Issue: Option to add concentrator
Setup: LoRaWAN Gateway -> Packet Forwarder
LoRa® Server: n/a
Details: There is a button in the lower-left corner to add a concentrator. Is there any documentation on how this works? I assume the 7240 is forwarding from two concentrators instead of one? I wasn’t able to figure out switching between them.
Hi @simplice,
I guess you mean GUI instead of RUI 
When you have the two concentrators, you are able to set up to 16 channels. When you have just 1 of them you can set only 8 channels. under “Channel Plan” in the menu of GUI, you have a blue button “Switch to Advanced Mode”. When you switch to this mode you will be able to configure more settings about the concentrators and channels.
Dang, I was hoping there was a button that would automagically install an extra concentrator out of thin air!
Jokes aside there is actually one, you can do it without having to go into advanced mode, the installation part that is.
As for how it works it depends a lot on the band you are using, but there is one thing to note. You get 8 more LoRa channels, this goes only for he uplink, downlink is still bottlenecked in a way, you still have one concentrator only handling it so it is not like you have 2 gateways in one.
And there isn’t actually any switching really. You can choose to use the main one or both, having only the second one is not an option, also they have to be in the same LoRa Band, kind of.
Installation itself is very simple. Open up the casing removing the screws on the back and simply populate the second mPCIe slot, tighten the card with 2 additional screws. This is for the concentrator only. Assuming you had a model with 8 channels to begin with you would need to connect a second LoRa antenna to the concentrator, basically reroute the secondary LTE antenna pigtail to the ufl connector on the concentrator. Additionally replace the antenna itself with a LoRa antenna.
Just out of curiosity, which band are you going to be using these 16 channels in ?
Regards
Vladislav
I’ve seen the space inside the RAK7240 so I’m happy with the mechanical side. I guess the most important question is can the two concentrators work so that you can get improved uplink coverage for 8 channels - I’m in the EU.
I don’t have a high density site yet that’s managed to hit a perfect storm of multiple devices hitting the gateway at once, but having the already centrally located gateway with more capacity is better than having more gateways at opposite ends of a site because they’d still be able to hear many of the devices so they’d not really provide anything extra.
For the rural areas it’s far less of a problem as the overlaps between gateways are easy to control, within the limits of power & backhaul.
I’m not sure that there’s really a way you can, since AFAIK the Semtech concentrator chips autonomously decide what to assign their demodulators to - the packet fowarder only collects the results, it is not actually involved. Having a second copy of the same thing would only seem like it would help on the random chance that when overloaded they made different rather than matching choices.
What might work would be to assign each concentrator to only four channels, and assign each channel twice, and use the other concentrator for the other four. But I don’t know that would actually help.
Switching to an SX1302 which theoretically has more processing paths might be an option; that’s not officially supported at this point but should be possible as a DIY effort; would probably make sense to test it in a pi first and see if you get any better performance.
Something that’s not clear to me is how two concentrators are actually handled at a system level - two packet forwarders? And if an uplink received on one triggers a downlink on the other, how can their hardware timestamp counters be synchronized. Does that only work in GPS PPS locked mode?
That I’m not sure I agree with; I think you’re more likely to get all of the packets with some distance between the gateways than with them co-located, so that you actually make a meaningful change in which node signals are strong, recognized, blanking others, etc. And you may be able to still receive strong packets with one while the other is transmitting (weak packets probably not; and you can’t even use a diplexor since in your bandplan the downlink channels are the same as the uplink ones)
Well is any of this really relevant, you have no spatial diversity, so 2 or 20 concentrators, they will probably have similarly perturbed signals so you wouldn’t really get any benefits RF wise.
So the option is there but not functional unless you have the 16 channel version correct?
I was going to use two directional antennas – one for each concentrator to cover a specific area. The thought was to use 7240/7249 – 16 channels to achieve that instead of two separate units. From your explanation, the extra 8 channels are uplink only so I could use a non-LTE gateway using that second LoRa port as a secondary antenna?
I could be way off base but more curious than anything…
Jeff
Hei @simplice
Yeah you can do this, should be a nice solution, honestly haven’t heard of anyone using directional, range of LoRa is pretty good anyways. Still it will be interesting, as for the Downlink you will be fine, the Network Server will take care of it so downlinks will be distributed as they should.
Still I would also like to have some performance data on such a setup to look at at. Might be building something similar now that you gave me the idea.
Regards
Vladislav
I have 7240 LTE’s now so I would have to get some other version or even the 7249.
Would I need to open the box to jumper anything? Could I use the second LTE antenna as LoRa if I disconnected from the modem? I would assume I would need to attach it to another connection on the board?
Jeff
I’d not use directional aerials, they can leave some serious bald patches in coverage.
In this instance, the single antenna is on the top of a very ornate & massive chimney stack - so I’d look at moving it down to the side and having one on each side, so sort of splitting the site in to two.
As you may guess, RF isn’t my strong suit, I’m more solving the problems, back end systems & a modicum of firmware.
