NTN Cell Selection Timing for Idle-State UE Mobility
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Solution Overview
Problem
The existing UE behavior in non-terrestrial networks (NTN) for cell selection is unclear, leading to potential premature or delayed cell selection, which degrades mobility performance due to undefined impact of NTN-specific parameters like Tservice and distanceThresh on cell reselection procedures.
Innovation Solution
A method and terminal node for determining a time period to initiate cell selection based on NTN parameters such as service time and location relationship with the serving cell, including receiving parameters from the network to facilitate timely cell reselection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE follows existing cell selection procedures in NTN without clear guidance on NTN parameters, then the procedure remains simple, but the mobility performance degrades due to premature or delayed cell selection
Solution Approach 1:
The patent applies preliminary action by having the UE determine a time period before actually initiating cell selection. The UE calculates this time period based on NTN parameters (Tservice, distanceThresh) in advance, so that when cell selection is needed, the UE already has the timing information ready. This resolves the contradiction by providing clear guidance on when to select cells without adding complex real-time decision-making during the actual selection process.
2Reliability
If the UE waits for clear guidance on NTN parameters before initiating cell selection, then the measurement behavior becomes well-defined, but the cell selection is delayed
Solution Approach 1:
The patent resolves this contradiction by having the UE preliminarily determine the time period for cell selection based on NTN parameters. Instead of waiting for clear guidance before acting, the UE proactively calculates the appropriate timing window (time period) and initiates cell selection within that pre-determined window. This ensures both clear measurement behavior guidance and timely cell selection.
3Speed
If the UE initiates cell selection immediately when serving cell becomes unsuitable, then the response time is fast, but the selection may be premature before considering NTN-specific parameters
Solution Approach 1:
The patent applies preliminary action by having the UE first determine the appropriate time period based on NTN parameters (Tservice, distanceThresh) before initiating cell selection. This pre-calculation ensures that the UE selects cells at the optimal moment considering satellite-specific characteristics, rather than reacting immediately. The time period determination happens in advance, allowing fast yet accurate cell selection.
Solution Approach 2:
The patent resolves this contradiction by changing the parameter used for timing determination from immediate reaction time to a calculated time period based on NTN-specific parameters. The UE adjusts the timing parameter (time period) according to Tservice and distanceThresh values, which optimizes both response speed and selection accuracy by accounting for satellite orbital characteristics and signal propagation delays.
Data Source
AI summary
A method (100′) in a terminal node for performing a cell selection procedure in a NTN system. The method (100′) includes: in response to receiving (s110′) at least one NTN parameter defining a time and/or location relationship between the terminal node and a serving cell, initiating (s120′) a cell selection procedure to find a cell meeting a cell selection criterion after a time period.