GNSS Signal Propagation Delay Test Device for 5G RAN Timing
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Solution Overview
Problem
Current methods for timing control in 5G RAN fronthaul networks face challenges in achieving precise timing synchronization due to unknown propagation delays in Global Navigation Satellite System (GNSS) antenna to Grandmaster Clock (GM) communication paths, which can lead to timing errors exceeding the stringent requirements of 5G networks.
Innovation Solution
A test device is used to determine unknown propagation delays in the GNSS signal distribution system, allowing for programming of a configurable delay offset in Grandmaster Clocks to correct timing errors, thereby improving the accuracy of 1PPS signals and reducing timing synchronization uncertainties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If propagation delay in GNSS signal distribution system is not measured and compensated, then device complexity is reduced, but timing synchronization precision deteriorates
Solution Approach 1:
The system performs self-diagnosis by automatically measuring propagation delay using existing test equipment and Grandmaster Clock resources. The GM measures round-trip time for test signals through the GNSS distribution system, calculates one-way propagation delay, and applies compensation without requiring external measurement devices or additional hardware infrastructure.
Solution Approach 2:
The system implements feedback by continuously monitoring propagation delay and dynamically adjusting delay offset parameters in the Grandmaster Clock. The measured propagation delay feeds back into the timing synchronization algorithm, which automatically compensates for delays by adjusting the 1PPS signal timing based on the measured values.
2Measurement precision
If propagation delay is accurately measured and compensated, then timing synchronization precision is improved, but measurement and detection difficulty increases
Solution Approach 1:
The system uses an intermediary test signal as a carrier to measure propagation delay. A test signal is injected into the GNSS distribution system and its round-trip transmission time is measured by the Grandmaster Clock. This intermediary approach converts the difficult direct measurement of propagation delay into a measurable round-trip time calculation.
Solution Approach 2:
The system performs preliminary measurement of propagation delay during system setup or maintenance windows before actual timing-critical operations. The measured propagation delay values are stored and applied as compensation parameters in advance, ensuring timing precision is maintained during normal operation without requiring continuous measurement.
Data Source
AI summary
A test device determines time error in a fronthaul network of a radio access network. A first Global Navigation Satellite System (GNSS) receiver receives GNSS signals from a GNSS satellite through a reference GNSS signal distribution system (GSDS) having a known signal propagation delay. The first GNSS receiver calculates and outputs a corresponding reference One Pulse Per Second (1PPS) signal. A second GNSS receiver receives the GNSS signals through a device under test including a GSDS having an unknown signal propagation delay. The second GNSS receiver calculates and outputs a corresponding DUT 1PPS signal. The test device determines the unknown signal propagation delay of the DUT by comparing the reference 1PPS signal to the DUT 1PPS signal.