Synchronization methods for wireless bio-sensing network

This paper deals with hardware and software methods, which improves wireless sensor network designed for acquiring human body biosignals. Due to defined parameters, accuracy better than 1ms is needed between samples time stamps, obtained by different wireless probes. Actually these methods are not allowed to affect data rate and performance of whole system. We used two different methods to reach this goal. The first method is based on absolute local time synchronization with respect to network topology and data flow, where ±20μs of absolute time synchronization was achieved. The second is automated software calibration of precision crystal oscillator with 10ppm accuracy, which was improved up to 0.0025ppm, what provides maximum clock error of 40 μs per 20 minutes. In this paper we introduce sensor network, describe developed synchronization methods and present partial experimental results.