Inter-RAT Handover Threshold Coordination
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Solution Overview
Problem
Current solutions for improving mobility robustness between different radio access technologies (RATs) do not effectively coordinate mobility parameter adjustments across neighboring RATs, leading to suboptimal or incorrect handover parameter settings, resulting in issues like too late or too early handovers and unnecessary handovers.
Innovation Solution
A method and system for communicating updated handover threshold values between radio network nodes of different RATs, including an indication of the measurement type associated with the threshold, to ensure accurate and coordinated adjustments across neighboring cells, preventing inter-RAT ping-pong and ensuring optimal handover parameter settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover threshold values are adjusted to trigger handovers earlier, then handover timing is improved and too late handovers are avoided, but unnecessary handovers increase
Solution Approach 1:
The patent implements a feedback mechanism where handover failure information is collected from the target RAT network node and fed back to the source RAT network node. The source node uses this feedback to adjust handover threshold values dynamically, increasing thresholds when failures occur due to too early handovers and decreasing thresholds when failures occur due to too late handovers. This closed-loop feedback system enables adaptive optimization of handover timing without requiring manual intervention.
Solution Approach 2:
The patent dynamically changes handover threshold parameters based on observed handover failure patterns. When handover failures are detected, the system modifies the threshold values (ho_thresh parameters) to adjust the triggering conditions. This parameter adaptation allows the system to optimize handover timing by learning from actual network conditions and failure scenarios, balancing between avoiding too late handovers and preventing unnecessary handovers.
2Productivity
If handover threshold values are adjusted to trigger handovers later, then unnecessary handovers are reduced, but too late handovers increase
Solution Approach 1:
The system uses feedback from handover failure reports to determine whether to increase or decrease threshold values. When handover failures are caused by too late handovers (use case 1), the feedback triggers an increase in threshold values to enable earlier handover triggering. When failures are caused by unnecessary handovers (use case 2), the feedback triggers a decrease in threshold values to delay handover triggering. This feedback-driven parameter adjustment resolves the contradiction by adapting thresholds to actual network conditions.
Solution Approach 2:
The patent transforms static handover threshold configurations into dynamic, adaptive parameters that automatically adjust based on network conditions and failure patterns. The thresholds are no longer fixed but change over time in response to observed handover performance, enabling the system to optimize the trade-off between handover timing reliability and efficiency dynamically rather than requiring manual reconfiguration.
3Productivity
If mobility parameters are adjusted in one RAT without coordinating with neighboring RATs, then local optimization is achieved, but inter-RAT ping-pong and suboptimal handovers occur
Solution Approach 1:
The patent introduces an intermediary communication mechanism between source and target RAT network nodes. When a handover failure occurs, the target RAT node (e.g., UTRAN) sends failure information back to the source RAT node (e.g., LTE eNodeB) through standardized interfaces. This intermediary feedback channel enables coordinated optimization across RAT boundaries, allowing each RAT to adjust its parameters based on actual handover performance observed in the target RAT, thereby preventing inter-RAT ping-pong effects.
Solution Approach 2:
The patent segments the handover optimization problem into independent, manageable components: failure detection at the target RAT, feedback transmission through the interface, and parameter adjustment at the source RAT. This segmentation allows each RAT to independently optimize its parameters based on specific failure patterns observed, rather than requiring complex centralized coordination, while still achieving inter-RAT mobility robustness through the feedback loop.
Data Source
AI summary
The present invention relates to a method in a first radio network node of a first radio access technology, for communicating mobility parameter changes to a second radio network node of a second radio access technology. The method comprises determining (610) an updated value of a first threshold controlling when a handover to the second radio access technology is triggered, and sending (620) information related to the updated value of the first threshold to the second radio network node, wherein the information comprises an indication of a type of a measurement associated with the first threshold.