PDN Connection Interworking with 5GS Parameter Storage
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Solution Overview
Problem
The interworking of Packet Data Network (PDN) connections between 4G LTE systems and 5G systems is not effectively supported during inter-system changes, particularly when transitioning between S1 mode and 2G/3G modes, due to undefined maintenance of 5GSM parameters such as PDU session ID, S-NSSAI, and QoS flow descriptions.
Innovation Solution
Both the user equipment (UE) and the network store and maintain mapped 5GSM parameters during inter-system changes from S1 (4G) mode to A/Gb (2G) or Iu (3G) mode, enabling the PDN connection to support interworking to 5GS by using the bearer resource modification procedure to allocate and indicate the PDU session ID or modify the 5GSM parameters in 2G/3G systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE performs inter-system change from S1 mode to A/Gb mode or Iu mode, then the UE can access 2G/3G networks, but the mapped 5GSM parameters (PSI, S-NSSAI, session AMBR, QoS flow descriptions) are deleted and interworking to 5GS cannot be supported
Solution Approach 1:
The patent applies preliminary action by storing the mapped 5GSM parameters (PSI, S-NSSAI, session AMBR, QoS flow descriptions) in the UE before the inter-system change to 2G/3G networks. This ensures that when the UE returns to S1 mode, the parameters are already preserved and can be used to re-establish interworking to 5GS without loss of connectivity information
Solution Approach 2:
The patent uses the EPS bearer context as an intermediary structure that carries and preserves the mapped 5GSM parameters during inter-system changes. This intermediary mechanism allows the parameters to be maintained across different network modes (S1, A/Gb, Iu) and enables seamless transition back to 5GS interworking capability
2Device complexity
If the mapped 5GSM parameters are deleted during inter-system change, then the network can simplify parameter management, but the PDN connection cannot support interworking to 5GS after returning to S1 mode
Solution Approach 1:
The patent makes the EPS bearer context universal by designing it to serve multiple functions: it acts as both the standard bearer management structure in EPS and as a container for mapped 5GSM parameters. This multi-functionality allows the same data structure to support both 4G EPS operations and 5GS interworking without requiring separate parameter storage mechanisms
Solution Approach 2:
The patent creates a copy of the 5GSM parameters (PSI, S-NSSAI, session AMBR, QoS flow descriptions) and stores them within the EPS bearer context. This copying mechanism preserves the essential 5G connectivity information while maintaining compatibility with 4G EPS parameter management, enabling interworking without increasing overall system complexity
Data Source
AI summary
A method of handling a Packet Data Network (PDN) connection to support interworking to 5G system (5GS) is proposed. In a first novel aspect, both UE and the network stores mapped 5GSM parameters of a corresponding Protocol Data Unit (PDU) session when inter-system change from S1 (4G, EPS) mode to A/Gb (2G) mode or Iu (3G, UMTS) mode. In a second novel aspect, the PDN connection is enable to support interworking to 5GS, and the UE is allowed to allocate and indicate the PDU session ID by using the bearer resource modification procedure in EPS, or the mapped 5GSM parameters can be provided and modified in 2G/3G system.