5G UE PDU Session Management with NAS Timer-Based Retry

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Solution Overview

Problem

In a 5G wireless communication system, where the network entity for managing mobility (AMF) and the network entity for managing a session (SMF) are separated, there is a challenge in efficiently managing sessions when session-related messages fail to be forwarded.

Innovation Solution

Implementing a method where a back-off timer is set in a DL NAS transport message to handle failed session establishment attempts, allowing the UE to retry session requests after the timer expires, and using cause information to differentiate between forwardable and non-forwardable sessions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If session management is separated from mobility management in 5G network, then network functionality and flexibility are improved, but complexity of session management when messages fail to forward increases

Engineering Contradiction:

Improvenetwork functionalityVSAvoidsession management complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments session management into two parts: forwardable sessions handled by AMF and non-forwardable sessions handled by SMF. This segmentation resolves the contradiction by maintaining the functional separation benefits while managing complexity through clear division of responsibilities between network entities.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a message forwarding mechanism with cause information as an intermediary that mediates between AMF and SMF. When session management messages fail to forward, the cause information acts as a mediator to indicate whether the session should be handled by AMF or SMF, reducing management complexity while preserving network flexibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If back-off timer is set in DL NAS transport message, then UE can retry session requests after timer expires improving session establishment reliability, but communication delay increases

Engineering Contradiction:

Improvesession establishment reliabilityVSAvoidcommunication delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements dynamic back-off timer values that can be adjusted based on session type and network conditions. Forwardable sessions may use shorter timers while non-forwardable sessions use longer timers, dynamically balancing reliability improvement against time loss for different scenarios.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses periodic retry mechanisms where UE attempts session establishment at intervals defined by the back-off timer. This periodic action allows the system to balance between establishing reliable connections and minimizing unnecessary delays by spacing out retry attempts appropriately.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentEP4075916B1Methods and devices for managing session in wireless communication system

Publication Date: 2025.07.30 SAMSUNG ELECTRONICS CO LTD

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AI summary

The present disclosure relates to a method and apparatus for allowing a user equipment (UE) to manage a session in a wireless communication system. According to an embodiment of the present disclosure, the UE may transmit a first uplink (UL) non-access stratum (NAS) transport message including a packet data unit (PDU) session establishment request to an access and mobility management function (AMF), receive a downlink (DL) NAS transport message from the AMF, and transmit a second UL NAS transport message including the PDU session establishment request based on a timer.