SyncSync: Time-of-arrival based localization method using light-synchronized acoustic waves for smartphones

In this paper we describe SyncSync, a novel time-of-arrival (ToA) localization method for smartphones. ToA measurements generally show better precision than time-difference-of-arrival measurements, but ToA systems require a synchronization mechanism between anchor and mobile nodes. For this synchronization, we employ modulated light with an acoustic signal for the time-of-flight distance measurement. 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, sufficient for precise acoustic ToA measurement. Experiments confirm operation of the system with localization errors within 10 mm.