Satellite Cell Tracking Area Code Handling for Forbidden Areas
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Solution Overview
Problem
Existing protocols for non-terrestrial networks (NTNs) in 5G New Radio struggle with handling forbidden tracking areas, leading to issues such as incorrect UE registration and delayed PLMN selection due to the inability to accurately identify and communicate forbidden tracking area codes (TACs) to user equipment (UEs) when multiple TACs are broadcasted.
Innovation Solution
Enhancements to registration and reject messages to include the TACs associated with forbidden tracking areas, allowing the network to indicate which TACs a UE does not have access to, and providing geographical area descriptions to the UE for remedial actions, enabling it to perform PLMN or cell selection when entering forbidden areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple TACs are broadcasted by NTN cells to increase network coverage and support roaming, then the network coverage and versatility are improved, but the UE registration accuracy and PLMN selection speed deteriorate due to inability to identify forbidden TACs
Solution Approach 1:
The core network provides feedback to the UE about which TACs are forbidden through the registration reject message. This feedback mechanism enables the UE to learn which TACs should be avoided, resolving the contradiction by allowing multiple TACs to be broadcasted while maintaining registration accuracy through informed UE behavior.
Solution Approach 2:
The network performs preliminary action by including forbidden TAC information in the registration reject message before the UE attempts to register using those TACs. This preliminary warning allows the UE to avoid making incorrect registration attempts, maintaining accuracy while supporting multiple TAC broadcasting.
2Loss of information
If the network includes all TACs in registration messages to ensure complete information transfer, then the information completeness is improved, but the message size and processing complexity increase
Solution Approach 1:
The patent extracts only the necessary information (forbidden TACs) from the complete set of TACs and includes only those in the registration reject message. This selective information transfer maintains completeness regarding forbidden areas while reducing the overall message processing complexity compared to transmitting all TAC information.
Solution Approach 2:
The patent applies local quality by providing detailed forbidden TAC information only where needed (in the reject message for forbidden TACs) rather than uniformly across all registration messages. This selective approach maintains information completeness for critical cases while reducing overall processing complexity.
3Reliability
If the UE waits for network indication of forbidden TACs before making PLMN selection, then the registration reliability is improved, but the PLMN selection time is delayed
Solution Approach 1:
The network performs preliminary action by including forbidden TAC information in the registration reject message before the UE needs to make PLMN selection. This allows the UE to immediately use this information for faster PLMN selection without waiting for additional network indications, thus reducing selection time while maintaining reliability.
Solution Approach 2:
The feedback mechanism in the registration reject message provides the UE with immediate information about forbidden TACs, enabling the UE to make informed PLMN selection decisions without delay. This feedback resolves the contradiction by providing reliable registration information while accelerating the PLMN selection process.
Data Source
AI summary
Disclosed are methods, systems, and computer-readable medium to perform operations including: receiving a request message from a user equipment (UE) served by a non-terrestrial access node, where the non-terrestrial access node is broadcasting a plurality of tracking area codes (TACs), and where a first TAC is associated with a first tracking area (TA) that is forbidden for the UE; and sending, to a core network node, the plurality of TACs in at least one information element.