UE E-UTRA Capability Re-enabling for PLMN Selection
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Solution Overview
Problem
Current 3GPP specifications do not adequately handle ATTACH reject messages with cause #14 in LTE, 2G, and 3G systems, leading to disabled E-UTRA capabilities and service disruptions, especially when manual PLMN selection is attempted or when SIM/USIM lacks preferred PLMN lists, resulting in missed calls, data stalls, and loss of LTE services.
Innovation Solution
A method for handling ATTACH reject messages with #14 cause by enabling E-UTRA capability and removing PLMNs from forbidden lists, allowing manual PLMN selection and maintaining CS service access while blocking unnecessary PLMN selection, thus ensuring uninterrupted service and access to LTE features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE disables E-UTRA capability upon receiving ATTACH reject message with cause #14, then the UE avoids attempting services not allowed in the PLMN, but the UE loses access to LTE services and high data throughput even after manual PLMN selection succeeds
Solution Approach 1:
The patent implements dynamic management of E-UTRA capability by introducing a conditional re-enabling mechanism. Instead of permanently disabling E-UTRA when cause #14 is received, the system now allows re-enabling when specific conditions are met (successful manual PLMN selection or receipt of ATTACH accept message). This dynamic approach resolves the contradiction by adapting the capability state based on current network conditions and user actions.
Solution Approach 2:
The patent changes the state parameter of E-UTRA capability from a static disabled state to a conditionally可变 state. By introducing conditions under which the capability can be re-enabled (manual PLMN selection success, ATTACH accept reception), the system transforms the rigid parameter into a flexible one that adapts to different operational scenarios, thereby restoring LTE access while maintaining service reliability.
2Adaptability or versatility
If the UE performs PLMN selection after receiving cause #14 reject, then the UE can find alternative networks, but the UE wastes time and resources traversing the complete PLMN list and may miss CS paging
Solution Approach 1:
The patent applies preliminary anti-action by proactively preventing unnecessary PLMN selection when the UE is already camped on a suitable PLMN for CS services. By blocking PLMN selection in this specific scenario, the system avoids the harmful effect of time wastage and CS paging misses while still allowing PLMN selection when genuinely needed (e.g., when manually selected by the user or when no suitable PLMN is available).
Solution Approach 2:
The system provides self-service by automatically determining when PLMN selection should be blocked based on the UE's current service state. The UE monitors its own camped status and service requirements, making intelligent decisions about whether to perform PLMN selection without user intervention, thereby optimizing time utilization and preventing service disruptions.
3Ease of operation
If the UE removes PLMN from forbidden lists after successful manual selection, then the UE can access the PLMN for PS services, but the UE may repeatedly attempt to register on networks that don't support PS services
Solution Approach 1:
The patent implements feedback mechanisms by monitoring the outcome of PS service registration attempts. When the UE receives an ATTACH accept message indicating successful PS service registration, the system provides feedback that confirms the PLMN is suitable for PS services, triggering removal from the forbidden list. This feedback loop ensures that only PLMNs with confirmed PS service support are added back to the allowed list, preventing repeated failed registration attempts.
Solution Approach 2:
The system performs preliminary verification by checking whether PS services are actually available before removing the PLMN from the forbidden list. Instead of immediately adding the PLMN back after manual selection, the system waits for confirmation through successful ATTACH acceptance, ensuring that the PLMN is genuinely suitable for PS services before allowing future registration attempts.
Data Source
AI summary
A method for handling an ATTACH reject message with packet radio service mobility management reject cause number (#14 cause) at a user equipment (UE) is provided. The method includes receiving, at the UE, an ATTACH accept message for a network service on a public land mobile network (PLMN) from a first network entity, wherein the PLMN is in a “forbidden PLMNs for general packet radio service (GPRS) service” list, detecting, by the UE, that the UE's evolved universal terrestrial radio access (E-UTRA) capability is disabled, and enabling, by the UE, the UE's E-UTRA capability and removing the PLMN from the “forbidden PLMNs for GPRS service” list.