How to beware station connection lost in AP side

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dear folks,

I have a problem on detecting station connection lost on AP side through power off STA directly,
I know there's event can be triggered when STA is disconnection in normal way, but it's seem not working under STA power off condition,
also, connection timeout is a option but the timeout value is fixed as far as I know, does any API provide function can report connection lost in real time? or should I just polling every STA to checking if they can still response?

Thanks!