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.
The Oyster3 has 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:
When connecting to the network, the device can identify if it is a 'local' or roaming SIM card.
- If we are on a Local SIM, it sets the profile to Ultra-Low Power
- If a Roaming SIM is detected, it sets the profile to Balanced
In balanced mode the device simply uses the network registration timeout (default of 3 min) This the recommended mode when using roaming sims, with a device roaming between countries. 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 - this can be done by Setting the Network Profile to limit the bands which are scanned.
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?
Most users will see great results with the default parameters. In addition it is highly important to set your network profile for best results.
If you experience upload issues, you could try setting the plan to Balanced. The device will use a bit more energy but may get online more easily.
If you are using a roaming SIM card, but it only ever resides in one country, you could try the Low Power or Ultra-Low power options to save some energy (however take care and test thoroughly)