RRC connection release to UE in NR/LTE cells scenario

Mobility
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1

Hi Experts.
This is a scenario involving one LTE cell and one NR cell.

  1. UE sends RRC connection request message to LTE cell.
  2. LTE cell sends RRC connection setup.
  3. Now UE sends NR RRC setup request to NR cell.

In this case does LTE cell need to send RRC connection release to UE?

2

#3 doesn’t make sense to me.
If it is ENDC, LTE will facilitate 5G attach through RRC Reconfig, not through RRC Conn Req.

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3

Why do we assume it is NSA scenario?

4

Not assuming, just put a condition.
If it isn’t, then the scenario is possible in a scenario that RRC Conn Setup didn’t reach UE.
UE found suitable 5G SA cell and sends another RRC connection request. In this case LTE doesn’t need to send release because UE’s attach wasn’t successful.

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5

Exactly. :wink:

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6

@Prasoon_P

RRC connection release will only be sent after RRC connection setup complete is recieved from UE

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7

Yes this is SA scenario.
Not seen this behaviour before.
May be due to rrc connection setup not received by UE.
Thank you all guys.

8

Sub question:
Why UE did not send RRC connection setup to NR before it send RRC setup to NR?
What factor control it?
Is it last used RAT UE was camped on?

9

Follow up question, UE was attempting RRC Setup on LTE, why was it still searching NR?

10

UE might have done reselection to NR cell?

11

First we have to understand if UE was in mobility or static.
If static it should have camp on NR as it has higher prio.

12

Completely agree.
I assumed its in mobility state.
So when SA UE is switched ON, it will first camp on lats user frequency/RAT.
Then as directed by SIB, it can perform reselection. Right?

13

@sadanandk2
It depends on cell reselection priorities