Session Continuity Handling for UE PDN Reconnection Overhead
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Solution Overview
Problem
In wireless communication systems, unnecessary signaling overhead occurs during inter-system changes from A/Gb or Iu mode to S1 mode due to the re-establishment of multiple PDN connections that do not support interworking with 5GS, leading to inefficient PDN connectivity procedures.
Innovation Solution
A method where the user equipment (UE) locally deactivates EPS bearer contexts for PDN connections that do not support interworking with 5GS, includes the EPS bearer context status in a tracking area update (TAU) request, and then initiates UE-requested PDN connectivity procedures to reduce signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE initiates individual PDN disconnection and reconnection procedures for each PDN connection during inter-system change, then session continuity is maintained, but signaling overhead increases significantly
Solution Approach 1:
The patent merges multiple individual PDN disconnection and reconnection procedures into a single batch operation. Instead of handling each PDN connection separately during inter-system change, the UE groups multiple PDN connections and processes them together through one unified procedure, significantly reducing the number of signaling messages exchanged between UE and network
Solution Approach 2:
The patent applies preliminary action by having the UE store and maintain PDN connection context information before the inter-system change occurs. This pre-prepared context data allows the UE to quickly resume PDN connections after mode switching without needing to re-establish each connection from scratch, reducing post-change signaling overhead
2Reliability
If the UE re-establishes multiple PDN connections individually during inter-system change, then connectivity is ensured, but the transition process becomes time-consuming
Solution Approach 1:
The patent combines multiple sequential PDN reconnection operations into a single batch reconnection procedure. By processing multiple PDN connections simultaneously rather than sequentially, the overall transition time from one system mode to another is significantly reduced while maintaining connectivity for all PDN connections
Solution Approach 2:
The patent uses preliminary action by maintaining PDN connection context information in advance. This pre-stored context includes necessary parameters and state data that enable rapid resumption of PDN connections after inter-system change, eliminating the need for time-consuming re-negotiation of each connection parameter
3Reliability
If the UE performs complete PDN disconnection and reconnection procedures, then session continuity is achieved, but system complexity increases due to multiple procedure steps
Solution Approach 1:
The patent simplifies the procedural complexity by merging the disconnection and reconnection phases into a single integrated batch procedure. Instead of managing separate procedure flows for each PDN connection, the system uses one unified procedure that handles multiple connections collectively, reducing the number of procedural states and decision points
Solution Approach 2:
The patent creates a universal batch procedure that can handle multiple PDN connections with different characteristics through a single standardized process. This multi-functional approach eliminates the need for separate specialized procedures for different connection types, simplifying the overall system architecture
Data Source
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AI summary
A method of enhancing session continuity for system interworking is proposed. Upon a UE performs inter-system change from A/Gb mode or Iu mode to S1 mode, the UE identifies that some PDN connection(s) are not associated with a PDU session ID, PSI, (602). In one novel aspect, the UE deactivates all EPS bearer contexts for such PDN connection(s) locally (603), includes the EPS bearer context status IE in a TRACKING AREA UPDATE REQUEST message of a tracking area updating, TAU, procedure (604) upon inter-system change from A/Gb mode or Iu mode to S1 mode, and then initiates UE requested PDN connectivity procedure(s) for such PDN connection(s) (605). Furthermore, if no EPS bearer exists after local deactivation and EMM-REGISTERED without PDN connection is not supported by the UE, then the UE initiates a re-attach procedure followed by the UE requested PDN connectivity procedure(s) for such PDN connection(s).