RRC Inactive Cell Selection via System Information Validity
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Solution Overview
Problem
Current radio access network architectures face challenges in efficiently managing multi-carrier communication systems, particularly in dynamically adapting modulation and coding schemes to optimize radio transmission based on varying conditions, which affects the quality of service and network performance.
Innovation Solution
The implementation of advanced radio access network architectures that incorporate next-generation Node B (gNB) and evolved Node B (ng-eNB) nodes, utilizing advanced modulation techniques like QAM and hybrid automatic repeat request (HARQ), along with dynamic scheduling and resource allocation mechanisms, to enhance the NR user plane and control plane protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a wireless device in RRC inactive state performs cell selection based on stored system information, then cell reselection speed is improved, but the accuracy and up-to-date nature of the system information may deteriorate
Solution Approach 1:
The network pre-configures validity durations for system information blocks before releasing the device to inactive state. This preliminary action allows the device to use stored information efficiently while the network maintains awareness of when that information expires, balancing speed and accuracy without requiring continuous updates during inactive state.
Solution Approach 2:
The network broadcasts system information validity durations and expiration indicators that provide feedback to the wireless device. This feedback mechanism enables the device to determine whether its stored system information is still valid, allowing it to proceed with cell selection using stored data when valid or trigger updates when expired, thus maintaining both speed and accuracy.
2Loss of information
If the network frequently updates system information for inactive devices, then information accuracy is improved, but network signaling overhead and energy consumption increase
Solution Approach 1:
The network performs preliminary configuration of system information validity durations during the transition to inactive state, establishing a predetermined lifecycle for stored information. This eliminates the need for frequent network-initiated updates, reducing signaling overhead and energy consumption while maintaining information accuracy within the valid period.
Solution Approach 2:
Instead of continuous or frequent updates, the system implements periodic action through validity durations that define when stored system information expires. This periodic mechanism allows the network to maintain information accuracy without constant communication, significantly reducing signaling overhead and energy consumption compared to frequent updates.
3Loss of information
If the wireless device continuously monitors for system information updates, then information freshness is improved, but device energy consumption increases
Solution Approach 1:
The device receives preliminary configuration of validity durations for system information blocks before entering inactive state. This preliminary action establishes a clear validity window during which stored information can be used without monitoring for updates, allowing the device to conserve energy by sleeping while maintaining information freshness within the configured validity period.
Solution Approach 2:
The system implements periodic action through validity duration timers that define when stored system information expires. Instead of continuous monitoring, the device periodically checks whether its stored information has expired based on the pre-configured validity duration, significantly reducing energy consumption while maintaining information freshness through structured, intermittent validation.
4Reliability
If the network stores detailed UE context for inactive devices, then service continuity is improved, but network memory requirements and processing complexity increase
Solution Approach 1:
The network extracts and releases the UE context from the RAN to the core network when transitioning the device to inactive state. This extraction reduces the memory and processing burden on the RAN while maintaining service continuity through core network storage. The RAN can quickly re-acquire necessary context information when the device returns to connected state, balancing service continuity with reduced network complexity at the RAN level.
Solution Approach 2:
The core network acts as an intermediary that stores and manages UE context information during the inactive state. This intermediary role allows the RAN to reduce its memory and processing requirements while the core network maintains the detailed context information needed for service continuity. The intermediary core network facilitates efficient context management by distributing storage responsibilities across the network architecture.
Data Source
AI summary
A wireless device receives from a base station, first message(s) comprising configuration parameters of at least one of: logical channel(s); or radio bearer(s). The wireless device receives from the base station, a second message indicating an RRC state transition of the wireless device from an RRC connected state to an RRC inactive state. The wireless device being in the RRC inactive state selects a first cell based on the configuration parameters. The wireless device transmits to the base station, a random access preamble via the first cell.