Modelling the Performance of Ultrasound Presence Detection

Ultrasound sonar range (USR) sensors are used to detect the presence of of¿ce workers in real time. An experimental setting deployed to measure the proximity of the user to the computer screen, shows that the measurements exhibit outages, i.e., false positives due to propagation effects, even at short range. Modelling the performance of USR is relevant for the analysis of the detection reliability, e.g., expressed in terms of missed presence and latency, and leads to an evaluation of possible energy savings from lighting control versus user annoyance by reduced light conditions at wrong instances. In this paper we propose a mathematical model, based on outages due to Rayleigh scattering and exponentially distributed gap lengths. Experimental data is used to ¿nd parameters for theoretical distributions.