SMF Handling MA PDU Session Interworking 5G to 2G/3G
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Solution Overview
Problem
The existing wireless communication systems face challenges in seamlessly handling interworking from 5G to 2G/3G networks, particularly in managing Multi-Access (MA) PDU sessions with 3GPP EPS PDN legs, where essential parameters for activating 2G or 3G PDP contexts are often missing, leading to issues with intersystem changes and data traffic routing.
Innovation Solution
A method is proposed for handling interworking from 5G to 2/3G networks by initiating network-requested PDU session release or modification procedures over non-3GPP access, allowing the MA PDU session to transfer traffic to non-3GPP access when essential parameters are absent for activating 2G or 3G PDP contexts, ensuring smooth intersystem changes and data routing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs intersystem change from 5GS to 2G/3G using existing EPS bearer parameters, then the PDP context activation should work, but the essential parameters (SAPI, radio priority, transaction identifier, R99 QoS) are often missing from the active EPS bearer context
Solution Approach 1:
The network performs preliminary actions by storing essential parameters (SAPI, radio priority, transaction identifier, R99 QoS) in the SMF before the intersystem change occurs. When the UE requests PDP context activation, the SMF retrieves these pre-stored parameters rather than relying on the UE to have them in the EPS bearer context, thus preventing the parameter loss issue before it occurs.
Solution Approach 2:
The SMF acts as an intermediary between the UE and the PDP context activation process. Instead of directly using parameters from the EPS bearer context, the SMF intercepts the activation request, retrieves the necessary essential parameters from its stored information, and provides them to complete the PDP context activation, thus mediating the parameter transfer gap.
2Adaptability or versatility
If the MA PDU session maintains both 3GPP EPS PDN leg and non-3GPP leg, then the network coverage is improved, but the complexity of managing intersystem changes and parameter mapping increases
Solution Approach 1:
The invention extracts the essential parameters (SAPI, radio priority, transaction identifier, R99 QoS) from the complex MA PDU session management context and stores them separately in the SMF. This extraction simplifies the parameter management by separating the critical interworking parameters from the overall session management, reducing the complexity of managing intersystem changes while maintaining multi-access capability.
Solution Approach 2:
The SMF is designed with universal functionality to handle parameter retrieval and PDP context activation for both 3GPP and non-3GPP accesses. By implementing a unified mechanism that works for both access types, the system reduces the complexity of managing different parameter sets for different access networks, allowing the same SMF logic to serve multiple access technologies.
3Ease of operation
If the UE activates PDP context without essential parameters, then the intersystem change can proceed, but the data traffic routing fails and connectivity is interrupted
Solution Approach 1:
The system applies preliminary anti-action by preventing the PDP context activation from failing due to missing parameters. The SMF proactively retrieves the essential parameters before the activation attempt, thus counteracting the potential failure mode in advance. This ensures that the intersystem change proceeds smoothly without interrupting data traffic routing.
Data Source
AI summary
A method of handling interworking from 5G system (5GS) to 2/3G for an PDU session with a 3GPP EPS PDN leg is proposed. Upon intersystem change from S1 mode to A/Gb mode or Iu mode, for a PDN connection which was established as a user plane resource of an MA PDU session: if the SM activates a PDP context using parameters from the default EPS bearer context of the PDN connection, then the SMF can initiate a network-requested PDU session release procedure over non-3GPP access or perform a local release of the MA PDU session; the UE can perform a local release of the MA PDU session. Otherwise, the SMF can initiate a network-requested PDU session modification procedure over 5G non-3GPP access to move traffic of the MA PDU session to 5G non-3GPP access, or initiate a network-requested PDU session release procedure over non-3GPP access.