We are using the XBee3 LTE-M/NB-IoT device (XB3-C-A2-UT-001) as the communication module for a battery powered microcontroller board. We send messages periodically (most often every 10 minutes) to an MQTT service.
On every transmission, the cellular module wakes up (it takes about 10 seconds to get a valid IP address), sends the data (another approximately 15 secs until the server confirmation is received) and then is set to sleep – either by MicroPython or by asserting the SLEEP_RQ pin high. This is followed by approximately 20 secs (best case) until the ASSOC pin is low (so power can be switched off). The radio module is in PSM and this seems to work correctly.
Question: Is there a method to shorten this 20 sec interval? In Direct USB mode the radio module itself, for example, executes the power off command much faster (AT+ CPWROFF is followed by OK in approximately 3 secs).