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Event driven time synchronization of mobile devices

Mobile devices are increasingly used for context recognition. Recognition accuracies partly depend on the time synchronicity between the mobile devices used for data recording and labeling. Mobile device synchronization can be done via the Internet or GPS, but both are not available in all areas. This paper presents our novel approach "Event Driven Time Synchronization of Mobile Devices" that works anytime, anywhere. The idea is to trigger sensor events on each device as much as possible at the same time. The time difference of the sensor event occurrences is interpreted as the time difference between the devices, called time offset between the devices. Our prototype utilizes proximity events to enable this. Our evaluation shows that 99% of the time offsets vary not more than 60 ms. Compared to this, only 17% are within this variance when using Network Time Protocol via a mobile High Speed Downlink Packet Access Internet connection.