Beam-Aware Conditional Mobility for Stable Cell Handovers
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Solution Overview
Problem
Existing handover procedures in LTE and NR are prone to radio link failures and ping-ponging due to the lack of consideration of beam information in mobility decisions, leading to inefficient handovers to cells with only one stable good beam or frequent handover changes.
Innovation Solution
Implementing a method for UEs to receive a conditional mobility configuration based on beam measurement information, including criteria for selecting a target cell with multiple good beams and optimizing handover decisions using beam-related information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover decisions are made without considering beam information, then the handover procedure is simple and fast, but radio link failures and ping-ponging occur frequently
Solution Approach 1:
The network node prepares conditional handover configurations in advance, including multiple potential target cells with their associated handover parameters. The UE stores these pre-configured options and automatically executes handover when beam conditions trigger the predefined criteria, eliminating the need for real-time network decision-making and reducing execution delay.
Solution Approach 2:
The UE autonomously monitors beam measurement quantities (such as RSRP, RSRQ, or SINR) of serving and neighbor cell beams, compares these measurements against configured thresholds, and independently determines when to execute handover based on the conditional criteria. This self-service mechanism reduces reliance on continuous network control signaling.
2Reliability
If handover is triggered based on cell-level measurement only, then the decision process is simple, but handovers to cells with single unstable beams occur frequently
Solution Approach 1:
The handover evaluation process is segmented into two independent levels: cell-level assessment (overall cell suitability) and beam-level assessment (individual beam quality). A cell is considered suitable for handover only when both levels are satisfied, and multiple beams within the target cell can be independently evaluated. This segmentation ensures that handover decisions are based on comprehensive beam information rather than aggregate cell measurements alone.
Solution Approach 2:
The patent evaluates the quality of individual beams within a cell separately, allowing different beams to have different measurement values and handover applicability. The UE can identify specific beams that meet the handover criteria and prioritize handover to cells with multiple high-quality beams, rather than treating all beams in a cell uniformly. This local quality assessment prevents handover to cells with only single unstable beams.
3Reliability
If conditional handover configuration includes multiple target cells, then handover robustness improves, but the configuration size and processing load increase
Solution Approach 1:
The network configures a conditional handover set containing multiple potential target cells, but the UE is required to evaluate and execute handover to the first cell that satisfies the predefined beam measurement criteria. The UE does not need to process all configurations simultaneously or make complex comparisons between multiple targets, reducing the effective processing load while maintaining the robustness benefits of having multiple options available.
Data Source
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AI summary
Methods performed by wireless devices and network nodes for conditional mobility procedures are disclosed. A method performed by a wireless device comprises receiving a conditional mobility configuration from a source network node containing at least a triggering condition for conditional mobility based on beam measurement information; and performing beam measurements for at least one beam of at least one cell, to obtain beam measurement information for the at least one beam. A method performed by a network node comprises defining a conditional mobility configuration containing at least a triggering condition for conditional mobility based on beam measurement information; and initiating the transmission of the conditional mobility configuration to at least one user equipment. Also disclosed are base stations and wireless devices configured to perform the methods.