Session Management Function Signalling Release Handling

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Solution Overview

Problem

In wireless communication networks, transferring session management responsibility from one session manager to another complicates the re-establishment of signalling sessions, leading to increased signalling overhead, processing complexity, and potential service disruptions, especially when maintaining backward compatibility and service continuity.

Innovation Solution

A session management function requests a user plane function to release a signalling session while indicating its re-establishment, allowing the user plane function to preserve context information, which is then used to efficiently re-establish the session with minimal overhead and maintain service continuity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a new procedure is introduced between the user plane entity and session manager to modify the signalling session for session manager transfer, then session manager transfer can be accommodated, but signalling overhead and processing complexity increase, and backward compatibility is jeopardized

Engineering Contradiction:

Improvesession manager transfer capabilityVSAvoidsignalling overhead and processing complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The existing session release procedure is made multi-functional by adding a re-establishment indication parameter. This allows the same procedure to serve both session release and session manager transfer purposes, eliminating the need for separate dedicated procedures while maintaining backward compatibility with legacy systems that ignore the new parameter.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

A new parameter (re-establishment indication) is added to the existing session release signalling messages. This parameter change enables the system to distinguish between regular session releases and session manager transfer scenarios without fundamentally altering the existing protocol structure, thus reducing complexity while enabling new functionality.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the signalling session is re-established with a new session manager, then session management responsibility can be transferred, but service continuity may be disrupted

Engineering Contradiction:

Improvesession management transferVSAvoidservice continuity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The user plane entity is instructed to preserve session context information before the actual session manager transfer occurs. This preliminary preservation of context (including session identifiers, IP addresses, and packet counter values) ensures that when the new session manager re-establishes the signalling session, service continuity is maintained without disruption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The session context information is copied and preserved by the user plane entity during the transfer process. This copying mechanism allows the new session manager to reconstruct the signalling session with identical parameters, ensuring seamless service continuity while transferring management responsibility.

Inventive Principle:

Principle #26Copying

3Adaptability or versatility

If the signalling session is completely released and re-established, then the new session manager can take over, but packet loss or delay may occur

Engineering Contradiction:

Improvesession manager takeoverVSAvoidpacket loss or delay

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The user plane entity preserves session context information including packet counter values before the session is released. This preliminary action ensures that when the signalling session is re-established with the new session manager, packet sequencing continues without interruption, preventing packet loss or delay while enabling the session manager takeover.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20240341009A1Handling of Session Context

Publication Date: 2024.10.10 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A network provides PDU sessions between wireless devices and data networks. UPFs in the network handle the user planes of these PDU sessions, while SMFs in the network manage the PDU sessions. The SMFs have dedicated interfaces for signaling sessions to the UPFs. In the occasion that managing of a PDU session has to be transferred from one SMF to another SMF, the first SMF has to release the signalling session with the UPF for the PDU session, and a second SMF has to re-establish the signaling session with the UPF for the same PDU session. To avoid that during the transfer of the management responsibility transfer the wireless device experiences a hick-up in the PDU session the first SMS includes a control element in the release message to the UPF, indicating to the UPF that the signaling session for the PDU session will be re-established by a second SMF, and that the UPF shall continue the handling of the PDU session till re-establishment.