UE Handover Control to Prevent VoLTE Call Drops on 5G SA
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Solution Overview
Problem
5G user equipment (UE) experiences call drops and mobile originated/terminated call setup failures when transitioning from LTE to 5G SA networks due to unsupported voice over new radio (VoNR), particularly in urban areas with overlapping LTE and 5G systems, as existing technologies lack predefined handling for such scenarios.
Innovation Solution
The UE delays sending measurement reports for specific events (B1 and B2) until an ongoing VoLTE call is completed, and only sends these reports or responds to handover commands if both the UE and the 5G network support VoNR, thereby preventing unnecessary handovers and call drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the UE sends measurement reports immediately when detecting 5G network, then handover to 5G network is triggered faster, but call drop occurs when VoNR is not supported
Solution Approach 1:
The UE performs preliminary checking of VoNR support capability before sending measurement reports and triggering handover. The network entity configures the UE with VoNR support information in advance, and the UE uses this pre-configured information to decide whether to send measurement reports, thereby preventing call drop before it occurs
Solution Approach 2:
The UE dynamically adjusts its measurement report sending behavior based on real-time conditions. When VoNR is supported, the UE sends measurement reports immediately for fast handover. When VoNR is not supported, the UE delays or suppresses measurement reports to prevent handover that would cause call drop
2Reliability
If the UE avoids handover to 5G network when VoNR is not supported, then call drop is prevented, but network resource utilization decreases
Solution Approach 1:
The solution applies different handover strategies to different local conditions. In areas where VoNR is supported, normal handover proceeds to utilize 5G network resources. In areas where VoNR is not supported, handover is prevented. This localized approach ensures call continuity where needed while maintaining network resource utilization where possible
3Reliability
If the UE checks VoNR support capability before handover, then call drop is prevented, but signaling overhead increases
Solution Approach 1:
The network entity performs the VoNR support capability configuration in advance during initial network registration or connection establishment. This preliminary action stores the VoNR support information in the UE, eliminating the need for repeated capability checking signaling during handover decisions, thus reducing ongoing signaling overhead
Data Source
AI summary
A method of handling an ongoing call performed by a UE in a wireless network is provided. The method includes initiating a voice over long term evolution call in a 4G network, detecting that a 5G network entity has configured an inter radio access technology measurement indicating a change from the 4G network to a 5G network based on identification of the 5G network, determining whether at least one of the UE or the 5G network does not support a voice over new radio (VoNR) call with a 5G cell, in response to determining that the at least one of the UE or the 5G network does not support the VoNR call, delaying sending a measurement report until the VOLTE call is completed, and in response to determining that both the UE and the 5G network support the VoNR call, sending the measurement report immediately for the 5G cell.