RRC Inactive Context Retention During 5G NR Out-of-Service
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Solution Overview
Problem
In the RRC inactive mode, user equipment (UE) faces challenges in managing access stratum (AS) inactive context when out of service, leading to uncertainty about whether and when to discard this context, which affects the ability to maintain RRC connection efficiency and power consumption.
Innovation Solution
The UE is configured to set an RNA parameter to refrain from discarding the AS inactive context, allowing it to report an RNA update when camping on a new cell, using timers and delta timers to manage context retention and reporting, ensuring timely synchronization with the base station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the UE discards the AS inactive context when out of service, then power consumption is reduced and device resources are freed, but the ability to quickly resume RRC connection is compromised
Solution Approach 1:
The UE performs preliminary actions by storing the AS inactive context and configuring RNA parameters before potentially needing to resume connection. When the UE returns to service, the context is already prepared and can be quickly activated without full re-establishment procedures, thus reducing both power consumption and resumption time.
Solution Approach 2:
The system dynamically manages the AS inactive context based on UE service status. The context is retained when needed for quick resumption and can be discarded when the UE has been out of service for extended periods, allowing the system to adapt between power saving and connection reliability based on current conditions.
2Loss of time
If the UE retains the AS inactive context during out of service period, then RRC connection resumption is faster, but device memory and processing resources are consumed
Solution Approach 1:
The UE changes the state parameter of the AS inactive context based on RNA update status. When an RNA update is pending or successful, the context is maintained in an active state for quick resumption. When the out of service period extends beyond timer thresholds, the context parameter is changed to allow discarding, thus managing memory resources while enabling fast resumption when applicable.
Solution Approach 2:
The patent replaces the traditional binary decision (keep or discard context) with a timed, state-based mechanism using RNA parameters and timers. This substitution allows automatic context management that balances memory usage and resumption speed without requiring complex UE decisions about resource allocation.
3Reliability
If the UE performs RNA update reporting when camping on a new cell, then synchronization with base station is maintained, but signaling overhead increases
Solution Approach 1:
The UE uses feedback from RNA update procedures to determine future behavior. When an RNA update is successfully reported, the UE receives confirmation of synchronization status and adjusts its context retention decisions accordingly. This feedback mechanism allows the UE to maintain synchronization when necessary while avoiding unnecessary signaling that would waste energy.
Data Source
AI summary
Aspects are described for a user equipment (UE) comprising a transceiver configured to enable wireless communication with a base station, and a processor communicatively coupled to the transceiver. The processor is configured to enter a radio resource control (RRC) inactive mode and camp on a first cell. The processor is further configured to detect an out of service (OOS) status and set a RAN-based notification area (RNA) parameter, wherein the UE refrains from discarding an access stratum (AS) inactive context based on the RNA parameter. The processor is further configured to camp on a second cell and transmit a message to the base station to report an RNA update responsive to camping on the second cell.