Time Synchronization in a Network of Bluetooth Low Energy Beacons
Farzad Asgarian, Khalil Najafi · 2017
Time synchronization is a vital feature in many wireless sensor networks with applications ranging from structural health monitoring systems to body area sensors used for rehabilitation and sport medicine. While different wireless protocols have been utilized in sensor networks, Bluetooth Low Energy (BLE) has drawn a lot of attention in the past years due to its low-power architecture and availability in many consumer electronics. Moreover, the added non-connectable beacon mode has increased its functionality for Internet of Things (IoT) and sensor fusion. However, in this mode as devices are not paired with each other no synchronization service is available. In this paper, we present a synchronization protocol based on BLE beacons that can be used in conjunction with BLE software stacks provided with a commercial Bluetooth System-on-Chip (SoC). Offset and frequency-drift estimation techniques are discussed, and the effects of number of synchronization packets and their intervals on the overall synchronization accuracy are investigated. Experimental results show that without any re-synchronization in ten minutes, average synchronization errors of less than 350 ns per minute (single hop) can be achieved.