Passive Keyless Entry Using RSSI and Motion Sensing
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Solution Overview
Problem
Existing vehicle security and convenience systems lack improved techniques for automatic activation and deactivation of features like locking, unlocking, and alarm control, with issues related to reliability and power consumption.
Innovation Solution
A method using a mobile device's RF transceiver and movement sensors to estimate distances with vehicle-installed beacons, triggering automatic actions based on predefined conditions, such as arrival and departure, to control vehicle access and security features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous monitoring and communication is used to improve automatic vehicle access reliability, then the reliability of automatic activation and deactivation is improved, but power consumption increases
Solution Approach 1:
The system uses periodic beacon transmissions from the vehicle and periodic distance estimation updates based on RF signal strength measurements. Instead of continuous monitoring, the mobile device estimates distance at intervals by measuring RF signal strength from periodic beacons, reducing power consumption while maintaining reliable detection of arrival and departure events
Solution Approach 2:
The mobile device uses its existing RF transceiver and movement sensors to perform distance estimation and trigger notifications autonomously. The system leverages already-present hardware components (RF transceiver, accelerometers, gyroscopes) to self-determine proximity status without requiring additional dedicated sensors or continuous high-power communication protocols
2Measurement precision
If multiple sensors and processing steps are used to improve distance estimation accuracy, then the measurement precision of distance is improved, but device complexity increases
Solution Approach 1:
The system combines RF signal strength measurements with movement sensor data (accelerometers and gyroscopes) to estimate distance and detect arrival/departure events. By merging data from existing hardware components already present in the mobile device, the system achieves improved measurement precision without adding external devices or significantly increasing system complexity
Solution Approach 2:
The RF transceiver serves multiple functions: it communicates with vehicle beacons for distance estimation and also detects movement through signal strength changes. The movement sensors originally designed for other purposes are repurposed to detect arrival and departure events, demonstrating multi-functionality that improves precision without proportionally increasing complexity
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
Enhances the reliability of automatic vehicle access and security feature operations while reducing power consumption by optimizing communication and response to user proximity.
Implementation Method 1
obtaining received signal strength indications (RSSIs) of a first beacon transmissions by a processor of a mobile device through a relatively-short range radio frequency (RF) transceiver of the mobile device; estimating by the processor distances between the mobile device and the first beacon corresponding to the RSSI-derived first values
Data Source
AI summary
In selected examples, a vehicle control system (VCS) includes Bluetooth beacons and an app running on a mobile device, such as a smartphone or a key fob equipped with movement sensors and a Bluetooth® transceiver. Passive keyless entry capability of the system uses received signal strength indications (RSSIs) together with movement-related indications of the movement sensors to determine when the mobile device moves away from the vehicle beyond a predetermined departure distance, and/or approaches the vehicle to within a predetermined arrival distance. When the user approaches the vehicle, the mobile device automatically transmits an arrival notification to the VCS, which automatically performs arrival actions, e.g., unlocking doors and disarming security features of the VCS/vehicle. When the user moves away from the vehicle, the mobile device automatically transmits a departures notification to the VCS, which performs departure actions, e.g., locking the vehicle and arming the security features of the VCS/vehicle.