CSG Cell Access Check Update Mechanism for PLMN Handover
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Solution Overview
Problem
User equipment (UE) experiences inaccuracies in identifying allowed Closed Subscriber Group (CSG) cells during handover between cells in different Public Land Mobile Networks (PLMNs) due to outdated PLMN and equivalent PLMN (EPLMN) lists, leading to false matches and missed matches, which affect handover decisions.
Innovation Solution
The system detects changes in PLMN and EPLMN lists between serving and target cells during handover and sends an indication to the UE, allowing it to update its lists and perform accurate access checks, ensuring correct identification of allowed CSG cells by utilizing updated PLMN information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the UE uses the stored PLMN and EPLMN lists for CSG cell access check during handover, then the access check can be performed quickly, but the accuracy of identifying allowed CSG cells deteriorates due to outdated PLMN information
Solution Approach 1:
The network performs preliminary action by detecting PLMN/EPLMN list changes between serving and target cells before handover execution, and sends change indications to the UE in advance. This allows the UE to update its lists beforehand, ensuring accurate CSG cell identification during handover without compromising handover speed.
Solution Approach 2:
The network implements feedback by monitoring PLMN list changes and actively notifying the UE when updates are required. The UE responds to change indications by updating its stored lists, creating a closed-loop system that maintains information accuracy while enabling fast handover execution.
2Measurement precision
If the UE updates PLMN and EPLMN lists frequently to maintain accuracy, then the identification accuracy improves, but the signaling overhead and processing complexity increase
Solution Approach 1:
The patent extracts only the essential update information by sending a compact change indication from the network to the UE, rather than transmitting complete PLMN lists frequently. The UE updates its stored lists selectively based on these concise notifications, reducing signaling overhead while maintaining accuracy.
Solution Approach 2:
Instead of continuous updates, the system employs periodic action by triggering PLMN list updates only when change indications are received from the network. This event-driven approach minimizes unnecessary signaling while ensuring the UE has current information when needed for handover decisions.
Data Source
AI summary
Solving dual errors for user equipment UE checking whether a private cell is allowed when handing over between serving and target cells, where the PLMN and/or EPLMNs list of the serving and target cells may differ. The serving cell may send a one-bit indication that there is a change in a handover command or system information SI6 message after which the UE may or may not refrain from reporting new cells until it performs a registration/location area update in the target cell. The target cell may trigger in the UE a registration update then provide the UE with the PLMN of the target cell. The serving cell can provide the PLMN of the target cell in a SI6 message or handover command, which the UE may use in place of or in addition to the PLMN/EPLMN of the serving cell when checking whether a private/closed subscriber group cell is allowed.