Research On Time Synchronization Technology Of Low Energy Consumption In WSN

WSN(Wireless Sensor Networks)is widely used in many fields of today's society.In practical application,it is required that the nodes in the network keep time synchronization.And the minor differences in the crystal of the sensor nodes will cause the nodes to be out of synchronization.Therefore,the WSN time synchronization algorithm is currently one research focus of WSN.For the classic Timing-sync Protocol for Sensor Networks algorithm(TPSN),the nodes of the entire network are hierarchically divided before the time synchronization,and then the time synchronization is performed layer by layer using a bidirectional message exchange.This algorithm can reach great accuracy of time synchronization.However,in the whole process,a large number of data packets are needed to be exchanged continually,which results in large energy consumption.To solve the problem of high energy consumption of the classic TPSN algorithm,a new algorithm is proposed in this paper,which is called L-TPSN(Low-energy Timing-Sync Protocol for Sensor Networks).The study was conducted at the stage of level discovery and the synchronization phase of the whole network.And the energy consumption of the algorithm is reduced on the premise of high synchronization accuracy of the algorithm.The main contributions of this thesis are as follows:(1)Select a certain number of nodes in the network as cluster heads according to the locations and energy of nodes,and then divide the network into several clusters.In the stage of network level discovery,only the cluster head nodes receive the network layer setup message broadcast by the upper layer nodes.After receiving network layer setup message,the cluster head nodes increase their own layer numbers by 1 and rebroadcast the layer setup message.When a node receives a message that contains a layer number greater than its own,it ignores the message until all the cluster head nodes have their own network layer numbers and form a new network topology.Compared with the case in the classic algorithm where each node needs to establish a hierarchy,the number of times of sending and receiving data packets is obviously reduced.In this way,the energy consumption is reduced.(2)Different time synchronization methods are used between cluster heads andintra-cluster nodes.Since the cluster heads will be used as the time reference nodes of the lower nodes,they may cause error accumulation.Therefore,for cluster heads,in addition to the original synchronization method,we adopt Bayesian estimation to reduce the error in the time synchronization process and improve the time synchronization accuracy of the algorithm.When the nodes in the cluster are time synchronized,the nodes in the cluster acquire the time information of the cluster head nodes by means of channel monitoring to synchronize the time of the nodes.The algorithm reduces the number of packets received and sent,thereby reducing energy consumption during synchronization.Finally,MATLAB is used to simulate the proposed L-TPSN algorithm and classic TPSN algorithm.The experimental results show that under the same conditions of other external conditions,L-TPSN algorithm's energy consumption is less than the classic TPSN algorithm.