Duty cycle warning in lora-network-server logs

[Tamas Bondar]

Hi All,

I’m wondering what might cause the Duty cycle limit met warning in the server logs below. I have one node, transmitting a few bytes every 5 minutes, 868MHz, confirmations are turned off. Neither the node or the gateway should even get close to the duty cycle limitations. Am I missing something here?

Thanks,
-Tamás

22:14:48:525|INFO| GW:00:80:00:00:00:00:b6:bb|FRAME-RX|Parsing 1 packets
22:14:48:527|INFO| ED:55-66-77-88-00-00-00-01|CHECK-PKT|FCNT: 0000000d LAST-FCNT: 0000000c Duplicate: no
22:14:48:527|INFO| ED:55-66-77-88-00-00-00-01|CHECK-MIC|ADDR: 00:00:00:01 passed
22:14:48:527|INFO| ED:55-66-77-88-00-00-00-01|PER|0.000000%
22:14:48:528|INFO| ED:55-66-77-88-00-00-00-01|FCTRL|ADR:1 ADRACK:0 ACK:0 CLASS:A OPTS:0 
22:14:48:547|WARNING| Duty cycle limit met - Band: 0 time-on-air available: 1077 ms
22:14:48:547|INFO| ED:55-66-77-88-00-00-00-01|SCHED-TX|Use RX2 TOA:1165 ms
22:14:50:281|INFO| ED:55-66-77-88-00-00-00-01|FRAME-TX|Nothing to transmit

[Jason Reiss]

What frequency was the transmission on?

The 863-868 frequencies are designated to 0.1% duty-cycle
If the band is limited to 865-868 frequencies a 1% duty-cycle can be used.

So if the Addition Channels Frequency is set to 867.5 then the lowest band should be 1%.

It looks like the mDot uses 1%, similar to the Semtech reference implementation. However, the network server is still using 0.1% leading to a mismatch of duty-cycle availability on those channels and use of Rx2 instead.

[Mike Fiore]

Tamas,

You know your application doesn’t have any downstream data for your node, but the Network Server doesn’t. It tries to reserve a spot to send data down in case any comes between when the packet was received and the RX windows.

In this case, the Network Server tried to reserve a slot in RX1 but it would have been too much time on air, so it got a slot in RX2 instead. Since the gateway didn’t actually transmit, there was no time on air, which means there was no time off air either.

Hope this helps!

Cheers,
Mike

[Tamas Bondar]

Thanks guys, this has been really helpful.

Mike, it makes sense now. It would be great to understand the details of all of the log messages. I guess, there’s no other way than reading the source code, is there? By the way, are the sources publicly available somewhere or it is a closed source product?

Jason, I think I should do a bit more reading about this. Could you recommend me something where these details are documented? Or is it just the source code again?

Many thanks,
-Tamás

[Mike Fiore]

Tamas,

Unfortunately, our network server is closed source. We try to make the log messages as clear as possible, but we’re definitely not perfect. We’ve all seen our fair share of cryptic log messages. 🙂

Please let us know if you have other questions or issues and we’ll do our best to help you get to the bottom of them!

Cheers,
Mike

[Tamas Bondar]

Thanks a lot Mike, I definitely will have more questions. I will ask them in a separate thread.

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