While on 5G NSA, when UE go to idle and initiate TAU request?

Specs & Protocol Testing
1

Hi Experts.

While UE is on 5G NSA, what issue can provoke UE to go to idle and initiate TAU request?

I think it cannot be drop on 5G side because I would see scgFailure or rrcreconfig to move UE to 4G first.

But even if it is eNB detected drop, why UE Initiating TAU request?

2

UE goes to Idle only for drop on 4G.

3

TAU request is happening because TAC on SIB is not the same with the previous registered TAC on SIM card. So UE needs to initiate a TAU request.

1 Like