Voice Over Wi-Fi Handover Logic for Cellular Fallback Control
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Solution Overview
Problem
Existing wireless communication systems face inefficiencies in managing voice over Wi-Fi to voice over cellular handovers, particularly due to unwanted fallbacks and suboptimal handover decisions that disrupt voice calls.
Innovation Solution
A method and apparatus for a user equipment (UE) to determine and manage handovers by assessing signal strengths and preferences across different radio access technologies (RATs) to avoid unnecessary fallbacks and optimize handover decisions, including storing cell identifiers and adjusting priorities based on signal strengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover from Wi-Fi to NR is performed based on signal strength conditions, then voice call continuity is improved, but unwanted fallbacks to LTE occur causing call disruption
Solution Approach 1:
The UE performs preliminary actions by measuring and storing signal strength thresholds for LTE and NR networks before handover decisions are needed. The UE also stores cell identifiers of NR cells that previously triggered unwanted fallbacks. This advance preparation enables the UE to make more informed handover decisions and avoid repeating past mistakes of unwanted fallbacks.
Solution Approach 2:
The system implements feedback mechanisms where the UE monitors whether a handover to NR actually results in unwanted fallback to LTE. This feedback information is stored and used to adjust future handover decisions. The UE uses feedback about signal strength conditions and handover outcomes to refine its decision-making process and avoid repeating harmful fallbacks.
2Speed
If handover decisions are based solely on signal strength, then handover speed is improved, but handover stability deteriorates due to unwanted fallbacks
Solution Approach 1:
The patent changes the parameters used for handover decisions from solely signal strength to a combination of signal strength, cell identifiers, and handover history. The UE considers multiple parameters including the signal strength of serving and neighboring cells, the identifier of the target NR cell, and whether this cell has previously triggered unwanted fallbacks. This multi-parameter approach maintains speed while improving stability.
Solution Approach 2:
The UE performs preliminary measurement and storage of cell identifiers and signal strength thresholds before handover decisions are needed. By pre-measuring and storing this information, the UE can make faster decisions without sacrificing stability, as the necessary data is already prepared and accessible.
3Adaptability or versatility
If frequent handovers between Wi-Fi, NR, and LTE are performed, then network adaptability is improved, but voice call quality deteriorates due to repeated fallbacks
Solution Approach 1:
The system uses feedback about previous handover outcomes to guide future decisions. The UE stores information about which NR cells previously triggered unwanted fallbacks and uses this feedback to avoid handovers to those cells. This feedback mechanism enables the system to adapt to network conditions while preventing repeated harmful fallbacks that would degrade voice quality.
Solution Approach 2:
The UE performs preliminary actions by pre-measuring signal strengths and pre-storing cell identifiers of potential target cells. This advance preparation allows the UE to quickly assess whether a handover would be beneficial or likely to trigger unwanted fallbacks, enabling adaptive decisions that protect voice quality while maintaining network flexibility.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may determine, during an active call on a first radio access technology (RAT), a signal strength associated with the first RAT is within a particular range above a handover threshold. The UE may determine, based at least in part on a signal strength of a second RAT, that the active call would be moved from the second RAT to a third RAT after a handover from the first RAT to the second RAT, and, may trigger mobility from the second RAT to the third RAT based at least in part on the determination that the signal strength associated with the first RAT is within the particular range and the determination that the active call would be moved from the second RAT to the third RAT. Numerous other aspects are provided.