LEO Satellite Synchronization Using Ephemeris Doppler Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Low Earth Orbit (LEO) satellite systems face challenges in network-level synchronization due to significant Doppler effects, which current technologies fail to effectively address by exploiting the predictable and deterministic nature of the LEO Doppler component.
Innovation Solution
A synchronization approach that utilizes the known ephemeris of LEO satellites and the positions of gateway and user terminals to continually track and compensate for time-varying offsets in frame timing, frame numbering, symbol timing, and Doppler-induced scaling, aligning transmissions with a GPS-derived system reference to simplify delay and Doppler domain uncertainty ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current LEO satellite systems use conventional synchronization approaches, then the system can operate with basic timing reference, but the delay and Doppler domain uncertainty ranges remain large and difficult to resolve
Solution Approach 1:
The patent applies preliminary action by pre-compensating for the deterministic portion of Doppler shift using satellite ephemeris data and ground station position information before signal reception. This advance preparation reduces the uncertainty range that the receiver must resolve, thereby improving synchronization precision without proportionally increasing receiver complexity
Solution Approach 2:
The patent changes the reference frame parameters by transforming the synchronization problem into a moving reference frame that accounts for satellite motion. By using known satellite ephemeris and ground station positions, the system dynamically adjusts timing and frequency parameters to compensate for Doppler effects, improving measurement precision while managing receiver complexity
2Adaptability or versatility
If LEO satellites move at high speeds relative to ground stations, then the satellite provides global coverage capability, but large Doppler effect causes significant offset in center frequency and timing
Solution Approach 1:
The patent implements feedback by continuously updating the Doppler compensation using real-time satellite ephemeris data and ground station position information. The system calculates the expected Doppler shift based on relative motion and applies corrective adjustments to maintain frequency and timing accuracy, enabling global coverage while preserving measurement precision
Solution Approach 2:
The patent applies dynamics by making the synchronization parameters adaptive rather than static. The system dynamically adjusts timing and frequency references based on the changing relative velocity between LEO satellites and ground stations, allowing the system to maintain accuracy across different orbital positions and velocities, thereby enabling global coverage capability
3Ease of operation
If the Doppler-induced rubber-band effect stretches or compresses symbol durations and signal bandwidth, then the received signal undergoes temporal scaling, but the receiver must resolve larger uncertainty ranges
Solution Approach 1:
The patent applies preliminary action by pre-calculating the expected temporal scaling factors based on satellite ephemeris and ground station positions before signal reception. This advance preparation allows the receiver to apply appropriate de-scaling operations, simplifying the reception process while reducing the uncertainty ranges that would otherwise require complex processing
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 enhances synchronization efficiency, reducing signal acquisition times, improving battery life, and decreasing satellite power and bandwidth consumption, while allowing for more accurate and targeted searches for timing and frequency synchronization, thereby improving overall system performance.
Implementation Method 1
The speed of a LEO satellite as observed from a location on the earth is high, which results in a large satellite motion induced Doppler effect. This large Doppler results in (i) a significant offset in the center frequency of the received signal, (ii) a scaling of the time and the frequency axes
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A synchronization approach is provided that compensates for the large Doppler offset of the satellites in a LEO satellite system by exploiting the predictable and deterministic nature of the Doppler component, and thereby simplifies the delay and the Doppler domain uncertainty ranges that the physical layer receivers have to resolve. The compensation is based on the known ephemeris information of the LEO satellite and the known positions of the gateway (GW) and the user terminal (UT) on the ground. Utilizing the deterministic component of the LEO Doppler, the synchronization process continually tracks and compensates for the time-varying offsets between the GW and UT frame timing, frame numbering (FN), symbol timings, and Doppler-induced scaling of center frequency and the signal bandwidth.