SNPN Registration Timing Using Forbidden List Expiry

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Solution Overview

Problem

Existing 3GPP LTE systems face challenges in efficiently managing registration and deregistration with Secure Network Public Land Mobile Networks (SNPNs), particularly in terms of time validity considerations during registration processes.

Innovation Solution

The proposed solution involves receiving time validity information from SNPNs and using it for informed SNPN selection during the registration process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the terminal performs registration with SNPN without considering time validity information, then the registration process is simple and fast, but the registration may be rejected due to time validity constraints

Engineering Contradiction:

Improveregistration success rateVSAvoidregistration process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The terminal obtains time validity information from the SNPN in advance before performing registration. This preliminary action allows the terminal to check whether the current time is within the valid time range, and only initiate registration if the time condition is satisfied, thereby avoiding registration rejection while maintaining a simple registration flow.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the terminal waits for time validity to expire before re-selecting SNPN, then the network can ensure service continuity, but the terminal cannot access the network during invalid time periods

Engineering Contradiction:

Improveservice continuityVSAvoidaccess time loss

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The terminal dynamically adjusts its behavior based on the time validity status of the SNPN. When the current time is within the valid time range, the terminal can perform registration or re-selection. When the time has expired, the terminal waits until the next valid time period begins. This dynamic adaptation ensures service continuity while minimizing access time loss by immediately utilizing valid time windows.

Inventive Principle:

Principle #15Dynamics

3Reliability

If the terminal stores SNPN information in forbidden list after registration reject, then the terminal avoids repeated failed registrations, but the terminal cannot re-select the SNPN within a short time period

Engineering Contradiction:

Improveregistration stabilityVSAvoidSNPN re-selection flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The terminal changes the parameter of forbidden list storage by storing not only the SNPN identity but also the time validity information and expiration time. This allows the terminal to automatically remove the SNPN from the forbidden list when the time validity period expires, enabling flexible re-selection after a predetermined time while avoiding repeated failed registrations during invalid periods.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP4712578A1SNPN communication method

Publication Date: 2026.03.18 LG ELECTRONICS INC

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AI summary

One disclosure of the present specification provides a method by which a UE communicates. The method comprises the steps of: receiving valid time information for a localized service of an SNPN from the SNPN; receiving a registration rejection message or a registration release message; storing the SNPN on a forbidden list on the basis of the registration rejection message or the registration release message; activating a timer on the basis of the valid time information; deleting the SNPN from the forbidden list on the basis of expiration of the timer; and selecting a cell for the localized service, wherein a network stored on the forbidden list is excluded as the target of the cell selection.