How RRC Inactive to RRC Idle transition happen in NR SA?

Is that correct?

From what I’ve read, the RRC INACTIVE state is essentially similar to RRC IDLE, as there are no SRBs (Signaling Radio Bearers) between the gNB and the UE.

So, for the gNB to force the UE into RRC IDLE, it would first need to transition the UE back to RRC CONNECTED and then directly release it to RRC IDLE.

When RRC INACTIVE is enabled in the network, IDLE mode usage is almost negligible, as the UE remains in INACTIVE (provided the UE supports it) due to a longer inactivity timer compared to IDLE mode.

Additionally, based on my understanding, the UE can transition directly from INACTIVE to IDLE when required.

Can a UE transition to RRC Inactive state with 2CC added, or does it need to release the SCell first?

The UE can transition to RRC Inactive state, and upon resumption, the CU will configure the stored context.

Thanks!

Will the UE release the SCell on its own, or will the network explicitly command SCell release before transitioning to the RRC Inactive state?

RRC Inactive is similar to RRC Release, except that the UE context is preserved in the RAN for an RRC Inactive UE.

This means that all RRC configurations are released from the UE side when transitioning to RRC Inactive state.

A UE cannot release an SCell on its own without a command from the network. Suppose a user with Carrier Aggregation (CA) enabled experiences inactivity triggers, and the network sends an RRC Release with suspend configuration. In this case, what happens to the SCell added at the UE’s end?

Alternatively, we can consider a different sequence: if inactivity triggers while CA is enabled, the network may first release the SCell before sending the RRC Release with suspend configuration.

Once the UE receives an RRC Release, the SCell is released on both the gNB and the UE without requiring separate signaling for SCell release.

Refer to 3GPP TS 36.331 for details.