What frequency band are you using? ISM is the only one that permits store-and-forward / automatic operation, as the gotenna people found.
You say a few miles per node - I am having trouble seeing how that's possible without elevating all the nodes
You say a few miles per node - I am having trouble seeing how that's possible without elevating all the nodes
But they're still cool and I still want some for non-hiking applications. With the very low power idle and low cost they could be set up with solar panels in the tops of trees or in similar high height above terrain positions.
At very low bit rates you need very little SNR.
There is probably very low noise out in hiking environments.
Yes, attenuation due to terrain is going to be a killer, but my experience with non line of sight 900 MHz links blasting through trees leads me to believe it would be workable for low bit rate data between a series of hikers along the same trail.
It is sending only location and text messages so intermittent link status or re-tries due to temporarily terrain/foliage obstructions will not cause degradation in service that you would experience trying to watch netflix over this mesh.
902-928 has almost no advantage over 2.4 GHz when it comes to line of sight issues with terrain. In fact, it's more problematic due to the increased size of the fresnel zone. Sure, it does better through trees but a slight rise of ground is just as much of a problem for 915 and 2400. The freq here isn't helping much. It's the chirp and LORA modulation helping the link budget. But no line of sight is no line of sight.
I would expect to be able to send a few bytes between two stations maybe 400m apart through non-line of sight forest with 900 MHz and both stations at the same elevation. Certainly the grandparent quoting miles would be for mountain top to mountain top.
(Also, the hardware they're using is fairly generic, and pretty much all the vendors selling them offer them in 915/920MHz and also 868MHz and 433MHz variants. I've seen claims of over 10km range with 433MHz LoRa gear without special antennas or clear line-of-sight...)
https://electronics.stackexchange.com/questions/278192/under...
If someone else's ISM radio is using a specific frequency (perhaps with CDMA or TDMA), a "chirp" that's spears over about a hundred kHz and -20db or so down in the noise is unlikely to bother them, but is quite useable/reliable for the LORA gear to detect.
I find it entirely believable that a lower data-rate modulation could get better range than that, even on less power and worse antennas.
And you can do a LOT with antennas on 900MHz.
OP is also talking about using off the shelf LoRa boards and their project is more about the software, so they are stuck with the bands available on the commercial LoRa transceivers those boards use.