Timing Advance Slew Rate Control in Non-Terrestrial Networks
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Solution Overview
Problem
In non-terrestrial networks, the timing advance (TA) slew rate control is challenging due to abrupt changes in uplink timing errors caused by double corrections when a user equipment (UE) updates its global navigation satellite system (GNSS) position fix, leading to increased errors in uplink reception timing at base stations.
Innovation Solution
The UE applies slew rate control by determining a differential UE-specific TA based on the difference between current and previous GNSS position fixes, gradually adjusting the TA to mitigate these errors, and transmitting uplink messages at times calculated using the differential TA to reduce abrupt changes and double corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE updates its GNSS position fix to improve location accuracy, then the uplink timing accuracy should improve, but abrupt TA changes cause double corrections that increase uplink reception timing errors
Solution Approach 1:
The patent applies dynamic control to the TA slew rate by adjusting the maximum rate of TA change based on UE mobility state. The UE determines its mobility state (e.g., stationary, pedestrian, vehicular) and accordingly adjusts the TA slew rate parameter, allowing faster TA adjustments when stationary and slower adjustments when mobile, thus optimizing both timing accuracy and stability
Solution Approach 2:
The patent changes the TA slew rate parameter based on UE mobility state. The maximum TA slew rate is set to different values depending on whether the UE is stationary or mobile, controlling the rate at which TA can change during GNSS position fix updates. This parameter adaptation resolves the contradiction by matching the adjustment rate to the actual UE movement characteristics
2Measurement precision
If the UE applies aggressive TA corrections to reduce timing errors, then uplink timing accuracy improves, but abrupt TA changes cause double corrections that destabilize reception timing
Solution Approach 1:
The patent applies preliminary anti-action by pre-limiting the TA correction rate through slew rate control before double corrections can occur. The maximum TA slew rate is imposed as a constraint on TA updates, preventing overly aggressive corrections that would cause instability. This preliminary constraint avoids the harmful effect of double corrections while still allowing timely adjustments
Solution Approach 2:
The patent makes the TA correction aggressiveness dynamic by adjusting the maximum slew rate based on UE mobility state. When the UE is stationary, faster corrections are permitted; when mobile, slower corrections are enforced. This dynamic adaptation allows optimal timing accuracy while maintaining stability across different operational conditions
3Ease of operation
If the UE uses fixed TA slew rate control, then implementation is simple, but it cannot adapt to varying UE mobility states leading to suboptimal timing performance
Solution Approach 1:
The patent implements self-service by having the UE autonomously determine its own mobility state based on GNSS position fix comparisons and automatically adjust the TA slew rate accordingly. The UE serves itself by monitoring its own movement characteristics and adapting the TA control parameters without external intervention, thus achieving both simplicity and adaptability
Solution Approach 2:
The patent uses feedback from GNSS position fix comparisons to determine UE mobility state. The UE compares current and previous position fixes, calculates the displacement and time delta, and uses this feedback to adjust the TA slew rate. This closed-loop feedback mechanism enables automatic adaptation to mobility changes while maintaining implementation simplicity
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may determine a differential UE-specific timing advance (TA) based at least in part on a difference between a first UE-specific TA associated with a current global navigation satellite system (GNSS) position fix and a second UE-specific TA associated with a previous GNSS position fix. The UE may transmit, to a non-terrestrial network (NTN) node, an uplink message at a time that is based at least in part on the differential UE-specific TA. Numerous other aspects are described.