UE Frequency Adjustment for NTN Doppler and Timing Drift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing satellite communication systems face challenges with rapid changes in propagation delay and Doppler shifts due to high-speed satellite motion, particularly in Low Earth Orbit (LEO) and Medium Earth Orbit (MEO) scenarios, leading to excessive signaling overhead and loss of uplink orthogonality in LTE and NR networks.
Innovation Solution
The proposed solution involves providing UEs with pre-calculated, cell-specific characterizations of Doppler variation rates and timing drifts, allowing them to autonomously adjust their local frequency and transmission timing without relying on frequent network commands, thereby reducing signaling overhead and maintaining synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequent network commands are used to adjust UE frequency and timing, then synchronization accuracy is improved, but signaling overhead increases
Solution Approach 1:
The network pre-calculates and provides UE-specific Doppler variation rates and timing drift parameters before the UE needs to adjust its frequency and timing. This allows the UE to autonomously perform adjustments using stored characterization data without requiring frequent real-time network commands, thereby reducing signaling overhead while maintaining synchronization accuracy.
Solution Approach 2:
The UE is empowered to autonomously adjust its own frequency and timing parameters by using pre-provided characterization data (Doppler variation rates and timing drift parameters). This self-service mechanism eliminates the need for continuous network intervention, significantly reducing signaling overhead while maintaining accurate synchronization.
2Stability of the object's composition
If real-time frequency adjustment is implemented, then uplink orthogonality is maintained, but network complexity increases
Solution Approach 1:
The UE autonomously maintains uplink orthogonality by self-adjusting its frequency based on pre-provided Doppler variation rates and timing drift parameters. This transfers the complexity from the network (which would need to calculate and command adjustments in real-time) to the UE, which simply applies stored parameters locally, thereby reducing network complexity while maintaining orthogonality.
Solution Approach 2:
The network pre-calculates Doppler variation rates and timing drift parameters and provides them to the UE before real-time adjustments are needed. This preliminary preparation allows the UE to maintain uplink orthogonality autonomously without requiring complex real-time network processing, reducing network complexity while preserving synchronization stability.
3Quantity of substance
If autonomous UE adjustment is enabled, then signaling overhead is reduced, but adaptability to rapid changes decreases
Solution Approach 1:
The system uses UE-specific characterization data (Doppler variation rates and timing drift parameters) that capture the dynamic nature of satellite-induced frequency and timing changes. The UE applies these parameters autonomously to adapt to rapid changes in propagation conditions without requiring continuous network signaling, thereby maintaining adaptability while reducing signaling overhead.
Solution Approach 2:
The network pre-calculates and provides UE-specific Doppler variation rates and timing drift parameters that characterize the expected rapid changes in propagation conditions. This preliminary provision of adaptive parameters allows the UE to autonomously track and compensate for rapid changes without requiring frequent real-time network commands, balancing adaptability with reduced signaling overhead.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient frequency and timing adjustments in UEs, reducing signaling overhead and maintaining uplink orthogonality in satellite networks, even with large Doppler shifts and timing drifts, by empowering UEs to self-compensate for time-varying conditions.
Implementation Method 1
frequency adjustment due to Doppler shift of uplink and downlink transmissions
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Systems and methods are disclosed herein for frequency adjustment in a wireless network, particularly a Non-Terrestrial Network (NTN). Embodiments of a method performed by a User Equipment (UE) are disclosed. In one embodiment, a method performed by a UE for compensating for a Doppler shift in a wireless network comprises obtaining, from a network node, a characterization of Doppler variations in a particular cell. The method further comprises tuning a local frequency reference ƒ Ref , of the UE to a received downlink frequency for the particular cell and adjusting the local frequency reference ƒ Ref , over time according to the pre-calculated characterization of Doppler variations in the particular cell. In this manner, the communication between the UE and the network node in the presence of large and varying Doppler shifts is enabled. Embodiments related to compensating for timing drift are also disclosed.