NSACF-Triggered UE Deregistration for Network Slice Mobility

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Solution Overview

Problem

Current 3GPP specifications do not address Network Slice Admission Control (NSAC) procedures during mobility between Evolved Packet Core (EPC) and Fifth Generation Core (5GC), particularly when the maximum number of User Equipments (UEs) has been reached, leading to incomplete handling of UE access and session continuity issues.

Innovation Solution

Implement a Network Slice Admission Control Function (NSACF) that triggers UE deregistration from overloaded network slices, ensuring session continuity by adjusting UE counts and allowing access even when maximum limits are reached, through mechanisms like AMF and SMF+PGW-C updates during interworking and inter-AMF mobility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the maximum number of UEs is enforced on a network slice, then network resource overload is prevented, but UE access and session continuity are blocked when mobility occurs between EPC and 5GC

Engineering Contradiction:

Improvenetwork resource stabilityVSAvoidUE access flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic UE count management by allowing the NSACF to override static maximum UE thresholds during mobility events. The system dynamically adjusts admission control behavior based on mobility detection, enabling temporary exceedance of maximum UE limits when UEs are transitioning between EPC and 5GC, thus resolving the contradiction between resource stability and access flexibility

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the admission control parameter state by switching from strict maximum UE enforcement to a mobility-aware mode. When mobility is detected, the NSACF modifies the effective threshold parameter, allowing UEs to maintain session continuity even when the network slice appears overloaded, thereby balancing resource protection with access flexibility

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the maximum number of UEs is strictly enforced, then network slice overload is avoided, but session continuity is disrupted during interworking and inter-AMF mobility

Engineering Contradiction:

Improvenetwork slice load managementVSAvoidsession continuity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies beforehand cushioning by detecting mobility events in advance and proactively allowing UE registration before the maximum UE threshold would be exceeded. The NSACF anticipates potential threshold violations during mobility and prepares by temporarily relaxing admission control, preventing session disruption before it occurs

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The NSACF acts as an intermediary between the strict maximum UE enforcement mechanism and the mobility management process. It mediates by intercepting admission control decisions, evaluating mobility context, and making informed adjustments that preserve both load management and session continuity, thus resolving the contradiction between these two requirements

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If NSACF denies access when maximum UEs are reached, then network resource protection is achieved, but UE registration and service access are blocked during mobility

Engineering Contradiction:

Improvenetwork resource protectionVSAvoidUE registration process

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system performs preliminary action by detecting mobility events before UE registration attempts occur. The NSACF proactively identifies UEs undergoing mobility between EPC and 5GC and prepares admission control exceptions in advance, ensuring that the UE registration process can proceed smoothly without encountering denial due to maximum UE thresholds

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent inverts the traditional admission control logic by allowing exceptions to the maximum UE rule rather than enforcing it universally. Instead of denying access when thresholds are reached, the system inverts the approach by selectively permitting access during mobility events, thus protecting network resources while maintaining ease of operation for moving UEs

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP4416987B1Network slice admission control function (NSACF) triggered UE deregistration

Publication Date: 2026.01.14 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

Systems and methods are disclosed for Network Slice Admission Control Function (NSACF) triggered User Equipment (UE) deregistration. In one embodiment, a method performed in a communications system comprises, at a NSACF, determining that one or more UEs need to be deregistered from a particular network slice and, responsive to determining that one or more UEs need to be deregistered from the particular network slice, sending a request to a network node to deregister one or more UEs from the particular network slice. The method further comprises, at the network node, receiving the request from the NSACF and deregistering one or more UEs from the particular network slice in response to receiving the request.