Vehicle Location Device Using Acceleration-RSSI Ratio for Distance Estimation
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Solution Overview
Problem
Existing methods for determining the position of a portable user device around a vehicle are inaccurate due to the human body's effect on antenna performance and variability in RSSI measurement across different smartphones, leading to incorrect distance estimation and inappropriate vehicle actions.
Innovation Solution
A method that measures and calculates the ratio of signal strength variation to acceleration variation, allowing for precise distance determination between the portable device and the vehicle, regardless of the device type, by using a location device on board the vehicle that communicates with the portable device via radio waves and incorporates acceleration measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RSSI measurement is used to estimate distance, then distance estimation is achieved, but measurement precision deteriorates due to human body interference and smartphone variability
Solution Approach 1:
The patent introduces acceleration as an intermediary parameter to mediate between RSSI measurements and distance estimation. By combining RSSI data with acceleration data from the smartphone's accelerometer, the system creates a more reliable distance estimation that compensates for RSSI variations caused by human body interference and device variability. The acceleration data serves as a mediator that helps distinguish between distance changes and orientation changes.
Solution Approach 2:
The patent changes the measurement parameters from relying solely on RSSI to using a combination of RSSI and acceleration parameters. By monitoring changes in acceleration over time and correlating them with RSSI variations, the system transforms the distance estimation process into a multi-parameter analysis that is more robust against single-parameter variability and environmental interference.
2Ease of operation
If antenna orientation is random during approach, then ease of operation is improved, but power loss increases due to body tissue absorption
Solution Approach 1:
The patent implements feedback by continuously monitoring acceleration data to detect the orientation and movement pattern of the smartphone during approach. This feedback information is used to interpret RSSI measurements more accurately, allowing the system to compensate for power loss due to body tissue absorption without requiring the user to manually adjust antenna orientation. The feedback loop enables the system to adapt to random orientations while maintaining accurate distance estimation.
3Adaptability or versatility
If different smartphone types are used, then adaptability is improved, but measurement precision deteriorates due to varying RSSI measurement characteristics
Solution Approach 1:
The patent achieves universality by designing a distance estimation method that works across different smartphone types. Instead of relying on smartphone-specific RSSI calibration, the system uses acceleration data as a universal reference that is consistently available across all smartphones with accelerometers. This multi-functional approach allows the same algorithm to accurately estimate distance regardless of the specific smartphone model being used.
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 enables accurate detection of the portable device's position, reducing errors caused by human body interference and smartphone variability, ensuring appropriate vehicle actions based on precise distance calculations.
Implementation Method 1
a location device placed on board said vehicle and communicating with the portable device by radio waves
Implementation Method 2
it measures the power of the signal, which in a known way is referred to as the RSSI (Received Signal Strength Indication)
Implementation Method 3
with second means for acceleration measurement
Data Source
AI summary
Disclosed is a method of determining the position of a portable user device around a vehicle by a location device placed on board the vehicle and communicating with the portable device by radio waves, including the execution of the following steps whenever the portable device receives a signal from the location device: step E3: Measuring and storing a value of strength of the signal) thus received; step E4: Measuring and storing a value of acceleration) of the portable device; step E5: Calculating a ratio between a variation of the strength value thus measured, relative to a strength value stored at a preceding instant-RSSI, and a variation of the acceleration value thus measured, relative to an acceleration value stored at the preceding instant-AC; step E6: Comparing the ratio thus calculated with at least one predetermined threshold, in order to determine a distance between the portable device and the vehicle.