Multi-SIM RRC State Synchronization for Low-Latency Resume
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Solution Overview
Problem
In 5G NR networks with dual SIM dual standby (DSDS) user equipment (UE), there is a mismatch in Radio Resource Control (RRC) status between the primary and secondary SIMs due to the secondary SIM suspending the primary SIM, leading to unnecessary latency and power consumption when the primary SIM resumes communication, as the network transitions it to an incorrect RRC state.
Innovation Solution
The UE synchronizes the RRC status with the base station by communicating estimated time durations and specific requests, such as RRC resume requests with cause values or coordinated leaving indications, ensuring both the UE and the network have the same RRC status for the primary SIM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the secondary SIM suspends the primary SIM to conduct high priority activities, then the secondary SIM can perform communications without interference, but the primary SIM's RRC status becomes mismatched with the network, leading to increased latency and power consumption during resume
Solution Approach 1:
The UE sends a notification message to the network before suspending the primary SIM, indicating the estimated suspension duration. This allows the network to proactively update the RRC status of the primary SIM to 'suspended' or 'inactive' state in advance, so when the primary SIM resumes, the network is already prepared with the correct RRC state, eliminating the need for lengthy status synchronization procedures and reducing latency.
2Productivity
If the secondary SIM suspends the primary SIM to conduct high priority activities, then the secondary SIM can perform communications without interference, but the RRC status mismatch causes the network to transition the primary SIM to an incorrect RRC state, increasing power consumption
Solution Approach 1:
The UE provides feedback to the network about the suspension status and estimated duration of the primary SIM. The network uses this feedback to adjust the RRC state of the primary SIM accordingly. When the primary SIM resumes, the UE notifies the network of the resume status, allowing the network to confirm or correct the RRC state, ensuring the primary SIM transitions to the correct state without unnecessary power-consuming re-transitions.
3Measurement precision
If the UE provides detailed estimated time duration to the network, then the network can accurately manage the RRC Inactive state retention, but this requires additional signaling messages and processing
Solution Approach 1:
The patent introduces new parameters in the signaling messages, specifically an estimated suspension duration parameter that the UE provides to the network. This parameter allows the network to accurately determine how long to retain the RRC Inactive state context without requiring multiple back-and-forth messages. The network uses this single parameter to adjust its state management behavior, achieving precise synchronization with minimal additional signaling overhead.
Data Source
AI summary
A multi-universal subscriber identity module (MUSIM) user equipment (UE) is configured to stay synchronized with a network. The UE registers to a first network for the first SIM, registering to a second network for the second SIM, prior to the UE conducting a high priority activity related to the second SIM, sends, to the first network via a connection associated with the first SIM, a first message comprising an estimated time duration during which the UE conducts the high priority activity related to the second SIM, receives, from the first network, a second message indicating a time period during which the first network will retain a connection context for the connection associated with the first SIM in an RRC Inactive state and when the UE completes the high priority activity, determines the connection context of the first network for the connection associated with the first SIM.