Satellite Frame Synchronization via Remote Drift Compensation
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Solution Overview
Problem
In TDMA-based satellite communication systems, traditional methods for frame synchronization, such as hub signal loopback and ephemeris data, are inadequate for tracking satellite motion, especially when the hub is not located within a spot beam, leading to potential collisions and inefficiencies in using shared frequencies.
Innovation Solution
A system and method that employs a hub with a communication and polling portion to estimate and compensate for satellite motion by calculating drift values from selected remotes, allowing for frame synchronization without relying on hub signal loopback or ephemeris data, using Closed Loop Timing (CLT) and polling-based approaches to minimize aperture size and ensure accurate timing adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hub signal loopback or ephemeris data methods are used for frame synchronization, then satellite motion tracking is achieved, but the system becomes complex and unreliable when the hub is not located within a spot beam
Solution Approach 1:
The remote unit autonomously measures the drift delay by comparing the received frame timing with its local clock, eliminating the need for hub signal loopback or ephemeris data. The system serves itself by having the remote unit independently determine and compensate for satellite motion effects through local measurement and calculation.
Solution Approach 2:
The synchronization method extracts only the necessary timing information from the received signal without requiring the hub to perform signal loopback or the system to process complex ephemeris data. The essential drift delay measurement is separated from the complex synchronization mechanisms, simplifying the overall system while maintaining reliability.
2Productivity
If traditional synchronization methods are used, then timing reference is maintained, but aperture size increases leading to inefficiencies in shared frequency usage
Solution Approach 1:
The remote unit continuously measures drift delay and adjusts its transmission timing based on this feedback. The system monitors the actual timing deviations caused by satellite motion and dynamically compensates for them, enabling precise aperture control and efficient shared frequency usage without requiring oversized timing margins.
3Reliability
If drift delay compensation is not implemented, then system operation is simple, but data bursts collide at the hub due to satellite motion
Solution Approach 1:
The remote unit proactively measures and compensates for drift delay before data burst transmission occurs. By calculating the expected timing deviation due to satellite motion in advance and adjusting the transmission timing accordingly, the system prevents data burst collisions without requiring complex real-time intervention mechanisms.
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5A
AI summary
Aspects of the invention provide a system and method to allow inroute frame timing synchronization without the aid of hub signal loopback or satellite ephemeris data. Furthermore, it allows tracking and compensating of the satellite motion to allow multiple remotes to use TDMA on the inroute frequencies, while minimizing the aperture. Two main techniques proposed are CLT and polling based approaches, which are used in combination for an optimum solution. In CLT based approach, hub transmits remote specific timing correction feedback messages on the outroute on as needed basis. In polling based approach, the remotes derive their timing based on a per-beam average delay estimate broadcast by the hub and a measured local delay specific to each outroute stream from a remote. An aspect of the invention uses triangulation method to determine satellite position. Furthermore, an aspect of the invention uses hub burst arrival method instead of polling approach.