Section: 7.5 RACH Optimisation Function
Content: The RACH Optimization Function in non-split gNB case is specified in TS 38.300[ NR; NR and NG-RAN Overall description; Stage-2 ]  [2]. In case of split gNB architecture, RACH configuration conflict detection and resolution function is located at the gNB-DU. To perform RACH optimisation at gNB-DU, gNB-CU sends the RA Report retrieved from the UE(s) to gNB-DU via F1AP signalling. The gNB-DU signals the PRACH configuration per-cell to gNB-CU. The gNB-CU may forward a limited set of neighbour cell’s PRACH configurations received from neighbour gNBs and other gNB-DUs to the gNB-DU to resolve the configuration conflict. RA Report retrieval When a UE performs successful random access attempts which are only known by the gNB-DU (e.g., beam failure recovery, UL synchronization issue, scheduling request failure, no PUCCH resource available), the gNB-DU may inform the gNB-CU about the occurrences of successful random access procedures in the gNB-DU via a RACH indication. The gNB-CU may then retrieve the RA Report from the UE(s) based on the RACH indication received via F1AP signalling from the gNB-DU.