Research On Mobile RPL Routing Protocol In Dynamic Low Power And Lossy Networks

The wireless sensor network(WSN)is composed of a large number of low-cost and low-power sensor devices,which monitor the environment and obtain data.The international Internet Engineering Task Force has designed a routing protocol for low power and lossy networks(LLN)(RPL).RPL was originally mainly applied to static wireless sensor networks,but mobile RPL is currently widely used in many emerging fields,such as smart home and construction,smart medical care,asset monitoring,etc.Based on the existing dynamic LLN routing algorithm,two improved mobility RPL routing protocols are proposed.The main research contents and innovations are as follows:Firstly,in view of the redundancy of control messages and candidate parent node sets in the current RPL research,the application scenario haven't universal adaptability.The mobile node(MN)disconnected from the parent node before sending a pathfinding request,causing problems such as data packet loss during the handover process.An efficient pathfinding RPL routing algorithm for nodes in mobile scenarios(EP-RPL)is proposed.EP-RPL contains four optimization ideas:(1)Modify the frame format of the control message to distinguish between MN and static node(SN),achieving compatibility with standard RPL;(2)Use an adaptive blacklist mechanism to establish the candidate parent node sets,reducing the processing delay and energy consumption of the MN;(3)Based on the moving speed and random moving direction of the MN,select the node with the longest estimated time to move out of the communication range from the candidate parent node sets as the preferred parent node,suitable for scenarios where the moving speed and direction are random;(4)Set the destination oriented directed acyclic graph(DODAG)information solicitation(DIS)timer before the link is interrupted,so that the MN can switch to the new parent node timely before disconnecting the link from the current parent node.The simulation results show that the EP-RPL protocol has significantly improved performance indicators such as average end-to-end delay,energy consumption of mobile node,and packet loss rate.Secondly,in view of the current research of mobile RPL on the MN pathfinding process,the parent node selection metric values only contain the current candidate parent node and ignore its upstream link energy,and don't reasonably consider the loss of the control message during the forwarding process,which affect the successful construction of communication links and other issues.A reliable RPL pathfinding algorithm based on link energy saving in dynamic LLN(LESD-RPL)is proposed.The algorithm proposes three optimization ideas:(1)Modify the message frame format to adapt to different interaction scenarios in the forwarding process for ensuring the compatibility of control messages;(2)The preferred parent node is selected based on the network depth and the upstream link energy of the candidate parent node and combined with the priority,which not only avoids unnecessary energy consumption of some SNs,but also effectively improves the survival time of the entire network;(3)Enabling the reachable timer effectively avoids link construction failures caused by the loss of control messages.The simulation results show that the LESD-RPL algorithm has significantly improved performance indicators such as the energy consumption of the relay node,the success rate of data transmission from the source node to the destination node,and the survival time of network.