Clock Synchronization For Networked Systems

Clock synchronization is a key issue in networked systems.Wireless sensor networks and industrial Ethernet are two typical forms of networked systems.Designing clock synchronization algorithm of these two systems can provide reference for clock synchronization in networked systems with various organizational forms.In wireless sensor networks,limited by the changing network topology,limited node power and less deterministic communication links,it is necessary to design a clock synchronization algorithm which can maintain long time synchronization and work well under the condition of network topology change and uncertainties in communication process.In industrial ethernet,IEEE1588 is usually used for clock synchronization.However,the accuracy of clock synchronization will be affected by link asymmetry and measurement and the noise in processing and measurement.In order to get higher accuracy,the IEEE1588 clock synchronization method needs to improve.Therefore,this paper designs a clock synchronization algorithm which can work normally in the presence of delay.At the same time,the clock offset obtained by IEEE1588 clock synchronization is further processed.Finally,this paper proposed a feasible scheme for clock synchronization in heterogeneous networks composed of industrial Ethernet and wireless sensor networks.The main work of this paper is as follows:(1)Based on the first-order average consensus principle,a distributed clock synchronization algorithm in wireless sensor networks is designed.At the same time,the influence of time delay on clock skew synchronization process and clock offset synchronization process is analyzed,and the method of estimating relative clock skew is changed.Thus,the first-order average consensus clock synchronization method with time delay can reach consensus.(2)The clock synchronization method based on IEEE1588 is used to synchronize the time of the nodes in industrial ethernet.At the same time,the clock offset obtained by IEEE1588 clock synchronization method and clock offset based on clock model are used to obtain more accurate clock offset by Kalman filter method.(3)By adding the interface of real-time clock and transmitting clock information to the multi-channel gateway connecting two heterogeneous networks,and using the gateway as the boundary clock in IEEE1588-based clock synchronization of industrial Ethernet and the reference clock in wireless sensor network clock synchronization,the clock synchronization of heterogeneous networks is realized.