gNB-DU Band Selection Feedback for Consistent UE Measurement Setup
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Solution Overview
Problem
The current 3GPP specification does not specify how the gNB-DU initiates band changes and informs the gNB-CU of the chosen band for Pcell/Pscell/Scell in cases of carrier aggregation or dual connectivity, leading to inconsistent UE configurations and potential issues like radio link failure or lack of measurement reports.
Innovation Solution
The gNB-DU selects the best band combination for optimal performance throughput and informs the gNB-CU of the chosen frequency bands for Pcell/Pscell/Scell through specific signaling mechanisms, ensuring aligned UE configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gNB-DU autonomously selects frequency bands to optimize throughput, then network performance is improved, but configuration consistency between gNB-DU and gNB-CU deteriorates
Solution Approach 1:
The gNB-DU sends measurement results and selected frequency band information back to the gNB-CU through F1 interface signaling (UE measurement report, selected BandCombinationIndex). The gNB-CU uses this feedback to update its configuration and send corrected measurement objects to the UE, ensuring both sides have consistent information while maintaining the gNB-DU's autonomy in band selection.
Solution Approach 2:
The F1 interface signaling mechanism acts as an intermediary between gNB-DU and gNB-CU. It carries measurement results, selected band combinations, and measurement object configurations, enabling coordinated operation and configuration consistency without requiring direct coupling or sacrificing the split architecture benefits.
2Adaptability or versatility
If the gNB-CU pre-configures measurement objects for all possible bands, then measurement coverage is improved, but signaling overhead and complexity increase
Solution Approach 1:
The gNB-CU pre-configures measurement objects with placeholder IDs for all possible frequency bands in the UE context setup request. This preliminary configuration enables the gNB-DU to later select specific bands and reuse the pre-assigned measurement object IDs without additional signaling, reducing overhead while maintaining comprehensive measurement coverage.
Solution Approach 2:
The measurement object configuration parameters are dynamically changed based on the selected band combination. The gNB-DU updates the measurement object frequency parameters to match the selected bands while reusing the same measurement object IDs, adapting the configuration to actual network conditions without increasing structural complexity.
3Adaptability or versatility
If the gNB-DU changes frequency bands dynamically, then network adaptability is improved, but configuration synchronization between gNB-DU and gNB-CU becomes difficult
Solution Approach 1:
When the gNB-DU dynamically changes frequency bands, it sends feedback to the gNB-CU including the selected BandCombinationIndex and updated measurement results. The gNB-CU processes this feedback and sends updated measurement object configurations through the F1 interface, maintaining synchronization without complex coordination protocols.
Data Source
AI summary
A method by a gNB-DU node is provided where the method includes receiving a UE context setup request from a gNB-CU node, the UE context setup request comprising an identification of frequency bands and measurement objects for the frequency bands. The method includes selecting frequency bands to optimize performance throughput. The method includes sending a UE context setup response to the gNB-CU node, the UE context setup response comprising a list of measurement object IDs associated to the frequency bands selected.