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The frequencies are what I was curious about as well. To have a half mile range at relatively low powers it would need to be a low frequency band.

I'm guessing they haven't bought licenses from the FCC, so my bet is that they're using the 900 MHz ISM band.

There's only 26 MHz of spectrum in that band, which isn't much, particularly for a mesh setup that won't be particularly spectrally efficient.

Even with a high 30 dB signal to noise ratio, the Shannon channel capacity in a 26 MHz band is 50 Mbps. MIMO helps a bit, but even in ideal real-world conditions you'll likely have at most 50 Mbps to share between all the users connected to a node. Spread that across a few users/mesh hops, throw in some packet retransmissions and noise, and it's not nearly enough to compete with LTE networks at any meaningful user density.

Incentivizing users to create as many nodes as possible is a good idea, as that allows lower power transmissions and better frequency reuse. It's still a huge struggle to get anywhere near commercial wireless speeds, particularly in areas where there are fewer nodes and a higher density of users.

They mention on Reddit that they are using 900 MHz.

https://www.reddit.com/r/VolkFi/comments/b1u7o3/spectrum/

I work with 900MHz radios and infrastructure, here's my thoughts:

> The frequencies are what I'm confused by as well. To have a half mile range at relatively low powers it would need to be a low frequency band.

> I'm guessing they haven't bought licenses from the FCC, so my bet is that they're using the 900 MHz ISM band.

Seems likely, and probably even works in controlled tests over relatively short distances. 900MHz meshing radios certainly exist, like this one (no affiliation with them, haven't used the product): https://www.rajant.com/products/breadcrumb-wireless-nodes/lx...

>Even with a high 30 dB signal to noise ratio, the Shannon channel capacity in a 26 MHz band is 50 Mbps.

Impossible in urban areas without highly directional antennas (which aren't small). The effective noise floor in most even semi-developed areas I've worked in is ~-100 to -80dBm - it can be a struggle even with expensive radios and fixed infrastructure. 30dB SNR just isn't going to happen over any appreciable amount of range on this sort of device (a high gain parabolic dish? sure). Using all 26MHz of the spectrum with an omni directional antenna (again, as would be required) also isn't going to happen except over relatively short distances.

900MHz is good technology, and can get robust, long distance links with the right infrastructure (I most work on 1-10mi links). The limitations on a pocket sized device with a pocket sized antenna mean this is unlikely to work @ 900MHz- especially in their fantasized scenarios of being in areas with no cell phone coverage (cell carriers have access to better bands, and far better infrastructure).

What if you used the noise as the carrier wave for the signal? Like, if in an urban area you have a "stable" probability distribution of noise, modulate that.

You're being downvited because, whilst this is a clever sounding idea, unfortunately it doesn't work like that.

The noise is random, so you can't modulate it because you can't predict what it will be. A probability distribution isn't enough; say you want to modulate by XORing with a random, uniformly distributed stream of zeros and ones. Knowing that distribution doesn't enable the receiver to extract the data.

(Fun fact: GPS signals are under the noise floor, but detectable because they are encoded with a predictable pseudorandom carrier which can be found even in the noise.)

Could you... modulate the amplitude of the PD?

Amplitude is about power, that what you want to minimize. If you can affect the amplitude of the noise, that means your signal has high amplitude: you have a high signal-to-noise ratio (SNR) and you already have won.

Do you know why digital pulse radios never happened?

> cell carriers have access to better bands, and far better infrastructure

What would be the best band for this kind of infrastructure? ( Disregarding any existing FCC licenses )

> What would be the best band for this kind of infrastructure? ( Disregarding any existing FCC licenses )

The frequency bands that have been licensed for cellular infrastructure.

Its all a trade-off. Higher frequencies get you better data bandwidth, but require more power and get attenuated more by stuff (buildings, trees). Lower frequencies get you much better range for a given power level and better building penetration, but lower data bandwidth.

Exceptions to this are the "crap" bands, like 2.4GHz and 60GHz. Microwave ovens (which are great interferers, BTW) use 2.4GHz because it is absorbed by water. Great for heating your food. No so great trying to transmit data in an outdoor environment with rain and fog.

60GHz gets absorbed by the oxygen in the atmosphere, so that's another band that's only good for very short ranges.

The bands the cellular carriers have now are a good trade-off between power requirements, data bandwidth, and other issues (like absorption). The ISM bands exist basically because nobody would pay to use them.

The biggest advantage to the cellular bands is that they are exclusively licensed, so noise is a non-issue, or at least an issue that you are in control of, since you are the only one allowed to build infrastructure in a given area.

Cell carriers have a wide variety of bands they can deploy, from frequencies above 1GHz, which doesn't propagate well through free space or obstructions, but allows for high-density, high-bandwidth use, to frequencies below 1GHz (600, 700 and 800MHz bands in the US), which propagate well in free space and reasonably well around and through obstructions (but cant be deployed with as high a density, since signals propagate well).

That being said, the infrastructure is the biggest advantage.

My gut says that absent FCC regulations and allocations, for wide area coverage something like 500-900 MHz is an ideal spot between propagation and required antenna size. Guess where TV stations are (historically at least)?

My real world wifi experience. Domestic 2.4ghz wifi ap with a directional antenna plugged in, 600m direct line of sight across valley to neighbours netgear ap with stock antenna, assumed in his window. Internet achieved. Wifi ap, stock antenna in my house window, looking unobstructed over field, I get wifi internet on my phone about 200m out. Indoors in my stone walled house wifi is perhaps 10-15m. So half a mile range or 600m is almost true in a marketing sense though a bit dishonest in a real world usage sense.

> I'm guessing they haven't bought licenses from the FCC, so my bet is that they're using the 900 MHz ISM band.

No FCC filings for this device yet that I found. I guess we'll have to see.

If a router isn't nearby, the phone will try to find another Volk phone to use as a hop, until it finally reaches a router.

If my volkfi phone is acting as a relay for someone else's phone to hop to an available router isn't that going to run my phone's battery down? That's not going to be a nice experience if I'm unlucky enough to be a relay for a lot of people.

Better push for fast adoption.

> If there are no routers or Volk phones nearby to hop to, you'll either not have service, have to use Wifi, or fallback to LTE if you have a SIM card installed and it has active service.

That does make the "Global Coverage: Our network is everywhere our users are" claim a bit dodgy, no? Sure, you'll have coverage in the middle of the desert—if there happens to be a chain of Volk phones from there to the nearest point with actual regular coverage... which is highly unlikely.

It is hard to create coverage from nothing. So they made an hybrid form. "Bring your own coverage unless there is coverage". Something is better than nothing i guess. Even with this hybrid version i think chances are very slim one node will meet another and create a tiny chain by pure coincidence.

If it works as a drop-in replacement for the Pixel line on Fi, I'm pretty much sold.

Sounds like a genius idea to me. In theory at least.

Practicality is an issue though. Mostly because of our current regulation, must be said.

s/because/thanks

Our current legislation gave us a relatively "clean" frequency space. Would be so much worse without it

I thought "because" is a neutral word (I'm not a native speaker). The distinction between regulatory and technological problems is an important one to make - regulations can be changed. E.g. what would happen if we separated a whole band with enough bandwidth for an open mesh network?

If government regulates away personal sovereignty, you just tell a hundred million people they have personal sovereignty, and watch them decide if it's worth it to impede.

Ok, I have the following idea: instead of having to do house chores ourselves, our phones do them. How? Well, at night they transform, like in Transformers, into household robots and do all the cleaning, maintenance and food prepping. Then when you wake up it transforms back into a simple phone.

Genius right?