| The cost of deploying industrial wired networks and security issues in the field have made industrial networks "wireless." However,the limited hardware resources,limited energy supply,and real-time transmission requirements of industrial field devices pose challenges to the deployment of industrial wireless networks.As a technology used in many industrial wireless network standards,Time Slotted Channel Hopping(TSCH)enables industrial wireless networks to have low power consumption and highly reliable transmission performance,thereby meeting the requirements of equipment and networks deployed in industrial fields.Time synchronization technology is a key technology in industrial wireless sensor networks,determining whether the network can be reliably transmitted and maintained with low power consumption.Wireless sensor networks are large and complex,and distributed methods are generally chosen to build the network.This thesis focuses on time synchronization in distributed wireless sensor networks.The main work contents are as follows:First,based on a project called Open WSN created by the University of California,Berkeley,this thesis proposes a new RF chip WISA470 that supports the IEEE802.15.4e protocol.And on the self-developed platform(STM32F103RCT6+WISA470)to achieve network synchronization,device joining and clock synchronization.After experiments,the time synchronization bias superposition in the multi-hop network requires modifying the time synchronization algorithm,which leads to the next adaptive time compensation synchronization protocol.Secondly,combined with literature 1,a low-overhead single-hop synchronization algorithm based on adaptive time compensation is used on hardware nodes,and the packet synchronization interval is adaptively adjusted by using the relationship between synchronization interval and synchronization "protection time".Compared with the synchronization method without time compensation,the adaptive time compensation algorithm can reduce the number of synchronous packets sent by 44%,while maintaining the synchronization accuracy of less than 100 microseconds between nodes.In view of the influence of temperature on the node clock,the algorithm uses the information collected by the temperature sensor to monitor the influence of temperature change on clock drift in real time,and when the temperature difference changes beyond the threshold,the node restarts the adaptive time-compensated synchronization algorithm by resetting the synchronization interval.Thirdly,in the face of multi-hop scenario,this thesis combines literature 1 to use a follow-up multi-hop network clock coordination synchronization algorithm that suppresses clock skew transmission on this hardware platform.Through the slot hopping beacon frame,the synchronization moment information is broadcast to the surrounding nodes,and the node synchronizes with the clock source node immediately after the clock source neighbor node synchronizes(the moment with the highest synchronization accuracy),so as to obtain a time synchronization accuracy within 100 microseconds.The multi-hop network coordination synchronization algorithm solves the problem that during deployment,due to the random synchronization time,the clock deviation of nodes far from the clock source of the whole network exceeds the "protection time",and therefore loses synchronization.In summary,this thesis conducts an in-depth study on the clock synchronization problem of TSCH mode for industrial Internet of Things applications,combined with the adaptive clock synchronization algorithm proposed by the predecessors,and shows through experimental tests that this method can fully reduce the power consumption of hardware nodes and improve the reliability of communication. |
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