CAT: High-precision Acoustic Motion Tracking

Abstract

Video games, Virtual Reality (VR), Augmented Reality (AR), and Smart appliances (<i>e.g.</i>, smart TVs) all call for a new way for users to interact and control them. This paper develops high-preCision Acoustic Tracker (CAT), which aims to replace a traditional mouse and let a user play games, interact with VR/AR headsets, and control smart appliances by moving a smartphone in the air. Achieving high tracking accuracy is essential to provide enjoyable user experience. To this end, we develop a novel system that uses audio signals to achieve mm-level tracking accuracy. It lets multiple speakers transmit inaudible sounds at different frequencies. Based on the received sound, our system continuously estimates the distance and velocity of the mobile with respect to the speakers to continuously track it. At its heart lies a <i>distributed</i> Frequency Modulated Continuous Waveform (FMCW) that can accurately estimate the absolute distance between a transmitter and a receiver that are separate and unsynchronized. We further develop an optimization framework to combine FMCW estimation with Doppler shifts and Inertial Measurement Unit (IMU) measurements to enhance the accuracy, and efficiently solve the optimization problem. We implement two systems: one on a desktop and another on a mobile phone. Our evaluation and user study show that our system achieves high tracking accuracy and ease of use using existing hardware.