GNSS Receiver Ionospheric Error Correction via IFLC Filtering

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Solution Overview

Problem

Current GNSS receivers face challenges in accurately correcting ionospheric errors in pseudo-range measurements, particularly during unpredictable solar activity, as existing methods either introduce noise or fail to provide location-specific and real-time corrections.

Innovation Solution

The method involves performing an Ionosphere Free Linear Combination (IFLC) on pseudo-range measurements from multiple satellite signals, followed by noise-removing filtering using a low pass filter with a constant calculated based on signal strength, to eliminate ionospheric errors and improve position, velocity, and time accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dual frequency GNSS receivers use Iono-Free Linear Combination to cancel ionospheric error, then ionospheric error compensation is improved, but measurement noise increases

Engineering Contradiction:

Improveionospheric error compensationVSAvoidmeasurement noise

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent segments the ionospheric error correction process into two independent parts: (1) using IFLC to eliminate ionospheric errors from pseudo-ranges, and (2) using separate ionospheric delay measurements from ionospheric receivers to provide correction values. This segmentation allows the system to benefit from both approaches without the noise amplification problem of traditional IFLC alone.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces ionospheric receivers as intermediary devices that measure ionospheric delays independently. These receivers act as mediators between the GNSS satellites and the user equipment, providing correction information that can be applied to GNSS measurements without the noise issues of direct dual-frequency combination.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If Klobuchar/Nequick models are used for ionospheric correction, then global coverage is improved, but location-specific accuracy deteriorates

Engineering Contradiction:

Improveglobal coverageVSAvoidlocation-specific accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies local quality by using ionospheric receivers deployed in specific geographic locations to provide ionospheric delay measurements tailored to local conditions. Each ionospheric receiver provides corrections optimized for its local environment, allowing the system to maintain global coverage through multiple receivers while achieving high location-specific accuracy through locally-measured corrections.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If SBAS systems are used for ionospheric correction, then location-specific compensation is improved, but real-time response capability deteriorates

Engineering Contradiction:

Improvelocation-specific compensationVSAvoidcorrection update time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by having ionospheric receivers continuously measure and report ionospheric delays in real-time. These pre-measured values are then immediately available for application to GNSS corrections, eliminating the delay inherent in SBAS systems that must process and broadcast corrections periodically.

Inventive Principle:

Principle #10Preliminary action

4Device complexity

If traditional ionospheric correction methods are used, then computational simplicity is improved, but correction effectiveness during solar storms deteriorates

Engineering Contradiction:

Improvecomputational simplicityVSAvoidcorrection effectiveness during solar storms

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies feedback by using ionospheric receivers to continuously monitor actual ionospheric conditions and provide real-time correction values. This feedback mechanism allows the system to adapt dynamically to changing ionospheric conditions, including solar storms, maintaining correction effectiveness without complex computational models.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20240329259A1Method for performing a correction of an ionospheric error affecting pseudo-ranges measurements in a GNSS receiver, corresponding receiver apparatus and computer program product

Publication Date: 2024.10.03 STMICROELECTRONICS INT NV

AI summary

A method performs a correction of an ionospheric error affecting pseudo-ranges measurements in a GNSS receiver receiving a plurality of satellite signals from a plurality of satellites of a constellation of satellites. The method is part of a navigation processing procedure performed at the GNSS receiver. The method utilizes pseudo range measurements previously calculated by the GNSS receiver, obtained from a plurality of carrier signals in the satellite signals. The method includes performing a correction procedure of the pseudo-range measurements, by calculating ionospheric error correction values for the pseudo-range measurements.