SRB3 info not present in NSA log

5G NR
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1

Hello dear Experts,
I am seeing in one NSA log both message RRC connection reconfiguration and RRC reconfiguration coming to UE but SRB3 info not present at UE side whether it supported or not.
Is it possible?

2

If it’s not present… it’s not supported.

3

But how come both message ie RRC connection reconfiguration and RRC reconfiguration coming without SRB3 to UE?

4

Over SRB1…LTE.

5

Srb1 for RRC connection setup complete.
Here query is for 5g NSA.

6

Isn’t all signalling for NSA through LTE only?

7

Yes but SRB2 used only if SRB3 not there.

8

Through LTE, still limited UE now supporting SRB3.

9

SRB3 is required both side network side and UE capability.

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10

RRC reconfiguration and RRC reconfiguration complete message carried by either SRB1 or SRB3 .
if RRC reconfiguration and RRC reconfiguration complete message coming via LTE then it will be using SRB1 , if gNB and UE want to send and Receive RRC reconfiguration and RRC reconfiguration complete directly without e-NB involvement then it uses SRB3 . if UE want to send Measurement report directly to gNB then uses SRB3 .

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11

SRB3 is for RRC messages transmitted on NR leg. If RRC is observed on LTE leg then it is not SRB3

12

Is there a way to know current Handsets/CPEs support SRB3?

13

Check UE capability message. If missing, then it is not supported

14

Any idea on which mesage to check?