In Management Based Trace Activation towards a gNB-CU-CP, gNB-CU-UP or a gNB-DU can be fulfilled with the Cell Traffic trace functionality defined in TS32.422 . The configuration parameters of the Trace Session that are received by a node in split RAN architecture are defined in TS32.422 .
The following description is valid for both an en-gNB and a gNB.
If the MDT measurement is initiated by the EM towards the gNB-CU-CP, and if the activation involves measurements collected by multiple nodes under the same gNB-CU-CP control in a split RAN architecture, the EM sends MDT measurement activation to the gNB-CU-CP and the gNB-CU-CP may further decide which gNB-DU(s) or which gNB-CU-UP(s) to perform the MDT measurement.
When gNB-CU-CP or a gNB-DU receive the Trace Session Activation message from the management system for a given cell or a list of cell(s) under its control, the gNB-CU-CP or gNB-DU shall start a Trace Session for the given cell or list of cell(s). For Management Based MDT sent directly to a gNB-CU-UP, no MDT Area Configuration (apart from PLMN IDs) is to be included in the MDT activation indication.
Each node receiving an MDT activation indication reports the measurements collected according to such activation directly to the TCE the node has been configured with.
The signalling flow for management based MDT in gNB-CU-CP, gNB-DU and gNB-CU-UP is shown in Figure 126.96.36.199-1, Figure 188.8.131.52-1 and in Figure 184.108.40.206-1 respectively.