GNSS Measurement Record Compression for Bandwidth-Limited Positioning
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Solution Overview
Problem
The increasing demand for bandwidth in communication systems for global navigation satellite systems (GNSS) poses a challenge as existing techniques, such as the Compact Measurement Record (CMR), require more bandwidth with the addition of satellites, which may not be available, especially in cost-sensitive or bandwidth-constrained environments.
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, allowing for efficient reconstruction of original data at the recipient, and 'trickling' extraneous information to optimize bandwidth usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Compact Measurement Record (CMR) format is used to transmit GPS data, then data transmission can be achieved, but the bandwidth requirement increases as more satellites are included in the constellation
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 full satellite ephemeris, complete signal structure details, and other data that can be reconstructed or obtained through other means. This selective extraction of critical data elements reduces the transmission payload while maintaining the core functionality of RTK positioning.
Solution Approach 2:
The patent assumes that both the reference station and rover have pre-loaded knowledge of the GPS signal structure, constellation geometry, and satellite orbits. This preliminary preparation allows the transmitting station to send highly compressed ambiguous data without needing to include comprehensive satellite information, as the receiving station can reconstruct the complete observation data using its pre-existing knowledge base.
2Measurement precision
If complete GPS observation data is transmitted to ensure accurate reconstruction at the recipient, then data accuracy is maintained, but the amount of data to be transmitted increases
Solution Approach 1:
Instead of transmitting complete original observation data, the patent transmits a compressed representation (ambiguous observation data) that serves as a sufficient copy for reconstruction. The receiving station uses this compressed data along with its pre-loaded signal structure knowledge to recreate the complete observation data, achieving the same positioning accuracy without transmitting the full original data set.
Solution Approach 2:
The patent changes the representation parameters of the GPS data from full-precision complete observations to ambiguous measurements with reduced information content. By transmitting code phase and carrier phase measurements in an ambiguous format rather than complete signal structures, the data volume is significantly reduced while the essential positioning information is preserved through the mathematical relationships inherent in the ambiguous data.
3Measurement precision
If more satellites are included in the GPS constellation to improve positioning accuracy, then measurement precision increases, but the bandwidth required for data transmission increases
Solution Approach 1:
The patent extracts only the essential ambiguous observation data for each satellite (code phase and carrier phase measurements) while eliminating redundant information. This approach allows the system to support an expanded satellite constellation with increased positioning accuracy while maintaining efficient bandwidth utilization, as the compressed data format scales linearly with the number of satellites rather than exponentially.
Data Source
AI summary
A format for providing messages among GNSS apparatus includes providing a message identification block and a message body. The message identification block includes information specifying a message length and a message type block specifying a message type. Rather than sending all data from one apparatus to another, ambiguous observation data is sent to conserve bandwidth. At the sender a deconstruction of GNSS code and carrier observations using knowledge of the signal structure and constellation geometry, together with simplifications of atmospheric models, allows removal from the observation data of that information which can be implicitly understood or recreated by the recipient. This enables only the necessary information to be packed for transmission to the recipient.