Phase Error Compensation for IoT NTN Uplink Signals
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Solution Overview
Problem
In non-terrestrial network (NTN) systems, timing advance (TA) drift due to the motion of satellites or other devices causes phase errors in uplink communication signals, leading to demodulation failures as the phase discontinuity exceeds the tolerance limits, especially in IoT and machine-type communications where long transmission times result in significant timing drift.
Innovation Solution
The solution involves estimating the TA drift rate using the UE's location and satellite ephemeris, and applying a phase compensation factor to pre-compensate the communication signal, either at the UE or the NTN node, to correct for the phase errors caused by the TA drift, ensuring phase continuity and successful demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long transmission times are used for IoT communications, then communication coverage and reliability are improved, but timing advance drift increases causing phase errors that exceed tolerance limits
Solution Approach 1:
The patent applies preliminary action by pre-calculating and applying phase compensation factors to the communication signal before transmission. The system estimates the TA drift rate based on UE location and satellite ephemeris, then applies the compensation factor to pre-compensate for expected phase errors, ensuring phase continuity throughout the long transmission without requiring continuous real-time adjustments
2Reliability
If phase compensation is applied to correct TA drift, then phase continuity is maintained, but system complexity increases due to additional estimation and compensation processing
Solution Approach 1:
The patent applies parameter changes by modifying the communication signal parameters - specifically the phase compensation factor - based on estimated TA drift rate. The system calculates the compensation factor using the formula: compensation factor = exp(j * 2π * TA_drift_rate * T_symbol), where T_symbol is the symbol duration. This parameter modification corrects the phase error while maintaining a relatively simple implementation structure
Data Source
AI summary
This disclosure presents methods to compensate for a phase drift in an uplink communication signal between a user equipment (UE) and a non-terrestrial network (NTN) node. Due to the change rate of velocity of the UE relative to the NTN node, a transmission signal can drift causing demodulation errors at the receiver. The UE can apply compensation processes to the transmission signal so that the received signal is closer to the original transmitted signal as compared to a non-compensated signal. Alternatively, the NTN node can apply compensation process to modify the reference phase to be closer to the phase of the received signal in the demodulation process. The location of the UE, as well as its relative elevation, can be used with the NTN node's location, to generate the compensation information. The compensation can be applied on a symbol-by-symbol basis or to a group of M symbols.