Redundant PDU Session Mapping During 5GS to EPS Inter-System Change
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Solution Overview
Problem
The existing technologies do not define how to support redundant PDU sessions during intersystem changes between 5G and EPS networks, which is crucial for ensuring reliability and low latency in Ultra Reliable and Low Latency Communication (URLLC) applications.
Innovation Solution
A method is proposed where a UE maintains a redundant PDU session associated with a PDU session pair ID and/or a redundancy sequence number (RSN), and during intersystem changes from N1 mode to S1 mode and back, these identifiers are mapped to and from the corresponding PDN connection, ensuring seamless transfer and support of redundant PDU sessions across 5GS and EPS networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant PDU sessions are transferred to EPS upon intersystem change, then the PDU session can be maintained in 4G network, but it is unclear whether the redundant PDU session can be supported when transferred back to 5GS
Solution Approach 1:
The patent uses the PDU session pair ID and redundancy sequence number as intermediary elements that bridge the 5GS and EPS networks. These identifiers are preserved and mapped during intersystem changes, allowing the redundant session relationship to be maintained across different network types. The intermediary identifiers enable the network to recognize and restore the redundant session context when moving between 5G and 4G networks.
Solution Approach 2:
The patent implements a universal mapping mechanism that works across both 5GS and EPS networks. The PDU session pair ID and RSN serve as universal identifiers that function in both network types, allowing the same redundancy mechanism to operate regardless of whether the UE is connected to 5G or 4G network. This multi-functionality ensures consistent redundant session support across heterogeneous networks.
2Ease of operation
If PDU session identifiers are mapped during intersystem change, then seamless transfer is achieved, but the complexity of session management increases
Solution Approach 1:
The patent applies preliminary action by establishing the PDU session pair ID and RSN associations before the intersystem change occurs. The UE prepares the redundancy identifiers in advance during the PDU session establishment in 5GS, so that when the intersystem change to EPS occurs, the mapping can be performed directly without complex real-time negotiations. This pre-preparation simplifies the actual transfer process.
Data Source
AI summary
A method for supporting redundant PDU session under intersystem change between 5GS and EPS is proposed. A UE maintains a PDU session that is a redundant PDU session, associated with a PDU session pair ID and/or a redundancy sequence number (RSN). When inter-system change from N1 mode to S1 mode occurs, the PDU session is transferred/mapped to a PDN connection. The UE shall associate the PDU session pair ID and/or the RSN with the PDN connection corresponding to the PDU session (e.g., associate with the default EPS bearer context of the PDN connection). When inter-system change from S1 mode to N1 mode occurs, the PDN connection is transferred/mapped back to the PDU session. The UE shall associate the PDU session pair ID and/or the RSN with the PDU session corresponding to the PDN connection.