Adaptive RLF Detection for IoT Non-Terrestrial Networks
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Solution Overview
Problem
Existing IoT technologies such as eMTC and NB-IoT face challenges in supporting non-terrestrial networks (NTNs) due to moving satellites causing cell switching, long propagation delays, and large Doppler shifts, leading to prolonged radio link failure (RLF) and service interruptions.
Innovation Solution
Adjusting radio link failure parameters based on satellite elevation angle, expected time to be served, or overlap period to declare RLF earlier, reducing the time taken to detect RLF and minimizing service interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional RLF detection parameters are used in NTN environments, then the detection accuracy is maintained, but the service interruption time is prolonged
Solution Approach 1:
The patent applies dynamics by making the RLF detection parameters adaptive rather than static. The network configures different RLF parameters (such as N310, T310, N311) based on satellite-specific conditions including elevation angle, Doppler shift characteristics, and propagation delay. This allows the system to dynamically adjust detection sensitivity and timing thresholds to match the current NTN environment, enabling earlier and more accurate RLF detection without causing false alarms, thereby reducing service interruption time while maintaining detection reliability.
Solution Approach 2:
The patent implements parameter changes by modifying key RLF detection parameters (N310 counter threshold, T310 timer duration, N311 counter threshold) based on NTN conditions. The network determines appropriate parameter values considering satellite elevation angle, Doppler shift rates, and propagation delays, then configures these parameters to the UE via RRC signaling. This parameter adaptation enables the system to detect RLF earlier in NTN environments compared to traditional LTE parameters, directly addressing the contradiction between detection accuracy and interruption time.
2Loss of time
If RLF parameters are adjusted to detect failure earlier, then service interruption is reduced, but false detection may increase
Solution Approach 1:
The patent employs feedback mechanisms where the network continuously monitors satellite position, elevation angle, Doppler shift, and propagation delay, then uses this information to dynamically adjust RLF parameters. The network configures appropriate N310, T310, and N311 parameter values based on current NTN conditions and provides feedback to the UE through RRC signaling. This closed-loop approach ensures that early detection parameters are only applied when appropriate for the current satellite geometry and channel conditions, preventing false detections while maintaining reduced interruption time.
Solution Approach 2:
The patent applies preliminary action by having the network pre-determine and configure appropriate RLF parameters before RLF detection is needed. Based on satellite ephemeris data, expected elevation angles, and predicted Doppler characteristics, the network proactively configures optimal N310, T310, and N311 parameters to the UE in advance. This preliminary configuration ensures that when RLF detection is triggered, the parameters are already optimized for the current NTN conditions, enabling early detection without false alarms.
Data Source
AI summary
According to some embodiments, a method is performed by a wireless device capable of operating in a non-terrestrial network (NTN). The method comprises determining an amount of time until a service link or feeder link switch and, based on the determined amount of time, modifying a radio link failure parameter used to determine when to declare a radio link failure (RLF).