question: where can I change the channel selection on class A.

[King-anderson]

Hi friends,
I want to add an ability to finding next "free" channel selection in uplinking a data.
I have provided the function to check the channel is free or not.
but I can't find where I should use it.
where does the lmic select the channel?

[terrillmoore]

The LMIC selects the channel for the next transmission (generally speaking) at the time of transmission, using a randomization algorithm. It's not easy to know in advance what channel it will use, and it's not supported for clients of the LMIC to choose on behalf of the LMIC.

The algorithm used is region specific (in that the data structures are different for regions like EU which have up to 16 programmable channels, compared to regions like the US, AU and CN with up to 96 fixed channels).

Your best bet if you want to experiment with this is to find the region/bandplan-specific files and functions that choose the next channel.

Be aware that the LoRaWAN spec requires randomization of uplink channel selection, so what you're doing is outside the LoRaWAN spec, and therefore is not likely to be a standard part of the LMIC.

Good luck!
--Terry

[King-anderson]

I don't want to change the next channel selection procedure. I want to check if the next selected channel is not free, I wait to be free or replay the next channel selection procedure.
I faced uplink loss in my networks and want to optimize the uplinking procedure.
Infact I want to use CAD procedure before tx.

[terrillmoore]

I don't know of a way to do this with the LMIC, sorry.