How eNodeB detects user inactivity for S1 release?

[ankgitm]

Ok

My understanding is that for UL grants UE need to send Scheduling Request.
For DL grants it’s by eNodeB if there is data for particular user.

[RFSpecialist]

@sadanandk2

Yes right. Inactivity timer is never given to UE till rel-13.
In rel-14 new inactivity timer is added called “UE inactivity timer”.
It’s recommended value is always higher than normal inactivity timer which eNB monitors.
This timer is introduced to avoid UE RRC state mismatch.
If sometime UE did not receive RRC release messgage, then after expiry of UE inactivity timer, UE explicitly releases all the resources and goes in to idle mode.

Can’t find UE inactivity timer in UE logs, not even in 5G ones.
Isn’t this just for NR SA?

[sadanandk2]

No it’s for LTE also.
OEM should develop and implement it.
It’s not mandatory thing.

[gkreddy]

@RFSpecialist

Can’t find UE inactivity timer in UE logs, not even in 5G ones.
Isn’t this just for NR SA?

From 36.331

[sadanandk2]

Yes i am talking about this only.
I wrongly name it as UE inactivity timer, it’s data inactivity timer introduced in rel-14.

[dtase]

Thank you for this post!
There is an observation where in S1 it is seen UEContextReleaseRequest with cause user-inactivity…
But in parallel the user is undergoing a process of establishing SIP call so in theory the chances that there is no scheduling in UL/DL at that moment are zero but in practice we have such user-inactivity reporting.
Does anyone have an answer why do we have “user-inactivity” in such case?

And Yes it is true that only DL resources are released only. Surprisingly UL is kept by keeping all resources around (GTP, Gx, Rx, Diameter) .

Thank you!

[ankit_katyal]

@dtase

Thank you for this post!
There is an observation where in S1 it is seen UEContextReleaseRequest with cause user-inactivity…
But in parallel the user is undergoing a process of establishing SIP call so in theory the chances that there is no scheduling in UL/DL at that moment are zero but in practice we have such user-inactivity reporting.
Does anyone have an answer why do we have “user-inactivity” in such case?

And Yes it is true that only DL resources are released only. Surprisingly UL is kept by keeping all resources around (GTP, Gx, Rx, Diameter) .

Thank you!

Hi…were you able to find out the reason behind that ? We are experiencing the same in our network. The SIP call establishment is in progress, PRACK and 200OK is released and then suddenly UEContextReleaseRequest with cause user-inactivity is send from eNodeB to MME. In various traces, the value of this was different, sometimes 13 secs other times 19 seconds. This does not match the inactivity timer that we have ( 6 secs).