IMU Sensor Initialization for Fast GNSS-Outage Dead Reckoning
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Solution Overview
Problem
Existing wireless communication systems face challenges in improving latency and accuracy of user equipment (UE) positioning during Global Navigation Satellite System (GNSS) signal outages by reducing sensor initialization time for inertial measurement unit (IMU) sensors.
Innovation Solution
A UE initiates a first positioning engine based on GNSS availability, measures a relative position without ambiguity, calibrates IMU sensors, and performs positioning calculations via the IMU sensor during GNSS unavailability, utilizing a fusion engine that receives positioning output from a relative positioning engine instead of a Real-Time Kinematics (RTK) engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RTK engine is used for positioning during GNSS outages, then positioning accuracy can be maintained, but sensor initialization time increases and latency worsens
Solution Approach 1:
The system performs IMU sensor calibration during GNSS availability using relative positioning data beforehand, so that when GNSS signals are lost, the pre-calibrated IMU can immediately take over for positioning without requiring time-consuming re-initialization or RTK convergence
Solution Approach 2:
The patent introduces a fusion engine that receives positioning output from a relative positioning engine instead of directly using RTK engine output. This intermediary fusion engine combines multiple positioning sources and can seamlessly transition between GNSS-based relative positioning and IMU-based dead reckoning, avoiding the long initialization period of RTK while maintaining positioning accuracy
2Measurement precision
If RTK engine is used for positioning during GNSS outages, then positioning accuracy can be maintained, but system latency increases
Solution Approach 1:
The system pre-calibrates IMU sensors during GNSS availability periods, preparing the inertial measurement system in advance so that when GNSS signals are lost, the IMU can immediately provide positioning updates without the 30+ second convergence time required by RTK engines, thus maintaining fast response speed while ensuring accuracy
Solution Approach 2:
The fusion engine acts as an intermediary that can quickly switch between positioning modes. It receives data from both the relative positioning engine (during GNSS availability) and IMU sensors, fusing them to provide continuous low-latency positioning output without waiting for RTK convergence, thereby maintaining fast positioning response speed
3Duration of action of stationary object
If IMU sensor calibration is performed during GNSS outages, then positioning can continue, but estimation accuracy deteriorates due to uninitialized sensors
Solution Approach 1:
The system performs IMU calibration during GNSS availability using accurate relative positioning data from the positioning engine. This pre-calibration ensures that when GNSS signals are lost, the IMU sensors are already initialized and calibrated, maintaining both positioning continuity and high estimation accuracy during the outage period
Solution Approach 2:
The system uses feedback from the relative positioning engine during GNSS availability to continuously calibrate and update IMU sensor parameters. This feedback loop ensures the IMU remains accurately calibrated before outages occur, so that when switching to dead reckoning during GNSS outages, the estimation accuracy is maintained rather than deteriorating
Data Source
AI summary
Aspects presented herein may enable a UE to reduce sensor initialization time for one or more sensors that are to be used for DR positioning during a GNSS signal outage. In one aspect, a UE initiates a first positioning engine based on an availability of a GNSS signal, where the first positioning engine measures a relative position of the UE without ambiguity processing. The UE calibrates at least one IMU sensor based on the relative position of the UE measured by the first positioning engine. The UE performs a positioning calculation of the UE via the at least one IMU sensor in response to the GNSS signal being unavailable.