Conditional Handover in Lower Layer Mobility Under Lost L1 Reports
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Solution Overview
Problem
Cell handover in lower layer mobility (LLM) can be problematic when L1 report messages are lost, leading to Radio Link Failure (RLF) and requiring cell reselection, which disrupts connectivity.
Innovation Solution
Implementing a conditional configuration that combines lower layer mobility with conditional handover, allowing for efficient resource reservation and interworking, and enabling the network to maintain control during fast network degradation, with mechanisms for autonomous handover initiation and network command waiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If lower layer mobility (LLM) is implemented for faster handover, then handover speed is improved, but reliability deteriorates when L1 report messages are lost
Solution Approach 1:
The patent applies preliminary action by configuring conditional handover parameters in advance before handover is actually needed. The UE receives and stores conditional configuration information including target cell configurations and execution conditions during normal operation, so that when L1 report messages are lost or handover is urgently needed, the UE can immediately execute handover using pre-configured parameters without waiting for network messaging, thus maintaining both speed and reliability
Solution Approach 2:
The patent introduces conditional configuration information as an intermediary between the network and UE handover execution. This intermediary contains pre-negotiated handover parameters and conditions that mediate the handover process, allowing the UE to autonomously decide when to execute handover based on pre-agreed conditions, thereby compensating for lost L1 reports while maintaining network control
2Productivity
If autonomous handover initiation is enabled at UE, then handover efficiency is improved, but network control deteriorates
Solution Approach 1:
The patent applies dynamics by making the handover initiation mechanism adaptable - the UE can autonomously initiate handover when configured conditions are met, but the network retains the ability to override or adjust conditions dynamically. The conditional configuration includes executable conditions that can be set by the network, allowing flexible balance between UE autonomy and network control based on actual network state
Solution Approach 2:
The patent uses parameter changes by allowing the network to configure specific execution conditions and parameters for conditional handover. These parameters (such as measurement thresholds, time triggers, and cell selection criteria) can be adjusted by the network to control when and how autonomous handover occurs, thus maintaining network control while enabling UE efficiency
3Reliability
If conditional handover configuration is implemented, then handover robustness is improved, but signaling complexity increases
Solution Approach 1:
The patent applies merging by combining conditional handover configuration with existing RRC reconfiguration procedures. The conditional configuration information is integrated into standard RRC messages, merging multiple functions (handover preparation, condition setting, and configuration) into a unified signaling flow, thereby reducing overall signaling complexity while maintaining robustness
Data Source
AI summary
Inter alia apparatuses for lower layer mobility are disclosed. Further an apparatus is disclosed comprising, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform:—Receiving a conditional configuration and a conditional configuration information; and—At least one of the following: determining a handover based on a layer 3 measurement of at least one candidate cell or a layer 1 measurement; or determining to wait for a network command for a handover based on the conditional configuration information. It is further disclosed according methods, computer programs and systems.