance.
>
> The issue here is that Lightsquared was too small.  The establishment
> wireless
> carriers know that commissioners don't work at the FCC for life, and have
> paid
> lobbyists crawling all over capital hill.
> --
> Bryan Fields
>
> 727-409-1194 - Voice
> http://bryanfields.net
>

Re: What do you think about this airline vs 5G brouhaha?

[Jay Hennigan]

On 1/19/22 18:31, Bryan Fields wrote:


The issue is not one of out of band emissions, but rather close but strong
signals near the receiver pass band.  This can cause compression of the first
RF amplifier stage and de-sensitize the receiver so it cannot hear the
intended signal.  I won't get into the physics, but it is difficult to realize
an effective filter that will permit 4200-4400 with low loss and attenuate
everything else starting at 4200 MHz and down. 


It only needs to attenuate from 3980 and down to solve this potential 
problem.



The narrower the filter is,
the higher the loss is. The greater the stopband attenuation is, the more
elements required and more ripple is present in the pass band.  Now granted
for avionics, this is doable in the thousands of dollars, but older radar
altimeters will not have this level of filtering, nor can you slap a filter on
avionics without manufacturer support.


While the passbands are different in these as they're designed to pass 
the C-band satellite signals and reject the radar, C-band filters with 
insertion loss in the 1.4 dB range with 60dB rejection 20 MHz down have 
been available for quite a while.


https://cdn.shopify.com/s/files/1/0529/5806/8919/t/9/assets/eBPF-C-Spec-Sheet.pdf


Further complicating this, radar altimeters in the 4200-4400 MHz band are
frequency modulating continuous wave transmitters.   In this configuration the
frequency is not closed loop controlled, it can be anywhere in the 200 MHz
band, as it's modulating a free running VCO nominally at 4300 MHz. This is a
non-issue as the transmitter is used for the receiver reference, so they are
locked to the same free-running oscillator.


Fair enough, but C-band below 4200 has hardly been a desert all of these 
years. TD-2 was on mountaintops all over the country pushing a couple of 
watts into huge KS-15676 horns with something like 39dB of gain. 4400 
and above is also licensed for mobile use.


The C-band satellite operators, having to deal with extremely weak 
narrowband signals, only have a 20 MHz guard band from the 5G allocation.



Only in recent avionics has the receiver been improved via DSP circuits and
FFT to do real time spectral analysis and pick out the right receive signal.
The older altimeters out there use simple zero crossing counting to determine
the frequency of the strongest signal.  This leaves them open to potential
interference by strong near band signals. Exasperating this is the poor
filtering on the RF receiver in 99% of altimeters when dealing with wide band
signals.


If that's the case, how have they dealt with the signals from other 
aircraft in busy airspace that are operating in the same band all of 
these years?


The poor filtering on the receiver is obviously the issue. However, 
suitable filters have been available for decades, adjacent frequencies 
have been in use for decades, and it isn't the FCC's fault nor the 
cellular carriers' fault that FAA has certified crappy receivers for use 
in mission-critical applications.


Somebody using a crystal set to listen to a 1KW AM station 20 miles away 
isn't going to get very far complaining to FCC about a new 5KW signal 
100 kHz below it and a couple of miles away. That the FAA would certify 
radars with a front-end like a crystal set is the problem.



So can this LTE at C band work? Yes.
Will it require upgrades to avionics and standards? Yep.


If the 5G allocation were shared spectrum with the radar altimeters, I'd 
concede your point. However, it's at least 220 MHz away, over 5% of the 
actual frequency in use.


All of this talk so far is speculation about potential harmful 
interference. Radar altimeters exist. Cell towers exist. Has anyone 
gathered any real world data demonstrating actual interference?


--
Jay Hennigan - j...@west.net
Network Engineering - CCIE #7880
503 897-8550 - WB6RDV

Re: What do you think about this airline vs 5G brouhaha?

[Bryan Fields]

On 1/18/22 9:03 PM, Brandon Martin wrote:
> One thing the FCC could potentially do to wipe some egg of their 
> collective faces, here, is mandate that transmitters operating in this 
> newly allocated wireless band face additional scrutiny for spurious 
> emissions in the radio altimeter band as well as the guard band between 
> the two services and a similar bandwidth above the radio altimeter band. 

The issue is not one of out of band emissions, but rather close but strong
signals near the receiver pass band.  This can cause compression of the first
RF amplifier stage and de-sensitize the receiver so it cannot hear the
intended signal.  I won't get into the physics, but it is difficult to realize
an effective filter that will permit 4200-4400 with low loss and attenuate
everything else starting at 4200 MHz and down.  The narrower the filter is,
the higher the loss is. The greater the stopband attenuation is, the more
elements required and more ripple is present in the pass band.  Now granted
for avionics, this is doable in the thousands of dollars, but older radar
altimeters will not have this level of filtering, nor can you slap a filter on
avionics without manufacturer support.

Further complicating this, radar altimeters in the 4200-4400 MHz band are
frequency modulating continuous wave transmitters.   In this configuration the
frequency is not closed loop controlled, it can be anywhere in the 200 MHz
band, as it's modulating a free running VCO nominally at 4300 MHz. This is a
non-issue as the transmitter is used for the receiver reference, so they are
locked to the same free-running oscillator.

Only in recent avionics has the receiver been improved via DSP circuits and
FFT to do real time spectral analysis and pick out the right receive signal.
The older altimeters out there use simple zero crossing counting to determine
the frequency of the strongest signal.  This leaves them open to potential
interference by strong near band signals. Exasperating this is the poor
filtering on the RF receiver in 99% of altimeters when dealing with wide band
signals.

So can this LTE at C band work? Yes.
Will it require upgrades to avionics and standards? Yep.

Last time this sort of change out was needed Sprint/Nextel bought every major
public safety agency new radios.  One could plot the decline of Sprint stock
to an uptick in Motorola stock.

This reminds me of the Lightsquared case where they were using adjacent
spectrum to GPS for low speed data from satellites, and wanted to add in
repeaters on the ground, or an ATC/ancillary terrestrial component.  Sirrus XM
does this, in tunnels and such and it's just the rather low power repeater of
the same signal from the satellite. Lightsquared wanted this the be a high
power LTE signal, which wouldn't "fill in" their satellite signal but make an
LTE network they would sell access on.  Do to the proximity to the GPS bands
and the rather poor selectivity of the GPS receiver, it would have
dramatically limited GPS performance.

The issue here is that Lightsquared was too small.  The establishment wireless
carriers know that commissioners don't work at the FCC for life, and have paid
lobbyists crawling all over capital hill.
-- 
Bryan Fields

727-409-1194 - Voice
http://bryanfields.net

Re: What do you think about this airline vs 5G brouhaha?

[Masataka Ohta]

Tom Beecher wrote:


It's also relevant that the spectrum surrounding the 4.2-4.4 range has not
been an empty desert. It has been used for satellite downlink since the 60s
I think?

Yes, there are surely tons of differences in RF characteristics between the
two.


The important difference is in power. Downlink signal from satellites
is, at the ground, attenuated a lot. Moreover, downlink signal comes
from above an aircraft, though some are scattered by the ground to
the aircraft.


But let's be honest. Analysis would have been done decades ago on the
impact of spurious emissions from sat downlinks on RAs, so there should be
at least a baseline to work from.


Possible saturation of radar altimeter by 5G signal is caused
by signal power having nothing to do with spurious emission.


Either way this should not be a discussion now. This clearly was discussed
early in FCC filings, questions were asked, data was presented, and all
these parties signed off.


True. FCC even doubled guard band.

Masataka Ohta

Re: What do you think about this airline vs 5G brouhaha?

[Jay]

Greetings,

On Wed, 19 Jan 2022, Masataka Ohta wrote:


Jay Hennigan wrote:


Radar receivers are typically some form of direct conversion with
rather good selectivity, synchronized to the frequency of the
transmitted pulse.


No. Direct conversion stage has no inherent frequency
selectivity and is subject to saturation by noise of
any frequency unless the noise is removed in advance.

Selectivity can be enjoyed only after successful
unsaturated conversion, direct or to IF.

But, the solution is to put an LC band pass/stop filter
between an antenna and a receiver, though I have no
idea on the difficulty to obtain FAA/FCC approval to
do so.


   By adding an LC bandpass filter will add to the propogation delay of 
the receiver.  When the round-trip time of the echo at 1000 feet is only 2 
microseconds, that added delay will throw the RA out of calibration. 
Perhaps the calibration circuitry can deal with this added delay.


  --- Jay Nugent  WB8TKL

Re: What do you think about this airline vs 5G brouhaha?

[Nick Hilliard]

nano...@mulligan.org wrote on 19/01/2022 21:57:
If you look at 5G deployments around Japan and Europe, generally they 
are NOT right up next to major airports.


You might want to fact-check this claim.  Most airports have cell towers 
nearby, particularly international airports.


Whatever about Japan, Europe assigned 3300 - 3800 Mhz for 5G, which is a 
good deal further away from the radio altimeter allocation than the US 
5G allocation of 3700 - 4000 MHz.


Nick

Re: What do you think about this airline vs 5G brouhaha?

[nanog08]

Yeah - I'm sure they do and that is my point.  The heads of Verizon and 
ATT are not flying commercial. Their planes are not commercial airlines 
with hundreds of passengers == so they can much more easily just divert...


Geoff


On 1/19/22 15:12, sro...@ronan-online.com wrote:
Considering Verizon has a very sizable fleet of private aircraft, I am 
fairly certain this will happen often.


Shane


On Jan 19, 2022, at 4:59 PM, nano...@mulligan.org wrote:

 Scott - a side note to clarify things...

The 737 Max8 problem was NOT due to lack of testing or 
non-incremental changes.  The system was well tested and put through 
it's paces.  It was a lack of proper pilot training in the aircraft 
and its systems and some carriers choosing to NOT purchase specific 
flight control options.


Full disclosure - my classmate was the Chief Test Pilot for the MAX8 
and another classmate is the current FAA Administrator.


But I digress - sorry...

If you look at 5G deployments around Japan and Europe, generally they 
are NOT right up next to major airports.


I would like to ask ATT and Verizon senior leadership to put their 
loved ones onto a commercial aircraft that is flying into ORD during 
a blizzard on a Zero-Zero landing (the pilots relying on radio 
altimeters) and the 5G network up and running and then ask how 
confident they are that NOTHING will interfere and 5G is perfectly safe.


Geoff

On 1/19/22 14:37, Scott McGrath wrote:
I’m guessing you are not a pilot,  one reason aviation is resistant 
to change is its history is written in blood,    Unlike tech 
aviation is incremental change and painstaking testing and 
documentation of that testing.


When that does not happen we get stuff like the 737 Max debacle

Aviation is the antithesis of ‘Move fast and break things mentality’ 
for a very good reason safety.


On my flying club’s plane every replacement part comes with a 
pedigree which is added to the plane’s maintenance log upon 
installation and the reason for removing the old one recorded


Imagine how much easier our networks would be to maintain if we had 
records down to the last cable tie in the data center.   If there 
was a bug in a SFP+ for instance all of them, when they were 
installed and by who and what supplier they came from was readily 
available sure would make my life easier.


The reasoning behind that massive pile of documents (pilot joke ‘a 
plane is not ready to fly until the weight of the paperwork equals 
the weight of the airplane’) is that if a failure is traced to a 
component all of them can be traced and removed from service.


On a Airbus for instance all the takeoff and landing safety systems 
are tied to the RadAlt.  The EU has strict rules about where the 
c-band can be used as does Japan both use the 120 second rule c-band 
devices not allowed in areas where the the aircraft is in its 
beginning/ending 2 minutes of flight.


So the REST of the world got c-band right the US not so much



On Wed, Jan 19, 2022 at 10:59 AM Dennis Glatting  wrote:

On Tue, 2022-01-18 at 12:29 -0800, Michael Thomas wrote:
>
> I really don't know anything about it. It seems really late to be
> having
> this fight now, right?
>

I worked in aviation as a technologist. Aviation is resistant to
change.
Any change. When you fly older aircraft, be aware that the
software is
old. Very old. As in some of the vendors long ago stopped
supporting the
software kind of old, assuming the vendors still exist.

Aviation didn't wake up one day with the sudden appearance of
5G. They
knew it was comming. They, aviation themselves, are heavily
involved in
standards. Aviation had plenty of time to test, correct, and
protest.

What aviation now wants is a 5G exclusion zone around airports,
or what
I sarcastically call "a technology exclusion zone," which tends
to be
businesses and homes. What is aviation going to do when 6G comes
along?
A new WiFi standard is implemented? Any other unforeseen future
wired/wireless technologies? Or perhaps cell phones should go
back to
Morse Code for aviation's sake?

路‍♂️️


-- 
Dennis Glatting

Numbers Skeptic

Re: What do you think about this airline vs 5G brouhaha?

[sronan]

Considering Verizon has a very sizable fleet of private aircraft, I am fairly 
certain this will happen often.

Shane

> On Jan 19, 2022, at 4:59 PM, nano...@mulligan.org wrote:
> 
>  Scott - a side note to clarify things...  
> 
> The 737 Max8 problem was NOT due to lack of testing or non-incremental 
> changes.  The system was well tested and put through it's paces.  It was a 
> lack of proper pilot training in the aircraft and its systems and some 
> carriers choosing to NOT purchase specific flight control options.
> 
> Full disclosure - my classmate was the Chief Test Pilot for the MAX8 and 
> another classmate is the current FAA Administrator.
> 
> But I digress - sorry...
> 
> If you look at 5G deployments around Japan and Europe, generally they are NOT 
> right up next to major airports.
> 
> I would like to ask ATT and Verizon senior leadership to put their loved ones 
> onto a commercial aircraft that is flying into ORD during a blizzard on a 
> Zero-Zero landing (the pilots relying on radio altimeters) and the 5G network 
> up and running and then ask how confident they are that NOTHING will 
> interfere and 5G is perfectly safe.
> 
> Geoff   
> 
>> On 1/19/22 14:37, Scott McGrath wrote:
>> I’m guessing you are not a pilot,  one reason aviation is resistant to 
>> change is its history is written in blood,Unlike tech aviation is 
>> incremental change and painstaking testing and documentation of that 
>> testing.  
>> 
>> When that does not happen we get stuff like the 737 Max debacle
>> 
>> Aviation is the antithesis of ‘Move fast and break things mentality’ for a 
>> very good reason safety.
>> 
>> On my flying club’s plane every replacement part comes with a pedigree which 
>> is added to the plane’s maintenance log upon installation and the reason for 
>> removing the old one recorded 
>> 
>> Imagine how much easier our networks would be to maintain if we had records 
>> down to the last cable tie in the data center.   If there was a bug in a 
>> SFP+ for instance all of them, when they were installed and by who and what 
>> supplier they came from was readily available sure would make my life 
>> easier. 
>> 
>> The reasoning behind that massive pile of documents (pilot joke ‘a plane is 
>> not ready to fly until the weight of the paperwork equals the weight of the 
>> airplane’) is that if a failure is traced to a component all of them can be 
>> traced and removed from service.
>> 
>> On a Airbus for instance all the takeoff and landing safety systems are tied 
>> to the RadAlt.  The EU has strict rules about where the c-band can be used 
>> as does Japan both use the 120 second rule c-band devices not allowed in 
>> areas where the the aircraft is in its beginning/ending 2 minutes of flight.
>> 
>> So the REST of the world got c-band right the US not so much
>> 
>> 
>> 
>> On Wed, Jan 19, 2022 at 10:59 AM Dennis Glatting  wrote:
>>> On Tue, 2022-01-18 at 12:29 -0800, Michael Thomas wrote:
>>> > 
>>> > I really don't know anything about it. It seems really late to be
>>> > having 
>>> > this fight now, right?
>>> > 
>>> 
>>> I worked in aviation as a technologist. Aviation is resistant to change.
>>> Any change. When you fly older aircraft, be aware that the software is
>>> old. Very old. As in some of the vendors long ago stopped supporting the
>>> software kind of old, assuming the vendors still exist. 
>>> 
>>> Aviation didn't wake up one day with the sudden appearance of 5G. They
>>> knew it was comming. They, aviation themselves, are heavily involved in
>>> standards. Aviation had plenty of time to test, correct, and protest.
>>> 
>>> What aviation now wants is a 5G exclusion zone around airports, or what
>>> I sarcastically call "a technology exclusion zone," which tends to be
>>> businesses and homes. What is aviation going to do when 6G comes along?
>>> A new WiFi standard is implemented? Any other unforeseen future
>>> wired/wireless technologies? Or perhaps cell phones should go back to
>>> Morse Code for aviation's sake?
>>> 
>>> 路‍♂️️
>>> 
>>> 
>>> -- 
>>> Dennis Glatting
>>> Numbers Skeptic
> 

Re: What do you think about this airline vs 5G brouhaha?

[nanog08]

Scott - a side note to clarify things...

The 737 Max8 problem was NOT due to lack of testing or non-incremental 
changes.  The system was well tested and put through it's paces.  It was 
a lack of proper pilot training in the aircraft and its systems and some 
carriers choosing to NOT purchase specific flight control options.


Full disclosure - my classmate was the Chief Test Pilot for the MAX8 and 
another classmate is the current FAA Administrator.


But I digress - sorry...

If you look at 5G deployments around Japan and Europe, generally they 
are NOT right up next to major airports.


I would like to ask ATT and Verizon senior leadership to put their loved 
ones onto a commercial aircraft that is flying into ORD during a 
blizzard on a Zero-Zero landing (the pilots relying on radio altimeters) 
and the 5G network up and running and then ask how confident they are 
that NOTHING will interfere and 5G is perfectly safe.


Geoff

On 1/19/22 14:37, Scott McGrath wrote:
I’m guessing you are not a pilot,  one reason aviation is resistant to 
change is its history is written in blood,    Unlike tech aviation is 
incremental change and painstaking testing and documentation of that 
testing.


When that does not happen we get stuff like the 737 Max debacle

Aviation is the antithesis of ‘Move fast and break things mentality’ 
for a very good reason safety.


On my flying club’s plane every replacement part comes with a pedigree 
which is added to the plane’s maintenance log upon installation and 
the reason for removing the old one recorded


Imagine how much easier our networks would be to maintain if we had 
records down to the last cable tie in the data center.   If there was 
a bug in a SFP+ for instance all of them, when they were installed and 
by who and what supplier they came from was readily available sure 
would make my life easier.


The reasoning behind that massive pile of documents (pilot joke ‘a 
plane is not ready to fly until the weight of the paperwork equals the 
weight of the airplane’) is that if a failure is traced to a component 
all of them can be traced and removed from service.


On a Airbus for instance all the takeoff and landing safety systems 
are tied to the RadAlt.  The EU has strict rules about where the 
c-band can be used as does Japan both use the 120 second rule c-band 
devices not allowed in areas where the the aircraft is in its 
beginning/ending 2 minutes of flight.


So the REST of the world got c-band right the US not so much



On Wed, Jan 19, 2022 at 10:59 AM Dennis Glatting  wrote:

On Tue, 2022-01-18 at 12:29 -0800, Michael Thomas wrote:
>
> I really don't know anything about it. It seems really late to be
> having
> this fight now, right?
>

I worked in aviation as a technologist. Aviation is resistant to
change.
Any change. When you fly older aircraft, be aware that the software is
old. Very old. As in some of the vendors long ago stopped
supporting the
software kind of old, assuming the vendors still exist.

Aviation didn't wake up one day with the sudden appearance of 5G. They
knew it was comming. They, aviation themselves, are heavily
involved in
standards. Aviation had plenty of time to test, correct, and protest.

What aviation now wants is a 5G exclusion zone around airports, or
what
I sarcastically call "a technology exclusion zone," which tends to be
businesses and homes. What is aviation going to do when 6G comes
along?
A new WiFi standard is implemented? Any other unforeseen future
wired/wireless technologies? Or perhaps cell phones should go back to
Morse Code for aviation's sake?

路‍♂️️


-- 
Dennis Glatting

Numbers Skeptic

Re: What do you think about this airline vs 5G brouhaha?

[Scott McGrath]

I’m guessing you are not a pilot,  one reason aviation is resistant to
change is its history is written in blood,Unlike tech aviation is
incremental change and painstaking testing and documentation of that
testing.

When that does not happen we get stuff like the 737 Max debacle

Aviation is the antithesis of ‘Move fast and break things mentality’ for a
very good reason safety.

On my flying club’s plane every replacement part comes with a pedigree
which is added to the plane’s maintenance log upon installation and the
reason for removing the old one recorded

Imagine how much easier our networks would be to maintain if we had records
down to the last cable tie in the data center.   If there was a bug in a
SFP+ for instance all of them, when they were installed and by who and what
supplier they came from was readily available sure would make my life
easier.

The reasoning behind that massive pile of documents (pilot joke ‘a plane is
not ready to fly until the weight of the paperwork equals the weight of the
airplane’) is that if a failure is traced to a component all of them can be
traced and removed from service.

On a Airbus for instance all the takeoff and landing safety systems are
tied to the RadAlt.  The EU has strict rules about where the c-band can be
used as does Japan both use the 120 second rule c-band devices not allowed
in areas where the the aircraft is in its beginning/ending 2 minutes of
flight.

So the REST of the world got c-band right the US not so much



On Wed, Jan 19, 2022 at 10:59 AM Dennis Glatting  wrote:

> On Tue, 2022-01-18 at 12:29 -0800, Michael Thomas wrote:
> >
> > I really don't know anything about it. It seems really late to be
> > having
> > this fight now, right?
> >
>
> I worked in aviation as a technologist. Aviation is resistant to change.
> Any change. When you fly older aircraft, be aware that the software is
> old. Very old. As in some of the vendors long ago stopped supporting the
> software kind of old, assuming the vendors still exist.
>
> Aviation didn't wake up one day with the sudden appearance of 5G. They
> knew it was comming. They, aviation themselves, are heavily involved in
> standards. Aviation had plenty of time to test, correct, and protest.
>
> What aviation now wants is a 5G exclusion zone around airports, or what
> I sarcastically call "a technology exclusion zone," which tends to be
> businesses and homes. What is aviation going to do when 6G comes along?
> A new WiFi standard is implemented? Any other unforeseen future
> wired/wireless technologies? Or perhaps cell phones should go back to
> Morse Code for aviation's sake?
>
> 路‍♂️️
>
>
> --
> Dennis Glatting
> Numbers Skeptic
>

Re: What do you think about this airline vs 5G brouhaha?

[Tom Beecher]

> Jay, one thing you’re missing is that a maximum of 2 (and almost always
1) radar altimeter will be in use per airfield, as one aircraft will be
landing at a time.

I believe that Lady Benjamin may have conflated the radar altimeter on
aircraft with the instrument landing system transmitters.

On Wed, Jan 19, 2022 at 3:52 PM Jay Hennigan  wrote:

> On 1/19/22 01:53, Lady Benjamin Cannon of Glencoe, ASCE wrote:
> > Jay, one thing you’re missing is that a maximum of 2 (and almost always
> 1) radar altimeter will be in use per airfield, as one aircraft will be
> landing at a time.
>
> Really? I was under the impression that radar altimeters were pretty
> much always active during flight. If not, what triggers the "PULL UP -
> TERRAIN" audible warnings that are often heard on CVR recordings just
> before an airplane flies into cumulo-granite weather (mountains) miles
> from an airport?
>
> If in fact they are only used for IFR approach, is there a lockout to
> ensure that the radar is only active on approach? If pilots forget to
> turn them off after landing, does the radar transmitter automatically
> shut itself off?
>
> > Apparently some old gear has trouble with even a 500MHz guard band,
> which I also find astonishingly bad for any time, but a lot of aviation
> tech is truly from another century.
>
> This is absolutely horrible receiver design on equipment critical to
> aviation safety and it's surprising that tighter specs weren't enforced.
> That adjacent spectrum hasn't exactly been silent until now. It's been
> in use for decades going way back to Bell System TD-2 microwave that at
> one point criss-crossed the country.
>
> > They also have main lobes approx 80* wide so they still function when
> the plane is in 40* of bank.
>
> That makes sense.
>
> --
> Jay Hennigan - j...@west.net
> Network Engineering - CCIE #7880
> 503 897-8550 - WB6RDV
>

Re: What do you think about this airline vs 5G brouhaha?

[Jay Hennigan]

On 1/19/22 01:53, Lady Benjamin Cannon of Glencoe, ASCE wrote:

Jay, one thing you’re missing is that a maximum of 2 (and almost always 1) 
radar altimeter will be in use per airfield, as one aircraft will be landing at 
a time.


Really? I was under the impression that radar altimeters were pretty 
much always active during flight. If not, what triggers the "PULL UP - 
TERRAIN" audible warnings that are often heard on CVR recordings just 
before an airplane flies into cumulo-granite weather (mountains) miles 
from an airport?


If in fact they are only used for IFR approach, is there a lockout to 
ensure that the radar is only active on approach? If pilots forget to 
turn them off after landing, does the radar transmitter automatically 
shut itself off?



Apparently some old gear has trouble with even a 500MHz guard band, which I 
also find astonishingly bad for any time, but a lot of aviation tech is truly 
from another century.


This is absolutely horrible receiver design on equipment critical to 
aviation safety and it's surprising that tighter specs weren't enforced. 
That adjacent spectrum hasn't exactly been silent until now. It's been 
in use for decades going way back to Bell System TD-2 microwave that at 
one point criss-crossed the country.



They also have main lobes approx 80* wide so they still function when the plane 
is in 40* of bank.


That makes sense.

--
Jay Hennigan - j...@west.net
Network Engineering - CCIE #7880
503 897-8550 - WB6RDV

Re: What do you think about this airline vs 5G brouhaha?

[Keith Stokes]

Being a former satellite downlink/uplink operator I loosely kept up with this 
and had some involvement.

The satellite vendors moved frequencies on some of their customers to make way. 
I forget the full economics and seem to remember one could get reimbursed from 
the FCC for the change.

However there wasn’t as much of an “agreed-upon signoff” as there was “move, go 
off the air or accept interference”. The FCC and telco deal was done no matter 
what.


--

Keith Stokes



On Jan 19, 2022, at 10:22 AM, Tom Beecher 
mailto:beec...@beecher.cc>> wrote:

It's also relevant that the spectrum surrounding the 4.2-4.4 range has not been 
an empty desert. It has been used for satellite downlink since the 60s I think?

Yes, there are surely tons of differences in RF characteristics between the 
two. But let's be honest. Analysis would have been done decades ago on the 
impact of spurious emissions from sat downlinks on RAs, so there should be at 
least a baseline to work from.

Either way this should not be a discussion now. This clearly was discussed 
early in FCC filings, questions were asked, data was presented, and all these 
parties signed off.

On Wed, Jan 19, 2022 at 11:13 AM Tom Beecher 
mailto:beec...@beecher.cc>> wrote:
Altimeter Band : 4.2Ghz - 4.4Ghz

VZ and AT agreed (long ago) to reduce power and stay inside 3.7Ghz - 3.98Ghz 
once the full deployment was done, staying 200MHz away from altimeters.

In Japan, they have been running 5G for over a year now up to 4,1Ghz, and 
restarting again at 4.5Ghz. Only 100MHz of guard on either side of the 
altimeter band. I think EU is close-ish, but not totally sure.

I can't find a single report or study that has shown radio altimeter issuers in 
Japan since 5G was turned on there.

Aside from a single study which a LOT of smart people have called out flaws in, 
there isn't much out there that proves there WILL be interference with 
altimeters, just a lot of FUD that says it MIGHT. I dunno what the angle is, 
but this has turned into a shitshow.


On Tue, Jan 18, 2022 at 3:32 PM Michael Thomas 
mailto:m...@mtcc.com>> wrote:

I really don't know anything about it. It seems really late to be having
this fight now, right?

Mike

Re: What do you think about this airline vs 5G brouhaha?

[Tom Beecher]

It's also relevant that the spectrum surrounding the 4.2-4.4 range has not
been an empty desert. It has been used for satellite downlink since the 60s
I think?

Yes, there are surely tons of differences in RF characteristics between the
two. But let's be honest. Analysis would have been done decades ago on the
impact of spurious emissions from sat downlinks on RAs, so there should be
at least a baseline to work from.

Either way this should not be a discussion now. This clearly was discussed
early in FCC filings, questions were asked, data was presented, and all
these parties signed off.

On Wed, Jan 19, 2022 at 11:13 AM Tom Beecher  wrote:

> Altimeter Band : 4.2Ghz - 4.4Ghz
>
> VZ and AT agreed (long ago) to reduce power and stay inside 3.7Ghz -
> 3.98Ghz once the full deployment was done, staying 200MHz away from
> altimeters.
>
> In Japan, they have been running 5G for over a year now up to 4,1Ghz, and
> restarting again at 4.5Ghz. Only 100MHz of guard on either side of the
> altimeter band. I think EU is close-ish, but not totally sure.
>
> I can't find a single report or study that has shown radio altimeter
> issuers in Japan since 5G was turned on there.
>
> Aside from a single study which a LOT of smart people have called out
> flaws in, there isn't much out there that proves there WILL be interference
> with altimeters, just a lot of FUD that says it MIGHT. I dunno what the
> angle is, but this has turned into a shitshow.
>
>
> On Tue, Jan 18, 2022 at 3:32 PM Michael Thomas  wrote:
>
>>
>> I really don't know anything about it. It seems really late to be having
>> this fight now, right?
>>
>> Mike
>>
>>

Re: What do you think about this airline vs 5G brouhaha?

[Tom Beecher]

Altimeter Band : 4.2Ghz - 4.4Ghz

VZ and AT agreed (long ago) to reduce power and stay inside 3.7Ghz -
3.98Ghz once the full deployment was done, staying 200MHz away from
altimeters.

In Japan, they have been running 5G for over a year now up to 4,1Ghz, and
restarting again at 4.5Ghz. Only 100MHz of guard on either side of the
altimeter band. I think EU is close-ish, but not totally sure.

I can't find a single report or study that has shown radio altimeter
issuers in Japan since 5G was turned on there.

Aside from a single study which a LOT of smart people have called out flaws
in, there isn't much out there that proves there WILL be interference with
altimeters, just a lot of FUD that says it MIGHT. I dunno what the angle
is, but this has turned into a shitshow.


On Tue, Jan 18, 2022 at 3:32 PM Michael Thomas  wrote:

>
> I really don't know anything about it. It seems really late to be having
> this fight now, right?
>
> Mike
>
>

Re: What do you think about this airline vs 5G brouhaha?

[Andy Ringsmuth]

> On Jan 18, 2022, at 4:34 PM, Dennis Glatting  wrote:
> 
> What aviation now wants is a 5G exclusion zone around airports, or what
> I sarcastically call "a technology exclusion zone," which tends to be
> businesses and homes. What is aviation going to do when 6G comes along?
> A new WiFi standard is implemented? Any other unforeseen future
> wired/wireless technologies? Or perhaps cell phones should go back to
> Morse Code for aviation's sake?

Clarity is critical to this discussion.

And as usual, the media is obfuscating it. Probably not deliberately this time, 
but it is happening nonetheless, because the talking heads on TV don’t have the 
remotest understanding of what is actually happening. Not surprising of course.

This isn’t an OMG 5G! thing whatsoever. It is specifically related to a 
frequency band that cell carriers are now able to use, which is adjacent or 
practically adjacent to an existing frequency band used by airplanes to safely 
land. Yeah, 5G is a fancy-schmancy buzz word but that is not really material to 
the conversation.

A ROUGH analogy would be something along the lines of - you buy some property 
and build your dream home there. Across the street is vacant land owned by the 
city, and the city’s comprehensive plan says it is zoned for recreational use 
and they plan to put a park there some day. Years go by and one day you wake up 
to find bulldozers on the empty lot. “Awesome, my grandkids will have a nice 
park now!” you think. And construction continues. As it nears completion, you 
realize “Hmmm, that doesn’t really look like a park.” Further investigation 
uncovers that the city sold the land to a private developer and they are 
building a brothel and strip club across the street, which will bring massive 
amounts of vehicular and pedestrian traffic to what for decades was your quiet 
little street.

You scream and complain to the city council about it. “I built my dream home 
there because YOU said there would be a nice park with playground equipment and 
a fishing pond built there some day!” The city says “Yeah, well, sucks to be 
you. We sold it, tough cookies.”


Of course like any analogy it doesn’t hold up 100 percent, but that’s a way to 
explain it to non-tech folks.


Andy Ringsmuth
5609 Harding Drive
Lincoln, NE 68521-5831
(402) 304-0083
a...@andyring.com

Re: What do you think about this airline vs 5G brouhaha?

[Dennis Glatting]

On Tue, 2022-01-18 at 12:29 -0800, Michael Thomas wrote:
> 
> I really don't know anything about it. It seems really late to be
> having 
> this fight now, right?
> 

I worked in aviation as a technologist. Aviation is resistant to change.
Any change. When you fly older aircraft, be aware that the software is
old. Very old. As in some of the vendors long ago stopped supporting the
software kind of old, assuming the vendors still exist. 

Aviation didn't wake up one day with the sudden appearance of 5G. They
knew it was comming. They, aviation themselves, are heavily involved in
standards. Aviation had plenty of time to test, correct, and protest.

What aviation now wants is a 5G exclusion zone around airports, or what
I sarcastically call "a technology exclusion zone," which tends to be
businesses and homes. What is aviation going to do when 6G comes along?
A new WiFi standard is implemented? Any other unforeseen future
wired/wireless technologies? Or perhaps cell phones should go back to
Morse Code for aviation's sake?

路‍♂️️


-- 
Dennis Glatting
Numbers Skeptic

Re: What do you think about this airline vs 5G brouhaha?

[Lady Benjamin Cannon of Glencoe, ASCE]

Jay, one thing you’re missing is that a maximum of 2 (and almost always 1) 
radar altimeter will be in use per airfield, as one aircraft will be landing at 
a time. 

2 at SFO in good weather. (Where it doesn’t matter if they work). 

Apparently some old gear has trouble with even a 500MHz guard band, which I 
also find astonishingly bad for any time, but a lot of aviation tech is truly 
from another century. 

They also have main lobes approx 80* wide so they still function when the plane 
is in 40* of bank.

Ms. Lady Benjamin PD Cannon of Glencoe, ASCE
6x7 Networks & 6x7 Telecom, LLC 
CEO 
l...@6by7.net
"The only fully end-to-end encrypted global telecommunications company in the 
world.”

FCC License KJ6FJJ

Sent from my iPhone via RFC1149.

> On Jan 18, 2022, at 2:25 PM, Jay Hennigan  wrote:
> 
> On 1/18/22 12:29, Michael Thomas wrote:
>> I really don't know anything about it. It seems really late to be having 
>> this fight now, right?
> 
> From a technical standpoint it seems to me to be a non-issue. There's a 220 
> MHz guard band. 5G signals top out at 3980 MHz and radar altimeters operate 
> between 4200 and 4400 MHz.
> 
> If a signal 220 MHz away is going to interfere, then radar altimeters on 
> other aircraft operating in the same band would clearly be a far greater 
> threat, and those radar altimeter signals will be rather numerous near 
> airports. In other words, if non-correlated signals 220 MHz away are going to 
> interfere, then signals within the same band are going to be a far greater 
> source of interference.
> 
> Radar receivers are typically some form of direct conversion with rather good 
> selectivity, synchronized to the frequency of the transmitted pulse. In 
> addition, radar altimeter antennas are pointed at the ground, perpendicular 
> to the horizon. Cell site antennas by design are aimed more or less toward 
> the horizon, not pointed straight up at the sky.
> 
> There's also an existing FCC mobile allocation from 4400 to 4500 MHz directly 
> adjacent to the aeronautical radar band on the high side with no guard band, 
> yet no complaints about that.
> 
> IMNSHO, the concern that 5G cellular signals will cause airplanes to fall out 
> of the sky has about this >< much more credence than the concern that 5G 
> signals cause coronavirus.
> 
> It shouldn't be that hard to instrument an aircraft with test equipment, buzz 
> a few operating cell towers, and come up with hard data.
> 
> -- 
> Jay Hennigan - j...@west.net
> Network Engineering - CCIE #7880
> 503 897-8550 - WB6RDV

Re: What do you think about this airline vs 5G brouhaha?

[Lady Benjamin Cannon of Glencoe, ASCE]

Let’s be clear, this is not a 5G issue.  LTE in the space spectrum would be an 
issue.  

This is a spectrum issue. Only.

Ms. Lady Benjamin PD Cannon of Glencoe, ASCE
6x7 Networks & 6x7 Telecom, LLC 
CEO 
l...@6by7.net
"The only fully end-to-end encrypted global telecommunications company in the 
world.”

FCC License KJ6FJJ

Sent from my iPhone via RFC1149.

> On Jan 18, 2022, at 2:15 PM, Mel Beckman  wrote:
> 
>  Apples and oranges Michael. The US domestic aviation environment is quite 
> different than even Europe or and especially smaller countries overseas. And 
> how long has 5G been out anyway? I hardly think that’s been available for 
> enough of a safety track record in any country.
> 
> -mel via cell
> 
>>> On Jan 18, 2022, at 2:06 PM, Mel Beckman  wrote:
>>> 
>>  Shane,
>> 
>> Incorrect. Owning spectrum also includes the right to interference-free 
>> operation. And you imply that the FAA and airline industry has done nothing, 
>> when in reality it’s the FCC who has done nothing. the FAA sponsored 
>> extensive engineering tests that demonstrate the interference is a concern, 
>> and they notified all the parties well in advance. The fCC et al chose to do 
>> no research of their own, and are basing all their assumptions on operation 
>> in other countries, which even you must admit can’t really be congruent with 
>> the US.
>> 
>> -mel via cell
>> 
>>> On Jan 18, 2022, at 2:01 PM, sro...@ronan-online.com wrote:
>>> 
>>>  The thing is aviation DOESN’T own this spectrum, they just assumed it 
>>> would always be unused. And they failed to mention it would be a problem 
>>> during the last 5 years of discussion regarding the use of this spectrum.
>>> 
>>> Shane
>>> 
 On Jan 18, 2022, at 4:25 PM, Mel Beckman  wrote:
 
 
 Michael,
 
 Here’s a recent PCmag editorial on the subject, and it seems like many 
 people want to put Internet speed above airline safety:
 
 https://www.pcmag.com/news/faa-goes-in-hard-to-kill-mid-band-5g
 
 This issue definitely impacts network operations for 5G providers, so 
 makes sense to discuss here.
 
 Here’s a comment from a friend of mine who has been both a network 
 engineer and a pilot for United Airlines, posted on the article linked 
 above:
 
 “As a pilot, I can tell you that landing in instrument conditions is by 
 far the most critical flight regime possible, during which the radar 
 altimeter reports are a matter of life and death. There is no alternative 
 technology, such as GPS, with the required accuracy and reliability, to 
 provide approach guidance down to the runway in zero-zero weather, which 
 is what the radar altimeter does. 
 
 The collective tech industry needs to admit that it made a huge blunder 
 when it urged the FCC’s clueless Ajit Pai to “blow off” the clearly 
 demonstrated FAA spectrum conflict. Sorry, passengers, but if you look out 
 your window, you’ll see that aviation owns this spectrum and is entitled 
 to interference-free operation. Replacing all radar altimeters isn’t going 
 to happen in time for 5G anyway — it took more than ten years just to 
 deploy anti-collision technology. So do what you should have done from the 
 beginning: follow the FCC rules of non-interference to existing users, who 
 have clear priority in this case.”
 
 I tend to agree with him, and it looks like the 5G providers and FAA 
 agreed last week to put some buffer safety zones around runway approaches 
 at 50 major airports:
 
 https://www.cnet.com/news/faa-lists-50-airports-getting-temporary-buffer-zones-blocking-new-5g-signals/
 
 
 -mel 
 
> On Jan 18, 2022, at 12:33 PM, Michael Thomas  wrote:
> 
> 
> I really don't know anything about it. It seems really late to be having 
> this fight now, right?
> 
> Mike
> 

Re: What do you think about this airline vs 5G brouhaha?

[Masataka Ohta]

Brandon Martin wrote:

However, as long as your receiver still has adequate dynamic range to 
receive "everything that's there",


That's not saturation.

Saturation means a receiver does not have adequate dynamic range.

With digital processing under saturation, effective number of bits
is reduced. That is, some necessary bits are lost, which is not
"everything that's there".

Masataka Ohta

Re: What do you think about this airline vs 5G brouhaha?

[Brandon Martin]

On 1/19/22 12:28 AM, Masataka Ohta wrote:

Digital technology can not be useful when RF stage is saturated,
which is why a patent to avoid saturation was essential for CDMA. 


Completely overloading the receiver frontend will of course render any 
kind of modulation or coding gain irrelevant, yes.


However, as long as your receiver still has adequate dynamic range to 
receive "everything that's there", effective gain via spread spectrum, 
FEC, etc. can be on the order of 20-30dB compared to a naive narrowband 
system operating at similar power when faced with a "jammer" within your 
RF receive mask, which is what I was getting at.


In this case, however, the system is basically a dumb radar, apparently, 
so none of that is going to be present. The fact that a signal 250MHz 
out of band can present meaningful issues is troubling nonetheless.


--
Brandon Martin

Re: What do you think about this airline vs 5G brouhaha?

[Masataka Ohta]

Brandon Martin wrote:

The system apparently also responds poorly to both narrowband and 
wideband jammers i.e. it does not employ what we'd consider robust, 
modern error-correction or coding systems or even digital error checking 
techniques.


Digital technology can not be useful when RF stage is saturated,
which is why a patent to avoid saturation was essential for CDMA.

Masataka Ohta

Re: What do you think about this airline vs 5G brouhaha?

[Masataka Ohta]

Jay Hennigan wrote:


Radar receivers are typically some form of direct conversion with
rather good selectivity, synchronized to the frequency of the
transmitted pulse.


No. Direct conversion stage has no inherent frequency
selectivity and is subject to saturation by noise of
any frequency unless the noise is removed in advance.

Selectivity can be enjoyed only after successful
unsaturated conversion, direct or to IF.

But, the solution is to put an LC band pass/stop filter
between an antenna and a receiver, though I have no
idea on the difficulty to obtain FAA/FCC approval to
do so.

Masataka Ohta

Re: What do you think about this airline vs 5G brouhaha?

[Brandon Martin]

On 01/18/2022 20:08, Michael Loftis wrote:
Remember that the RA is sub 1W looking for reflected emissions. It’s 
very possible the ground equipment for a cell base station to have 
spurious harmonics…where they land requires more RF engineering chops 
than I’ve got, and would obviously be very system dependent. So yes in 
my understanding due to the RF voodoo of how they transmit and receive


This is run-of-the-mill testing for not just transmitters but anything 
that could possibly, maybe, emit RF energy in the USA.  The out-of-band 
(spurious emission) limits are quite strenuous, and the test criteria 
are specifically designed to catch even fairly intermittent blips that 
might crop up just about anywhere let alone in a band of particular 
interest.  There's a reason (just about) all FCC compliance houses have 
70GHz spectrum analyzers even if they don't normally look at intentional 
emissions above 6 or so.


One thing the FCC could potentially do to wipe some egg of their 
collective faces, here, is mandate that transmitters operating in this 
newly allocated wireless band face additional scrutiny for spurious 
emissions in the radio altimeter band as well as the guard band between 
the two services and a similar bandwidth above the radio altimeter band. 
 If the quasi-peak detector runs across that swath for an hour while 
the operating conditions of the device being tested are continuously 
varied both within and somewhat outside its normal and even 
extraordinary (but functional) operating range and still doesn't see 
anything that isn't outside the femtowatt range, you're probably good. 
FAA and aviation industry can even advise on these standards.  That's 
not unheard of and a good example of industry cooperation.


Note that this would be above and beyond the existing general rules for 
spurious emissions that are already tested as part of pretty much any RF 
transmitter in the USA.


I'm curious at what point the possibility of spurious emissions from an 
old-fashioned TVRO C-Band receiver becomes concerning.  It would be very 
sporadic, but the gain off the ground station dish is rather 
non-trivial.  AFAIK, the design of most receivers would mean it would 
have to be a modulation product of two LOs, but I suspect it's possible 
to have something come within 500MHz of this band just like this 
wireless allocation does.  Those users have been around for 35+ years 
and are widespread and unlicensed (as they are receive only).


--
Brandon Martin

Re: What do you think about this airline vs 5G brouhaha?

[John Levine]

It appears that Michael Thomas  said:
>
>I really don't know anything about it. It seems really late to be having 
>this fight now, right?

Harold Feld did an excellent explainer about this in November:

https://wetmachine.com/tales-of-the-sausage-factory/what-the-eff-faa-my-insanely-long-field-guide-to-the-faa-fcc-5g-c-band-fight/

tl;dr while interference is certainly possible in theory, the putative
evidence can charitably be described as weak, and the FAA has been
complete jerks throughout the process.

R's,
John

Re: What do you think about this airline vs 5G brouhaha?

[Lady Benjamin Cannon of Glencoe, ASCE]

Interference with radar altimeters is a serious issue.   As a pilot myself, if 
this fails, you crash with all hands lost.  

That said, we should be able to eliminate the possibility of any interference. 

So this shouldn’t be a thing.

But also, you don’t f- with radar altimeters.

Ms. Lady Benjamin PD Cannon of Glencoe, ASCE
6x7 Networks & 6x7 Telecom, LLC 
CEO 
l...@6by7.net
"The only fully end-to-end encrypted global telecommunications company in the 
world.”

FCC License KJ6FJJ

Sent from my iPhone via RFC1149.

> On Jan 18, 2022, at 12:32 PM, Michael Thomas  wrote:
> 
> I really don't know anything about it. It seems really late to be having this 
> fight now, right?
> 
> Mike

Re: What do you think about this airline vs 5G brouhaha?

[Michael Loftis]

On Tue, Jan 18, 2022 at 17:49 Jay Hennigan  wrote:

> On 1/18/22 15:51, Brandon Martin wrote:
>
> > Further, it seems that good engineering practice was not used in the
> > design of these vulnerable systems and that they are subject to
> > interference from broad-spectrum "jammers" (i.e. signals that, in terms
> > of modulation and timing, don't necessarily correspond to what they're
> > expecting to receive) transmitting well outside their allocated band (by
> > separation comparable to the entire band in which they operate) let
> > alone outside the expected, tuned frequency of signal reception.  All of
> > these are typically very high on the list of consideration when
> > designing an RF receiver and seem to have been either ignored entirely
> > or at least discounted in the design of these instruments from what I'm
> > hearing.
>
> This simply doesn't make sense. Radar receivers are usually direct
> conversion driven from the same frequency source as the transmitter,
> meaning that they are going to have rather good selectivity with regard
> to frequency.
>
> Furthermore, a radio altimeter used for approach and landing is going to
> have a very short time window. I'm by no means familiar with the
> internal workings of these devices, their specifications, or their
> effective range, but if the altitude to be measured is 5000 feet or less
> the device will send a pulse and then open a receive window of no more
> than about 11 microseconds to look for its return. If you're only
> concerned about being 1000 feet or less above terrain, the window is
> about 2 microseconds. The pulses are presumably sent relatively
> frequently, probably several times a second, and the results averaged.
> In addition, the radar antenna beamwidth is going to be relatively small
> and pointed more or less straight down.


GPWS, and all rescue/medevac/etc helicopter operations also use the RA, and
this is NOT just in the landing/approach of a runway. Think about landing a
helicopter at night on the  freeway or a nearby field. TAWS uses GPS to
locate in space and I don’t know where it’s altitude source is - probably
the baro altimeter until the RA starts getting a return (or thinks it is)


>
> Intentional broadband jamming isn't going to be very effective against
> an airplane as the jammer would need to be directly beneath a fast
> moving target and get the timing exactly right with microsecond accuracy.
>
> Accidental interference from a source at least 220MHz out of band with a
> beam pointed at the horizon is even more far-fetched unless, as you say,
> the radar unit's receiver is complete garbage in which case how did it
> get a TSO in the first place? Avionics equipment that is critical to a
> precision approach isn't, or at least shouldn't be, crap.


They’ve never been required to have immunity. Last spec update was AFAIK
1980s. It’s definitely a stack of problems…part of which is the FCC
auctioning the Spectrum, it puts them in conflict as both the enforcement
and beneficiary. Billions of dollars being the CTIA on one hand. On the
other RTCA, AOPA, and some other small $ fish they stand nothing to gain
from.

Remember that the RA is sub 1W looking for reflected emissions. It’s very
possible the ground equipment for a cell base station to have spurious
harmonics…where they land requires more RF engineering chops than I’ve got,
and would obviously be very system dependent. So yes in my understanding
due to the RF voodoo of how they transmit and receive, and the .. field of
view .. those factors mitigate interference for certain…but why did the FCC
auction that chunk? Why not say ok you’ve got two years to develop a
standard, update that 1980s requirement, and 5 or 10 to implement? Instead
we’re just barely four years on and going to be seeing potentially
interesting deployments.  Interference that only can happen and only
matters in critical flight phases….





>
> --
> Jay Hennigan - j...@west.net
> Network Engineering - CCIE #7880
> 503 897-8550 - WB6RDV
>
-- 

"Genius might be described as a supreme capacity for getting its possessors
into trouble of all kinds."
-- Samuel Butler

Re: What do you think about this airline vs 5G brouhaha?

[Brandon Martin]

On 01/18/2022 19:48, Jay Hennigan wrote:
Intentional broadband jamming isn't going to be very effective against 
an airplane as the jammer would need to be directly beneath a fast 
moving target and get the timing exactly right with microsecond accuracy.


Just to clarify, I wasn't referring to intentional (and naive) "jammers" 
that simply attempt to disable a system, here, but rather using a more 
academic notion of the concept to refer to a 5G NR system acting in an 
unintentional context with the same outcome similar to how one might 
consider modern OFDM-based WiFi a "jammer" to a conventional narrowband 
communication system operating on the same or a nearby carrier frequency 
like the classic Bluetooth PHY.


5G NR is (or should be, from what I know of it and its relation to other 
OFDM systems) a pretty broad-band, flat-spectrum PHY operating at only 
moderate power and for essentially infinite duration in the scope of a 
radar receiver.  It would by no means be an ideal means to disable such 
a system, but it does represent RF energy that the receiver needs to 
contend with.


--
Brandon Martin

Re: What do you think about this airline vs 5G brouhaha?

[Jay Hennigan]

On 1/18/22 15:51, Brandon Martin wrote:

Further, it seems that good engineering practice was not used in the 
design of these vulnerable systems and that they are subject to 
interference from broad-spectrum "jammers" (i.e. signals that, in terms 
of modulation and timing, don't necessarily correspond to what they're 
expecting to receive) transmitting well outside their allocated band (by 
separation comparable to the entire band in which they operate) let 
alone outside the expected, tuned frequency of signal reception.  All of 
these are typically very high on the list of consideration when 
designing an RF receiver and seem to have been either ignored entirely 
or at least discounted in the design of these instruments from what I'm 
hearing.


This simply doesn't make sense. Radar receivers are usually direct 
conversion driven from the same frequency source as the transmitter, 
meaning that they are going to have rather good selectivity with regard 
to frequency.


Furthermore, a radio altimeter used for approach and landing is going to 
have a very short time window. I'm by no means familiar with the 
internal workings of these devices, their specifications, or their 
effective range, but if the altitude to be measured is 5000 feet or less 
the device will send a pulse and then open a receive window of no more 
than about 11 microseconds to look for its return. If you're only 
concerned about being 1000 feet or less above terrain, the window is 
about 2 microseconds. The pulses are presumably sent relatively 
frequently, probably several times a second, and the results averaged. 
In addition, the radar antenna beamwidth is going to be relatively small 
and pointed more or less straight down.


Intentional broadband jamming isn't going to be very effective against 
an airplane as the jammer would need to be directly beneath a fast 
moving target and get the timing exactly right with microsecond accuracy.


Accidental interference from a source at least 220MHz out of band with a 
beam pointed at the horizon is even more far-fetched unless, as you say, 
the radar unit's receiver is complete garbage in which case how did it 
get a TSO in the first place? Avionics equipment that is critical to a 
precision approach isn't, or at least shouldn't be, crap.


--
Jay Hennigan - j...@west.net
Network Engineering - CCIE #7880
503 897-8550 - WB6RDV

Re: What do you think about this airline vs 5G brouhaha?

[Brandon Martin]

On 01/18/2022 16:57, Mel Beckman wrote:

Bo, it’s the radar altimeter, not the barometric altimeter. This is a radar 
distance measurement device for determine the precise height above the ground,  
critical for low-visibility approaches.

Where frequency interference is concerned, under FCC rules the existing users 
have priority, and are entitled to interference-free operation.


Hmm, I'm seeing that "radar altimeter" and "radio altimeter" can indeed 
refer to the same class of instrument, so perhaps there's confusion 
(perhaps including by myself).


Nonetheless, while indeed existing users are granted some reprieve from 
interference by new users of other services, this is mostly in the 
planning stage of things and not the actual operations.  The time to get 
this addressed would have been back when this portion of the band was 
re-allocated to wireless systems (from space-to-ground satellite 
systems) several years ago.


Further, it seems that good engineering practice was not used in the 
design of these vulnerable systems and that they are subject to 
interference from broad-spectrum "jammers" (i.e. signals that, in terms 
of modulation and timing, don't necessarily correspond to what they're 
expecting to receive) transmitting well outside their allocated band (by 
separation comparable to the entire band in which they operate) let 
alone outside the expected, tuned frequency of signal reception.  All of 
these are typically very high on the list of consideration when 
designing an RF receiver and seem to have been either ignored entirely 
or at least discounted in the design of these instruments from what I'm 
hearing.


That is, I have yet to see any source (even from the aviation industry) 
claiming that there is in-band interference issues from the new wireless 
systems or that these radio altimeter systems somehow need such extreme 
receiver sensitivity that a several hundred-MHz guard band between 
services (with an existing service in between, albeit one with the 
transmitter usually in the other direction) is not sufficient to ensure 
proper receiver isolation from unwanted signals.

--
Brandon Martin

Re: What do you think about this airline vs 5G brouhaha?

[Michael Loftis]

New to the public eye but not orgs like AOPA who’ve been fighting since
2020 but there not multi billion dollar lobby groups. US is more affected
because we have more general aviation, and an older fleet overall.

And it’s not cheap to replace these radio altimeters (but that’s kind of
like everything aviation)

On Tue, Jan 18, 2022 at 13:32 Michael Thomas  wrote:

>
> I really don't know anything about it. It seems really late to be having
> this fight now, right?
>
> Mike
>
> --

"Genius might be described as a supreme capacity for getting its possessors
into trouble of all kinds."
-- Samuel Butler

Re: What do you think about this airline vs 5G brouhaha?

[Brandon Martin]

On 1/18/22 5:06 PM, Mel Beckman wrote:
Incorrect. Owning spectrum also includes the right to 
interference-free operation. And you imply that the FAA and airline 
industry has done nothing, when in reality it’s the FCC who has done 
nothing. the FAA sponsored extensive engineering tests that 
demonstrate the interference is a concern, and they notified all the 
parties well in advance. The fCC et al chose to do no research of 
their own, and are basing all their assumptions on operation in other 
countries, which even you must admit can’t really be congruent with 
the US.
Owning spectrum includes the right to interference-free operations from 
IN BAND interference (or not, depending on how you "own" it).


The FAA and airlines are (presumably) correct that there is de-facto an 
interference issue.  The FCC is also (presumably) correct that it's "not 
their problem" as the interference is due to grossly out-of-band 
signals, and the FCC has provided what they believe to be (and, 
according to most RF engineering practices I know of, is) a more than 
sufficient guard band between the two users.


Interference from out-of-band sources is on the operator of the 
receiving equipment to correct EVEN IF they are a licensed, primary user 
of their spectrum since the interference is from outside their 
allocation. This is always true so long as the folks sourcing the 
interference are complying with the limits of their spectrum (there are 
some other wiggles for Part 15 unlicensed users) including power limits 
and applicable transmit spectrum masks.


The FCC's job is to make sure that they set the rules such that folks 
with licensed spectrum do not experience practical problems when 
presented with out-of-band signals. When doing this, they attempt to use 
established guidelines of good engineering practice as well as reports 
from "the field", but they can't possibly account for users with what is 
arguably simply (very) faulty equipment.


If my 1kW HAM FM radio transmitter on 145MHz causes receive problems on 
your aviation band AM receiver (108-137MHz), that is YOUR problem as 
long as I'm complying with all the rules and regs of part 97. That is, 
your receiver sucks, and you need to fix it - possibly by replacing it. 
Likewise, if I'm getting receiver desense issues on my 145MHz FM 
handheld near the airport because of ATC's AM transmitter a few dozen 
MHz down, it's on ME to fix it (or live with it).


The issue that cropped up appears to be that, since the C-band spectrum 
under discussion went unused for so long, a LOT of sucky receivers got 
deployed, and nobody really noticed or cared. Now, it's a big deal to 
try to replace them all, and it's made even worse by how difficult 
changing anything in aviation is and how comparatively old and hence 
simple (perhaps too simple) the radio altimeter RF physical layer 
apparently is.


--
Brandon Martin

Re: What do you think about this airline vs 5G brouhaha?

[Shane Ronan]

Except that the FAA isn't claiming interference in their LICENSED band,
they are claiming interference OUTSIDE their licensed band. You can't squat
on a frequency and then expect the licensed users to accommodate you.

Shane

On Tue, Jan 18, 2022 at 5:06 PM Mel Beckman  wrote:

> Shane,
>
> Incorrect. Owning spectrum also includes the right to interference-free
> operation. And you imply that the FAA and airline industry has done
> nothing, when in reality it’s the FCC who has done nothing. the FAA
> sponsored extensive engineering tests that demonstrate the interference is
> a concern, and they notified all the parties well in advance. The fCC et al
> chose to do no research of their own, and are basing all their assumptions
> on operation in other countries, which even you must admit can’t really be
> congruent with the US.
>
> -mel via cell
>
> On Jan 18, 2022, at 2:01 PM, sro...@ronan-online.com wrote:
>
>  The thing is aviation DOESN’T own this spectrum, they just assumed it
> would always be unused. And they failed to mention it would be a problem
> during the last 5 years of discussion regarding the use of this spectrum.
>
> Shane
>
> On Jan 18, 2022, at 4:25 PM, Mel Beckman  wrote:
>
> 
>
> Michael,
>
>
> Here’s a recent PCmag editorial on the subject, and it seems like many
> people want to put Internet speed above airline safety:
>
>
> https://www.pcmag.com/news/faa-goes-in-hard-to-kill-mid-band-5g
> 
>
>
> This issue definitely impacts network operations for 5G providers, so
> makes sense to discuss here.
>
>
> Here’s a comment from a friend of mine who has been both a network
> engineer and a pilot for United Airlines, posted on the article linked
> above:
>
>
> *“As a pilot, I can tell you that landing in instrument conditions is by
> far the most critical flight regime possible, during which the radar
> altimeter reports are a matter of life and death. There is no alternative
> technology, such as GPS, with the required accuracy and reliability, to
> provide approach guidance down to the runway in zero-zero weather, which is
> what the radar altimeter does. *
>
>
> *The collective tech industry needs to admit that it made a huge blunder
> when it urged the FCC’s clueless Ajit Pai to “blow off” the clearly
> demonstrated FAA spectrum conflict. Sorry, passengers, but if you look out
> your window, you’ll see that aviation owns this spectrum and is entitled to
> interference-free operation. Replacing all radar altimeters isn’t going to
> happen in time for 5G anyway — it took more than ten years just to deploy
> anti-collision technology. So do what you should have done from the
> beginning: follow the FCC rules of non-interference to existing users, who
> have clear priority in this case.”*
>
>
> I tend to agree with him, and it looks like the 5G providers and FAA
> agreed last week to put some buffer safety zones around runway approaches
> at 50 major airports:
>
>
>
> https://www.cnet.com/news/faa-lists-50-airports-getting-temporary-buffer-zones-blocking-new-5g-signals/
> 
>
>
>
> -mel
>
> On Jan 18, 2022, at 12:33 PM, Michael Thomas  wrote:
>
> 
> I really don't know anything about it. It seems really late to be having
> this fight now, right?
>
> Mike
>
>

Re: What do you think about this airline vs 5G brouhaha?

[Jay Hennigan]

On 1/18/22 12:29, Michael Thomas wrote:


I really don't know anything about it. It seems really late to be having 
this fight now, right?


From a technical standpoint it seems to me to be a non-issue. There's a 
220 MHz guard band. 5G signals top out at 3980 MHz and radar altimeters 
operate between 4200 and 4400 MHz.


If a signal 220 MHz away is going to interfere, then radar altimeters on 
other aircraft operating in the same band would clearly be a far greater 
threat, and those radar altimeter signals will be rather numerous near 
airports. In other words, if non-correlated signals 220 MHz away are 
going to interfere, then signals within the same band are going to be a 
far greater source of interference.


Radar receivers are typically some form of direct conversion with rather 
good selectivity, synchronized to the frequency of the transmitted 
pulse. In addition, radar altimeter antennas are pointed at the ground, 
perpendicular to the horizon. Cell site antennas by design are aimed 
more or less toward the horizon, not pointed straight up at the sky.


There's also an existing FCC mobile allocation from 4400 to 4500 MHz 
directly adjacent to the aeronautical radar band on the high side with 
no guard band, yet no complaints about that.


IMNSHO, the concern that 5G cellular signals will cause airplanes to 
fall out of the sky has about this >< much more credence than the 
concern that 5G signals cause coronavirus.


It shouldn't be that hard to instrument an aircraft with test equipment, 
buzz a few operating cell towers, and come up with hard data.


--
Jay Hennigan - j...@west.net
Network Engineering - CCIE #7880
503 897-8550 - WB6RDV

Re: What do you think about this airline vs 5G brouhaha?

[Nick Hilliard]

Mel Beckman wrote on 18/01/2022 21:25:
/The collective tech industry needs to admit that it made a huge blunder 
when it urged the FCC’s clueless Ajit Pai to “blow off” the clearly 
demonstrated FAA spectrum conflict. Sorry, passengers, but if you look 
out your window, you’ll see that aviation owns this spectrum and is 
entitled to interference-free operation. Replacing all radar altimeters 
isn’t going to happen in time for 5G anyway — it took more than ten 
years just to deploy anti-collision technology. So do what you should 
have done from the beginning: follow the FCC rules of non-interference 
to existing users, who have clear priority in this case.”/


The original fixed satellite comms (space-to-earth) allocation was 
3700-4200MHz, which was split into two parts in 2020: a mobile wireless 
spectrum allocation on 3700MHz to 4000MHz (for 5G) with 4000-4200MHz 
remaining allocated to satellite comms. The 4200-4400MHz range is 
allocated to aeronautical navigation and is used for radio altimeters.


So by rights, aviation doesn't now and never did own this spectrum. 
That said, spectrum bleed on radio transmitters is something that 
happens, and I've no doubt that there are plenty of broken altimeter 
receiver antennas out there which will pick up signals outside their 
formal allocation of 4200-4400MHz.  Regularly tested band pass filters 
should deal with most of this.


Even if technically the aeronautical sector doesn't own this spectrum, 
the consequences of transmitter or receiver bleed from nearby 
allocations could be serious for the same reason that if someone walks 
out on a pedestrian crossing without checking and gets mown down by a 
drunk driver, they're not going to be jubilantly talking at their 
funeral about how at least they were acting within their rights.


Nick

Re: What do you think about this airline vs 5G brouhaha?

[Mike Hammett]

What I've seen so far from the airline industry is a joke. 




- 
Mike Hammett 
Intelligent Computing Solutions 
http://www.ics-il.com 

Midwest-IX 
http://www.midwest-ix.com 

- Original Message -

From: "Mel Beckman"  
To: sro...@ronan-online.com 
Cc: nanog@nanog.org 
Sent: Tuesday, January 18, 2022 4:06:46 PM 
Subject: Re: What do you think about this airline vs 5G brouhaha? 

Shane, 


Incorrect. Owning spectrum also includes the right to interference-free 
operation. And you imply that the FAA and airline industry has done nothing, 
when in reality it’s the FCC who has done nothing. the FAA sponsored extensive 
engineering tests that demonstrate the interference is a concern, and they 
notified all the parties well in advance. The fCC et al chose to do no research 
of their own, and are basing all their assumptions on operation in other 
countries, which even you must admit can’t really be congruent with the US. 


-mel via cell 



On Jan 18, 2022, at 2:01 PM, sro...@ronan-online.com wrote: 






The thing is aviation DOESN’T own this spectrum, they just assumed it would 
always be unused. And they failed to mention it would be a problem during the 
last 5 years of discussion regarding the use of this spectrum. 


Shane 




On Jan 18, 2022, at 4:25 PM, Mel Beckman  wrote: 







Michael, 


Here’s a recent PCmag editorial on the subject, and it seems like many people 
want to put Internet speed above airline safety: 


https://www.pcmag.com/news/faa-goes-in-hard-to-kill-mid-band-5g 


This issue definitely impacts network operations for 5G providers, so makes 
sense to discuss here. 


Here’s a comment from a friend of mine who has been both a network engineer and 
a pilot for United Airlines, posted on the article linked above: 


“As a pilot, I can tell you that landing in instrument conditions is by far the 
most critical flight regime possible, during which the radar altimeter reports 
are a matter of life and death. There is no alternative technology, such as 
GPS, with the required accuracy and reliability, to provide approach guidance 
down to the runway in zero-zero weather, which is what the radar altimeter 
does. 


The collective tech industry needs to admit that it made a huge blunder when it 
urged the FCC’s clueless Ajit Pai to “blow off” the clearly demonstrated FAA 
spectrum conflict. Sorry, passengers, but if you look out your window, you’ll 
see that aviation owns this spectrum and is entitled to interference-free 
operation. Replacing all radar altimeters isn’t going to happen in time for 5G 
anyway — it took more than ten years just to deploy anti-collision technology. 
So do what you should have done from the beginning: follow the FCC rules of 
non-interference to existing users, who have clear priority in this case.” 


I tend to agree with him, and it looks like the 5G providers and FAA agreed 
last week to put some buffer safety zones around runway approaches at 50 major 
airports: 


https://www.cnet.com/news/faa-lists-50-airports-getting-temporary-buffer-zones-blocking-new-5g-signals/
 



-mel 



On Jan 18, 2022, at 12:33 PM, Michael Thomas  wrote: 







I really don't know anything about it. It seems really late to be having this 
fight now, right? 

Mike 

Re: What do you think about this airline vs 5G brouhaha?

[Mel Beckman]

Apples and oranges Michael. The US domestic aviation environment is quite 
different than even Europe or and especially smaller countries overseas. And 
how long has 5G been out anyway? I hardly think that’s been available for 
enough of a safety track record in any country.

-mel via cell

On Jan 18, 2022, at 2:06 PM, Mel Beckman  wrote:

 Shane,

Incorrect. Owning spectrum also includes the right to interference-free 
operation. And you imply that the FAA and airline industry has done nothing, 
when in reality it’s the FCC who has done nothing. the FAA sponsored extensive 
engineering tests that demonstrate the interference is a concern, and they 
notified all the parties well in advance. The fCC et al chose to do no research 
of their own, and are basing all their assumptions on operation in other 
countries, which even you must admit can’t really be congruent with the US.

-mel via cell

On Jan 18, 2022, at 2:01 PM, sro...@ronan-online.com wrote:

 The thing is aviation DOESN’T own this spectrum, they just assumed it would 
always be unused. And they failed to mention it would be a problem during the 
last 5 years of discussion regarding the use of this spectrum.

Shane

On Jan 18, 2022, at 4:25 PM, Mel Beckman  wrote:



Michael,


Here’s a recent PCmag editorial on the subject, and it seems like many people 
want to put Internet speed above airline safety:


https://www.pcmag.com/news/faa-goes-in-hard-to-kill-mid-band-5g


This issue definitely impacts network operations for 5G providers, so makes 
sense to discuss here.


Here’s a comment from a friend of mine who has been both a network engineer and 
a pilot for United Airlines, posted on the article linked above:


“As a pilot, I can tell you that landing in instrument conditions is by far the 
most critical flight regime possible, during which the radar altimeter reports 
are a matter of life and death. There is no alternative technology, such as 
GPS, with the required accuracy and reliability, to provide approach guidance 
down to the runway in zero-zero weather, which is what the radar altimeter does.


The collective tech industry needs to admit that it made a huge blunder when it 
urged the FCC’s clueless Ajit Pai to “blow off” the clearly demonstrated FAA 
spectrum conflict. Sorry, passengers, but if you look out your window, you’ll 
see that aviation owns this spectrum and is entitled to interference-free 
operation. Replacing all radar altimeters isn’t going to happen in time for 5G 
anyway — it took more than ten years just to deploy anti-collision technology. 
So do what you should have done from the beginning: follow the FCC rules of 
non-interference to existing users, who have clear priority in this case.”


I tend to agree with him, and it looks like the 5G providers and FAA agreed 
last week to put some buffer safety zones around runway approaches at 50 major 
airports:


https://www.cnet.com/news/faa-lists-50-airports-getting-temporary-buffer-zones-blocking-new-5g-signals/


-mel

On Jan 18, 2022, at 12:33 PM, Michael Thomas  wrote:


I really don't know anything about it. It seems really late to be having this 
fight now, right?

Mike

Re: What do you think about this airline vs 5G brouhaha?

[Mel Beckman]

Shane,

Incorrect. Owning spectrum also includes the right to interference-free 
operation. And you imply that the FAA and airline industry has done nothing, 
when in reality it’s the FCC who has done nothing. the FAA sponsored extensive 
engineering tests that demonstrate the interference is a concern, and they 
notified all the parties well in advance. The fCC et al chose to do no research 
of their own, and are basing all their assumptions on operation in other 
countries, which even you must admit can’t really be congruent with the US.

-mel via cell

On Jan 18, 2022, at 2:01 PM, sro...@ronan-online.com wrote:

 The thing is aviation DOESN’T own this spectrum, they just assumed it would 
always be unused. And they failed to mention it would be a problem during the 
last 5 years of discussion regarding the use of this spectrum.

Shane

On Jan 18, 2022, at 4:25 PM, Mel Beckman  wrote:



Michael,


Here’s a recent PCmag editorial on the subject, and it seems like many people 
want to put Internet speed above airline safety:


https://www.pcmag.com/news/faa-goes-in-hard-to-kill-mid-band-5g


This issue definitely impacts network operations for 5G providers, so makes 
sense to discuss here.


Here’s a comment from a friend of mine who has been both a network engineer and 
a pilot for United Airlines, posted on the article linked above:


“As a pilot, I can tell you that landing in instrument conditions is by far the 
most critical flight regime possible, during which the radar altimeter reports 
are a matter of life and death. There is no alternative technology, such as 
GPS, with the required accuracy and reliability, to provide approach guidance 
down to the runway in zero-zero weather, which is what the radar altimeter does.


The collective tech industry needs to admit that it made a huge blunder when it 
urged the FCC’s clueless Ajit Pai to “blow off” the clearly demonstrated FAA 
spectrum conflict. Sorry, passengers, but if you look out your window, you’ll 
see that aviation owns this spectrum and is entitled to interference-free 
operation. Replacing all radar altimeters isn’t going to happen in time for 5G 
anyway — it took more than ten years just to deploy anti-collision technology. 
So do what you should have done from the beginning: follow the FCC rules of 
non-interference to existing users, who have clear priority in this case.”


I tend to agree with him, and it looks like the 5G providers and FAA agreed 
last week to put some buffer safety zones around runway approaches at 50 major 
airports:


https://www.cnet.com/news/faa-lists-50-airports-getting-temporary-buffer-zones-blocking-new-5g-signals/


-mel

On Jan 18, 2022, at 12:33 PM, Michael Thomas  wrote:


I really don't know anything about it. It seems really late to be having this 
fight now, right?

Mike

Re: What do you think about this airline vs 5G brouhaha?

[sronan]

The thing is aviation DOESN’T own this spectrum, they just assumed it would 
always be unused. And they failed to mention it would be a problem during the 
last 5 years of discussion regarding the use of this spectrum.

Shane

> On Jan 18, 2022, at 4:25 PM, Mel Beckman  wrote:
> 
> 
> Michael,
> 
> Here’s a recent PCmag editorial on the subject, and it seems like many people 
> want to put Internet speed above airline safety:
> 
> https://www.pcmag.com/news/faa-goes-in-hard-to-kill-mid-band-5g
> 
> This issue definitely impacts network operations for 5G providers, so makes 
> sense to discuss here.
> 
> Here’s a comment from a friend of mine who has been both a network engineer 
> and a pilot for United Airlines, posted on the article linked above:
> 
> “As a pilot, I can tell you that landing in instrument conditions is by far 
> the most critical flight regime possible, during which the radar altimeter 
> reports are a matter of life and death. There is no alternative technology, 
> such as GPS, with the required accuracy and reliability, to provide approach 
> guidance down to the runway in zero-zero weather, which is what the radar 
> altimeter does. 
> 
> The collective tech industry needs to admit that it made a huge blunder when 
> it urged the FCC’s clueless Ajit Pai to “blow off” the clearly demonstrated 
> FAA spectrum conflict. Sorry, passengers, but if you look out your window, 
> you’ll see that aviation owns this spectrum and is entitled to 
> interference-free operation. Replacing all radar altimeters isn’t going to 
> happen in time for 5G anyway — it took more than ten years just to deploy 
> anti-collision technology. So do what you should have done from the 
> beginning: follow the FCC rules of non-interference to existing users, who 
> have clear priority in this case.”
> 
> I tend to agree with him, and it looks like the 5G providers and FAA agreed 
> last week to put some buffer safety zones around runway approaches at 50 
> major airports:
> 
> https://www.cnet.com/news/faa-lists-50-airports-getting-temporary-buffer-zones-blocking-new-5g-signals/
> 
> 
> -mel 
> 
>>> On Jan 18, 2022, at 12:33 PM, Michael Thomas  wrote:
>>> 
>> 
>> I really don't know anything about it. It seems really late to be having 
>> this fight now, right?
>> 
>> Mike
>> 

Re: What do you think about this airline vs 5G brouhaha?

[Michael Thomas]

On 1/18/22 1:47 PM, Brandon Martin wrote:

On 01/18/2022 16:34, Michael Thomas wrote:
Is this the band that has really really short range for 5G? If so, it 
doesn't seem like a very big deal to give them the airspace on 
approaches. I mean, if you live under a flight path by the airport, 
not getting fast 5G is hardly your biggest problem.


This is the C-band spectrum near 4GHz.  The super short-range (or, 
rather, highly direction and subject to attenuation by almost 
anything) that you're probably thinking of is likely the UWB mmWave 
band up at ~30GHz.


C-band has moderate structure penetration and limited foliage 
penetration.  With line of sight and at the power levels the carriers 
would consider running, several miles of usable range would be 
unsurprising, though I suspect many typical deployments would have 
design cells smaller than that while using existing "4g" (and newly 
opened ex-TV broadcast space) low- and mid-band frequencies for wider 
area coverage at reduced speeds. Interference considerations, 
especially high above the horizon (planes...) would be present for 
potentially dozens of miles away.


An article I read said that other countries are accommodating them. What 
are they doing different?


Mike

Re: What do you think about this airline vs 5G brouhaha?

[Mike Hammett]

Fearmongering. 




- 
Mike Hammett 
Intelligent Computing Solutions 
http://www.ics-il.com 

Midwest-IX 
http://www.midwest-ix.com 

- Original Message -

From: "Michael Thomas"  
To: nanog@nanog.org 
Sent: Tuesday, January 18, 2022 2:29:53 PM 
Subject: What do you think about this airline vs 5G brouhaha? 


I really don't know anything about it. It seems really late to be having 
this fight now, right? 

Mike 

Re: What do you think about this airline vs 5G brouhaha?

[Mel Beckman]

Brandon,

Bo, it’s the radar altimeter, not the barometric altimeter. This is a radar 
distance measurement device for determine the precise height above the ground,  
critical for low-visibility approaches. 

Where frequency interference is concerned, under FCC rules the existing users 
have priority, and are entitled to interference-free operation. 

-mel via cell

> On Jan 18, 2022, at 1:43 PM, Brandon Martin  wrote:
> 
> On 01/18/2022 15:29, Michael Thomas wrote:
>> I really don't know anything about it. It seems really late to be having 
>> this fight now, right?
> 
> The issue seems to be old aviation equipment that has poor receiver 
> selectivity on its radio (not radar) altimeter.  This is, apparently, a 
> secondary, but still very important, instrument for instrument approaches 
> upon landing.
> 
> This older equipment can be subject to meaningful interference by signals as 
> much as 500MHz outside the actual assigned radio altimeter band limit.  Note 
> that the radio altimeter band is only about 500MHz wide itself, so even a 
> naive single-conversion receiver could/should have better selectivity that 
> this.  The reason for this poor selectivity seems to simply be that, at the 
> time, there was nothing else using the RF spectrum nearby, so they could get 
> away with it, and it made the receiver somewhat simpler.
> 
> The system apparently also responds poorly to both narrowband and wideband 
> jammers i.e. it does not employ what we'd consider robust, modern 
> error-correction or coding systems or even digital error checking techniques.
> 
> Both of these are basically issues with how old the system is and how old a 
> large amount of deployed equipment using it is.  The former is probably hard 
> to fix in a backwards compatible way, but the latter is mostly a matter of 
> upgrading your instruments more than once every 25 years which, for planes 
> that are actually routinely making use of this system (largely commercial and 
> charter operators), doesn't really seem like that big of an ask.
> 
> I think the issue is that the FCC did some rulemaking assuming that existing 
> service users were being reasonable with their equipment design, then a giant 
> game of chicken got started, and nobody blinked in time for anything to get 
> done until a collision was imminent.
> 
> The C-band spectrum at issue here has become very valuable, both economically 
> and from a public usage perspective, for mid- and short-range wireless 
> communications.  The FCC allocated some of it based on "reasonable" 
> expectations of existing users and provided an ample (arguably rather large) 
> guard band between services.
> 
> In the end, I'd say that aviation folks are in the wrong, here, but they also 
> have a lot of history to contend with and a large install base of gear that, 
> whether it "should" or not, apparently does need to be upgraded to prevent 
> detrimental interference to an important flight safety and operations 
> facility.  A pause in deployment seems reasonable in that light, though it 
> would have been nice if folks could have gotten this resolved sooner.
> 
> --
> Brandon Martin

Re: What do you think about this airline vs 5G brouhaha?

[Brandon Martin]

On 01/18/2022 16:34, Michael Thomas wrote:
Is this the band that has really really short range for 5G? If so, it 
doesn't seem like a very big deal to give them the airspace on 
approaches. I mean, if you live under a flight path by the airport, not 
getting fast 5G is hardly your biggest problem.


This is the C-band spectrum near 4GHz.  The super short-range (or, 
rather, highly direction and subject to attenuation by almost anything) 
that you're probably thinking of is likely the UWB mmWave band up at ~30GHz.


C-band has moderate structure penetration and limited foliage 
penetration.  With line of sight and at the power levels the carriers 
would consider running, several miles of usable range would be 
unsurprising, though I suspect many typical deployments would have 
design cells smaller than that while using existing "4g" (and newly 
opened ex-TV broadcast space) low- and mid-band frequencies for wider 
area coverage at reduced speeds.  Interference considerations, 
especially high above the horizon (planes...) would be present for 
potentially dozens of miles away.


--
Brandon Martin

Re: What do you think about this airline vs 5G brouhaha?

[Brandon Martin]

On 01/18/2022 15:29, Michael Thomas wrote:
I really don't know anything about it. It seems really late to be having 
this fight now, right?


The issue seems to be old aviation equipment that has poor receiver 
selectivity on its radio (not radar) altimeter.  This is, apparently, a 
secondary, but still very important, instrument for instrument 
approaches upon landing.


This older equipment can be subject to meaningful interference by 
signals as much as 500MHz outside the actual assigned radio altimeter 
band limit.  Note that the radio altimeter band is only about 500MHz 
wide itself, so even a naive single-conversion receiver could/should 
have better selectivity that this.  The reason for this poor selectivity 
seems to simply be that, at the time, there was nothing else using the 
RF spectrum nearby, so they could get away with it, and it made the 
receiver somewhat simpler.


The system apparently also responds poorly to both narrowband and 
wideband jammers i.e. it does not employ what we'd consider robust, 
modern error-correction or coding systems or even digital error checking 
techniques.


Both of these are basically issues with how old the system is and how 
old a large amount of deployed equipment using it is.  The former is 
probably hard to fix in a backwards compatible way, but the latter is 
mostly a matter of upgrading your instruments more than once every 25 
years which, for planes that are actually routinely making use of this 
system (largely commercial and charter operators), doesn't really seem 
like that big of an ask.


I think the issue is that the FCC did some rulemaking assuming that 
existing service users were being reasonable with their equipment 
design, then a giant game of chicken got started, and nobody blinked in 
time for anything to get done until a collision was imminent.


The C-band spectrum at issue here has become very valuable, both 
economically and from a public usage perspective, for mid- and 
short-range wireless communications.  The FCC allocated some of it based 
on "reasonable" expectations of existing users and provided an ample 
(arguably rather large) guard band between services.


In the end, I'd say that aviation folks are in the wrong, here, but they 
also have a lot of history to contend with and a large install base of 
gear that, whether it "should" or not, apparently does need to be 
upgraded to prevent detrimental interference to an important flight 
safety and operations facility.  A pause in deployment seems reasonable 
in that light, though it would have been nice if folks could have gotten 
this resolved sooner.


--
Brandon Martin

Re: What do you think about this airline vs 5G brouhaha?

[Michael Thomas]

On 1/18/22 1:25 PM, Mel Beckman wrote:


Michael,


Here’s a recent PCmag editorial on the subject, and it seems like many 
people want to put Internet speed above airline safety:



https://www.pcmag.com/news/faa-goes-in-hard-to-kill-mid-band-5g 




This issue definitely impacts network operations for 5G providers, so 
makes sense to discuss here.



Here’s a comment from a friend of mine who has been both a network 
engineer and a pilot for United Airlines, posted on the article linked 
above:



/“As a pilot, I can tell you that landing in instrument conditions is 
by far the most critical flight regime possible, during which the 
radar altimeter reports are a matter of life and death. There is no 
alternative technology, such as GPS, with the required accuracy and 
reliability, to provide approach guidance down to the runway in 
zero-zero weather, which is what the radar altimeter does. /


/
/

/The collective tech industry needs to admit that it made a huge 
blunder when it urged the FCC’s clueless Ajit Pai to “blow off” the 
clearly demonstrated FAA spectrum conflict. Sorry, passengers, but if 
you look out your window, you’ll see that aviation owns this spectrum 
and is entitled to interference-free operation. Replacing all radar 
altimeters isn’t going to happen in time for 5G anyway — it took more 
than ten years just to deploy anti-collision technology. So do what 
you should have done from the beginning: follow the FCC rules of 
non-interference to existing users, who have clear priority in this 
case.”/



I tend to agree with him, and it looks like the 5G providers and FAA 
agreed last week to put some buffer safety zones around runway 
approaches at 50 major airports:




Is this the band that has really really short range for 5G? If so, it 
doesn't seem like a very big deal to give them the airspace on 
approaches. I mean, if you live under a flight path by the airport, not 
getting fast 5G is hardly your biggest problem.


Mike

Re: What do you think about this airline vs 5G brouhaha?

[Mel Beckman]

Michael,


Here’s a recent PCmag editorial on the subject, and it seems like many people 
want to put Internet speed above airline safety:


https://www.pcmag.com/news/faa-goes-in-hard-to-kill-mid-band-5g


This issue definitely impacts network operations for 5G providers, so makes 
sense to discuss here.


Here’s a comment from a friend of mine who has been both a network engineer and 
a pilot for United Airlines, posted on the article linked above:


“As a pilot, I can tell you that landing in instrument conditions is by far the 
most critical flight regime possible, during which the radar altimeter reports 
are a matter of life and death. There is no alternative technology, such as 
GPS, with the required accuracy and reliability, to provide approach guidance 
down to the runway in zero-zero weather, which is what the radar altimeter does.


The collective tech industry needs to admit that it made a huge blunder when it 
urged the FCC’s clueless Ajit Pai to “blow off” the clearly demonstrated FAA 
spectrum conflict. Sorry, passengers, but if you look out your window, you’ll 
see that aviation owns this spectrum and is entitled to interference-free 
operation. Replacing all radar altimeters isn’t going to happen in time for 5G 
anyway — it took more than ten years just to deploy anti-collision technology. 
So do what you should have done from the beginning: follow the FCC rules of 
non-interference to existing users, who have clear priority in this case.”


I tend to agree with him, and it looks like the 5G providers and FAA agreed 
last week to put some buffer safety zones around runway approaches at 50 major 
airports:


https://www.cnet.com/news/faa-lists-50-airports-getting-temporary-buffer-zones-blocking-new-5g-signals/


-mel

On Jan 18, 2022, at 12:33 PM, Michael Thomas  wrote:


I really don't know anything about it. It seems really late to be having this 
fight now, right?

Mike

What do you think about this airline vs 5G brouhaha?

[Michael Thomas]

I really don't know anything about it. It seems really late to be having 
this fight now, right?


Mike