IMS Voice Fallback Indication for Roaming Reliability
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Solution Overview
Problem
In wireless networks, particularly in 5G environments, voice calls may be interrupted when a user equipment (UE) roams to a network that provides limited 5G roaming services, as the UE may not be able to determine whether the visited network supports Voice over New Radio (VoNR) or Evolved Packet System (EPS) fallback.
Innovation Solution
The proposed solution involves setting an IMS voice over PS session supported indication to enable the UE to fallback to its Home Public Land Mobile Network (HPLMN) if compatibility issues exist with the Equivalent Public Land Mobile Network (EPLMN) providing limited 5G roaming services. Additionally, support for inter-operator EPS fallback is described to redirect the UE to its HPLMN for voice services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE attempts to use 5G roaming services on an EPLMN, then 5G service coverage is extended, but voice service reliability deteriorates due to compatibility issues with limited 5G roaming support
Solution Approach 1:
The network performs preliminary capability matching between the UE and EPLMN before voice service establishment. The AMF determines whether the EPLMN supports the UE's preferred voice service mode (VoNR or EPS fallback) in advance, and proactively provides fallback indication information to the UE through RRC release messages or system information blocks, preventing voice service interruption before it occurs.
Solution Approach 2:
The patent introduces an intermediary indication mechanism (fallback indication information) that mediates between the UE's voice service requirements and the EPLMN's capabilities. This indication acts as a bridge, guiding the UE to select appropriate voice service modes or fallback options, thereby resolving the compatibility conflict between 5G roaming adaptability and voice service reliability.
2Reliability
If the UE falls back to HPLMN for voice services, then voice service reliability is maintained, but network switching complexity increases
Solution Approach 1:
The UE autonomously determines the appropriate voice service mode based on the fallback indication information received from the network. The UE self-services by selecting either VoNR, EPS fallback, or HPLMN redirection without requiring complex network-controlled switching procedures, thereby maintaining voice service reliability while minimizing network switching complexity.
Solution Approach 2:
The network provides fallback indication information in advance through RRC release messages or system information blocks, enabling the UE to make informed decisions about voice service mode selection before actual service establishment. This preliminary guidance simplifies the switching process by providing clear directives rather than requiring complex real-time negotiation.
3Adaptability or versatility
If the network provides detailed voice service capability information, then service compatibility is improved, but signaling overhead increases
Solution Approach 1:
The patent extracts only the essential fallback indication information from the complete voice service capability set and transmits it to the UE. Rather than providing comprehensive capability details, the network extracts and communicates only the critical indication needed for UE decision-making (whether EPLMN supports UE's preferred voice mode), thereby improving service compatibility while minimizing signaling overhead.
Solution Approach 2:
The fallback indication information is provided locally at the EPLMN level through RRC release messages or system information blocks, rather than requiring global capability exchange between HPLMN and EPLMN. This localized information provision achieves sufficient service compatibility for roaming scenarios while avoiding the signaling overhead of comprehensive capability negotiation.
Data Source
AI summary
The present application relates to devices and components including apparatus, systems, and methods for supporting voice services during roaming.