KPI (Core/BSS/RAN) or other way-forward for getting Out Of Coverage time of any UE

Telecom & ICT
1

Hi Experts,
Can you please suggest any KPI (Core/BSS/RAN) or other way-forward for getting Out Of Coverage time of any UE?
Time when UE was not in coverage. In LTE.

2

I think you can get it only from handset. if your app is installed on OS or any applet installed via ota to sim.