Ultrasonic Locationing in Non-Line-of-Sight Environments
Solution Overview
Problem
Ultrasonic locationing systems face challenges in indoor environments due to non-line-of-sight issues, multipath impairments, and interference, leading to inaccurate locationing and poor position update rates, especially when multiple devices interact with emitters simultaneously.
Innovation Solution
The system employs a method using a three-dimensional model of the environment to predict non-line-of-sight conditions, adjusts locationing system parameters by ignoring or weighting signals from obstructed emitters, and modifies transmit power or detection thresholds to ensure accurate locationing, switching between flight time and signal strength measurement modes as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic emitters transmit signals to locate mobile devices, then locationing capability is provided, but multipath impairments and non-line-of-sight issues degrade locationing accuracy
Solution Approach 1:
The system performs preliminary actions by predicting non-line-of-sight conditions before they affect locationing accuracy. The three-dimensional environment model is used to anticipate obstructed signal paths and preemptively adjust locationing parameters or ignore signals from emitters that will be blocked, preventing accuracy degradation before it occurs.
Solution Approach 2:
A three-dimensional model of the environment serves as an intermediary between the ultrasonic emitters and the locationing calculation. This model mediates the interaction by providing predictive information about signal propagation paths, allowing the system to compensate for non-line-of-sight conditions without requiring direct measurement of the obstructed paths.
2Area of stationary object
If multiple mobile communication devices simultaneously interact with all emitters to establish position, then locationing coverage is expanded, but signal interference increases and position update rate decreases
Solution Approach 1:
The system performs preliminary signal strength threshold adjustments based on predicted non-line-of-sight conditions. By pre-adjusting thresholds before signal transmission, the system prevents interference between multiple devices from degrading position update rates, while still maintaining comprehensive locationing coverage across the environment.
Solution Approach 2:
The locationing system dynamically adjusts parameters such as signal strength thresholds and emitter selection based on real-time conditions and device positions. This dynamic adaptation allows multiple devices to simultaneously utilize the emitter network without causing mutual interference that would reduce position update rates.
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 enhances locationing accuracy and update rates by preemptively addressing non-line-of-sight conditions, reducing errors from reflected and attenuated signals, and optimizing system performance in environments with obstacles.
Implementation Method 1
Fixed ultrasonic emitter(s) can transmit ultrasonic energy in a short burst which can be received by an ultrasonic transducer (audio microphone) in the ultrasonic receiver
Implementation Method 2
reflected signals may reach the mobile communication device better than a direct signal from the emitter
Implementation Method 3
measuring time-of-flight, time difference of arrival, or signal strength of the emitter signals
Data Source
AI summary
An apparatus and method for improved locationing system performance in non-line of sight conditions of a mobile device within an environment includes providing a model of the environment that maps transmitters within and objects that obstruct signals from the transmitters, including mapped areas where the signal from a nearby transmitter is obstructed. A location of a device moving within the environment is tracked using the signals. When it is determined that the device is moving into a mapped area having an obstructed signal from a nearby transmitter, a locationing system parameter is modified for that obstructed signal so that the mobile communication device can be located using at least the modified signal parameter.