IMS Signaling Bearer Mapping in 5GS EPS Inter-System Change
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Solution Overview
Problem
In the transition between 5G and 4G wireless communication systems, there is a challenge in determining which EPS bearer or QoS flow is associated with IP Multimedia Subsystem (IMS) signaling due to the complexity of intersystem changes and multiple QoS flow associations.
Innovation Solution
The method involves mapping QoS flows to EPS bearers during inter-system changes, ensuring that the EPS bearer or QoS flow associated with IMS signaling is consistently identified and utilized for seamless IMS signaling across both 5GS and EPS systems, by designating the EPS bearer or QoS flow with the default QoS rule for IMS signaling in each system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple QoS flows are associated with a single EPS bearer during inter-system change, then the adaptability of the system is improved, but the difficulty of detecting and measuring which bearer or flow is for IMS signaling increases
Solution Approach 1:
The patent applies preliminary action by establishing a default QoS rule association before inter-system change occurs. The UE identifies and marks the default QoS flow in advance (before switching between 5GS and EPS), so that during inter-system change, the mapping to the correct EPS bearer for IMS signaling is automatically determined without ambiguity. This pre-establishment of the default QoS rule association resolves the identification difficulty while maintaining multiple QoS flow associations.
2Reliability
If the UE determines which QoS flow or EPS bearer is for IMS signaling after inter-system change, then the reliability of IMS signaling is improved, but the loss of time for determining the correct bearer increases
Solution Approach 1:
The patent eliminates determination time by performing the identification action in advance. The UE establishes the default QoS rule association and identifies the IMS signaling bearer before inter-system change occurs. This preliminary identification ensures that when the system switches between 5GS and EPS, the correct bearer is already known, maintaining both reliability and eliminating time loss.
Solution Approach 2:
The patent applies self-service by enabling the UE to autonomously identify and maintain the default QoS rule association with EPS bearers without requiring network assistance during inter-system change. The UE independently determines which QoS flow is for IMS signaling and maintains this association through the change, making the system self-sufficient and eliminating determination delays.
3Measurement precision
If the IM CN Subsystem Signaling Flag is included in 5GSM messages, then the precision of identifying IMS signaling is improved, but the complexity of the messaging protocol increases
Solution Approach 1:
The patent applies universality by making the default QoS rule association mechanism applicable to both 5GS and EPS systems. Instead of relying on system-specific signaling flags that increase protocol complexity, the patent uses a universal default QoS rule concept that functions across both systems, simplifying the messaging protocol while maintaining precise IMS signaling identification through the association mechanism.
Data Source
AI summary
A method of supporting IMS signaling over EPS bearer or QoS flow upon inter-system change between EPS and 5GS is proposed. When inter-system change from 5GS to EPS occurs, a PDU session is converted to a PDN connection having multiple EPS bearers. The EPS bearer mapped from the QoS flow that is used for IMS signaling in 5GS is the EPS bearer for IMS signaling in EPS. When inter-system change from EPS to 5GS occurs, a PDN connection is converted to a PDU session having multiple QoS flows. The QoS flow that is associated with the default QoS rule is the QoS flow for IMS signaling in 5GS, regardless of which EPS bearer is used for IMS signaling in EPS.