GNSS UTC Time Estimation Using Stored TOW and Offset
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Solution Overview
Problem
Current methods for calculating Coordinated Universal Time (UTC) from Global Navigation Satellite System (GNSS) signals are inefficient, requiring significant time to achieve high accuracy, especially when GNSS connectivity is lost and then reestablished, due to the need for precise onboard clocks and lengthy signal decoding processes.
Innovation Solution
The method involves storing time parameter values such as Time of Week (TOW), Week Number (WN), and Offset between GNSS time and UTC in non-volatile memory, allowing rapid estimation of UTC upon reconnection using an onboard oscillator and stored data, eliminating the need for precise clocks and reducing decoding time to estimate UTC accurately within one second.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional GNSS signal decoding methods are used to calculate UTC, then high accuracy can be achieved, but significant time is required especially after connectivity loss
Solution Approach 1:
The system performs preliminary actions by storing time parameter values (TOW, WN, OFFSET) in non-volatile memory before GNSS connectivity is lost. When connectivity is reestablished, these pre-stored values are immediately retrieved and used to calculate UTC, eliminating the need to wait for complete signal decoding and achieving accurate UTC within one second.
2Measurement precision
If precise onboard clocks are used to maintain accurate UTC, then high accuracy can be achieved, but device cost increases
Solution Approach 1:
Instead of using expensive precise onboard clocks, the system creates a copy of the accurate GNSS time information by storing time parameter values (TOW, WN, OFFSET) in non-volatile memory. This copied time data is then used to calculate UTC accurately without requiring continuous GNSS connectivity or expensive clock hardware.
Solution Approach 2:
The system replaces expensive precise clocks with inexpensive non-volatile memory storage. The stored time parameter values serve as a disposable backup that can be quickly retrieved and used to reconstruct accurate UTC time without requiring ongoing expensive clock maintenance or continuous GNSS signal acquisition.
Data Source
AI summary
A method is described for estimating the coordinated universal time (UTC). The method involves receiving, by a satellite navigation receiver, signals broadcast by a global navigation satellite service (GNSS) satellite. The signals encode a first time of week (TOW) value. The method also involves estimating a first week number (WN) value and a first relationship between the UCT and a reference time of an onboard clock of the GNSS satellite (OFFSET) from time parameter values stored at a local memory. The method determines a first estimate of the UTC from the first TOW value, the first WN value, and the first OFFSET.