Research Of Hierarchical Timesynchronization For Wireless Sensor Networks

As a widely used and much concerned integrated technology, wireless sensornetwork plays an important role in people’s daily life and work environment. Itsdevelopment prospect also obtains great attentions in industry and academia at homeand abroad. Time synchronization is one of the key supporting technologies in thedistributed network and plays an important role in the design and widespreadapplication. Due tothe constraint of the energy, volume, communication and storage,traditional time synchronization protocol is no longer meet the requirement of wirelesssensor networks.It’s significant to study the time synchronization algorithmwhichadapts to the characteristics of wireless sensor networks.This paper analyses the principle of diverse existing classic algorithms of timesynchronization carefully, and proposes the solutions to the issuesof accuracy andenergy consumption when nodes synchronized in hierarchical topology. The details ofthe research works mainly contain the following three aspects:①The principle of time synchronization technologyand the existing timesynchronization mechanisms are further analyzed and studied in this paper. Accordingto thedifferent interactions methodsof messages among nodes, the classicalsynchronization algorithms can be divided into three types of synchronizationmechanisms, and the advantages and shortcomings of each type of algorithms areanalyzed to prepare for the further research work.②Due to the impact of node clock skew and the delay in information transmission,the issues of deviation of the receipt time and low synchronization precision are existedin the classic time synchronization algorithms. Therefore, an improved referencing timesynchronization algorithm based on the hierarchical topology networks is presented inthis paper.The proposed algorithm adopts Bayesian estimation methods to calculate thereceipt time of each node,narrow the error scope of time deviation and obtain moreprecise synchronization time offset. Meanwhile,it adoptsthe characteristics of wirelesschannel broadcast andmechanism of bi-directional synchronization to minimize thecommunication load and balance node energy consumption.③Aiming at the issues that it focuses on increasing the network synchronizationprecision but ignores the network energy consumption, path hops and erroraccumulation when typical time synchronous algorithms being adopted in multi-hop wireless sensor network,cluster-based and energy-efficient hierarchical timesynchronization algorithmwhich based on a cluster hierarchical topology is proposed inthis paper. A cluster node is selected to take a two-way synchronization with its clusterhead, and its neighbor nodes achieve bidirectional synchronous indirectly through thepassive monitoring mode. In such a way the quantity of the packet’s transmission isreduced.Meanwhile, the safety of transmission is ensured by the digital signaturespattern. What’s more, the quote of cycle update coefficient of synchronous group delayfurther reduces the overhead of synchronization packets.The simulations show that Bayesian estimation method is applied to perfect theperformance of the receipttime of the time synchronizationalgorithm and significantlyimprove the accuracy of hierarchical synchronization algorithm in theestablishedalgorithm model. CEHTS (Cluster-based and energy-efficient hierarchicaltime synchronization algorithm)can effectively reduce the energy consumption, prolongthe network life time and has a good practicality.