Are there any thoughts on how to create a high availability radio node, i.e. a situation where LoRa coverage can be maintained even when a gateway fails? For adding redundancy, is it possible to put two gateways and their antenna’s close together (or even multiplex 2 gateways on the same antenna?) or would those gateways just interfere with each other, to a level possibly so bad that the transmitter or phase noise from one gateway could clog up the receive channel on the other gateway?
Are there any gateways that already have built-in redundancy features?
Gateway antennas should be positioned at least 3 meters apart in the horizontal plane to avoid transmissions from one damaging the input circuits of the other. They can be mounted closer in the vertical plane.
The easiest way to create redundancy is deploy gateways with overlapping coverage, but not at the same site. In that way you avoid dependency on a sites power and network infrastructure as well as the gateway hardware.
1 Like
Thanks for your reply, @kersing
Unfortunately, in this specific situation overlapping coverage from different sites is not possible since both gateways need to make use of the same mast.
Is it an option to limit the channels on each gateway on that same site, so that they don’t share any channels other than the 869.525 MHz?
I remember that @jpmeijers had good experiences placing antennas of different gateways above each other to minimalize interference.
1 Like
You should of course still keep in mind that LoRa operates in ISM spectrum where 100% reliability is practically impossible. As a rule of thumb, assume ± 10% message loss at all times. If that’s not acceptable for your use case, you’re probably better off with licensed spectrum.
@htdvisser we are not looking for 100% reliability in terms of packet loss. We are aware that’s not possible and the device software will take care of that. We are looking for 100% uptime in terms of the gateway functionality. So if one gateway fails, another should take over seamlessly, preferably in a load sharing configuration.
Given a sufficiently smart back-end (which TTN has) there is no problem with gateways sharing the same channels. The issue with gateways close together in the horizontal plane is RX energy. Using slightly different channels won’t solve that.
BTW, EU868 mandates at least 3 shared channels so limiting the shared channels to RX2 frequency would violate spec.
A mast sounds like you are using vertical separation which is fine as long for the usual antenna radiation pattern (sideways). In my separation statement I should have said the separation plane needs to be in the direction the antennas radiate least. So for a vertical mounted dipole in the vertical plane. If you would (foolishly) mount it horizontally the separation needs to be in the horizontal plane).
1 Like
I have one site where I’m running two gateways in parallel. My antennas are horizontally separated by about 50cm and I have not seen any issues yet. It is however much better to separate them vertically directly above each other so that the two antennas sit in each other’s radiation pattern null.
My two gateways both listen and transmit on the same channels.
1 Like