| With the application and development of information technology in industry,the Industrial Internet of Things came into being.It upgrades the industrial chain of traditional industries and comprehensively improves the automation and intelligence of products from production,inventory,transportation and sales.The industrial wireless network has been widely used due to its basicity and flexibility,thus promoting the further development of Industry 4.0.However,with the diversification of industrial wireless network application scenarios and the complexity of the application environment,industrial wireless networks have changed from previously supported soft real-time applications to hard real-time applications and high sampling rate control applications,the adaptation of industrial wireless networks poses various challenges.This paper first summarizes the communication protocols and scheduling algorithms of industrial wireless networks,and proposes the asynchronous scheduling strategy that can ensure reliable transmission of messages and determine delay without considering the local clock of the synchronization node.At the same time,the application of this strategy in distributed multi-hop industrial wireless networks is also studied.Finally,simulation experiments prove the feasibility of the distributed asynchronous deterministic guarantee mechanism.The main research work of this article includes:1.In view of the centralized network architecture control node failure affecting the stable operation of the system,the existing algorithms to ensure real-time network communication are based on clock synchronization,the asynchronous scheduling strategy is proposed.In a single-hop network,the nodes send data packets redundantly in a cycle to ensure that all nodes have no conflicting transmission time slots in any cycle.There is no need to consider the synchronization of the local clock of the node,ensuring a certain communication delay and reliable data transmission.2.Considering that the asynchronous scheduling strategy in a single-hop network is constrained by the number of nodes and the communication distance of nodes,it cannot be widely used in industrial wireless network scenarios where the number of nodes requires more.Therefore,it is necessary to set up a routing node to extend the network by means of relaying and forwarding.In this paper,the problem is modeled as a vertex coloring problem of connected graphs.The graph partition algorithm is used to plan the topology model and subnets.The graph coloring algorithm is used to assign a corresponding scheduling mode to each node,the number of nodes in all subnets is controlled within the preset range,the communication problem of the nodes in the subnet is reduced to the data transmission problem of the single-hop network.In the case of interference between subnets,the coloring allocation strategy of the graph coloring algorithm is changed,thereby effectively improving the reliability of data transmission.Distinguish between ordinary non-real-time traffic and emergency real-time traffic by quality of service to ensure timely forwarding of data streams and ensure a certain end-to-end transmission delay.3.Use the Contiki software simulation platform to verify the distributed asynchronous deterministic guarantee mechanism implemented in the multi-hop industrial wireless network.In the collection data stream communication,the ACK response mechanism is added to reduces the transmission delay,and uses the priority queue to realize the real-time forwarding of event-triggered streams and the deterministic delay of periodic data stream transmission.In terms of dissemination data stream communications,by comparing the latest enqueued data packets before enqueuing,repeated enqueuing and redundant transmission are avoided,ensuring a certain communication delay and reliable data transmission. |
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