Vehicle Authentication Distance Sensing Using I/Q Signal Power
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Solution Overview
Problem
Current methods for determining the distance between a smartphone and a vehicle using Bluetooth Low Energy signals are unreliable due to signal bouncing off surrounding objects, leading to inaccurate distance calculations.
Innovation Solution
A method that computes the power of the received signal using both in-phase and quadrature components of a modulated reference signal, allowing for precise and quick distance determination by reducing signal disruptions through the use of consecutive 0s or 1s in the data frame, and employing a specific formula PdBm=10*log(10*(IM^2+QM^2) to calculate the signal power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional RSSI measurement is used to determine distance, then the method is simple to implement, but the measurement precision deteriorates due to signal bouncing off surrounding objects
Solution Approach 1:
The patent changes the measurement parameters from traditional RSSI to a composite metric incorporating signal strength, phase information, and temporal characteristics. This parameter transformation enables more accurate distance determination by capturing multiple aspects of signal propagation rather than relying on a single noisy measurement
Solution Approach 2:
The patent introduces an intermediary processing layer that analyzes signal characteristics through multiple parameters (strength, phase, temporal patterns) before determining distance. This intermediary approach filters out noise from signal bouncing by considering the combined information from multiple measurement dimensions
2Measurement precision
If RSSI measurement duration is extended to 10 seconds to improve reliability, then measurement precision improves, but the loss of time increases significantly
Solution Approach 1:
The patent employs periodic signal exchanges between vehicle and smartphone, analyzing multiple periodic signal cycles within a short time window. This periodic measurement approach captures sufficient statistical information for reliable distance determination without requiring extended measurement durations
Solution Approach 2:
The patent performs preliminary analysis of signal characteristics (phase relationships, temporal patterns) that enable accurate distance determination in advance, reducing the need for prolonged measurement averaging
3Ease of operation
If the user is continuously moving while approaching the vehicle, then the ease of operation improves, but the measurement precision deteriorates because the distance determined at the end of measurement duration does not reflect the actual distance
Solution Approach 1:
The patent dynamically tracks distance throughout the measurement period and identifies the distance at the moment of authentication confirmation rather than averaging over the entire duration. This dynamic approach captures the relevant distance metric even when the user is in motion
Solution Approach 2:
The patent uses feedback from the authentication process itself to determine the effective measurement endpoint. The distance is determined based on when authentication succeeds, providing feedback-driven timing that correlates measurement results with actual operational moments
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 approach provides a reliable and efficient means to determine the distance between the authentication device and the vehicle, improving accuracy and speed compared to traditional RSSI measurements.
Implementation Method 1
modulated by the transmitter by changing the phase of a reference signal comprising a component, called 'in-phase' component, characterized by a maximum amplitude value, and a second component, called 'quadrature' component, phase-shifted by 90° in relation to the in-phase component
Data Source
AI summary
A method for determining the distance between an authentication device carried by a user and a motor vehicle, each including a wireless communication module so as to exchange a data frame, the data frame being modulated by changing the phase of a reference signal. The method includes the following steps of: the vehicle receiving a modulated reference signal, sent by the device, demodulating the received signal in order to extract an in-phase component and a quadrature component therefrom, computing the power value of the signal on the basis of the maximum amplitude value of the in-phase component and of the maximum amplitude value of the quadrature component, and determining the distance between the device and the vehicle on the basis of the computed power value.