Precise synchronization time stamp generation for Bluetooth low energy
Carl Christian Rheinländer, Norbert Wehn · 2016
Nowadays wearable sensor devices are a growing industry field. Smart gadgets like fitness trackers monitor sport exercises and daily movements of the wearer. Sensor data is wirelessly transferred to smartphones and processed by sports and fitness apps. Depending on the application, a single sensor might not be sufficient. In ubiquitous computing, sport science and medicinal appliances, complex scenarios require multiple distributed sensors. However proper sensor data fusion is not possible without precise time synchronization among all units. The common wireless technology of wearables is Bluetooth Low Energy (BLE), which is integrated in every nowadays smartphone. But the architecture of BLE makes implementation of accurate time synchronization nearly impossible due to nondeterministic delays. In this paper we present two principles to obtain precise synchronization hardware time stamps, based on the power consumption of BLE System on Chips (SoC). Our concept exceeds the best-known accuracy for BLE and is more energy-efficient compared to related work. Using a common BLE SoC, we achieved a standard deviation of 0.9 microseconds.