Satellite Fronthaul Clock Synchronization Using Ephemeris Correction
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Solution Overview
Problem
Integrating non-terrestrial components like satellites into terrestrial wireless networks introduces challenges in synchronizing clocks due to varying propagation times, leading to errors and misalignment of transmit/receive windows, which can cause increased latency and service disruptions.
Innovation Solution
A method and system for synchronizing clocks in non-terrestrial fronthaul networks using ephemeris data to determine propagation times and generate correction factors, ensuring accurate time synchronization between terrestrial and non-terrestrial components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If satellite is used to extend wireless network coverage, then network coverage area is improved, but clock synchronization accuracy deteriorates due to varying propagation times
Solution Approach 1:
The system performs preliminary calculations of propagation times based on ephemeris data before clock synchronization occurs. The satellite gateway computes expected propagation times for clock synchronization messages using satellite position data from ephemeris, allowing the system to pre-compensate for timing variations before they affect synchronization accuracy
Solution Approach 2:
The system dynamically adjusts clock synchronization parameters by calculating correction factors based on varying propagation times. The satellite gateway determines propagation time variations using ephemeris data and applies these as correction factors to maintain synchronization accuracy despite changing satellite positions and distances
2Device complexity
If propagation time variations are not compensated, then system complexity is reduced, but network reliability deteriorates due to misalignment of transmit/receive windows
Solution Approach 1:
The satellite gateway acts as an intermediary that calculates and applies propagation time correction factors. It receives ephemeris data, computes propagation time variations, generates correction factors, and applies them to clock synchronization messages, thereby isolating the complexity from the radio unit while ensuring reliable synchronization
3Measurement precision
If clock synchronization correction is applied, then time synchronization accuracy is improved, but processing complexity increases
Solution Approach 1:
The satellite gateway performs preliminary calculation of propagation times and correction factors before clock synchronization messages are exchanged. By pre-computing these values based on ephemeris data, the system reduces real-time processing complexity at the radio unit while maintaining high synchronization accuracy
Solution Approach 2:
The radio unit applies the correction factor to its local clock using the formula: offset = (t2 - t1) - correction_factor. This self-service approach allows the radio unit to autonomously synchronize its clock without requiring complex processing or additional communication rounds, balancing accuracy with simplicity
Data Source
AI summary
Techniques for supporting non-terrestrial fronthaul network architectures are provided. In one example, a wireless network system includes: a satellite comprising a radio unit; a distributed unit located on Earth that manages the radio unit; and a satellite gateway in communication with the distributed unit and the satellite. The satellite gateway is configured to: receive ephemeris data for the satellite; initiate a sequence of clock synchronization transmissions between the radio unit and the satellite gateway; and determine, using the ephemeris data and a location of the satellite gateway, a first propagation time for a first clock synchronization transmission and a second propagation time for a second clock synchronization transmission. Based on the propagation times, the satellite gateway generates and transmits a clock synchronization correction factor that the radio unit will use to determine an offset between clock signals of the radio unit and the distributed unit.