GNSS Receiver Time Acquisition Using Pre-Stored Clock Relationships
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Solution Overview
Problem
GNSS receivers face challenges in obtaining accurate initial time when powering on, due to unknown leap seconds, low resolution of real-time clocks, and time delays during synchronization, leading to inaccurate initial GNSS time values.
Innovation Solution
The method involves obtaining time relationships between clock signals and frame numbers from cellular networks to calculate GNSS time, using processing modules like frame pulse controllers and navigation engines to synchronize and update clock values, eliminating the need for real-time clock time and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If UTC time from RTC is used to obtain initial GNSS time, then the process is simple, but the accuracy is low due to leap second uncertainty, low RTC resolution, and clock drift
Solution Approach 1:
The patent applies preliminary action by obtaining a time relationship between a first clock signal and received GNSS time before power-off, storing this relationship in memory. When the receiver powers on, this pre-stored time relationship enables accurate initial GNSS time calculation without relying on low-precision RTC time, thus resolving the contradiction between operational simplicity and measurement precision.
2Productivity
If RTC time is converted directly to GNSS time, then the conversion is straightforward, but time delay during synchronization causes inaccuracy
Solution Approach 1:
The patent introduces an intermediary approach by using a time relationship between a first clock signal and received GNSS time as a mediator. Instead of directly converting RTC time to GNSS time (which introduces synchronization delays), the system uses this intermediate time relationship to calculate the initial GNSS time value, eliminating synchronization delay issues while maintaining fast conversion speed.
3Loss of energy
If all components except RTC are powered down, then energy consumption is reduced, but the resolution and accuracy of timekeeping deteriorate
Solution Approach 1:
The patent applies preliminary action by obtaining and storing the time relationship between the first clock signal and received GNSS time before power-off. This pre-acquired information is saved in memory and used after power-on to calculate accurate initial GNSS time without requiring high-power components to remain active, thus resolving the contradiction between energy conservation and timekeeping precision.
Data Source
AI summary
A method and apparatus for obtaining Global navigation Satellite System (GNSS) time in a GNSS receiver are provided. The following steps are included: obtaining a time relationship between a first clock signal and the received GNSS time; obtaining a first clock value of a second clock signal and an first associated clock value of the first clock signal at a first time point; calculating a first GNSS time corresponding to the first clock value of the second clock signal according to the first associated clock value and the time relationship; obtaining a second clock value of the second clock signal and an second associated clock value of the first clock signal at a second time point; and calculating a second GNSS time corresponding to the second associated clock value, according to the first GNSS time, the first clock value and the second clock value of the second clock signal.