GNSS Correction Messaging Using Zenith-Referenced Compression
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Solution Overview
Problem
The increasing demand for bandwidth in global navigation satellite system (GNSS) data transmission, particularly in real-time kinematic (RTK) positioning applications, exceeds the available bandwidth, especially in scenarios where expanding bandwidth is costly or not feasible, necessitating a more efficient data transmission method.
Innovation Solution
The Compressed Measurement Record-Extended (CMRx) technique reduces the amount of data transmitted by sending only ambiguous observation data, utilizing knowledge of signal structure and constellation geometry to eliminate redundant information, and employing algorithms to reconstruct necessary data at the recipient, thereby minimizing bandwidth usage while ensuring full data reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete GNSS observation data is transmitted to ensure full information availability, then data integrity is maintained, but bandwidth consumption increases
Solution Approach 1:
The patent extracts and transmits only the essential ambiguous observation data (code phase and carrier phase measurements) while eliminating redundant information such as satellite ephemeris, clock corrections, and atmospheric models that can be obtained from other sources or reconstructed at the receiver end
Solution Approach 2:
The receiver reconstructs the complete observation data by combining the transmitted ambiguous data with locally stored satellite almanac information and atmospheric models, creating a full replica of the original observation record without transmitting all original data
2Measurement precision
If more satellites are included in the constellation to improve positioning accuracy, then positioning precision increases, but data transmission bandwidth requirements increase
Solution Approach 1:
The patent changes the parameter representation by encoding satellite identifiers using differential encoding where only changes in satellite PRN numbers are transmitted, and by representing observation data as ambiguities relative to a reference epoch rather than absolute values, significantly reducing the data volume per satellite
3Speed
If real-time data transmission is implemented to enable dynamic positioning, then positioning speed is improved, but bandwidth requirements exceed available capacity
Solution Approach 1:
The patent implements periodic transmission of ambiguous observation data at standardized epochs (e.g., every second) rather than continuous transmission, allowing the system to maintain real-time positioning capability while utilizing bandwidth efficiently through regular, predictable data bursts
Solution Approach 2:
The receiver performs preliminary processing by combining transmitted ambiguous data with pre-stored satellite almanac information and atmospheric models before final position calculation, enabling real-time positioning with minimal additional data transmission
Data Source
AI summary
A method of communicating corrections for information related to satellite signals among global navigation satellite system (GNSS) receivers is described. An ionosphere correction for ionosphere signal path delay is determined for a first satellite. This ionosphere correction is then compared to an ionosphere correction for ionosphere signal path delay for a satellite assumed to be directly over the receiver. The receiver then sends a message which includes only the difference between the ionosphere correction for the actual observation and the ionosphere correction for a satellite assumed to be at the zenith.