What happens after an LTE device attaches and sends or receives data?
It doesn’t stay in RRC Connected state permanently, that would waste both network resources and device battery. Instead, the network sends a RRC Connection Release to move the device to Idle Mode.
In Idle Mode, the device is pagable and ready to respond to:
Mobile-terminated traffic
Network signalling events (such as a Detach request)
It can also then enter PSM or eDRX if those modes are configured.
How fast does the release happen?
The timing is controlled by the RRC inactivity timer, which is typically between 5 to 10 seconds depending on operator settings.
Here’s an example from field testing:
After final packet activity, the RRC Connection Release occurs after 5.11 seconds (see timestamp).
Why is this important for IoT?
Correct release behaviour ensures:
Devices don’t remain in high-power Connected mode unnecessarily
Paging and low-power cycles work as expected
Network capacity is used efficiently.
Another essential behaviour to validate in real-world testing!
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