UE Timer Management for NTN PLMN Access During Coverage Gaps
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Solution Overview
Problem
IoT NTN systems face challenges with discontinuous coverage, where UE access stratum is deactivated due to intermittent satellite coverage, preventing periodic attempts to access higher priority PLMNs, as the timer expires during coverage gaps, leading to delayed service acquisition.
Innovation Solution
A method where a UE in a VPLMN with discontinuous coverage starts a timer for periodic attempts to access a higher priority PLMN, deactivates access stratum functions during coverage loss, and postpones attempts until coverage is restored, activating the stratum and retrying upon re-establishment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the UE deactivates access stratum functions during coverage gaps to optimize power consumption, then power efficiency is improved, but the ability to periodically attempt access to higher priority PLMNs is lost
Solution Approach 1:
The patent extracts the timer T functionality from the access stratum and places it in the non-access stratum layer. This allows the timer to continue running independently of access stratum activation state, enabling periodic PLMN selection attempts to occur even when access stratum is deactivated for power saving, thus resolving the contradiction between power efficiency and service acquisition reliability
Solution Approach 2:
The patent implements preliminary action by having the non-access stratum timer T run in advance and prepare periodic PLMN selection attempts before access stratum is activated. When coverage becomes available, the UE can immediately execute the pre-scheduled access attempts without waiting for timer re-initialization, ensuring timely service acquisition while maintaining power-saving operation during coverage gaps
2Use of energy by moving object
If the UE stops the timer T when access stratum is deactivated, then power consumption is reduced, but service acquisition is delayed until coverage returns
Solution Approach 1:
The patent extracts the timer T from the access stratum domain and relocates it to the non-access stratum domain. This architectural separation allows the timer to maintain its counting function independently of access stratum activation, preventing time loss while still enabling power-saving deactivation of access stratum functions during coverage gaps
Solution Approach 2:
The patent ensures continuity of useful action by maintaining the timer T operation continuously even when access stratum is deactivated. The timer's periodic expiration triggers continue to generate PLMN selection attempts, ensuring that service acquisition processes continue uninterrupted in the background without requiring access stratum to remain active, thus eliminating time loss while preserving power-saving benefits
3Reliability
If the UE periodically attempts to access higher priority PLMN while in VPLMN, then service reliability is improved, but power consumption increases during discontinuous coverage
Solution Approach 1:
The patent implements periodic action through timer T in the non-access stratum, which periodically triggers PLMN selection attempts at predefined intervals. This periodic mechanism ensures reliable service acquisition attempts are made at regular intervals while allowing the access stratum to remain deactivated between periods, optimizing the balance between service reliability and power consumption by concentrating active transmission only at scheduled intervals
Solution Approach 2:
The patent extracts the periodic timing control function from the access stratum and places it in the non-access stratum layer. This allows periodic PLMN selection attempts to be controlled and triggered independently of access stratum activation state, enabling the system to maintain reliable periodic service attempts while keeping power consumption low by deactivating access stratum between periodic intervals
Data Source
AI summary
A method of periodically attempting to access the HPLMN or an EHPLMN with higher priority in NTN systems with discontinuous coverage is proposed. A UE registered in VPLMN starts a timer T to periodically attempt to obtain service on its HPLMN or EHPLMN. When access stratum is deactivated due to discontinuous coverage in NTN, the UE does not stop the timer T, and postpone the periodic attempts to a later time, e.g., upon or after the UE activates the access stratum.