NR Measurement Report Pruning for VoNR EPS Fallback
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Solution Overview
Problem
IMS voice session failures occur due to inappropriate inter-RAT redirection between 4G and 5G networks during EPS fallback procedures, leading to reduced user experience and increased signaling overhead, especially when NR cells do not support VoNR or the UE lacks VoNR capabilities.
Innovation Solution
The UE generates and maintains a whitelist of NR cells that support VoNR, allowing it to prune non-supporting cells from measurement reports before sending them to the 4G network, thereby preventing redirection to cells that do not support VoNR and avoiding IMS voice session failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE includes all measured NR cells in measurement reports during EPS fallback, then the network can make informed handover decisions, but IMS voice session failures occur when redirection is performed to NR cells that do not support VoNR
Solution Approach 1:
The UE performs preliminary filtering of measurement reports by removing NR cells that do not support VoNR before sending the report to the network. This preliminary action prevents the network from making erroneous handover decisions to incompatible cells, thereby ensuring IMS voice session success while maintaining measurement report utility.
2Adaptability or versatility
If the network performs inter-RAT redirection between 4G and 5G during EPS fallback, then network flexibility and load balancing are improved, but unnecessary redirections occur to NR cells without VoNR support causing voice session failures
Solution Approach 1:
The UE provides feedback to the network about which NR cells support VoNR by filtering measurement reports to exclude incompatible cells. This feedback mechanism enables the network to maintain redirection flexibility while avoiding voice session failures, as the network receives accurate information about cell compatibility without requiring explicit capability signaling.
3Loss of information
If the UE sends complete measurement reports including all NR cells, then network signaling contains comprehensive information, but unnecessary signaling overhead increases when redirecting to non-VoNR supporting cells
Solution Approach 1:
The UE extracts and removes information about NR cells that do not support VoNR from measurement reports before transmission to the network. This extraction process reduces signaling overhead by eliminating unnecessary cell information that would lead to failed redirections, while preserving complete information about compatible cells for informed handover decisions.
Data Source
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AI summary
An apparatus for wireless communication of a UE is disclosed. The apparatus may initiate, at a new radio (NR) serving cell, a voice session with an IMS. The apparatus may determine whether the first NR cell supports voice over NR (VoNR) when the voice session is initiated. The apparatus may perform an EPS fallback procedure to establish the 5 voice session with the IMS when it is determined that VoNR is not supported by the first NR cell. The apparatus may update a whitelist of NR cells that support VoNR to include the first NR cell when it is determined that the first NR cell supports VoNR.