GNSS Navigation Message Synchronization Symbol Pattern
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Solution Overview
Problem
The synchronization data broadcast in Galileo open service GNSS signals lacks robustness, particularly in challenging environments like urban canyons or indoors, affecting the performance of receivers in terms of acquisition time.
Innovation Solution
Incorporating a pattern of synchronization symbols within data packets of the navigation message, using an error-correcting convolutional code, and employing a bit buffer to ensure the synchronization pattern's integrity, along with alternating synchronization patterns across data packets to increase ambiguity time and relax system time precision constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronization data is broadcast in the navigation message using conventional methods, then the navigation message can be transmitted with standard structure, but the robustness of synchronization detection deteriorates in challenging environments
Solution Approach 1:
The patent embeds synchronization bit fields at predetermined positions within the navigation message structure before transmission. These synchronization patterns are pre-placed in specific data packets (e.g., every sixth packet or in specific subframes) to enable receivers to quickly acquire and lock onto the signal even in challenging environments with low signal-to-noise ratio
Solution Approach 2:
The patent modifies the navigation message structure by incorporating dedicated synchronization bit fields with specific binary patterns (e.g., alternating 0s and 1s or specific repeating sequences). These parameter changes in the message structure create distinct synchronization signatures that improve detectability and robustness against signal degradation in urban canyons and indoor environments
2Adaptability or versatility
If the navigation message contains comprehensive data including ephemeris, clock corrections, and additional services, then the service coverage is improved, but the acquisition time increases due to larger message size
Solution Approach 1:
The navigation message is divided into multiple data packets organized in frames and subframes, with synchronization bit fields embedded at specific intervals. This segmentation allows receivers to quickly acquire synchronization using the embedded patterns without having to decode the entire comprehensive message, thereby reducing acquisition time while maintaining full service coverage
Solution Approach 2:
The synchronization bit fields act as intermediary elements within the navigation message structure. These intermediate synchronization patterns provide a quick-reference mechanism for receivers to lock onto the signal before processing the full comprehensive message, thus bridging the gap between rapid acquisition and complete service delivery
Data Source
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AI summary
A GNSS radio signal comprises a navigation message transmitted as a sequence of data packets. Each data packet is contained in the GNSS radio signal as a sequence of symbols obtained by applying a code preceded by a synchronisation symbol header. The data packets are organised internally into data fields. At least some data packets of the sequence of data packets contain a synchronisation bit field translated by applying the code in a synchronisation symbol pattern.