Vehicle Control System Using LF and RF Signal Comparison
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Solution Overview
Problem
Existing vehicle control systems face challenges in accurately determining the distance between a portable device and a vehicle based on RF signal field intensity, leading to potential unsafe operations and vulnerability to relay attacks, as RF signals are influenced by environmental factors and cannot reliably distinguish between direct and reflected waves.
Innovation Solution
A vehicle control system that uses bidirectional communication between a vehicle and a portable device, employing LF-band and RF-band radio waves to transmit and receive signals, where the vehicle transmits an LF signal and the portable device responds with an RF signal, allowing the electronic control unit to determine if the portable device is within a predetermined area by comparing signal intensities, thereby preventing unsafe operations and relay attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the field intensity of RF signal is used to determine distance between portable device and vehicle, then the operation can be simplified, but the measurement precision deteriorates due to environmental influence and inability to distinguish direct and reflected waves
Solution Approach 1:
The patent segments the signal transmission path analysis into two parts: using LF signal for area determination (binary inside/outside vehicle vicinity) and RF signal field intensity for distance determination. This segmentation allows each signal type to be used for what it is best suited for, maintaining measurement precision while keeping operations simple.
Solution Approach 2:
The patent introduces LF-band radio wave as an intermediary to establish a baseline for area determination. By first confirming the portable device is within the vehicle's vicinity area using LF signal, then measuring RF field intensity, the system creates a two-stage verification process that improves overall measurement reliability.
2Ease of operation
If the vehicle operates in-vehicle devices based on RF signal reception, then the ease of operation is improved, but the reliability deteriorates due to vulnerability to relay attacks and environmental interference
Solution Approach 1:
The patent performs preliminary area verification using LF signal before allowing RF-based device operations. By first confirming the portable device is within the predetermined area around the vehicle, the system prevents relay attacks where a portable device far from the vehicle could otherwise trigger operations through signal relaying.
Solution Approach 2:
The patent implements feedback by continuously monitoring both LF signal presence and RF field intensity, and using this information to dynamically control whether in-vehicle devices can be operated. The electronic control unit adjusts operation permission based on the combined feedback from both signal measurements.
3Device complexity
If only absolute field intensity value is used for distance determination, then the device complexity is reduced, but the measurement precision deteriorates due to environmental factors like reflective objects
Solution Approach 1:
The patent changes the parameter basis from absolute field intensity to relative field intensity comparison. By comparing the field intensity of the third signal (received when portable device transmits after receiving LF signal) with the field intensity of the second signal (received when portable device transmits in response to LF signal), the system eliminates the need for complex environmental calibration while improving precision.
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 system effectively determines the position of the portable device with high accuracy, preventing unauthorized vehicle operations and reducing the risk of relay attacks, thereby enhancing safety and security.
Implementation Method 1
a first transmitter configured to transmit a predetermined first signal over a predetermined area outside a vehicle cabin through an LF-band radio wave
Implementation Method 2
a first receiver configured to receive a signal transmitted from the portable device through an RF-band radio wave
Implementation Method 3
A detector is configured to detect a field intensity of the signal received by the first receiver
Data Source
AI summary
A vehicle control system includes a first transmitter that transmits a predetermined first signal over a predetermined area, a first receiver and a second receiver that receive second and third signals, a detector that detects the field intensities of the received signals, a second transmitter that transmits a signal through an RF-band radio wave, and an electronic control unit that operates an in-vehicle device based on the third signal received by the first receiver and restrains or prohibits the in-vehicle device from being operated based on the third signal when the field intensity of the third signal is lower than the field intensity of the second signal by a value greater than a predetermined standard.