Section: 8.22.3 Intra-DU direct path addition on top of indirect path
Content: The signaling flow for intra-DU direct path addition is shown in Fig. 8.22.3-1. This procedure is only applicable to the MP Remote UE using PC5 link. Figure 8.22.3-1: Signalling procedure of intra-DU direct path addition on top of indirect path 1. The Uu measurement configuration and measurement report signalling are performed between MP Remote UE and gNB-CU to evaluate both 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). 2. The gNB-CU decides to add the direct path to MP Remote UE under the same gNB-DU. 3. The gNB-CU sends the UE CONTEXT MODIFICATION REQUEST message for the MP Remote UE to the gNB-DU, which contains at least the direct path configuration. 4. The gNB-DU responds to the gNB-CU with a UE CONTEXT MODIFICATION RESPONSE message. 5. The gNB-CU sends an RRCReconfiguration message to the MP Relay UE to update the indirect path configuration if necessary. 6. The gNB-CU sends the DL RRC MESSAGE TRANSFER message for MP Remote UE by including the RRCReconfiguration message to the gNB-DU. The contents in the RRCReconfiguration message may include at least direct path addition configuration, RLC channel configuration, bearer mapping and the associated radio bearer(s). 7. The gNB-DU sends the RRCReconfiguration message to the MP Remote UE. 8. The MP Remote UE performs random access procedure at the gNB-DU. 9. The MP Remote UE sends the RRCReconfigurationComplete message to the gNB-DU via direct path in order to complete the direct 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. 10/10a. The gNB-DU sends the UL RRC MESSAGE TRANSFER message to gNB-CU by including the RRCReconfigurationComplete message.