RRC State Mismatch Prevention in Multi-PLMN User Equipment

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Solution Overview

Problem

Current technologies lack standardized support for multi-SIM user equipment (UEs) in wireless networks, leading to inefficiencies and state mismatches when managing multiple subscriptions across different public land mobile networks (PLMNs).

Innovation Solution

The proposed solution involves methods for UEs configured with multiple PLMN subscriptions to manage their reduced-energy states and perform recovery procedures, including transmitting indications to PLMNs, initiating timers, and performing NAS recovery procedures to maintain synchronized RRC states across multiple networks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a UE manages multiple PLMN subscriptions concurrently, then the UE can maintain connectivity to multiple networks, but the UE may experience RRC state mismatches between different PLMNs

Engineering Contradiction:

Improvemulti-PLMN connectivityVSAvoidRRC state synchronization

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The UE implements a feedback mechanism by monitoring timer expiration events and RRC state transitions. When a timer associated with a PLMN expires, the UE detects this event and triggers a recovery procedure to realign the RRC state with that PLMN, ensuring state synchronization across multiple networks

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary actions by establishing timers before RRC state transitions occur. These timers are configured in advance to anticipate potential state mismatches, and when they expire, they proactively trigger recovery procedures to prevent or correct RRC state desynchronization

Inventive Principle:

Principle #10Preliminary action

2Use of energy by moving object

If the UE enters reduced-energy states for one PLMN while maintaining connected state for another, then energy consumption is reduced, but data loss may occur due to state mismatches

Engineering Contradiction:

Improveenergy consumptionVSAvoiddata loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of information

Solution Approach 1:

The UE implements periodic action through timer-based mechanisms that regularly check and maintain RRC state synchronization. While in reduced-energy states, the UE uses these periodic timer expirations to detect and recover from state mismatches, ensuring data integrity is maintained even during low-power operation

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system provides beforehand cushioning by implementing recovery procedures that are triggered before actual data loss can occur. The timer mechanisms detect potential state mismatches early and initiate recovery actions to prevent data loss from occurring in the first place

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the UE performs recovery procedures for each PLMN independently, then RRC state synchronization is maintained, but excessive delays in network paging may occur

Engineering Contradiction:

ImproveRRC state synchronizationVSAvoidpaging delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The UE implements dynamic behavior by adjusting its recovery procedure execution based on current operational context. The system dynamically determines whether to perform recovery procedures immediately or defer them, optimizing the balance between maintaining RRC state synchronization and minimizing paging delays based on real-time network conditions

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20250159747A1Preventing Radio Resource Control (RRC) State Mismatch between Network and User Equipment

Publication Date: 2025.05.15 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Method for a user equipment, UE, configured with user credentials for a plurality of public land mobile networks, PLMNs, including, while registered in first and second PLMNs, in a connected state for the second PLMN, and in a reduced-energy state for the first PLMN, transmit (620) to the second PLMN an indication that the UE wants to enter a reduced-energy state for the second PLMN, initiating (630) a timer upon transmitting the indication and initiating (660) a recovery procedure towards the second PLMN based on expiration of the timer without receiving a responsive message from the second PLMN. Other embodiments include a complementary method for a network node configured to operate in the second PLMN, as well as a UE and network node configured to perform such methods.