Time-of-Arrival-Based Indoor Smartphone Localization Using Light-Synchronized Acoustic Waves

Takayuki AKIYAMA  Masanori SUGIMOTO  Hiromichi HASHIZUME  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E100-A   No.9   pp.2001-2012
Publication Date: 2017/09/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E100.A.2001
Type of Manuscript: PAPER
Category: Measurement Technology
acoustic localization,  ToA measurement,  LED light modulation,  time synchronization,  DOP,  

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We describe SyncSync, a time-of-arrival (ToA)-based localization method for smartphones. In general, ToA measurements show better precision than time-difference-of-arrival (TDoA) measurements, although ToA systems require a synchronization mechanism between anchor and mobile nodes. For this synchronization, we employ modulated LED light with an acoustic wave for time-of-flight distance measurements. These are detected by the smartphone's video camera and microphone. The time resolution in consumer video cameras is typically only a few tenths of a second, but by utilizing a CMOS image sensor's rolling shutter effect we obtain synchronization resolutions of a few microseconds, which is sufficient for precise acoustic ToA measurements. We conducted experiments to confirm operation of the system, and obtained ToA localization errors within 10mm. The characteristics of the error distributions for both TDoA and ToA measurements were explained by dilution of precision.