Dear All,
I am working on an application where I am connecting to the network, sending some data and then disconnect using CFUN=4, in order to achieve low power for my application.
This seems to work pretty well in most cases.
But if my device exceeds the data budget of the provider it gets blocked by the provider. When this happens it seems that the device is not able to connect to the network, even if the provider allows the device to connect.
My theory on this is that the modem keeps track of the cells that it was rejected from and for that reason it does not try to connect to these cells again (at least for some time days, as my device is triggered to reset every 3 days. After that reset the device is able to connect to the network again).
While experimenting a bit with the device I have noticed the following behaviour:
After AT+CFUN=1 for the first time in my test the device will detect a cell that my SIM card cannot connect to. After performing CFUN=4 and again CFUN=1, I will not longer the +CEREG message related to that cell, I make sure to allow the device to scan for networks until it gives up).
Now if I do CFUN=0 and then CFUN=1, I will see that cell once again.
So my questions are these:
Is my above observation correct or is it a struck of luck (I have run this test several times with the same result: Once the device detects a cell that it cannot connect to, in any subsequent scan attempt I will not the CEREG message for that cell, except if I use CFUN=0 instead of CFUN=4 in between)?
Does CFUN=4 allow the device to maintain some information about previously scanned cells?
Does this information play a role in connecting faster to the cell the device was connected to before the CFUN=4 command? If I was to use CFUN=0 will it cause the device to have to do a "cold" scan in order to connect?
Will there be a difference in the time needed to connect if I do CFUN=0 instead of CFUN=4?
What are the differences between offline and air-plane mode?
I am using modem firmware version 1.3.0 and nRF SDK 1.6.0
