UE TAI Selection in Non-Terrestrial Networks
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Solution Overview
Problem
In non-terrestrial network (NTN) communications, selecting a current tracking area identifier (TAI) among multiple TAIs is challenging due to the dynamic broadcasting of tracking area codes (TACs) by satellites, which complicates the determination of the current geographical location of user equipment (UE).
Innovation Solution
A method and apparatus where a processor in a UE initiates a procedure with a satellite-accessing cell, constructs a TAI or a list of TAIs based on the broadcast TACs, and receives either an accept or reject message from the network, allowing the UE to select the current TAI, either autonomously or with network assistance, depending on the availability of multiple TACs per public land mobile network (PLMN).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the satellite broadcasts multiple TACs at different times, then the coverage area and service capability are improved, but the complexity of selecting the current TAI increases
Solution Approach 1:
The network pre-configures multiple TAIs in the UE before the mobility procedure. When the UE needs to update its location, it already has candidate TAIs available, eliminating the need for real-time TAI selection during the procedure. This preliminary configuration allows the satellite to broadcast different TACs at different times while the UE maintains a ready list of potential TAIs to use.
Solution Approach 2:
The network acts as an intermediary by providing assistance information that helps the UE determine the current TAI from multiple candidates. Instead of the UE independently selecting from multiple broadcast TACs, the network provides guidance (such as indicating which TAC corresponds to the current geographical area), simplifying the UE's selection process while maintaining support for multiple TACs.
2Productivity
If the UE autonomously selects current TAI from multiple TAIs, then the registration efficiency is improved, but the accuracy of TAI selection may deteriorate
Solution Approach 1:
The network provides feedback in the form of assistance information that guides the UE's autonomous selection. The UE uses this feedback (such as current geographical area information or direct indication of the current TAC) to accurately identify which of its candidate TAIs corresponds to its current location, combining autonomous action with network guidance for both efficiency and accuracy.
Solution Approach 2:
The UE is pre-configured with multiple candidate TAIs before needing to select the current one. This preliminary configuration allows the UE to quickly autonomously select from pre-evaluated candidates rather than processing multiple broadcast TACs in real-time, improving registration efficiency while maintaining selection accuracy through pre-computation.
3Measurement precision
If the network provides assistance information for TAI selection, then the TAI selection accuracy is improved, but the signaling overhead increases
Solution Approach 1:
Instead of providing complete and frequent TAI selection assistance, the network provides partial assistance only when needed (such as during initial registration or when the UE enters a new area). The UE performs autonomous selection in normal operation, reducing signaling overhead while maintaining accuracy when network assistance is provided.
Solution Approach 2:
The UE performs self-service by autonomously selecting its current TAI from pre-configured candidates using its own resources (such as geographical location information from GNSS). This reduces dependency on network signaling while maintaining selection accuracy, balancing the trade-off between assistance accuracy and signaling overhead.
Data Source
AI summary
Examples pertaining to selection of a current tracking area identifier (TAI) among multiple current TAIs in non-terrestrial network (NTN) communications are described. A user equipment (UE) initiates a procedure in a satellite-accessing cell of a selected public land mobile network (PLMN). The UE selects a tracking area code (TAC) from a plurality of TACs of the selected PLMN broadcast by the cell as a current TAC such that a tracking area identifier (TAI), constructed from the current TAC and a PLMN identifier (PLMN ID) of the selected PLMN, is a current TAI associated with a geographical area in which the UE is located.