UE Session Release Logic for PDU Establishment Limits

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Solution Overview

Problem

In 5G mobile communications, the establishment of PDU sessions is limited by the upper limits of PDU sessions, QoS flows, and DRBs, leading to low PDU session establishment success rates and increased service data transmission delays due to rejected session establishment requests.

Innovation Solution

User equipment (UE) determines when preset conditions are met, such as reaching thresholds for PDU sessions, DRBs, or QoS flows, and sends session release or modification requests to the network, allowing for the release of specific sessions or flows to create space for new ones, thereby improving success rates and reducing delays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the UE establishes multiple PDU sessions, QoS flows, and DRBs to meet diverse service requirements, then the service capability and adaptability are improved, but the device complexity and resource consumption increase, leading to rejection when reaching upper limits

Engineering Contradiction:
Improveservice capabilityVSAvoidsession management complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements automatic session release when upper limits are reached. The UE monitors the quantities of PDU sessions, QoS flows, and DRBs, and when any reaches its upper limit, the UE automatically releases sessions according to predetermined criteria (such as releasing sessions with lowest priority or longest idle time). This allows the system to recover resources and maintain operational capability without manual intervention, resolving the contradiction between maintaining high adaptability and managing device complexity.

Inventive Principle:
Principle #34Discarding and recovering

2Productivity

If the UE establishes sessions up to the upper limit to maximize resource utilization, then the productivity is improved, but the reliability decreases when new sessions cannot be established due to reaching limits

Engineering Contradiction:
Improveresource utilizationVSAvoidsession establishment success rate
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent implements proactive session release mechanisms. Before the system reaches its absolute upper limit and before service rejection occurs, the UE proactively releases sessions based on monitored quantities and predetermined release criteria. This preliminary action ensures that resources are continuously available for new session establishment, maintaining both high resource utilization and high session establishment success rate, thus resolving the contradiction between productivity and reliability.

Inventive Principle:
Principle #10Preliminary action

3Stability of the object's composition

If the UE maintains existing sessions to preserve service continuity, then the stability is improved, but the loss of time increases when session establishment requests are rejected

Engineering Contradiction:
Improveservice continuityVSAvoidsession establishment delay
Core Design Contradiction:
Stability of the object's compositionVSLoss of time

Solution Approach 1:

The patent implements a feedback-based session management system. The UE continuously monitors the quantities of PDU sessions, QoS flows, and DRBs, and based on this feedback information, dynamically decides whether to release sessions. When the monitor indicates that upper limits are approaching or reached, the system automatically triggers session release actions. This closed-loop feedback mechanism ensures service continuity is maintained while preventing time loss from rejection delays, resolving the contradiction between stability and time efficiency.

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP3993349B1Session management method and apparatus
Publication Date: 2026.03.25 HUAWEI TECH CO LTD
  • EP3993349B1 patent drawingFigure 1~2
  • EP3993349B1 patent drawingFigure 3~4
  • EP3993349B1 patent drawingFigure 5

AI summary

A session management method and apparatus are provided, relate to the field of communications technologies, and can resolve a problem of a low PDU session establishment success rate. The method includes: When UE determines that a preset condition is met, the UE sends a session release request message or a session modification request message to a network device. The session release request message is used to request to release a first PDU session, the session modification request message is used to request to release a first quality of service QoS flow, and the first PDU session is one of existing PDU sessions in the UE. The preset condition includes at least one of the following: A quantity of existing PDU sessions in the UE reaches a first threshold; a quantity of data radio bearers DRBs associated with the existing PDU session in the UE reaches a second threshold; and a quantity of quality of service QoS flows associated with the existing PDU session in the UE reaches a third threshold. This method is used in a session management process.