UWB ToF Passive Entry Signal Quality Retry Strategy

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Solution Overview

Problem

Traditional passive entry systems using RF and LF wireless signals are vulnerable to security attacks due to their reliance on signal strength, which can lead to unauthorized access when the portable device is in close proximity to the vehicle.

Innovation Solution

Implementing ultra-wide band (UWB) time of flight (ToF) distance measurements with a communication retry strategy adjusted based on signal quality calculations, where satellites with higher signal quality are selected for ToF distance measurements, and correction factors are applied to improve accuracy and reduce latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional RF and LF wireless signal strength methods are used to detect fob location, then the system is easier to implement, but the system becomes vulnerable to security attacks and unauthorized access

Engineering Contradiction:

Improvesecurity reliabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces traditional RF/LF signal strength-based location detection with UWB time-of-flight measurement technology. This substitution uses precise timing measurements of signal propagation time rather than signal strength, fundamentally changing the detection mechanism to achieve higher security reliability while resisting relay and amplification attacks.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from signal strength (amplitude-based) to time of flight (time-based). By measuring the propagation time of UWB signals between fob and vehicle, the system achieves more accurate and secure location detection that cannot be easily spoofed by signal amplification or relay attacks.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If communication retry strategies are used to improve ToF measurement reliability, then measurement accuracy improves, but total latency increases and battery consumption increases

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidtotal latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary signal quality assessment before conducting ToF measurements. By evaluating signal conditions in advance and selecting optimal satellites based on this assessment, the system prepares the best measurement paths beforehand, reducing the need for multiple retries and thereby lowering total latency while maintaining high reliability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where signal quality metrics from initial assessments are used to dynamically adjust the communication retry strategy. Satellites with poor signal quality are excluded from measurement attempts, while high-quality satellites are prioritized, creating a feedback loop that optimizes measurement reliability without unnecessary retries.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If multiple satellites are used for ToF measurements to improve accuracy, then location accuracy improves, but processing complexity and time increase

Engineering Contradiction:

Improvelocation accuracyVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality assessment to each satellite's signal independently, evaluating signal strength, noise level, and propagation conditions for each satellite-fob pair. Based on this localized assessment, the system selectively uses only those satellites with high signal quality for ToF measurements, rather than uniformly processing all satellites, thereby reducing processing complexity while maintaining accuracy.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses a partial action approach by selecting only the subset of satellites with the best signal quality for ToF measurements, rather than using all available satellites. This selective approach achieves sufficient location accuracy with fewer processing operations, reducing computational complexity and time while maintaining measurement precision.

Inventive Principle:

Principle #16Partial or excessive action

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 accuracy and reliability of UWB ToF distance measurements in non-ideal environments, reducing battery consumption and minimizing the need for retries, thereby improving the overall performance and security of the passive entry system.

Implementation Method 1

time of flight (ToF) distance measurements

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS9924318B2Passive entry systems employing time of flight distance measurements

Publication Date: 2018.03.20 LEAR CORP

AI summary

Systems and methods employ ultra-wide band (UWB) time of flight (ToF) distance measurements for locating a portable device relative to a target. Performance and reliability of UWB ToF distance measurements for locating the portable device is improved by adjusting a communication retry strategy based on signal quality calculations. The quality of an UWB signal received by each satellite of a base station is assessed based on factors like signal strength, noise level, and ratio of first path signal power to total signal power. This data is used to direct the retry strategy to the satellites receiving the best signal quality for these satellites to conduct ToF distance measurements with the portable device and/or to add correction factors to calculated ToF distance measurements.