Comment by toast0 | Hacker News Reader

Comment by toast0 | Hacker News Reader

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5G is kind of three things.

5G on existing frequencies can do more data with the same spectrum. Something something MIMO. This is broadly useful, if you have an 5G capable device and your network updated their base station equipment. 5G and 4G are supposed to be better at sharing spectrum on demand vs 4G and 2/3G.

5G on new, nearby frequency, in the US, there was a second round of taking historically TV spectrum and reallocating it for communications. These bands will most likely need new antennas on towers as well as on handsets. These tend to be lower frequencies, which could be useful for distance and structure penetration, but may not always be built out.

Then there's the millimeter wave stuff. Very high frequency, very fast, great for density, like maybe transit stations and arenas. This is the stuff that needs a tower on every light pole or whatever. I don't think this is going to get a lot of deployment, but it gets a lot of press. I think this is the part the FAA is objecting to for now.

The FAA is objecting to the use of the 3.5GHz band, as it's supposedly too close to the 4400-4700MHz radar altimeter band. This band is the primary one for 5G deployment world wide and interestingly no planes have been dropping or crashing due to it's use. Strange how the same planes landing in European capitals with widespread 3.5GHz 5G deployments seem to do fine there, but will experience dangerous problems on USA soil.

3.5GHz is also exlusively 5G and not used for anything cellular before. Outside of some old wimax deployments here and there, but those ware usually for fixed users not mobiles.

3.5GHz is also firmly in the centimeter bands. :)

Europe is only using 3.4-3.8 GHz. The US is going up to 4.2 GHz.

Ah! That certainly explains some of it. I even checked and sure enough, the highest allocated block here is 3670 - 3800 MHz.

AIUI the European usage of this band only goes up to 3.8GHz (see https://www.everythingrf.com/community/5g-frequency-bands-in... for example), but the FCC auctioned off band space up to 3.98GHz. Aircraft altimeters use the 4.2-4.4GHz band, so the new US allocation nearly halves the band gap. That is what the FAA is worried about.

>halves the band gap. That is what the FAA is worried about.

It's worth noting that a band gap of 200mhz is ridiculously wide, at least according to the top comment from the last thread https://news.ycombinator.com/item?id=29642777

The UK makes available shared access licences in the 3.8 to 4.2 GHz band. These are power limited and location constrained, to manage interference with satellite earth stations.

You can get a license in this band and run your own private 5G network in it. There doesn't appear to be any concern from the UK aviation regulator (the CAA).

Perhaps they're able to achieve sufficient spatial separation from airports and their final approach paths, or perhaps they've found there aren't issues with the reduced transmit power available on these shared access licences? Nonetheless, it will be interesting to see if this 200 MHz guard really is insufficient in the US - at a certain point you need to consider if existing equipment needs to be replaced (like with the swapping of 800 and 700 MHz from digital TV to mobile, and the need for some people to put a band-stop filter onto their TV antenna feed to avoid interference from mobile networks).

Using this band is only an aviation problem if you're in the middle of an approach (approximately 20 miles from a runway, but not a big circle). Hence the location and power limitations.

3.5 is fine, that's CBRS. This is about C-Band, which is 3.7ghz to 4.2ghz in the US.

NTT Docomo operates n79 (4.5GHz) for 5G in Japan. Maybe it's the only network use n79. (It's hard to find supported phones in open market rather than docomo model, except iPhone) https://en.wikipedia.org/wiki/List_of_5G_NR_networks

According to assignment map, it uses 4500-4600MHz. https://www.tele.soumu.go.jp/resource/search/myuse/use/10000...

> Then there's the millimeter wave stuff. [...] I think this is the part the FAA is objecting to for now.

mmWave 5G signals are in the 24-54 GHz range (f = c / 0.001 m ≈ 30 GHz)

This makes me nervous. The O2 peak at 60GHz. What are your opinions on it? If we get that peak of attenuation at 60GHz, what's happening to that energy?

The common wisdom would say it heats up but that's not guaranteed.

https://i.imgur.com/KUR4XmX.png

https://i.imgur.com/iUD2v4D.png

https://www.5gamericas.org/wp-content/uploads/2020/12/InDesi...

What else would happen to the energy? It’ll turn into heat + some re-emissions.

Not to feed the trolls but here is one example:

Tumor Treating Fields are an FDA-approved mechanism for treating certain cancers (mostly gliomas). The exact mechanism isn’t understood, but it seems that prolonged exposure to low power alternating electrical fields in the 100-500kHz region interferes with cell mitosis [1]. I haven’t read about it recently but at the time the speculation was that it was basically disrupting microtubule formation by physically agitating polar molecules involved with the process.

The application from Optune and others uses contact electrodes to drive a small potential gradient though the skull and into the brain.

We know radio frequency also affects polar molecules, mostly to heat up meals. Obviously at multi-GHz carrier frequencies we wouldn’t expect to see this behaivor emerge. However, most digital protocols don’t operate with continuous carriers..the break comms into frames and do things like frequency hopping at much lower periodicity than the carrier. If there was something dumping energy into the cytoplasm on a 2-10 microsecond interval, it could have similar effects.

Do i think 5g is going to cure brain cancer? Probably not, but the body is ridiculously complex and can be surprising. I think we just have to find a way to be able to talk about these concerns fruitfully rather than just try to squash them, because that’s generally where the trouble seems to start.

1 - https://pubmed.ncbi.nlm.nih.gov/33080774/

Thank you. Pretty much the answer I wanted to give, but much better than I could.

And I am not just trying to latch onto the first unknown that's brought up under my comment, these are very similar to the concerns that I had in mind and wanted to bring up.

At the wavelengths we would now be dealing with and exposing ourselves to, there may be - and with some evidence already pointing there probably being surprising and not immediately intuitive (mostly) biological interactions or disruptions to interactions our biology relies on that we are yet unaware or haven't understood leading to phenomenons we haven't considered such as the example you've given.

I tend to be a bit of a fence rider when it comes to these types of things.

Re: 5g we have so much accumulated knowledge and experience dealing with RF that the likelihood that we're going to be caught completely offguard and have no reasonable mitigation seems pretty low. At the same time, it's pretty obvious that our biology didn't have an opportunity to adapt to the types of energy we're putting into the environment and we'd be well served to keep an open mind about what the possible effects could be and how we would test and/or monitor for them.

There are other contemporary topics that suffer this same pathology. Reasonable questions raised in good faith get slapped down regularly and I think we pay a collective price for it. Of course some questions aren't reasonable and certainly not all are raised in good faith, so it's not exactly an easy problem to solve.

I keep wondering if any insects are going to discombobulated by thinking along those lines - but am a complete layman

Affected, absolutely. Unknown to what degree or if it would be any worse then the billions smashed on windshields or fogged out of existence every year.

Interesting paper on using EM simulations on finely detailed insect models to determine net energy absorption and associated properties: https://www.nature.com/articles/s41598-018-22271-3

Keep in mind that the EM field described in that study is quite strong and the transmitter is very close (actually in contact with the patient's skin). They talk about field intensities of 0.6V/cm. That means that if you put the two probes of a multimeter in the air separated by 1cm, it would read 0.6V. That's quite a lot. I'm not sure how to translate that to RF power, but it is many orders of magnitude more intense than what you could ever expect to receive from a mobile phone tower. Radio receivers are basically very fast and very sensitive voltmeters that work with field strengths on the order of microvolts per meter.

Totally agree there's extremely limited risk here from towers. The broader issue to me is that all of the conspiracy talk and bizarre science fiction around the topic of 5G (or vaccines or flat earth) has created a sort of conversational countermeasure where its acceptable to clap back and shut the topic down any time people appear to be wandering in those woods. As a result, some folks with legitimate questions and concerns end up frustrated and looking for answers elsewhere.

Endless patience for off the wall ideas isn't a sustainable option either, so I'm not claiming to have all the answers, I just wish we were maybe a step or two in that direction.

I asked for more details on the implication as the parent quote

> what's happening to that energy? The common wisdom would say it heats up but that's not guaranteed.

As the first and second laws of thermodynamics are well understood and tested theoretical principals that have been experimentally and theoretically verified for ~170 years, there is far more than "the common wisdom" backing the expectation that the system would heat up.

A common conversational tactic to lead the conversation into conspiracy territory is to cast unsubstantiated doubt on a settled topic - then frame the orthodox view as something pushed by an "establishment". A far more interesting discussion emerges when data is presented, or absent data a plausible mechanism for harm.

There is nothing wrong with studying the biological effects of EM fields. We certainly know that small quantities of Benzene, or Arsenic have large impacts on biological organisms - and that biological organisms react to certain portions of the EM spectrum in complex manners e.g. Visible light, and infrared. However we do have some good bounds on how much impact there can be and where it is likely to emerge based on ~120 years of radio spectrum deployments.

"The common wisdom would say it heats up but that's not guaranteed."

If it does something other than turn into heat the laws of thermodynamics are wrong which is somewhat unlikely.

Sure, 60 GHz may be a resonant frequency of O₂ molecules and signals at that frequency may transfer energy to them and thus heat them up.

However, remember that radio signals lose energy to free space proportional to the (distance and frequency) _squared_ [1]. A 60GHz signal is attenuated by 88dB at 10 meters. That means that if it is transmitted with 100 W (20dBW), the RF power that arrives at your position is -68dBW, or 0.000158 milliwatts. That isn't going to heat up much.

[1] https://en.wikipedia.org/wiki/Free-space_path_loss

Note that this math is misleading for calculating how much things will heat up, because effective antenna aperture of the thing that you'd heat up increases with the square of frequency. So the square terms of frequency cancel each other out.

It's still small, but the best simple approximation is just to take the 100W and divide by the proportion of the antenna pattern your target occupies.

A 100W source on 2GHz or 60GHz at 10 meters distance is going to dump about the same amount of energy into you. If the transmit antenna has 3dB of gain, that's going to be about 50mW.

That's interesting. I'm not quite sure how that works but I'll look into it. If you have some resources, I'd appreciate it!

See the derivation section in your link. It's assuming an isotropic antenna at the receiver, whose effective area gets smaller as the frequency increases.

But people do not get smaller as the frequency increases: they occupy the same fraction of the 10m radius sphere around the antenna.

The power levels are low to begin with, so heating up the air is hard to even measure, let alone notice.

It's why 60GHz is license free and used for WiGig, wireless HDMI and short haul microwave links like the ones from Mikrotik.

The heavy oxygen attenuation makes it commercially worthless.

Same reason why there's a license free band on 24GHz too. 24GHz suffers from water vapor absorption and has heavier attenuation than adjecent bands thanks to that. For example Ubiquiti AirFiber uses license free 24GHz.

Stop spreading FUD. ~60ghz radar has been used by cars for for cruise control and parking for many years now at much higher power levels than what phones can transmit. Some phones have mmWave radar for gestures too. We’d use even higher frequencies if it wasn’t for the terahertz gap.

Spreading FUD isn't my intention. If anything I am hoping to alleviate the FUD that open-mindedly reading these documents and plans induce in my mind.

I appreciate and read the honest and detailed technical takes on the topic here.

Especially acknowledging uncertainty and a healthy amount of doubt are pretty essential to the epistemological pursuit. And fear may arise when the uncertainty and doubt are not dispelled with reason.

There's also the issue that with 5G phased array antennae, tx power limits are not restricted as tightly. With a standard single tx antenna, it's easy to calculate the amount of EM energy it can create in the 3D space around the antenna. With phased array beamforming, you're using using multiple small antennae and amplifying the signal beyond the sum of the individual outputs. The safety ratings for EM radiation around phased arrays tend not to be calculated on the theoretical maximum TX power, but on the typical usage. The result is that with low enough level access to the firmware, someone could theoretically weaponize a 5G antenna to produce unsafe levels of RF energy, as well as aim the antenna without physically moving the hardware.

This sounds far-fetched, and it is, but I wouldn't be surprised if we see it done in a lab, like some of the other practically infeasible but bleeding edge cool hacks.

> With phased array beamforming, you're using using multiple small antennae and amplifying the signal beyond the sum of the individual outputs.

No, that's impossible. The RF power imparted onto the EM field by any antenna array is equal to or less than the sum of the output power of each antennae.

I think the argument is that while the total power over the full 4π is equal to the sum of the input power, the constructive/destructive interference cause there to be higher power output within some solid angle. But my understanding is that the limit are for avoiding interference from other devices, not for human safety, and that any reasonable amount of non-ionizing radiation is incredibly safe for humans. Congestion wouldn't be impacted by the beamforming, because on average any increase in intensity at one angle would be countered by a decrease at some other angle.

Higher power density, not higher power. You aren't going to get more watts anywhere than went in, but you will potentially get more watts per cm^2 than at the antenna.

It’ll be a boon for fixed wireless where last mile issues prevent running cable

I want to think it also handled congestion better. I wanna think I've experienced aread (airports? Downtown) where apparent thruput is better than I was used to when places were full of people.

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