PLMN Selection in RRC_INACTIVE State via NAS Interaction
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Solution Overview
Problem
Current wireless communication systems, particularly in the transition to 5G, face challenges in PLMN selection when a user equipment (UE) is in the RRC_INACTIVE state, as existing methods do not allow PLMN selection in this state, leading to service availability degradation for roaming UEs until they transition to RRC_IDLE.
Innovation Solution
A method and device for performing PLMN selection by the access stratum (AS) layer of a UE, allowing PLMN searching and selection even in the RRC_INACTIVE state, by interacting with the non-access stratum (NAS) layer, and stopping the search upon receiving RAN paging or uplink data/signaling, with options for state transitions to RRC_IDLE or RRC_CONNECTED for completing the selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PLMN selection is performed only in EMM_IDLE and RRC_IDLE states, then the existing protocol structure is maintained, but service availability is degraded for roaming UEs in RRC_INACTIVE state
Solution Approach 1:
The patent applies dynamics by enabling PLMN selection functionality to be dynamically activated in the RRC_INACTIVE state through NAS layer requests, rather than being statically restricted to only EMM_IDLE and RRC_IDLE states. This allows the system to adaptively enable PLMN selection based on actual service needs while maintaining the original state restrictions when not needed.
Solution Approach 2:
The patent changes the parameter of state availability for PLMN selection from a fixed set (EMM_IDLE, RRC_IDLE) to a dynamic set that includes RRC_INACTIVE when NAS layer requests it. This parameter change enables roaming UEs to perform PLMN selection while maintaining the RRC_INACTIVE state, improving service availability without requiring state transitions.
2Reliability
If PLMN searching is performed in RRC_INACTIVE state, then service availability is improved, but interaction complexity between AS and NAS layers increases
Solution Approach 1:
The patent uses the NAS layer as an intermediary that mediates between the service requirement and the AS layer execution. The NAS layer receives service requests, determines that PLMN selection is needed, and sends requests to the AS layer to perform the actual PLMN searching. This intermediary approach manages the complexity by centralizing the decision-making logic in the NAS layer while keeping the AS layer execution relatively simple.
Solution Approach 2:
The patent segments the PLMN selection functionality into two distinct parts: the decision-making logic in the NAS layer (which determines when PLMN selection is needed) and the execution logic in the AS layer (which performs the actual PLMN searching). This segmentation allows each layer to focus on its specific function, managing overall system complexity while enabling the enhanced service availability.
3Measurement precision
If PLMN searching continues until completion or interruption, then selection accuracy is improved, but time consumption increases
Solution Approach 1:
The patent applies dynamics by making the PLMN searching process interruptible rather than requiring completion. The search can be dynamically stopped when specific conditions are met (RAN paging received or uplink data/signaling detected), allowing the system to balance between achieving sufficient selection accuracy and responding timely to higher-priority events.
Solution Approach 2:
The patent implements feedback mechanisms where the PLMN searching process monitors for specific conditions (RAN paging, uplink data/signaling) and automatically interrupts when these conditions are detected. This feedback-driven interruption allows the system to stop the search early when external events indicate that continued searching is no longer necessary or appropriate, reducing time consumption while maintaining acceptable selection accuracy.
Data Source
AI summary
Provided are a method of performing public land mobile network (PLMN) selection and a device supporting the method. According to one embodiment of the present invention, a method for performing PLMN selection in a wireless communication system includes: entering an RRC_INACTIVE state; transmitting, to a non-access stratum (NAS) layer of the UE, information on whether or not there is on-going data; receiving, from the NAS layer of the UE, a request of a PLMN searching when there is no on-going data; and performing the PLMN searching based on the request of the PLMN searching.