5G NR Conditional Handover and CPAC for Reliable Mobility
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Solution Overview
Problem
Existing mobility management protocols in 5G NR networks face challenges in ensuring high reliability and minimal interruption during handovers and secondary cell changes, particularly for services requiring ultra-reliability and low latency, such as remote control and augmented/virtual reality applications.
Innovation Solution
Implementing conditional handover (CHO) and conditional primary secondary cell addition or change (CPAC) procedures, including mechanisms to indicate the selected SpCell or PSCell to the target gNB-CU, transfer RRCReconfigurationComplete messages directly to the target node, and utilize F1-C, F1-U signaling to ensure seamless handover and cell change processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional handover procedures are used, then the handover process is simpler, but reliability and interruption time during handover are insufficient for ultra-reliable low-latency services
Solution Approach 1:
The patent implements conditional handover (CHO) and conditional primary secondary cell addition or change (CPAC) procedures where the wireless communication device receives configuration information in advance including multiple candidate cells and their associated execution conditions. The device autonomously evaluates these conditions and executes handover to the appropriate target cell when conditions are met, without requiring real-time network intervention. This preliminary preparation of multiple candidate cells and conditions enables reliable handover execution while reducing interruption time for ultra-reliable low-latency services.
2Reliability
If conditional handover and CPAC procedures are implemented with multiple candidate cells, then handover reliability improves, but the complexity of mobility management increases
Solution Approach 1:
The patent enables the wireless communication device to autonomously evaluate execution conditions for multiple candidate cells and autonomously select and execute handover to the appropriate target cell based on current radio conditions and configured criteria. The device independently determines when to trigger CHO or CPAC procedures without continuous network control, reducing the operational complexity burden on the network while maintaining high reliability through pre-configured multiple candidates and conditions.
3Loss of time
If direct message transfer to target node is implemented, then handover interruption time is reduced, but signaling complexity increases
Solution Approach 1:
The patent implements direct transfer of RRCReconfigurationComplete messages from the wireless communication device to the target gNB-CU during conditional handover execution. By pre-establishing the direct signaling path and target node configuration information before handover execution, the system enables immediate message routing when handover is triggered, eliminating intermediate forwarding steps and reducing handover interruption time despite the increased signaling complexity of direct node-to-node communication.
Data Source
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AI summary
A method includes receiving a first radio resource control (RRC) message including at least one of a conditional handover (CHO) configuration and a conditional primary secondary cell addition or change (CPAC) configuration. The CHO configuration includes a CHO configuration index, a CHO candidate cell configuration, and a CHO execution condition. The CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration, and a CPAC execution condition. The method includes selecting, responsive to receiving the first RRC message and based on at least one of the CHO execution condition and the CPAC execution condition, a special cell (SpCell) of a wireless communication node to perform a random access procedure (RAP); and transmitting, to the wireless communication node, a second RRC message to inform the wireless communication node that the wireless communication device selected the SpCell to perform the RAP.