Physical-Layer Time Synchronization For Wireless Sensor Networks Using UWB Signals

As is known, wireless sensor network (WSN) is a typical distributed information system, where time synchronization is an important problem, and all nodes in the network are equipped with their own local clocks. The aim of time synchronization is to provide a unified timescale for part or all of the sensor nodes in network.This paper focuses on the time synchronization method for WSN. A new physical-layer time synchronization scheme for WSN with the use of UWB (ultra-wideband) signals is proposed. The synchronization is performed by emitting reference UWB signals at pairs of neighboring nodes alternatively, and recording the local time instant information respectively, which is similar to the sender-receiver scheme. The frequency drift of the target node is corrected step by step, using the gradient decent algorithm, and converges to the frequency drift of the beacon node finally. Then the difference between the time offsets of the pair nodes is estimated, and the local clock of the target node is aligned with that of the beacon node. The proposed time synchronization scheme also provides a method for determining synchronization cycle under the constraint of maximal synchronization error bound.To confirm the effectiveness of the synchronization scheme we proposed, the computer simulations are performed using Matlab. The simulation results and analysis confirm the effectiveness of the proposed method. It can prolong the synchronization cycle greatly, and on a linear network composed of ten sensor nodes, the synchronization errors of all target nodes are less than 10ns.