Conditional Handover Timing for Low-Activity Source Cells
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Solution Overview
Problem
Existing conditional handover technologies for network energy saving (NES) face issues such as increased processing load on target cells due to simultaneous handovers triggered by source cell NES mode indications, high signaling load, and unclear procedures for SI changes notifying UEs of NES mode changes.
Innovation Solution
Implementing a radio terminal and RAN node configuration that executes conditional handovers based on a threshold time period after receiving a signal indicating low activity of the source cell, and using Layer 1 signaling to indicate source cell inactivity or access barring, allowing for staggered execution conditions and reduced signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the network transmits NES mode indication signals to trigger conditional handover, then network energy saving is improved, but the processing load on target cells increases due to simultaneous handovers
Solution Approach 1:
The patent segments the handover execution by introducing multiple staggered time periods (first threshold time period, second threshold time period, third threshold time period) after the NES mode indication signal. This divides the simultaneous handover traffic into multiple batches, reducing the processing load on target cells while maintaining energy saving benefits.
Solution Approach 2:
The patent configures conditional handover parameters in advance including multiple threshold time periods and execution conditions before the NES mode indication signal is transmitted. This preliminary configuration allows UEs to be ready for handover without immediate execution, spreading the load over time.
2Speed
If traditional handover triggering mechanisms are used for NES mode changes, then responsiveness is improved, but signaling overhead increases
Solution Approach 1:
The patent merges the NES mode indication signal transmission with existing system information blocks (SIB1, SIB2, or SIB3) or paging messages. This combines multiple functions into a single signaling transmission, reducing overall signaling overhead while maintaining fast notification of NES mode changes to UEs.
3Adaptability or versatility
If SI modification is used to notify UEs of NES mode changes, then backward compatibility is improved, but handover execution speed decreases due to SI modification period constraints
Solution Approach 1:
The patent implements dynamic handover execution conditions based on UE capabilities. NES-capable UEs can execute handover upon receiving the NES mode indication signal with configurable threshold time periods, while legacy UEs follow traditional SI modification procedures. This dynamic approach allows different execution speeds for different UE types while maintaining backward compatibility.
Data Source
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AI summary
A radio terminal receives a first message containing configuration information for a conditional handover. The radio terminal executes the conditional handover on a condition that a first threshold time period has expired, after receiving a first signal regarding low activity of a source cell of the conditional handover, following reception of the first message. For example, this contributes to improving a trigger for executing a conditional handover.