Experimental evaluation of a pairwise broadcast synchronization in a low-power Cyber-physical system

Increasing development of Cyber-physical systems (CPS) has made it possible to enhance the brain-computer interface (BCI) with other multimodal vital sensors e.g. video, acceleration, pulse oximetry (SpO2-Measurment) that allow the neurophysiologist to monitor data in real-time. However to correlate the diverse data from distributed sensor nodes possess a huge challenge in terms of defining a global time in the network and thereby generates a demand for time synchronization in the network. Before employing time synchronization in such a CPS based network it is required to carefully consider number of parameters including precision, security, reliability, processing time, memory requirement and energy costs. In this paper an energy-efficient clock synchronization method using two-way message exchange protocol which was recently proposed and theoretically proved namely pairwise-broadcast synchronization (PBS) and another similar method called timing-sync protocol for sensor networks (TPSN) were implemented. For this purpose a novel autarkic hardware pair was designed to enable the interoperability with existing infrastructure. Bluetooth low energy (BLE) medium was taken into consideration to ease the medical certification procedure and low power consumption. An experimental evaluation of the methods focusing on their reproducibility, precision, and performance overhead was discussed.