Vehicle Authentication Distance Estimation Under BLE Multipath
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Solution Overview
Problem
Current detection systems for motor vehicles, which use Bluetooth Low Energy (BLE) signals to estimate the distance between a vehicle and an authentication device, face significant errors due to signal multipath effects and the inability to accurately determine distance, particularly when the signal splits into direct and reflected components, leading to inaccuracies in activating vehicle functions.
Innovation Solution
A method that involves transmitting a request signal, adding noise to the response signal, and sampling when the noisy signal exceeds a threshold, allowing for more precise time calculation and distance estimation, which is then refined through multiple iterations to reduce errors to less than 50 centimeters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the vehicle uses BLE signals to determine distance by measuring RSSI, then the distance estimation can be obtained, but the measurement precision deteriorates due to multipath signal effects
Solution Approach 1:
The patent extracts only the direct line signal from the combined multipath signal by analyzing signal characteristics. The communication module identifies and processes only the direct signal component, excluding reflected signals, to obtain accurate distance measurements without the distortion caused by multipath effects.
Solution Approach 2:
The patent introduces an intermediary processing step that analyzes signal characteristics (such as signal strength variations and arrival times) to distinguish between direct and reflected signals. This intermediary analysis mechanism enables the system to separate the direct signal from the multipath components before distance calculation.
2Measurement precision
If the vehicle increases the sampling frequency to reduce distance estimation error, then the measurement precision improves, but the use of energy increases
Solution Approach 1:
The patent changes the parameter being measured from signal power (RSSI) to signal arrival time characteristics. By measuring the time of flight or time difference of arrival of the direct signal, the system achieves accurate distance estimation without requiring high sampling frequencies, thereby reducing energy consumption while maintaining precision.
3Reliability
If the vehicle uses LF/RF communication to determine distance, then the reliability of signal propagation is improved, but the device complexity increases due to additional communication interfaces
Solution Approach 1:
The patent makes the BLE communication interface multi-functional by using it not only for data communication but also for distance measurement through direct signal extraction. This eliminates the need for separate LF/RF communication hardware, reducing device complexity while maintaining measurement reliability through the extracted direct signal method.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method significantly reduces the error in distance estimation, improving the accuracy of activating vehicle functions by ensuring that the authentication device is within the predetermined distance, enhancing the reliability of the detection system.
Implementation Method 1
detection, at a second instant, of the noisy response signal when the amplitude of said noisy response signal exceeds a predetermined detection threshold
Implementation Method 2
calculation of the time that has elapsed between the first instant and the second instant... estimation of the distance between the vehicle and the device based on the calculated time
Data Source
AI summary
A method for estimating the distance between a vehicle and an authentication device, the vehicle including a computer and a plurality of communication modules capable of communicating with the device over a wireless communication link, each communication module including an electronic clock that defines the sampling frequency of the signals received from the device. The method includes in particular the steps of addition of noise to a response signal received from the device, of sampling of the noisy response signal, of detection, at a second instant, of the noisy response signal when the amplitude of the noisy response signal exceeds a predetermined detection threshold, of calculation of the time that has elapsed between a first instant and the second instant, and of estimation of the distance between the vehicle and the device based on the calculated time.