Conditional PSCell Reconfiguration in Inter-MN Handover
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Solution Overview
Problem
Current specifications do not adequately handle the transfer of Conditional PSCell Addition/Change (CPAC) configurations during inter-Master Node (MN) handovers in Multi-Radio Dual Connectivity (MR-DC), leading to potential loss of configuration information and reduced robustness due to unknown CPAC configurations at the target MN.
Innovation Solution
A method where the source Master Node (MN) receives a message from the source Secondary Node (SN) containing the CPAC configuration, and transmits a handover request to the target MN with an indication of the UE's CPAC configuration, allowing the target MN to keep, modify, or release these configurations accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the source MN does not transfer CPAC configuration to the target MN, then the handover signaling is simpler, but the CPAC configuration information is lost and the target MN cannot manage it effectively
Solution Approach 1:
The CPAC configuration information is nested within the UE context information that is transferred from the source MN to the target MN during handover. The source MN includes the CPAC configuration in the handover request message, which is then processed by the target MN to determine whether to keep, modify, or release the configuration.
Solution Approach 2:
The source MN acts as an intermediary that collects the CPAC configuration from the source SN and transfers it to the target MN. This intermediary role ensures that the configuration information is preserved during handover while managing the signaling complexity through structured message exchange.
2Reliability
If the target MN receives and processes CPAC configuration, then the robustness of Dual Connectivity is enhanced, but the handover signaling becomes more complex
Solution Approach 1:
The source MN prepares the CPAC configuration information in advance and includes it in the handover request message before the handover is executed. This preliminary preparation ensures that the target MN receives the configuration information ready for processing, enhancing robustness without adding complexity during the actual handover execution.
Solution Approach 2:
The target MN processes the received CPAC configuration and determines whether to keep, modify, or release it based on the current network state and UE context. This feedback mechanism ensures that the CPAC configuration is managed appropriately to maintain Dual Connectivity robustness while adapting to changing conditions.
3Reliability
If the CPAC configuration is not preserved during handover, then the signaling overhead is reduced, but the connectivity robustness decreases
Solution Approach 1:
The CPAC configuration is nested within the existing handover signaling structure, specifically included in the handover request message from the source MN to the target MN. This nesting approach preserves the configuration information during handover without requiring separate dedicated signaling messages, thus maintaining connectivity robustness while minimizing additional signaling overhead.
Data Source
AI summary
A method performed by a source master node performing a handover of a wireless device to a target node includes receiving, from a source secondary node, a first message comprising the secondary node configuration and a conditional reconfiguration. The source master node transmits, to the target node, a handover request message that includes an indication that the wireless device is configured with the conditional reconfiguration. The source master node receives, from the target node, a handover acknowledgement message indicating that the wireless device is to keep, modify, and/or release the conditional reconfiguration.