Reference-Point Ionospheric Messaging for NSS Scintillation Mitigation
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Solution Overview
Problem
Existing navigation satellite systems (NSS) face limitations in positioning accuracy due to ionospheric disturbances, which degrade signal quality and compromise the precision of positioning solutions, particularly in regions with high ionospheric scintillation and gradient changes.
Innovation Solution
A method to generate and transmit ionospheric disturbance information, including link-specific ionospheric disturbance levels, to NSS receivers and processing entities, allowing them to adapt noise models, switch to ionosphere-free observations, or selectively use observables to mitigate the effects of ionospheric disturbances on positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier phase measurements are used to achieve high positioning precision, then positioning accuracy is improved, but the system becomes vulnerable to ionospheric disturbances that degrade signal quality
Solution Approach 1:
The system computes ionospheric disturbance levels for multiple satellite-station links and uses this feedback information to adaptively adjust the noise models of navigation estimators. This feedback mechanism allows the system to respond to ionospheric conditions in real-time, maintaining reliability while preserving positioning accuracy by dynamically adjusting estimator parameters based on measured disturbance levels.
Solution Approach 2:
The system changes the parameters of the noise models in navigation estimators based on computed ionospheric disturbance levels. When disturbance levels exceed thresholds, the system modifies estimator parameters such as noise standard deviations, switches between different observable types (code vs. carrier phase), or adjusts the weighting of different satellite links, thereby adapting to degraded signal conditions while maintaining optimal positioning performance.
2Reliability
If ionospheric disturbance information is provided to all NSS receivers, then positioning reliability is improved, but the quantity of transmitted information increases
Solution Approach 1:
The system computes ionospheric disturbance levels for multiple specific satellite-station links rather than providing a single global ionospheric parameter. This local quality approach allows different receivers to receive disturbance information tailored to their specific geometric relationship with satellites, providing locally optimized reliability information without transmitting excessive data. Each receiver uses the link-specific disturbance levels corresponding to its visible satellites.
3Measurement precision
If noise models are adapted based on ionospheric disturbance levels, then positioning precision is improved, but the complexity of the processing entity increases
Solution Approach 1:
The system performs preliminary computation of ionospheric disturbance levels for multiple satellite-station links before the actual positioning estimation process. By pre-computing these disturbance levels and making them available to receivers, the complexity of real-time processing is reduced. The receiver can then use these pre-computed values to adaptively adjust its noise models without performing complex ionospheric calculations during the positioning epoch, thereby maintaining precision while managing processing complexity.
Data Source
AI summary
Some embodiments pertain to generating, transmitting, and using ionospheric disturbance information applicable to at least a part of the Earth's surface. The ionospheric disturbance information is transmitted in the form of at least one message comprising reference point ionospheric disturbance levels, i.e. levels associated with a plurality of reference points on a reference ionospheric shell. On the receiver side, an estimator is operated, and, for each of at least one NSS signal observed by a NSS receiver, the reference point ionospheric disturbance levels are used to decide whether to adopt some ionospheric disturbance mitigation measures in the context of estimating parameters useful to determine a position. The ionospheric disturbance information may for example comprise ionospheric amplitude scintillation information, ionospheric phase scintillation information, and/or ionospheric gradient information. Systems, vehicles, and computer programs are also disclosed.