Time-Synchronization Schemes Based On Spanning Tree For Wireless Sensor Networks

Energy-efficient time synchronization is crucial for Wireless Sensor Networks(WSNs).This theme mainly studies on improving accuracy,reducing energy consumption.For isolated nodes and failed nodes,it is necessary to ensure the completeness of algorithm.At the same time,we try to achieve high accuracy under low energy consumption aiming to existing time synchronization models.PBS is an energy-efficient and high-accuracy time synchronization algorithm.It significantly incorporates SRP and RRP model.Based on PBS model,this theme proposes an energy-efficient time synchronization scheme based on spanning tree,namely R-Sync.A pulling timer is used to pull isolated nodes into synchronized networks.The initial value of timer is set according to level of spanning tree to shorten the period of time synchronization.Then,another timer is set up to select backbone node which also used to avoid collision in Mac layer.We also give a root node selection algorithm relating to energy to balance the energy consumption.In addition,we present PBS-2NLS,a high-accuracy time synchronization scheme,which is also based on PBS.PBS-2NLS uses SRP model to estimate propagation time error.And it combines the 2 points N times least squares and Mac layer timestamp to significantly improve the accuracy of PBS and reduce the impact of clock drift.Without changing timing chart,our scheme inherits the high energy efficiency from PBS.Moreover,PBS-2NLS gives a topology construction strategy based on spanning tree.It selects backbone nodes according to the number of child nodes,keeping the low energy consumption.The experimental results show that R-Sync makes all the nodes get synchronized and gets the better performance in terms of accuracy and energy consumption,compared with three existing time synchronization algorithms TPSN,GPA,STETS.Compared to PBS,PBS-2NLS improves the time synchronization accuracy.The strategy of topology construction ensures that energy consumption in PBS-2NLS is less than that in PBS.Aiming to time synchronization accuracy,PBS-2NLS reduces the defect of clock drift.