Hey Robert,
- Could the short distance be a problem?
well you have interference between the nodes and the typical throughput limitations because of the half-duplex nature of WiFi. But if you take that into consideration and don't expect the same throughput as on a single link, 3-4 meter should be fine.
Do you have any good literature/link recommendation where I could learn more about the low level WiFi mechanics?
Mhm, I'd generally recommend the Matthew Gast books on 802.11, these are very good.
The throughput limitation I'm talking about is a mesh-network specific problem when you use single radios only: as a wifi radio can only transmit or receive at the same time, the throughput will be cut to 50% with the first hop, and will decrease furhter with more hops. I don't know if there are books about such effects, but there are certainly papers ...
It also depends on what kind of data you will send (many industrial applications use broadcast, for example).
Broadcast is not necessary, all traffic is generated somewhere on the line and sent out to the Gateway. The datasets are in the 500 KiB range, it could be UDP or TCP, not decided yet. But it's definitely unicast.
OK, then you can use high datarates too.
Is it possible to regulate the transmission power in order to avoid
disturbance?
There are WiFi driver which allow that, yes.
Can you give me a hint which feature I need to search for in the kernel drivers?
ath9k supports that for example. you can set the txpower using "iw wlan0 set txpower 1500" for example to set to 15dBm output pwoer
As the stations will be built from scratch (SoC+RAM+Flash+Wifi-Chipset), we can chose the right chipsets, as long as it's possible to buy them somewhere.
I'd definitely recommend to buy WiFi modules (e.g. pci-e) or off-the-shelf boards with WiFi SoCs on it. If you don't have experience in building WiFi routers, you might have a lot of fun otherwise. :)
However I'd recommend to keep it as it is and change the broadcast rate to something higher (e.g. 18M or more) to force to only use good links, even if they are a little shorter.
Ok. I'll setup a bunch of prototype devices in the first place anyway, so we can try it out then.
Thanks for the infos!
Good luck! Simon