Conditional Primary Secondary Cell Change With Nested RRC Signaling
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Solution Overview
Problem
Existing wireless communication technologies lack support for inter-SN, MN-initiated conditional primary secondary cell change (CPC) in Multi-Radio Dual Connectivity (MR-DC), leading to uncertainties in resource preparation, potential failures, and inefficient data forwarding during handover processes.
Innovation Solution
A method where the Master Node (MN) sends an SN Addition Request message to a target candidate Secondary Node (T-SN) for CPC, receiving an RRC Reconfiguration in SN format, and then generates a nested RRC Reconfiguration in MN format for the UE, including execution conditions, allowing delayed release of source SN resources until confirmation of CPC execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MN sends SN Addition Request early for CPC preparation, then the target SN can prepare resources in advance, but the source SN resources cannot be released until CPC execution is confirmed, causing resource holding time increase
Solution Approach 1:
The target SN performs resource preparation in advance by receiving the SN Addition Request message from the MN before CPC execution. This preliminary action ensures that when CPC is executed, the target SN already has resources ready, reducing execution failure risk and improving reliability without extending the resource holding period unnecessarily
Solution Approach 2:
The system implements feedback through the RRCReconfigurationComplete message flow. The UE sends RRCReconfigurationComplete to the MN upon successful CPC execution, and the MN forwards this confirmation to the target SN. This feedback mechanism ensures that source SN resources are only released after confirmed successful execution, preventing premature release while avoiding indefinite holding
2Reliability
If the MN initiates inter-SN CPC with full resource preparation, then CPC execution success rate improves, but signaling overhead increases due to multiple RRC reconfiguration messages
Solution Approach 1:
The patent implements nested RRC reconfiguration where the MN generates an RRCReconfiguration message that contains a nested RRCReconfiguration message from the target SN. This nested structure allows the target SN's detailed configuration to be embedded within the MN's overarching reconfiguration message, reducing the number of separate signaling exchanges while maintaining full resource preparation capability
Solution Approach 2:
The MN merges multiple configuration elements into a single RRCReconfiguration message sent to the UE. This includes combining the MCG configuration, the nested SCG configuration from the target SN, and execution conditions into one unified message, thereby reducing signaling overhead while ensuring complete resource preparation for successful CPC execution
Data Source
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AI summary
A method performed by a network node operating as a Master Node (MN) for conditional Primary Secondary Cell Change (CPC) includes sending, to a target candidate secondary node (SN) an SN Addition Request message and receiving, from the target candidate SN, an SN Addition Request Acknowledge message comprising a RRC Reconfiguration message (RRCReconfiguration**) for a target candidate cell. The network node sends, to a wireless device, an RRC Reconfiguration message (RRCReconfiguration), which includes at least one conditional reconfiguration for the CPC. The conditional reconfiguration includes: another RRC Reconfiguration message (RRCReconfiguration*); at least one execution condition for the CPC; and a conditional reconfiguration identity associated with the CPC for the target candidate cell. The RRCReconfiguration* includes the RRCReconfiguration**. The network node receives, from the wireless device, a first reconfiguration complete message (RRCReconfigurationComplete) and a second RRCReconfigurationComplete message (RRCReconfigurationComplete*), which includes another RRCReconfigurationComplete message (RRCReconfigurationComplete**).