[Battlemesh] mesh protocol for lora

Kristoff kristoff at skypro.be
Sat Sep 3 13:50:40 CEST 2016


Hi Jonathan,


Yes, that is a very good and interesting analysis of APRS.

(The only thing I can add is that APRS on HF is not 1200 baud but 300 
baud. But as it is mainly used by hams on a boat "as a cheap way to 
notify the people at home where I am sailing today", it's being replaced 
by techniques that use some of the more specialised HF 
keyboard-to-keyboard modes.


Anycase, about lora.

As much as it is not my goal to recreate a lora IoT network, I do not 
want to "re-implement APRS" neither. APRS has a very solid 
installe-based and althou it is an old protocol and a lot can now be 
done better I do not think there are that much need to "replace 
something that does work".
For me, this is more to learn about RF networking, mesh-protocols, 
applications and how to "mix it all together". APRS is for me a very 
interesting idea of how to do mesh-networking which is very different 
from -say- HSMM.


As you explained yourself, one of the basic principles of APRS is it's 
limited hopcount. It's a "broadcast" network, but messages are limited 
to (usually) 3 hops. The idea is that APRS is mainly used for 
"located-related information", say the location of a voice-repeater. And 
"locality" is the key to this.
It does not make sense to know there is a voice-repeater 100 km further 
down to the south, as there is no way you will be able to work that 
repeater.
A hop-count of 3 on a usual "big stick" APRS network (high-power 
transmittors are high location) is roughly some 50 to 60 km, so that is OK.

Now, the network I try to build is different. Instead of "a few big 
sticks", it's "a lot of low-power transmittors". It's a network of 10 to 
20 nodes spanning a small city. So the actual diameter (in hops) of a 
network will be much larger.
So it may be necessairy to rethink some of the ideas of ARPS. (but that 
is what learning


That is my though at this time. More to follow once we start 
implementing and testing things.


This evening, I'll start with testing out the "RadioHead" protocol on 
top of these lora-modules. (radiohead is a library for embedded devices 
for RF modules).
RH can run on top of "serial" radio-modules (like the lora-modules I 
have) ... and it also includes basic routing and a mesh mode!
As far as I see, it's based on "on demand requesting routing-information 
when you want to reach somebody" which is probably best for a network 
with few users and low usage, like my current setup.



Kristoff (ON1ARF)




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