Wireless sensors exploiting IEEE802.15.4a for precise timestamping

This paper deals with the application of the Chirp Spread Spectrum (CSS) modulation for the synchronization of wireless sensors. Chirp modulation is a well known technique for precise localization, originally developed for RADAR applications. When CSS is used for communication purposes, radio frequency pulses are modulated in order to convey also user data. This approach allows for robustness, thanks to processing gain deriving from pulse compression, and for high accuracy estimation of the Time of Arrival of frames. In this paper, the CSS properties have been exploited in order to arrange a robust timestamping mechanism for distributed wireless sensor networks. The proposed system is based on the CSS modulation of the IEEE802.15.4a. Since commercial transceivers do not have synchronization support, the paper is based on a CSS modulation module implemented using a software defined radio approach. The outcome is a highly flexible solution that offers the desired synchronization support, confirmed by the simulation results showing a packet timestamping capability well below one nanosecond.