Section: 8.22.4 Intra-DU indirect path addition on top of direct path
Content: The signaling flow for intra-DU indirect path addition is shown in Fig. 8.22.4-1. Figure 8.22.4-1: Signalling procedure of intra-DU indirect path addition on top of direct path 1. If the MP Remote UE is connected with the MP Relay UE using PC5 link, the Uu measurement configuration and measurement report signalling are performed between MP Remote UE and gNB-CU to evaluate relay link measurement and Uu link measurement. The MP Remote UE may report Uu measurement results of neighboring cells and one or multiple candidate MP Relay UE(s). In case that the MP Remote UE is connected with the MP Relay UE using N3C and the MP Relay UE is in RRC_CONNECTED state, the MP Remote UE reports at least the list of the C-RNTI and the cell ID of one or multiple candidate MP Relay UE(s). 2. The gNB-CU decides to add the indirect path via MP Relay UE to MP Remote UE under the same gNB-DU. 3. The reconfiguration to MP Relay UE is performed among MP Relay UE, gNB-DU and gNB-CU if MP Relay UE is in RRC_CONNECTED state. The gNB-CU sends an RRCReconfiguration message to the MP Relay UE. If the MP Relay UE is in RRC_IDLE/INACTIVE state, this step is skipped. 4. The gNB-CU sends the UE CONTEXT MODIFICATION REQUEST message for the MP Remote UE to the gNB-DU, which contains the indirect path addition configuration at least. 5. The gNB-DU responds to the gNB-CU with a UE CONTEXT MODIFICATION RESPONSE message. 6. The gNB-CU sends the DL RRC MESSAGE TRANSFER message for MP Remote UE by including the RRCReconfiguration message to gNB-DU. If the MP Remote UE is connected with the MP Relay UE using the PC5 link, the contents in the RRCReconfiguration message may include at least indirect path addition configuration, PC5 Relay RLC channel configuration for relay traffic, bearer mapping and the associated radio bearer(s). If the MP Remote UE is using N3C, the contents in the RRCReconfiguration message may include at least indirect path addition configuration, bearer mapping and the associated radio bearer(s). 7. The gNB-DU sends the RRCReconfiguration message to the MP Remote UE. 8. If the MP Remote UE is using the PC5 link, the MP Remote UE establishes PC5 connection with the target MP Relay UE. If the MP Remote UE is using N3C, this step is skipped. 9. The MP Remote UE sends the RRCReconfigurationComplete message to the gNB-DU via direct path to complete the indirect path addition procedure. 9a. In case the SRB1 with duplication is configured, the RRCReconfigurationComplete message is also sent to the gNB-DU via indirect path. NOTE: In the case that the target MP Relay UE for indirect path addition is in RRC_IDLE/INACTIVE state, how the MP Remote UE triggers the MP Relay UE to be in RRC_CONNECTED state is specified in TS 38.300[ NR; NR and NG-RAN Overall description; Stage-2 ]  [2]. 10/10a. The gNB-DU sends the UL RRC MESSAGE TRANSFER message to gNB-CU by including the RRCReconfigurationComplete message.