A Connection Event Based Time Synchronization scheme for BSN enabled BLE nodes

Time synchronization is very important for sensing nodes in a body sensor network (BSN). The uncertainty of the wake-up time of Bluetooth Low Energy (BLE) air link makes it is a great challenging of achieving precise time synchronization between nodes. Hence, we propose a connection event based BLE-BSN node time synchronization scheme to ensure accuracy clock between nodes. We firstly analyzed the factors cause the time error of CC2642R sensor nodes in a star network, and proposed a BLE connection event based pulse synchronization method to estimate the time error between the master node and the slave nodes. The estimated time error was compensated at each connection beats, which strictly guarantees time coherence of node in the application of physiological measurement. We tested the proposed time synchronization scheme with a four-nodes network. Experimental results show that with the proposed method, the time error of the node is less than ±150ps under the 200ms connection interval. The proposed method has good potential using in BSN physiological measurement application.