It sounds like you're going to be experimenting with high gain antennas connected to whatever nodes you use.
Slot antennas are something flat and high-gain which might be easiest to deploy, once you get constructing them figured out.
Ask HN: What's with the DIY state of the art long-range Wi-Fi?
21–30 of 67 posts
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#22Reach out to various existing infrastructure projects that build and maintain large community-owned P2P WiFi deployments, the two largest ones are Freifunk and Guifi. They would surely be able to and wanting to help you, if you reach out to them. Try https://freifunk.net/en/contact/ and https://matrix.guifi.net/ Most of them are using commodity hardware from Mikrotik, Teltonika and Ubiquiti. Basic setup for a persona…
A curiousity about Ubiquiti firmware. It seems like the AP firmware is based on openwrt
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#23Why not just use off-the-shelf equipment with modified external antennas? Use OpenWRT on cheap equipment that will accept an external antenna.
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#24Freifunk should work fairly easily; take 2-3 2X2 MIMO routers (like 20 bucks each), adjust the firmware for them, get the P2P directional link to either use existing satellite dishes (not sure what the easy orthomode splitter is, here, as you need same-source-spot signals for both horizontal/vertical or left/right polarization), or simple DIY'd axial helix antennas (made on plastic/cardboard tube of appropriate diame…
Seconded, Freifunk is easy to use and pretty resilient, there is also a pretty large community of people with knowledge about it and the hardware requirements are as low as they will go. Beware of some of the possible downsides: the default is for Freifunk nodes to be placed on a map and I'm not sure if this is a requirement or not but it might provide easy targeting information for the Russians. This will have to be…
While being placed on a map is clearly bad, commodity WiFi is not great for anything that shouldn't be located, as it is obviously radiating in RF and will be detectable some distance further than the signal can actually be decoded.
Tactical radios are specially designed for the problem. Eg using spread spectrum approaches, and plain not transmitting most of the time and only by the choice of the operator.
It's possible that open source SDR could be applied, but I guess that the Ukrainian side have been supplied with military radios by their allies.
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#25Heyo. I run a small rural ISP using off-the-shelf Mikrotik P2P hardware. Cost per AP is about 80 dollars a unit for 100mb bi-directional link that hits out on average 16km, depending on your LOS.
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#26>> point-to-point over anywhere from 5-20km
I think 20km point to point is not to be sniffed at if my back of a napkin calculations are correct (would love someone more knowledgeable to correct!)
Firstly on LOS - that’s like 15m+ masts at each end of the link (assuming perfect LOS path with no clutter like trees or buildings).
Then on free space path loss you’d be looking to overcome around 100db+ of path loss i think assuming 2.4ghz ISM band and perfect atmospheric conditions.
10dbi / 12 dbd log periodics for 2.4ghz are available off the shelf and are very reasonable to use (not too big, not too much wind loading at 15m elevation, weatherproof etc.)
Recieve sensitivity should be around -110dbm maybe? Assuming fairly rural conditions so that you’re not also dealing with a man made noise floor (and also benefitting from a very directional antenna to miss most noise too).
You’d need a 1 watt power amplifier minimum, again that’s more or less off the shelf but there’s restrictions globally on use and that may make sourcing harder.
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#27For emergency communications (probably lower than 0.1/1mbps at 5/20km though), you might be able to get away with a LoRA.. Probably would be a lot cheaper to build and lighter to carry around (all with a smaller antenna).
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#28A project I worked on did 802.11(b)? over about 30+ kilometers. The wireless stack was custom written though. The closer devices had planar directional antennas. The further devices had parabolic antennas. There was 3 different towers servicing ~180 detectors. Planar antennas near other towers had to have a shield added. This was 2007.
I don’t recall bitrates. The area was well over 500 km^2
project is here: telescopearray.org
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#29For emergency communications (probably lower than 0.1/1mbps at 5/20km though), you might be able to get away with a LoRA.. Probably would be a lot cheaper to build and lighter to carry around (all with a smaller antenna).
LoRa would indeed allow cheaper and more lightweight installations, but the bandwidth comparison between WiFi and LoRa makes LoRa basically not a comparison, unless you want to build something text-only over it. Forget being able to browse the web for example (besides HN probably).
Edit: I see now you mention the bandwidth difference and saying to use LoRa just for emergency broadcasts, that'd make sense.
Re: Ask HN: What's with the DIY state of the art long-range Wi-Fi?
#30It's not state of the art (and it's showing it's age) but I've always loved the Wireless Networks in the Developing World book [0]. It covers the basics about propagation, antennas, infrastructure and such, but software has changed a bit since last edition.
Also, keep an eye on different editions, as I believe last one is a little less tech focused and more into how to run a community project, both sets of knowledge are highly important but second edition might be outdated in regards to software availability in OpenWRT and Linux in general.