MA PDU Session Handling for Non-3GPP Leg Parameter Mismatch

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Solution Overview

Problem

Challenges arise when adding a non-3GPP leg to an MA PDU session already established with a 3GPP PDN leg due to potential incompatibility of parameters, necessitating a method to handle such scenarios effectively.

Innovation Solution

The UE performs a local release of the MA PDU session if critical parameters in the PDU SESSION ESTABLISHMENT ACCEPT message differ from the stored values, and initiates registration and tracking area update procedures to ensure compatibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a non-3GPP leg is added to an MA PDU session already established with a 3GPP PDN leg, then multi-access connectivity is improved, but parameter incompatibility may cause session establishment failure

Engineering Contradiction:

Improvemulti-access connectivityVSAvoidsession establishment success

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The UE performs parameter comparison before finalizing the MA PDU session establishment. By checking whether parameters in the PDU SESSION ESTABLISHMENT ACCEPT message match stored parameters from the 3GPP PDN leg in advance, the system can detect incompatibilities before they cause session failure, allowing for preventive actions to be taken.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements a feedback mechanism where the UE monitors parameter consistency between 3GPP and non-3GPP legs. When parameter mismatches are detected, the system provides feedback by triggering session release and re-establishment procedures, ensuring that only compatible parameter configurations are accepted, thereby maintaining session establishment reliability.

Inventive Principle:

Principle #23Feedback

2Reliability

If parameter comparison and validation procedures are implemented, then session compatibility is improved, but processing complexity increases

Engineering Contradiction:

Improveparameter compatibilityVSAvoidUE processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The UE performs parameter comparison only for critical parameters that are essential for session compatibility, rather than checking all possible parameters. This partial action approach focuses validation efforts on the most important parameters (such as PDU session type, SSC mode, S-NSSAI, DNN), achieving sufficient reliability without excessive processing complexity.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If the UE releases and re-establishes the MA PDU session upon parameter mismatch, then parameter consistency is improved, but service interruption time increases

Engineering Contradiction:

Improveparameter consistencyVSAvoidservice interruption time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

When parameter incompatibility is detected, the system accepts that the current MA PDU session configuration is invalid and discards it. Rather than attempting complex parameter adjustments or negotiations, the system performs a clean release and re-establishment of the session with corrected parameters. This approach treats the incompatible session configuration as a disposable element that should be quickly replaced, minimizing the time spent on futile adjustment attempts.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS12550205B2Method for adding non-3GPP leg to an MA PDU session with 3GPP PDN leg

Publication Date: 2026.02.10 MEDIATEK INC

AI summary

A method of handling multi-access (MA) Protocol data unit (PDU) session establishment procedure for an MA PDU session already established with a 3GPP PDN leg is proposed. In one novel aspect, for a 5GS MA PDU session already established on 3GPP access via an EPS PDN connection, upon receipt of a PDU SESSION ESTABLISHMENT ACCEPT message over non-3GPP access, the UE performs a local release of the MA PDU session if any value of at least one of the critical MA PDU session parameters, including the PDU session type, selected SSC mode, 5GSM cause, PDU address, S-NSSAI, and DNN IEs in the PDU SESSION ESTABLISHMENT ACCEPT message is different-from/un-sync/not-matched/not-compatible-with the corresponding stored value of the MA PDU session mapped from the (default EPS bearer of the) PDN connection. The UE also performs a REGISTRATION procedure over non-3GPP access and a TAU procedure over 3GPP access.