UE doesn't initiate PDU session although all call flow is successfully done

5G NR
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1

Hi all 5G Experts.

Anyone knows why this happens and what could be the reason?

Issur is: UE doesn’t initiate PDU session although all call flow is successfully done. And there is attach to 5g SA cell but no mobile data - realme 8 5G UE.

Changed cell config from two dedicated searchspaces to one dedicated searchspace then UE successfully attach with mobile data.

Any idea what could be the reason why UE won’t initiate pdu session although there is attach?

2

TDD or FDD?

3

Hi, TDD.

4

Both the SS are you using for DL or UL only?

5

For both it used DL or UL.

Even if I specify them one for DL and other for UL, it doesn’t work either (UE not attaching).

6

It’s because the MAC is using only 1 SS for DL & UL, and other non working (SS) overlapping with PUCCH format or SSB transmission or other configurations hence UE attach itself does not happen.

7

But specifically the MAC is using two dedicated SS since configured that on DU and that’s what I see one UE that succeeded to connect.

Nord succeeded to connect with two dedicated SS configured.

Exynos UEs (all different models of UEs of Samsung) like S21 doesn’t succeed with two dedicated SS only with one dedicated SS.

S21 UE of chipset qualcom succeeded to connect with two dedicated SS configured.

8

Yes, this observation is there.

Check how DCI is scheduled when 2 SS configure and 1 SS configure.

9

Simply when two dedicated SS scheduled, one DCI format 1_1 goes to first dedicated SS and second DCI format 0_0 goes to second dedicated SS.

Compatible to what configured on DU.

But it seems like Exynos Samsung chipsets DCI format 0_0 shall only be on common and only dedicated SS it supports, not two dedicacated.