Getting into PSM when not registered on network


We have a customer board based on BG77 (BG77LAR02A04_01.006.00.000).
PSM is working quite well and we prefer this to powerdown as there is a 10uA less current consumption.
However during stress testing we found that if by chance the modem loses network registration due to weak or no network (say the device is on the move and loses registration), then the module does not enter PSM and in fact keeps trying and wastes a lot of battery.
We have worked around this by powering down rather than going to PSM when we detect not registered.
However we do not want to suffer the 10uA penalty as stated above.

So can someone help with some PSM configurations or sequence of commands which will take the module into PSM even if not on the network. We were thinking of commands like QPSMCFG or QPSMEXTCFG but unsure if they will work or what settings to give via these commands.


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If the network connection fails or the radio signal coverage is weak, the module will continue to search the network and the camp base station cell, and cannot enter the PSM state for a short time. It is more effective to save power if you take the power off mode

Where can I read information about this? In which document?
If there is no network registration, will the module search forever (in this state, the current is extremely large) or will it automatically enter the PSM after a certain period of time?


You can configure the corresponding parameters through this command to control the module into the Sleep mode, the current mainstream design scheme is to directly power off after the search timeout

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but if I do it, the module won’t be able to wake up automatically after a TAU period to send data to the server?
I think after searching timeout, the module will return to idle mode and when the network connection is back it can automatically enter PSM mode. is it right?

Doesn’t your terminal need to think about saving power? If the module continues to search the net, the power consumption will be large, which is allowed for you?

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Thank you so much! After research and testing, I can conclude:

  1. when the network connection fails or the radio signal coverage is weak, the module cannot enter the PSM mode until module is registered network. Because it needs permission of network operators to avoid network congestion
  2. Current Consumption of module depends on the current working state of the module ( it can large when module is connecting network, can small when mudule is in sleep mode, e.g.).

Do you have any comments?
Thank you so much again!!

Yes, your understanding is correct, in order for the terminal to save power better, you need to control the time that device cannot successfully register the network or continue to search the network by the program

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Thank you so much for your response!