Low Complexity UWB Radios for Precise Wireless Sensor Network Synchronization

Abstract

Wireless sensor networks are becoming widely diffused because of the flexibility and scalability they offer. However, distributed measurements are significant only if the readout is coupled to time information. For this reason, network-wide time synchronization is the main concern. The objective of this paper is to exploit a very simple hardware implementation of an IR-UWB radio for realizing an accurate synchronization system for wireless sensors. The proposed solution relies on commercial-off-the-shelf discrete electronic components (rather than on specialized transceivers). It is designed for providing accurate timestamping of the packet time of arrival (TOA) to an adder-based tunable clock, which tracks the network time reference. The comprehensive set of experimental results based on prototypes, shows a TOA detection error with a standard deviation well below 1 ns. On the other hand, in the FPGAbased prototype, the synchronization performance reaches an overall synchronization error of few nanoseconds. Finally, in order to highlight the tradeoff between timestamping accuracy, clock stability, and synchronization performance, some additional simulations have been carried out: a synchronization error in the order of 1 ns is possible, if good local oscillator sources are available in the nodes and if the adjustable clock has a sufficient resolution.

Timestamp Validation Strategy for Wireless Sensor Networks Based on IEEE 802.15.4 CSS

“…More comprehensive results are presented in Section V, which is followed by some concluding remarks. the standard [13], has been analyzed in depth by the research community; timestamp perfomance of low cost, full analog, custom UWB device can reach standard deviation of tens of femtoseconds on short observation windows (e.g., 10 ms), whereas over longer observation time (e.g., >1 s), the standard deviation grows in the range of picoseconds, as confirmed by [8] and [25]. Commercially available transceivers for localization (e.g., decaWave, TIMEDOMAIN) declare position accuracy in the order of 10 cm, which means a timestamp standard deviation of ∼50 ps.…”

“…Points marked by a blue square are associated with the initial transient of the KF, corresponding to symbols having index k < k trans = 500, and should not be considered. Finally, timestamps nonsatisfying the condition given in (8) have been marked by red circles and considered as unreliable.…”

“…The latest edition of IEEE Standard 802.15.4 for wireless personal area networks permanently includes two physical layers, already introduced in the IEEE 802.15.4a-2007 amendment, whose features are well-suited to support localization [7], [8]. In particular, although not expressly announced for this purpose, the chirp spread spectrum (CSS) physical layer has the potential for achieving very accurate timestamping.…”

A practical clock synchronization algorithm for UWB positioning systems

“…Among positioning system-level issues, clock synchronization is a crucial factor that relates directly to the accuracy of time-based positioning techniques [2]. In TOA/TDOA mode, the travel time of signals is used to deduce the absolute or relative distances between the reference nodes and the target node.…”

Experimental demonstration of nanosecond-accuracy wireless network synchronization

“…UWB systems have been used previously to demonstrate high-precision tlmmg synchronization between two nodes. In [8], a commercial IEEE 802.14.5 radio was employed to obtain an accurate Time of Arrival (TOA) detection algorithm; the authors also proposed an Adder-Based Clock (ABC) approach for timing synchronization and implemented a prototype to show the accuracy of the synchronization block with nanoseconds precision. However, no network experiments were carried out.…”