Ultrasonic Device-Free Localisation System Modelling for Performance Analysis

Indoor Device-Free Localisation (DFL) systems are receiving increasing attention to replace traditional active ones in some applications, such as those that support independent living for vulnerable people who are not able to carry sensors. These systems analyse the influence in the channel transmission response of certain emitted signals when interacting with the human body in order to locate it. Whereas the most widespread DFL systems make use of radio-frequency signals through Radar, WiFi or BLE (Bluetooth Low Energy) sensors, this work focuses on those that use acoustic signals, at ultrasound (US) frequencies, to estimate the position of the person. The emitted acoustic signals are altered by reflections, absorptions and frequency shifts (Doppler effect), derived from the medium and other elements existing in the environment, which are interesting to study in order to develop DFL systems. For this purpose, this work proposes a simulator that models all the phenomena that compose the channel response for the recreation of a real environment. In addition, a preliminary analysis of an ultrasonic positioning system that makes use of ultrasound reflections from the person’s head is presented. The proposed tool is useful to develop new ultrasonic DFL systems that take advantage of the acoustic properties with the aim of obtaining preliminary results previously to address a real prototype.