The signalling flow for signalling of RLF information from gNB-CU to gNB-DU is shown in
Figure 8.14.1.1-1, where the example where NG-RAN nodes exchange the RLF Report via the Xn: FAILURE INDICATION message has been considered.
Step 1.
A UE with a logged RLF Report connects to a cell in gNB2 and it signals the RLF Report to gNB2 by means of the RRC UE Information Request/Response procedures.
Step 2.
The gNB2 sends an Xn: Failure Indication to gNB1-CU where the UE may have previously been connected prior to the connection failure. This includes also the RLF Report.
Step 3.
The gNB1-CU sends the F1: Access and Mobility Indication message to the gNB1-DU, including the RLF Report.
It is also possible for the gNB-CU receiving the RLF Report from the UE to signal it directly to the gNB-DU by means of the F1: Access and Mobility Indication procedure.
The signalling flow for signalling of RACH information from gNB-CU to gNB-DU is shown in
Figure 8.14.1.2-1, where the example where NG-RAN nodes exchange the RACH Report via the Xn: ACCESS AND MOBILITY INDICATION message has been considered.
Step 1.
A UE with a RACH Report concerning cells of gNB1 connects to a cell in gNB2 and it signals the RACH Report to gNB2 by means of the RRC UE Information Request/Response procedures.
Step 2.
GNB2 sends an Xn: Access and Mobility Indication message to gNB1-CU where the UE may have previously been connected. This includes also the RACH Report.
Step 3.
GNB1-CU sends the F1: Access and Mobility Indication message to the gNB1-DU, including the RACH Report.
It is also possible for the gNB-CU receiving the RACH Report from the UE to signal it directly to the gNB-DU by means of the F1: Access and Mobility Indication procedure.
For MRO analysis, a gNB-CU may request to a gNB-DU to collect and report DL LBT failure information related to mobility failures for a UE, as defined in
TS 38.300, via the UE CONTEXT SETUP REQUEST message, or the UE CONTEXT MODIFICATION REQUEST message, or to trigger report via the UE CONTEXT RELEASE COMMAND. The gNB-DU may report the information to the gNB-CU via the DU-CU ACCESS AND MOBILITY INDICATION message.