Enhanced MBB Handover Failure Control With Dynamic RLF Declaration

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Solution Overview

Problem

Existing wireless communication systems experience handover failures during enhanced make-before-break handovers, leading to threshold failure rates and ping-pong signaling, which consume processing and network resources and reduce communication reliability.

Innovation Solution

A UE dynamically controls radio link failure declaration and notifies the source BS of handover failure, allowing the source BS to maintain communication while transitioning to a target BS, thereby reducing handover failure impacts and conserving resources.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If enhanced MBB handover with two protocol stacks is used, then handover reliability and latency are improved, but handover failure rate reaches a threshold causing ping-pong signaling

Engineering Contradiction:
Improvehandover reliabilityVSAvoidhandover failure rate
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent implements dynamic control of radio link failure declaration by the UE during handover. Instead of static automatic declaration, the system dynamically adjusts RLF declaration behavior based on handover phase and source connection status. The UE monitors handover completion and selectively declares RLF only when appropriate, preventing premature failure declarations that trigger ping-pong signaling while maintaining reliability benefits of enhanced MBB handover.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent establishes feedback mechanisms where the UE notifies the source BS of handover failure through controlled RLF declaration and signaling. This feedback loop allows the source BS to awareness of handover status and maintain source connection accordingly. The feedback prevents information asymmetry that leads to unnecessary ping-pong signaling while ensuring proper handover failure handling.

Inventive Principle:
Principle #23Feedback

2Reliability

If automatic radio link failure declaration is implemented, then connection reliability is maintained, but ping-pong signaling increases consuming processing resources

Engineering Contradiction:
Improveconnection reliabilityVSAvoidprocessing resources
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The system transitions from static automatic RLF declaration to dynamic conditional declaration. The UE evaluates multiple factors including handover completion status, source connection quality, and network instructions before declaring RLF. This dynamic approach maintains connection reliability by declaring RLF only when truly necessary while reducing unnecessary processing from ping-pong signaling caused by premature declarations.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of RLF declaration timing and conditions. Instead of fixed automatic declaration upon handover initiation, the system modifies declaration parameters based on real-time handover progress and connection status. The UE adjusts RLF declaration behavior as a controllable parameter, declaring failure only when handover exceeds timeout thresholds or source connection degrades, thereby reducing false positives and processing overhead.

Inventive Principle:
Principle #35Parameter changes

3Productivity

If source connection is released upon handover failure, then resources are freed, but communication loss occurs for the UE

Engineering Contradiction:
Improveresource allocationVSAvoidcommunication continuity
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent implements preliminary maintenance of source connection during handover failure. Instead of immediately releasing the source connection upon handover failure, the system keeps the source connection active as a backup communication path. The UE and source BS maintain the connection in a suspended state, allowing quick resumption of communications if target connection fails, thereby preventing communication loss while resources are still allocated.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system provides a cushioning mechanism by maintaining the source connection as a safety net during handover transitions. This beforehand cushioning ensures that if the target connection fails or experiences issues, the UE still has an active communication path through the source BS. The source connection acts as a protective buffer against communication loss, releasing resources only after confirming target connection success or after a extended failure period.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentEP3821642B1Enhanced make-before-break (MBB) handover failure
Publication Date: 2025.09.03 QUALCOMM INC
  • EP3821642B1 patent drawingFigure 1
  • EP3821642B1 patent drawingFigure 2
  • EP3821642B1 patent drawingFigure 3

AI summary

The present disclosure relates to a make-before-break handover in wireless communication. In some aspects, a user equipment (UE) may detect that a handover failure timer has expired prior to completing a handover of the UE from a source base station (BS) to a target BS. In some aspects, the UE may selectively declare, based at least in part on detecting that the timer has expired, a radio link failure.