Single Registration Mode for 5GC-EPC Interworking
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Solution Overview
Problem
The integration of 4G and 5G networks poses challenges due to registration issues and compatibility problems, particularly in intersystem changes without the N26 interface, leading to potential loss of session management contexts and IP address continuity.
Innovation Solution
The user equipment (UE) employs a single registration mode to handle default EPS bearer contexts and PDU session contexts as if the N26 interface were supported, mapping active PDU session contexts to default EPS bearer contexts and setting their states to inactive during intersystem changes, allowing for seamless transitions between 4G and 5G systems without relying on the N26 interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the N26 interface is not supported during intersystem changes between 5GC and EPC, then device complexity is reduced, but registration reliability deteriorates due to loss of session management contexts and IP address continuity
Solution Approach 1:
The patent introduces a mapping mechanism that acts as an intermediary between PDU session contexts in 5GC and EPS bearer contexts in EPC. This mapping relationship preserves session continuity information across the intersystem change, enabling the network to maintain registration reliability without requiring the N26 interface.
Solution Approach 2:
The patent creates a copy of session management context information by establishing a mapping relationship between PDU session contexts and EPS bearer contexts. This copied information allows the target network to reconstruct session state without direct interface communication, resolving the contradiction between interface reduction and reliability maintenance.
2Reliability
If dual registration mode is used to maintain session continuity during intersystem changes, then registration reliability is improved, but device complexity increases due to additional hardware and software links required
Solution Approach 1:
The patent extracts the essential function of session continuity maintenance from the N26 interface and implements it through a lightweight mapping mechanism. By separating the session context mapping function from the physical interface, the solution achieves reliability without requiring additional hardware and software links.
Solution Approach 2:
The patent changes the state parameters of session contexts by establishing mapping relationships that track PDU session contexts to EPS bearer contexts. This parameter transformation enables session continuity to be maintained through information mapping rather than through complex dual registration hardware and software infrastructure.
Data Source
AI summary
Systems and methods of enabling intersystem changes between 4G and 5G are described. The UE in single registration mode handles default EPS bearer contexts and PDU session contexts as if the N26 interface were supported before making the determination whether N26 interface is supported or not during an initial EPS Attach procedure. After determining that the N26 interface is unsupported, the UE maps active PDU session contexts to default EPS bearer contexts and modifies the PDU session context state from active to inactive before completing the intersystem change. The UE either acts as if the N26 interface were supported and loses all the PDN connections or PDU sessions during the intersystem change, or enters a modified single registration mode in which the states of the EPC and 5G system are partially isolated from each other during the intersystem change.