Hi,
At the moment, my current location does not have an NB-IoT network for the nRF9160 DK to attach to. This means that the device is unable to activate PSM mode (which requires an active NB-IoT connection to confirm T3412 and T3324 between the device and eNodeB) and attempts to connect over and over again.
What I have noticed is that these attach attempt periods are about 1 minute and 50 seconds long with a gap between attempts that follows a sequence (1st-2nd gaps -> 10s, 3rd gap -> 20s, 4th-nth -> 40s). Is there a way to manipulate the attempt periods and the gap intervals or are these fixed in the modem firmware? I have implimented my own checking code into my application that will use the k_uptime of the device when enabling NB-IoT to start a time based check for attach attempts and gap intervals but it would obviously be more useful to be able to edit the modem's own intervals.
It is unlikely that our devices will be able to reach the NB-IoT network at all times and will need some form of power saving, the first stage would be smart connection attempts (since the modem will forever drain an average current of 42mAs as it tries to connect.
Is there a way to reduce the idle current of the device, with the modem set to CFUN=4 the average current is 11.6mAs with all samples, including the AT Client application? I have seen the blog on power measurement that stated a 7uA~ current measurement but without a network, running that set-up yielded the same results as shown below which will be what our deployed devices will see if unable to connect and therefore not really a good way to save power. (i.e. power saving that is independant of network status)
Asset Tracker power measurement with modem retry intervals, this includes CONFIG_POWER_OPTIMIZATION_ENABLE=y:
at_client power measurement using AT+CFUN:
Custom Firmware using AT+CEREG and AT+CFUN to manipulate modem power consumption:
