Research On Collaborative Time Synchronization Mecha-nism For Wireless Sensor Network

With the help of technological advances in micro-electro-mechanical systems(MEMS), wireless communications and embedded technology, low-cost, low-power,and multi-functional wireless sensor networks (WSN) has been developed. And WSNshows broad application prospects in the fields of military defense, disaster prediction,traffic management, health care, environmental science and everyday life. However,the practical applications of WSN are faced with many challenges, such as the problemof time synchronization. Large numbers of applications of wireless sensor networksrequire each sensor node in the network to keep the consistency of the time. How todesign time synchronization algorithm for WSN in the conditions of limited energy,harsh wireless channel and topological time-varying, to meet the applicationrequirements, is the vital significance for WSN.The existing time synchronization algorithms aim at general wireless sensornetworks, are not available to WSN with large data and high network performancerequirement. Therefore, in order to ensure large WSN performing normally, trading-offbetween computation quality and good scalability must be make for synchronizationalgorithms running on wireless sensors. In this paper, a new time synchronizationprotocol was proposed based on pulse-coupled oscillators and distributed diffusioninstead of the typical algorithm thought.Firstly, we analyzed the research dynamic of time synchronization technology athome and abroad, and then compared some existing algorithms of timesynchronization, and which is theoretical basis for the synchronization algorithmdesign. At the same time, the advantages and disadvantages of existing algorithmswere studied in detail.Secondly, this makes use of the idea of firefly synchronization in biology,introduced the idea into wireless sensor network. We focus on the M&S model andRFA algorithm. Based on RFA algorithm, a late sensitivity window and a distributed sequence number mechanism are used in multi-hop network. And besides, weimplement and simulate the new protocol N-RFA.Thirdly, a novel cooperative time synchronization protocol based on pulse-coupled oscillators and distributed diffusion (PCODD) is proposed. The protocoldivides the synchronization into two phases: clock tick synchronization phase and timesynchronization phase. In the first phase, the pulse-coupled oscillator’s phases arechanged by the pulse coupled signal. The tick synchronization is achieved bydistributed diffusion. In second phase, the average time of master-node domain isspread to a limited number of hops based on two-way message exchange mechanism.It adopts the method of mutual diffusion to finish the approximately synchronizationbetween the node time and the average time of all nodes. After the optimal design iscompleted, N-RFA and PCODD algorithms are achieved on Matlab SimulationPlatform and result of that is analyzed. The experimental results show that the PCODDalgorithms can synchronize the network and obtain the synchronization precision ofnearly hundred microseconds for different scales networks. And besides, PCODDalgorithms can synchronize the network quickly with good precision convergencespeed, the energy consumption of wireless sensor nodes effectively and improve thenetwork scalability.