GNSS Receiver Time Base Synchronization via Network PTP
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Solution Overview
Problem
GNSS receivers face challenges in acquiring and synchronizing GPS signals, especially in environments with high signal attenuation and multipath propagation, leading to inaccurate position fixing and performance degradation due to variability in frequency and phase errors.
Innovation Solution
The method involves using 'lucky' PTP packets with lower delay values to adjust the frequency and phase of the local time base, employing linear regression analysis and selective data culling to refine frequency estimates, and synchronizing the local time base with GPS signals using pseudo-random number sequences for accurate time and phase corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional GNSS signal acquisition methods are used, then position fixing can be achieved in open environments, but signal attenuation and multipath propagation in urban canyons and indoor environments cause acquisition failure and inaccurate positioning
Solution Approach 1:
The patent introduces an intermediary network-based time and frequency recovery system that mediates between the GNSS receiver and the positioning function. By using network time synchronization protocols (PTP, NTP) and server-based time transfer, the system provides alternative timing references that can compensate for GNSS signal degradation in urban canyons and indoor environments, enabling reliable positioning without direct GNSS signal acquisition.
Solution Approach 2:
The patent makes the time and frequency recovery system universal by supporting multiple synchronization protocols (PTP, NTP, STRAP) and multiple time transfer methods (one-way, two-way, round-trip). This multi-functional approach allows the same receiver to operate in diverse environments (urban canyons, indoors, satellite-constrained) by switching between different timing sources and methods, thereby achieving reliable positioning across all scenarios.
2Measurement precision
If network-based time synchronization is used to supplement GNSS signals, then position fixing accuracy improves, but frequency and phase variability in the local time base causes performance degradation
Solution Approach 1:
The patent implements feedback mechanisms where the receiver continuously monitors time and frequency differences between its local oscillator and network-synchronized time references. By using round-trip time measurements, two-way time transfer, and time offset adjustments, the system receives feedback about frequency and phase deviations and automatically corrects them through time base adjustment, thereby maintaining stability while improving positioning accuracy.
Solution Approach 2:
The patent changes the operating parameters of the local time base by dynamically adjusting frequency and phase based on network-synchronized references. Through time offset correction, frequency offset compensation, and phase adjustment, the system modifies the local oscillator parameters to match network time, thereby eliminating frequency and phase variability that would otherwise degrade positioning performance.
3Measurement precision
If continuous time and frequency measurements are performed to maintain synchronization, then synchronization accuracy is improved, but measurement uncertainty and processing complexity increase
Solution Approach 1:
The patent applies partial action by performing time and frequency measurements at strategic intervals rather than continuously. By using periodic synchronization packets, discrete time offset corrections, and selective frequency adjustments, the system achieves sufficient synchronization accuracy without the measurement uncertainty and processing overhead of continuous monitoring. The excessive action principle is applied by using multiple redundant measurement methods (one-way, two-way, round-trip) to cross-validate results and reduce uncertainty.
Data Source
AI summary
Determination of one or more timing (phase) and/or frequency corrections to be made to a local time base of a receiver device to synchronize the local time base with the time of GPS or other highly accurate time base. Timing packets from one or more grandmaster devices whose time bases are substantially the same as that of GPS or the like and/or positioning system signals (e.g., GPS signals) directly from a positioning system are received and manipulated to determine the timing and/or frequency corrections. The corrected time base may be used to assist in acquiring such positioning signals to allow for higher accuracy correction and/or for downstream communication operation. The present utilities are advantageous such as when a sufficient number of channels (e.g., four) from the receiver device to positioning system satellites are unavailable to synchronize the local time base to the GPS or other accurate time base.