In which message inactivity timer signalled to UE in LTE?

Hi Experts,
Please help to tell in which message inactivity timer signalled to UE in LTE.
How eNodeB knows UE is inactive to move it to idle state?
In ZTE I’ve seen we have separate inactivity timer for enodeb and UE.
For Nokia only common parameter inactivitytimer so need to check how UE come to know value configured.

Do you mean RRC inactivity timer?
If so, it is not communicated to UE.
eNodeB maintains this timer and releases RRC connection after timer expiry.
UE will go to inactive on eNodeB instructions.

Hope you people are talking about Discountinous Reception…

Yes, thanks for clarification. It mean only eNodeB controlled it.

No it’s not DRX.

If ue is not send some message to enb in several times that reach inactivity timer, ue will released from erab /connected mode to idle mode. Cmiiw

what is the optimal value for this parameter? on Nokia the default value is 30 s. what happens if we reduce this value?

If we reduce this timer, UE will less stay in RRC connected mode, more offen release by enb. This will save resource, KPI such as RRC-SSR, ERAB-SSR, DCR, improved due to more number of attempts. But user experience is affected because UE often transit between idle and connected, call setup time increase, csfb failure increaed.
Earlier RAN sw-version, Huawei set this timer default as 20s. But now, just 10s.
This timer should be trade-off between kpi and user experience.

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Ok thanks what is the perfect value for this?

I see some networks set 10s