NSS Positioning Estimation Using Skewed Multipath Error Models
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Solution Overview
Problem
Existing navigation satellite systems (NSS) face challenges in providing accurate positioning due to multipath errors, which cause positive bias and increased noise in code measurements, particularly in urban and suburban environments.
Innovation Solution
A method that determines a positively skewed distribution based on multipath-related information to estimate NSS code observations, using a skewed weighting function to deweight positive errors, thereby improving positioning accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard NSS code observations are used for positioning, then positioning can be obtained, but multipath errors cause positive bias and increased noise reducing accuracy
Solution Approach 1:
The patent applies asymmetry by using a positively skewed distribution instead of a symmetric distribution to model code observation errors. This asymmetric distribution better represents the actual error characteristics where positive errors (multipath) are more prevalent and have different statistical properties than negative errors, allowing the estimator to more accurately weight and process observations in the presence of multipath
Solution Approach 2:
The patent changes the statistical parameters used in the estimation process by determining a positively skewed distribution based on multipath-related information. This parameter change allows the system to adapt the error distribution model to match actual operating conditions, improving the robustness of positioning in environments with significant multipath effects
2Measurement precision
If symmetric error distribution is assumed in estimation, then standard processing is simpler, but asymmetric multipath errors are not properly accounted for reducing accuracy
Solution Approach 1:
The patent introduces asymmetry into the estimation process by using a positively skewed distribution that captures the asymmetric nature of multipath errors. This allows the system to properly account for the different statistical characteristics of positive and negative errors, improving positioning accuracy despite the increased complexity of the estimation process
3Measurement precision
If multipath mitigation is not applied, then processing is simpler and faster, but positioning accuracy deteriorates in urban and suburban environments
Solution Approach 1:
The patent changes the statistical parameters of the error distribution model to a positively skewed distribution that incorporates multipath characteristics. This parameter change enables the system to maintain processing efficiency while improving accuracy, as the skewed distribution provides a more realistic error model that can be efficiently processed by standard estimation algorithms
Data Source
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AI summary
Some embodiments pertain to methods carried out by a navigation satellite system (NSS) receiver for estimating parameters useful to determine a position. The receiver observes NSS signals from NSS satellites. Multipath-related information indicative of an expected or estimated level of multipath where the NSS receiver antenna(s) is located is obtained. A positively skewed distribution is then determined based on the multipath-related information. Further, an estimation process, referred to as "estimator", is operated, wherein the estimator uses state variables, computes the values of its state variables based on NSS code observations by the NSS receiver, and operates under an assumption that errors in the NSS code observations follow the determined skewed distribution. Systems, vehicles, and computer programs are also disclosed.