Hello,
It seems that the rx2_dr option from the toml region definition file is ignored for the join sequence, do you confirm this ?
I think that the specification for EU868 for instance says that DR0 is the default RX2 datarate, but I’m not sure that it forbids to use something else, right ?
I was trying to test RX2 window using an LLCC68 radio chip which only supports SF7-SF9 at 125khz, but when I set rx2_dr to 3, the gateway still gets a downlink request at SF12 from chirpstack LNS.
How would a device know the Rx2 datarate when it hasn’t gotten any information from the server yet?
The JoinAccept is like a goodie-bag: once you’ve arrived, you know what’s in there. But before you got there, you don’t know what’s going to happen so it’s all default.
Depending on the stack you use, you may be able to configure the Rx2 datarate before the device has joined. (I guess you’re trying RadioLib, which does support this.)
Hello,
Yes, I’m aware that this configuration would be an “out of band” configuration.
For example, for some reason, a private network doesn’t want to use SF12, never, because the devices use an LLCC68 radio which doesn’t support this spreading factor.
Of course, the end-device should be configured accordingly to configure its RX2 window with the same datarate as the network server configuration.
But I don’t think that this is forbidden by LoRaWAN specification, right ?
As long as both the end-device and the network server are aware of the same settings, then it is all good. If it were forbidden, the option wouldn’t be there
But the point of my question here is that, in chirpstack LNS, there is a rx2_dr configuration option which seems to be taken into account only after join.
So the question to the Chirpstack developpers was, could it be possible that it is also taken into account for join accept.
This is not possible with OTAA, as already explained above, there are default settings that are used until the join-accept has been processed by the end-device. The default RX2 parameters are described in the Regional Parameters specification.
An other option is to implement ABP, in which case you can pre-configure the device with different RX2 parameters (and configure the same within ChirpStack).
The Regional parameters specifications says:
“The RX2 receive window uses a fixed frequency and data rate. The default parameters are 869.525 MHz / DR0 (SF12, 125 kHz)”
According to me, “the default parameters are” doesn’t mean that something else cannot be used. Some network servers use SF9 BW125 for RX2.
So I don’t think that it is not possible with OTAA due to the specification. Again, the end-device and the LNS just need to know in advance what is being used. It is an “out of band” configuration, that’s all.
But ok, I understand that Chirpstack won’t support this. We can close the thread.
