Applicable to next-gen devices using the Nordic NRF9160 modem
A failed upload uses up to 20 times the power of a successful upload. This is because a failed upload scans the bands for 3 minutes (registration timeout), while a successful upload is typically done within 5 – 10 seconds.
A failed upload is just a complete waste of energy! Since we spend all that time trying to connect, and in the end don't even see any data on the server.
Saving Power - Early Cellular Registration Abort.
Our new range of devices have the ability to detect early when the device is out of coverage, and quit the upload early - saving a heap of power!
The modem tells us when it has done a “best guess” scan of the bands, and when it has finished scanning all the bands, so we have added a new registration strategy option to the upload parameters:
In balanced mode the device simply uses the network registration timeout (default of 3 min) This is the default mode, and the recommended mode when using roaming sims, especially multi IMSI roaming sims which typically need to be powered long enough to change the IMSI (E.G multi IMSI Emnify sims require this timeout to be 5 minutes).
In this mode the device aborts the upload attempt when it has finished scanning all the bands and has not found a suitable network. This mode works best when there are fewer bands enabled.
For example, with the bands limited to Telstra CAT-M1 and NB-IoT bands, this timeout triggers after 40 seconds which is 5x shorter than the default 180 seconds. With all bands enabled this generally takes 2 minutes so there is only a marginal power saving.
Ultra Low Power
In this mode the modem tells us when it has done a “best guess” scan. Essentially it uses information about the network such as the last successful band it used to abort early, typically within 5 – 10 seconds.
This option makes failed uploads comparable in power to successful uploads, but it comes at the sacrifice of upload reliability when on the edge of coverage. This option would not be recommended for roaming sims that switch between carriers.
Which to choose?
The Balanced plan is for many applications, a bit conservative. It favours upload reliability (which is important) over the lowest energy usage, and ensures roaming SIM cards will perform.
For many users, who use home network SIM cards, and who's devices don't move between regions/countries, the Ultra Low Power, or Low Power settings should be used. It is worth trying the Ultra Low Power setting if you use a home network SIM (i.e. Telstra). Monitor the device, if uploads begin failing, you can move back to Low Power, and then Balance if required.