Dragino LPS8 sometimes does not transmit downlink

#1

I have just started using a Dragino LPS8 in the AU-band, and after noticing that the downlinks seemed unreliable I took a closed look, did a test, and I noticed that the gateway on a regular basis does not transmit the downlink, although the TTN console shows that one was generated and forwarded in due time (usually takes 200 - 300 ms).
I have a spectrum analyser constantly logging the downstream band in parallel to my test messages running back and forth, so I can see exactly if the gateway transmits anything or not.
If a downlink is skipped, it always seems to be in RX1, according to the TTN console. It does not seem to be channel or SF dependent.
Is there anyone Dragino user who has noticed this? I have found similar problems with earlier versions of the Dragino gateway, but I haven’t found any similar observations for the LPS8

[edit/add] it’s about one in three downlinks in RX1 that fail, so the majority does come through, but still for my application this is very annoying.

#2

It doesn’t seem like that gateway supports listen before talk, so that wouldn’t be the issue, thought it could still (perhaps?) be doing its own duty cycle enforcement.

Or it could simply be a bug.

That looks like an OpenWRT based platform so you can probably get a shell on it (serial port if not network) and look at logs (try logread or logread -f).

It also seems they’ve published their source, so you can probably build your own image with extra logging or correcting any issues you find.

It’s also possible (especially if you are using UDP…) that the transmit request never reaches the gateway. You might be able to sniff packets on the gateway, or to connect it through a gateway (or PC with internet sharing) on which you can run a sniffer. The UDP protocol is documented in the packet forwarder github, it’s basically a binary header followed by printable json.

#3

@cslorabox That UDP-remark made a coin drop! :smiley: I checked my router and noticed I did not have a port 1700 forwarding outside in. That fact, in combination with the fact that I also have an EU-band gateway in the same network seem to have caused this problem!
I fixed it and did some quick tests: seems to have solved it!
Many thanks!

#4

I don’t think you normally need to do that - routers with workable NAT create dynamic paths for reply in response to the outbound traffic.

#5

Yes, correct and it worked OK when there was only one gateway in this network segment. Problems started apparently by adding the second gateway…

#6

Are you still having issues with your dragino gateway?

#7

Note that what was described was a backhaul network issue, not a gateway issue.

#8

@OtvorenaMreza my setup with two gateways in one network is still not working properly, but it’s a networking issue. If I have a port forwarding on port 1700 in my router, downlinks only work for the gateway to which the port forwarding is pointing, and if I leave out the port forwarding, it’s not working properly either.
But because I am never using two gateways at the same time anyway, and because the AU-band Dragino is for testing purposes only, I keep that one switched off, and if I need to do some testing, I adjust the port forwarding in my router temporarily for the test.
That works for me at the moment :wink: