When the eNodeB detects a UE which does not have any traffic to send and receive during a defined period of time, usually referred to an inactivity timer (20s, 10s etc…) which is defined in eNodeB and also is configurable, then the eNB can initiate procedures to place the UE in idle mode. In this state, the UE doesn’t have any connectivity to the EPC, and all context relating to the UE is removed from the E-UTRAN.
When the UE is idled with inactivity timer, existing connections such as SRBs and DRBs are removed. S1-MME control plane and S1-U user plane connections are also removed.
Smaller value of inactivity timer shows improvement in Call Drop Rate statistics, but in high loaded network it might be cause for setup degradation due to congestion which is related with more frequent RRC connection setup requests.
I’m a bit confused. How will a smaller value of inactivity timer show improvement in call drop rate stats? The ENB will release (drop) the bearers after 10s (more quickly/frequently) as compared to after 30s resulting in more number of releases/drops.
Please correct me if I’m wrong but plz elaborate on the point.
Thanks in advance.
Thanks for your comment.
Here eNodeB release is not counted as dropped connection, it is normal release. So if the connection duration is 30 seconds during inactive state then abnormal release risk is higher than the state which is 10 sec.
e.g.
– 10 sec inactivity timer duration, after this timer expires the eNodeB will release the RRC connection as normal release and will move to idle mode.
– 30 sec inactivity timer duration, the eNodeB should wait 20 seconds more in connected mode to release the connection. So, now the drop risk is higher even there is no active traffic.
As a conclusion, does it mean we do optimization in the network with reducing the mentioned timer value ? No, we just increase number of RRC attempts and consequently Call Drop Rate will show “improvement”.
I had the same doubt, so I tried 30 s instead of 10 and then I got a drop increase beacuse of the normal release increase, the inactivity part got an lower part. I work with not loadee network.
Thanks for your comment, please see above reply to the similar doubt.
Very nice description.
//When the eNodeB detects a UE which does not have any traffic to send and receive during a defined period of time,//
in addition to this i think ENB check also, before releasing the UE to idle –
– UE is not in ANR measurement
– NAS protection timer is expired.
Thanks Jalloul for your valuable opinion 🙂