By using a long distance communication device this eliminates the proximity strike problem. This could easily be extended to say like distributing the voting rights to different generals at different regions, and given that the device is genuine and not modified, can be a hardware voting key to say like launch the nuke in secrecy or not.
Whether adversarials can use the radio signals that it emits to triangulate you and thus track you is another story, though.
There are some significant regulatory issues with the current popular mesh network protocols in the USA, namely that neither MeshCore or Meshtastic are compliant with the actual FCC regulations. 100x bandwidth because you're breaking the rules isn't the same as 100x bandwidth legally.
Here is the issue discussing this in the MeshCore repository: https://github.com/meshcore-dev/MeshCore/issues/945
It doesn't seem like this would be that useful except that the protocol is LoRa so you can have higher bandwidth between two devices if they happen to be close enough together.
E.g. drones geographically organize themselves into a chain with each of them serving as a mesh-network node, then each of them, including the tip of a chain, can be controlled by operators, and the whole setup is a closed network which works without requiring Internet access
I'm trying to envision the application of a mesh like this. These could be examples?
- interconnected nodes need to share data (like images)
- interconnected nodes are acting as a collective array of sensors (eg. geolocation)
- interconnected mesh nodes provide redundant pathways back to the central node
- interconnected mesh nodes provide spatial diversity in case of interference or jamming
- nodes are mobile (eg. drone or vehicle) and mesh provides alternative connectivity based on node location and RF attenuation (also provides longer range with mesh connectivity)
No. Free space loss increases with frequency.
FSP loss for 915 MHz at 10 kms is ~ -111.67 dB while for 2.4 GHz is -120 dB.
That is a 9 dB loss which is significant. It could mean the difference between a copy or just plain static though the LoRa is supposed to be copyable down to -140 dBm.
The max tx power is around 150 mW (21.76 dBm), so at 10 kms, the RSSI is 21.76-120 = -98.24 dBm which is above the -140 dBm limit.
This calculation is assuming there is no loss due to vegetation or humidity or other barriers.
So you could probably pull off a 2.4GHz mesh outdoors in rural areas? It'd be feasible in the same places a microwave-laser hilltop-to-hilltop link would, but instead of "fast but point-to-point" it's "slow but meshed" (and with much larger tolerance for slop — you don't need to put everything on fixed masts so they have perfect line-of-sight, you can just stick them on the tops of trees or whatever and if they wave in the wind it still works.)
Mind you, the authors' motivating use-case for the hardware seems to be their project (https://github.com/datapartyjs/MeshTNC) to (AFAICT) bridge LoRa (or some specific LoRa L2 protocol — Meshtastic, probably?) to packet radio, i.e. digital packet-switched signalling over amateur (HAM) radio bands.
In that context, the tradeoff of high throughput for low propagation makes sense. Insofar as you're working with LoRa, and want to build and experiment with a bunch of site-local devices that mesh between themselves and interoperate with LoRa data-link protocols, you'd likely be speaking something like LoRA over 2.4GHz (LoRa itself doesn't spec a way to do that, but you could make it happen within the closed ecosystem of your own home/office.)
And in that context, you could use a MeshTNC device as something like "LoRaLAN" router. It'd be something you'd keep somewhere central in your house (like a wi-fi router), plugged into power + an antenna (internal to your house, like a wi-fi router) and plugged into a packet-radio transceiver with its own even-bigger antenna, outside your house. (Like a wi-fi router being plugged into a gateway modem on its upstream WAN port.)
This MeshTNC device would then pick up signals from:
- regular LoRaWAN IoT devices and Meshtastic handsets in your building
- more custom devices in your building†, that you've built yourself, that use another MeshTNC module; where these other devices do their part of the meshing only on the 2.4GHz band, which means they don't need big fiddly external antennas like LoRa devices do, but can be quite compact
- and possibly, a separate bidirectional LoRa repeater (made from any existing "high-gain" LoRa module, i.e. the kind used in mains-powered LoRaWAN base stations) — which brings in LoRa mesh traffic from outside your building, and picks up and carries away "destined for elsewhere in this area" LoRa mesh traffic that your "LoRaLAN" device has emitted (either due to forwarding it from your 2.4GHz-only mesh handsets/devices, or due to forwarding it after receiving it from packet radio.)
Though keep in mind you only need that complexity for the 2.4GHz-only mesh devices, since there isn't an existing mesh to forward those packets. But this whole setup is still also a regular LoRa mesh, and so you can still use regular LoRa (e.g. meshtastic) handsets, and put out packets that make their way through your regional mesh, back to the packet-radio bridge in your building; and from there to who-knows-where.
† To be clear, the 2.4GHz mesh handsets would only work reliably inside your building (if the 2.4GHz antenna is inside your building); but knowing HAMs, half the point would be seeing how far away you could get from your house/office and have your 2.4GHz mesh handsets keep working. (You'd probably want to have a second MeshTNC "base station" with a building-external antenna to try that. Pleasantly, that doesn't complicate the topology; it's all still just mesh, so you can just drop that in.)
Meshing two digit number of drones on a military grade reliability is a real uphill battle with chirp based protocols, as the high ToA reaches congestion fast.
https://trellisware.wpengine.com/waveforms/tsm-waveform/
Nodes can cooperate to beamform and reach greater distances.
I’m struggling to see the value here. At $50, this seems hard to justify given the availability of cheaper, well-supported options like MuziWorks Duo, Ebyte, and other newer LR1121/LR2021-based designs. Those chips offer both 2.4 GHz and sub-GHz support in a single modern package, often at roughly half the price, which makes the SX1281 feel fairly outdated.
As far as I know there's not actually anything particular to 2.4 GHz allowing higher throughput for LoRa than that the corresponding Semtech chip happens to support wider bandwidths. (I.e. no legal barrier.)
The tradeoff is less range due to lower link budget. Doubly so because 2.4 GHz has higher free-space path loss. You're not going to get outside your house with these speeds. The primary use (as stated in the original post) is likely through clear space with a directed antenna.
(The 2.4 GHz band is better suited to this use since you can use antennas with higher than 6 dBi gain. If my math is correct, anything higher than 11 dBi is a win even accounting for FSPL and the power derating the FCC imposes.)
(Aside, I am the author of that MeshCore ticket.)
> each of them serving as a mesh-network node
might have worked for a bit in the past, but is easily disrupted by jammers, and forced a switch to fiber-optic in-theater. People have learned from that and don't bother with radio anymore, even in new theaters.
https://www.thethingsnetwork.org/article/new-lora-world-reco...
But, that's receiving 3 of maybe thousands of packets.
There's work on bouncing of LoRA signals off the moon:
https://engprojects.tcnj.edu/lora-eme/
Yes, but Joe Shmoe won't see this on their home setup trying to talk to a buddy 2 miles away behind a hill.
> Wifi HaLow 802.11ah. LoRa is another level. It works down to -146dBm. 802.11ah dies around -100dBm.
https://news.ycombinator.com/item?id=47890598
LoRa looks like someone is dropping a saw wave on the spectrum. It so clearly looks like such a blunt force user of spectrum. Just wild.
WiFi sensitivity is about -90dB, while LoRa sensitivity is around-150dB…. So that’s about a million times more sensitive. So you need about a million times more signal strength to use low bandwidth WiFi (still impossibly fast by LoRa standards) than to use low bandwidth LoRa.
Those are radio specifications. Real links require about 10db more to get any kind of reliability, but the comparison stands.
lower than 430 you start to run into severe bandwidth issues though. and its not allowed to transmit lora/dss on 430 in the us without license hence the 900mhz
at 2.4ghz the real world usage is limited. might as well use wifi. the only advantage is short range bandwidh while keeping lora compat.
Fiber optic tethers limit range and target conditions. You can't go into a forest or even an urban canyon, you basically need to run the drone along roads and fields. And you have to drag it with you, which reduces what you can carry. The fiber itself is very light weight and has a habit of getting sucked up into the props on quadcopters.
There's a lot of frequency hopping and chirp systems being used now, with a mix between analog radios mostly for FPV and digital radios or Starlink for larger ISR drones or larger gliders. Digital still gets used a lot for FPV because of how readily available it is, but good drone FPV pilots want the lower latency of analog and will take it if they can get it.
Depends on the context, I guess. Distance, jamming probability, availability of relays, etc.
Fiber-optics are close-range.
HN has a lot of us that have ~0 idea what you'd use this for, even when we steelman, all we can do is vaguely handwave about easier to setup wireless internet on a vast compound we own.
Would be really cool if someone could hop in and just give a couple one off examples, i guess? Only other one handwave I can think of is IOT x assembly line stuff for businesses, but I'm real curious why individuals are so into it -- or maybe they're not, and that's why the codebase quality is so poor? Idk.
Thanks for educating us!
If IP were designed today the packets would have 500+ bytes of plain text JSON as headers and the spec would support hundreds of extensions.
The legal power limit in these bands is 1 W. If you spread that out over 500 kHz, that signal is weaker than background noise at any given frequency for anyone more than about a city block away. (Give or take many factors.)
But, if you compress that 1 W into, say, 12.5 kHz (typical for FM voice), your signal is now detectable (and will interfere with other, possibly licensed, users) at over 6 times the distance.
There are probably other factors. For example, it's not legally sufficient to simply reduce your power by a corresponding factor. I suspect it may simply be the FCC's goal to reduce conflict between users by mandating spread-spectrum technologies for unlicensed use.
Note also that 47 CFR 15.247(e) [1] gives a spectral power limit which corresponds approximately with the 1 W max / 500 kHz min specified in (b)(3) and (a)(2).
Final side note – https://docs.fcc.gov/public/attachments/FCC-02-151A1.pdf is interesting reading as to how the current form of 15.247 came to be. Specifically it changed the rule from specifically DSSS to digital modulation generally, which in turn allowed the transition from 802.11b (DSSS) to 802.11g (OFDM) on 2.4 GHz.
[1] https://www.ecfr.gov/current/title-47/part-15/section-15.247...
It's a mechanism to try to make the 900Mhz band more useful to uncoordinated users.
- emergency communication
- low power data transfer for sensors
- low data rate data transfer for mobile groups. Air softers use it to transmit information to each other while playing.
HaLow:
- "high" data rate over shorter range, though much higher range than 2.4 wifi - data sharing between mobile groups like above, but high enough bandwidth for low quality video
- large area wifi deployments
Meshtastic should be the obvious answer for this but in my limited experience the app(s) and code are buggy on even the most typical hardware. Wish it wasn’t the case but it is.
I've been tinkering with the tech to make city-wide flrc meshes joined together over the internet, my estimates are that it should be at least able to support thousands of users per region.
In the end: LoRa is only good for very short text messages at somewhat long distance (up to 10km without special setup) and without bad conditions (obstacles on line of sight, rain/fog). There is an ongoing fight between each of the two frequencies to be used as default and this publication adds another frequency into the battle.
There is WiFi HaLow, a relatively new WiFi protocol which seems to solve the low bandwidth issues with LoRa on relatively confortable distance (likely up to 8km, same as with LoRa in regards to Line of Sight), albeit slightly less affected by weather conditions. The advantage here is permitting to send images and binary data in general, but think about something being sent at the speed levels from 2005 (which in any case is good speed for most usable things).
Then there are other relevant mesh protocols yet to mention here like ESPnow which is my personal favorite. Whereas the other two options above are exotic and with transceivers around the 50 EUR and above. With ESPnow you just need any cheap ESP32 embedded device with an optional antenna to increase range for about 3 EUR (antenna included). With that you get similar returns to WiFi HaLow with less range (about 3 kilometers max on my experiments) but cheap like heck.
To setup internet on a vast compound, WiFi HaLow might be a good investment. If you are with a constrained budget, then ESP32 is your friend. To remember, long distance is limited so if you are considering more than 8 devices exchanging heavy data, you should just go for proper WiFi long range transmitters.
I think people need to think more about what the actual scenario they have in mind is because it seems most people think of mesh radio as some backup for the government shutting the internet down. When in reality it’s almost useless for that since it’s so easy to jam or flood mesh radio.
The mesh networks are dealing with, by definition, a sparse and widely distributed set of devices which are independently configured and controlled, and in their current widely available form are only dealing with terrestrial communication. Without that point of centralisation you would need to focus on targetted regional jamming, as from a practical standpoint you cannot perform wideband RF jamming over an entire country - signal jammers don't scale that well, and geographic features come into play. As an example you might effectively block mesh networks from operating reliably in a given city, but if people were to move outside of that area then the mesh would operate again. Geography is both a strength and a weakness here: a mountain range will impede direct communication with someone on the other side, but it will also have the same effect on jammers which will vastly increase the cost to deploy them in a ubiquitous fashion.
Jamming is done in military scenarios too, but in that case it’s limited by the fact that a jammer is a big transmitter painting itself with a big sign that says “fire missile here.” Civilian mesh doesn’t have that fallback.