Is the ability to use 16 channels a hardware or software limitation?
If this is a software limitation, can I ask you to add channel extensions to the backlog for your development team?
(this greatly extends the possibilities of using RAK devices in high load networks + allows you to make full use of your cool 16 channel gateway, but right now your ecosystem doesn’t look quite right)
It is partly a hardware restriction, because to use 16 channels, you need a 16 channel gateway and they are not very common. Our gateways are sold as 8 channel versions, the 16 channel version requires a second LoRa concentrator, which makes them more expensive. And (not 100% sure) our gateway firmware has the same settings as RUI3 which allows to use 16 channels only on a few regions.
Your gateways support 16 channels perfectly! As in the default settings (although some of the default frequencies are not set quite right). The expansion fee is very modest, which makes your gateways very attractive for high-load solutions.
I’ve already tested your gateways with devices that support 16 channels. Everything works great!
So, is it possible to extend the functionality as part of the RUI3 software enhancements?
RAK has options for a16-channel gateway vs an 8-channel. We’re deploying RAK7289s with 16-channels even though we’re still only using the 8-channel US915 SB2. In theory, someday when we’ve eliminated the 8-channel GWs from our deployment, we could change to 16 channels (but this someday may never come since we mix 8-channel local GWs such as LR9s into our network).
IIRC, proper LoRa Alliance certification for US915 requires motes to support all 64+8 channels - at activation/join time, the LNS sends down the channel map with channels in use (such as SB2). The downside is potentially longer activation time as motes step through the sub-bands until they receive a join accept. In the case of SB2, it’s not terrible because the mote starts at SB1. Our RAK4631-based motes are limited to SB2; our RAK3172/STM32WLxx motes use the ST LoRaWAN stack and do not use hybrid mode.
Besides spreading traffic over more channels, 56- or 64-channel GWs permit higher TXpower in the US - LoRaWAN US915 regional support limits TXpower to +20dBm when fewer than 50 channels are in use (I think this might be a too-literal reading of 47CFR15, but I digress). With 50 or more channels, max TXpower is +30dBm. Even with one of the high-power modules (such as those from eByte) that are capable of +30dBm, the LoRaWAN stack limits TXpower to +20dBm as a result.
At the moment there are no plans to support 16 channels in RUI3. What you can do to balance the load is to use 16 channel gateways and setup half of your RAK3172 to use the first 8 channels of the gateway and the other half to use the second 8 channels.
