Bluetooth mesh node with radio mostly turned off

[TYRI]

Hi!

I may have asked about this earlier in a lengthy question:

https://devzone.nordicsemi.com/f/nordic-q-a/35576/low-power-remote-control

But I'd like to be sure about how often a node needs to be present on a Bluetooth mesh network. The spec states in "3.10.5 IV Update procedure":

"Note: This above requirement allows a node to be away from the network for 48 weeks. A node that is away from a network for longer than 48 weeks must be reprovisioned."

Is it possible for a Bluetooth mesh node to keep its radio turned off most of the time and only once every 48 weeks turn it on and still be connected to its network? Or is this only for Low Power nodes connected to a Friend node?

Thank you!

[TYRI]

...and just to clarify. A more specific scenario would be to have a certain number of lamps which are all turned on simultaneously, including their radio, hence keeping the network "active" (although they may all be turned off when not used).

The node which "mostly keeps its radio turned off" is a remote control that is used to control the lamps. For instance, we'd like to keep the radio on only for a short period when the user presses a button.

[Bjørn Kvaale]

Yes, you should be able to keep the radio turned off for 48 weeks without the device having to be reprovisioned. You might want to turn the device back on after 47 weeks for example, as clock drift could lead the device to believe it is turning on after 48 weeks, but it might actually be turning on after 48 weeks. In this case, the remote may need to be reprovisioned.

You have two options: either you can turn on the device every 96 hours to be able to listen for when the IV Index is incremented & update its IV Index. This way, the remote will be able to communicate with the mesh network all of the time.

The second option: turn off the device for 47 weeks or so, turn the device back on & listen for the secure network beacon. The Secure Network beacon contains info about any key refresh being done & the current IV Index. The low power device will need to be on for around five seconds to listen for this beacon.