SyncEcho: Echo-Based Single Speaker Time Offset Estimation for Time-of-Flight Localization

Hiroaki Murakami, Takuya Sasatani, Masanori Sugimoto, Issey Sukeda, Yukiya Mita, and Yoshihiro Kawahara

Abstract

Low-cost and accurate indoor location information can add spatio-temporal context to information systems, enabling new location-aware applications. Time-of-Flight (ToF)-based acoustic localization using speakers and microphones allows for localization accuracy within a few tens of centimeters, outperforming RF-based techniques. However, ToF-based localization requires synchronization between the speaker and microphone, i.e., the time offset between them must be known. Previous time offset estimation methods required custom hardware for speakers, limiting their practical use. Estimating the time offset using a single, unmodified speaker is essential for leveraging widely deployed speakers and enhancing coverage. This paper presents the first method for time offset estimation using a single speaker and a microphone, enabled by two key factors: (i) a time offset computation method that utilizes higher-order floor-ceiling reflections as multiple geometrically-constrained virtual speakers, and (ii) a signal processing pipeline that isolates these critical reflections from numerous others by leveraging the speaker’s frequency-dependent radiation pattern. Experiments show that the proposed technique can achieve time offset estimation with a 90th percentile error of 259 𝜇s at a 5 m distance. Furthermore, we implemented a ToF localization systembased on SyncEcho, demonstrating a 11.0 cm localization accuracy with a 90th percentile error.

22nd ACM Conference on Embedded Networked Sensor Systems (SenSys 2024)

Published: November 2024

Pages: 718 - 729

City: Hangzhou, China