PSM (Power Saving Mode) deep dive

How PSM Works

Power Saving Mode (PSM), specified in 3GPP TS 23.682, lets a cellular IoT device essentially turn off its radio while remaining "registered" with the network. The device negotiates two timers with the network during attach or TAU: T3412 (Tracking Area Update timer) sets how often the device performs a periodic TAU — confirming network registration and obtaining any pending downlink. T3324 (active timer) sets how long the device remains in connected mode after a transaction before entering PSM. Once T3324 expires after a transaction, the device enters PSM. The radio is essentially off…